Man-made materials – glass, steel and concrete – carry the day in modern building design.  Architects are fascinated by the possibilities offered by these material, we can build what was never possible before: structures of fantastical shapes, great heights, colossal spans.  And in all the excitement, we let fall by the wayside one of the most ancient, tried-and-true materials of them all, the one Mother Nature created for us. Wood.

And yet, wood is a wondrous material.  In Europe, especially in the North rich in timber, wood has always been the main building material.  Wood architecture has created some extraordinary examples, daring in shape and size, and most importantly, durable.  There is the 120-feet high wooden Church of Transfiguration in Russia, built in the 17^th century.  There is a wooden arcade in Bologna built in 13^th century.  Any of the modern glass, steel and concrete buildings have yet to prove that they can match this.

It is also true, that most of the wood-based houses built today carry little resemblance to these remarkable structures.  The standard 2×4 “stick- frame” houses are considered a “budget” option and are often of poor quality.  These houses are built to last no more than 50 years, and often start sprouting problems long before then.

Still, as we become more aware of our impact on Earth, and of the necessity to behave in a more sustainable manner if we want to continue to live here and to maintain a decent standard of living, our choices change.   We start to recognize one very simple fact:  wood needs only the energy of the sun to grow and is endlessly renewable, while man-made materials are made using non-renewable fossil fuels.

Wood as a Green Material

Trees need no energy, but the free energy of the sun to grow.

Trees are renewable, and with proper management, we can have the supply of timber forever.

Trees sequester the carbon dioxide, and a wooden house is a storehouse of carbon.

Wood is completely reusable and recyclable, in fact, wood can be reused for its original purpose with little or no loss of value.

Wood positively impacts indoor air quality and, as shown in a recent study from the University of British Columbia and FPInnovations, promotes wellness of occupants.

Wood has low embodied energy – the energy required to harvest, manufacture and transport a material or product.

Wood requires a minimal amount of energy-based processing

So, do we save the planet by building with wood?  Is wood a green material?

For decades, environmentalists fought the logging industry for clear-cutting forests, polluting rivers and destroying wildlife habitat.  In view of many people, intensive logging, poor reseeding efforts and replacing virgin forests with fast-growing timber monocultures nullified all environmental positives from using wood.

Therefore, to be truly green, wood needs to be harvested properly.

Sustainable forest management must ensure the long-term health and diversity of forests, and produce stronger and healthier forests.

Architects, product designers, and homeowners are increasingly asking for building products that are certified to be from a sustainable source.  This demand resulted in creation of forest certification programs.  Certification programs not only ensure that the wood is harvested in a sustainable fashion, but also that land management plans include issues of biodiversity, habitat protection, and indigenous peoples’ rights.

Wood construction – Positive Developments

At the celebration of the International Year of the Forest, Agriculture Secretary Tom Vilsack announced plans by the Agriculture Department and the Forest Service to use more wood in its buildings.  He directed other USDA agencies to adopt the Forest Service policy of using “domestic sustainable wood products” as its preferred green building material.  Furthermore, Forest Service says that the government’s role is to “look for opportunities to demonstrate the innovative use of wood as a green building material” for buildings over 10,000 square feet.

One of the most effective ways to promote the use of wood in buildings, is to demonstrate its reduced environmental impact as compared to alternative building materials.  One of the most effective ways to demonstrate comparative environmental costs of materials is to use Life-Cycle Analysis (LCA).  LCA measures the environmental impacts of building products throughout their life.

By focusing on the entire lifecycle of a tree, it became possible to demonstrate that harvesting, transporting, manufacturing and ultimately disposing of wood used in construction, produces fewer air emissions, including greenhouse gases, than other materials.  A recent study from the University of Oregon showed that wood framing used 17% less energy than steel construction for a typical house built in Minnesota, and 16% less energy than a house using concrete construction in Atlanta.  Also, in these two examples, the use of wood had 26% – 31% percent less global warming.

LCA serves as a basis for Environmental Product Declaration (EPD) which is a standardized way of quantifying the environmental impact of a product.  While many industries are adopting EPDs, there is still a long way from readily available comprehensive life-cycle information on most commonly used building products, including wood.

However, for wood to gain widespread acceptance as a green building material, several key components first have to come together:

• Building and Material codes should include provisions for the use of LCA and EPD in selection of building materials.
• LCA and EPD should continue to develop and evolve to the point where life-cycle information and simple comparison methods for different materials are readily available to building professionals and consumers.
• Research and development of wood products and building systems should catch up to that of other materials.  Currently, it is significantly behind.

Politics of Wood

As was widely reported recently, the U.S. Congress tried to restrict the military’s use of LEED in its recent budget law.  Main and Georgia effectively banned LEED certification for State building projects.  The declared reason given by the politicians is that “LEED rating systems harm producers of homegrown forestry products, hurting the economy and killing jobs”.

In fact, both these events are the results of “wood wars” between advocates of the Forestry Stewardship Council (FSC) and the Sustainable Forestry Initiative (SFI).  SFI was originally set up by the lumber industry as an alternative to FSC.  SFI is more industry-friendly than FSC, which has stronger rules against clear-cutting, and in support of indigenous peoples and workers.

LEED recognizes only certification from the FSC in awarding points for sustainably harvested forest products.  For the last decade, other groups, especially SFI, have sought entry.  When they were unable to persuade USGBC, they seem to have decided to go after LEED itself.

The current LEED 2012 Wood Credits are:

• Building reuse and whole-building life-cycle assessment (1–3 points)
• Material life-cycle disclosure and assessment (2 points) (a controversial point as it rewards transparency without regard to environmental performance, i.e. even an unsustainably harvested product, but with an LCA, will still gain a point)
• Responsible extraction of raw materials (1–2 points)
• Disclosure of chemicals of concern (1 point) (for composite wood products)
• Avoidance of chemicals of concern (2 points) (for composite wood products)

Building with wood

As we turn our attention back to wood, in order to make the right design choices and maximize its potential as a building material, it is important to recognize both advantages and challenges of building with wood:

Advantages of building with wood

Aesthetic appeal – wood is naturally beautiful and visually engaging

Range of applications – wood is versatile and lends itself to a variety of both exterior and interior applications.

Cost – usually, wood is the most economical alternative for frame construction.  It can be locally sourced, so the costs of transportation are lower.

Ease of use – wood construction can proceed in any season and almost any climate.  Workers of varying skill levels can quickly learn wood-construction techniques.  Wood can be cut and sized on-site.

Humidity regulation – wood’s moisture content always matches the ambient air, as it naturally absorbs and releases moisture, providing natural humidity regulation.  Wood construction moderates indoor humidity, reducing air conditioning and heating costs.  High humidity doesn’t compromise wood’s structural integrity, making it a great choice for the wettest climates and high-humidity applications, such as aquatic centers.

Fire-resistance – solid wood performs in a measurable, predictable way in a fire, so buildings can be designed to meet fire-resistance ratings.  Heavy timbers just char on the outside while retaining strength, slowing combustion and allowing time to evacuate the building.  However, this doesn’t apply to modern engineered timbers, which in fact, are prone to collapse quickly in the fire.

Seismic and wind performance – wood’s low mass and high flexibility make wood-frame buildings more resistant to earthquake and wind damage than concrete or steel-framed buildings.

Acoustic performance – wood has excellent acoustic properties, with many high-end architectural projects featuring internal timber applications.

Thermal performance – wood has low thermal conductivity, thus it is a naturally insulating material.

Challenge of building with wood

Poor timber quality – wood sold these days is too soft compared to one used in houses even 50 years ago.  In the past, framing timber came from old, often hundreds years old, trees.  Clearly, this practice is unsustainable.  Wood today is farmed, like corn or wheat, and harvested in about 25 years.  Young trees pass building codes, but they’re not as dense, straight and free of knots as the old timber.  They are also moist, which makes construction unstable.

Material properties limitations –wood is a natural material, and so it is not uniform, and there is large variability in properties between species and within a species.

Susceptibility to water – as mentioned above, wood absorbs or loses water to match the moisture content of the ambient air.  However, it also means that water changes wood’s dimensions, as it swell or shrinks.  This makes wood structures less dimensionally stable.  Use of young trees with high moisture content exacerbates this problem.  Once a house is sealed up and the heat turned on, wood dries making floor joists and wall studs shrink or warp, causing drywall and floor tiles to crack, and caulked seams to pull apart.

Susceptibility to deteriorations from natural causes – as wood is an organic living thing, it is a nutritional product for some plants and animals.  This makes wood susceptible to termites, woodworm, fungi, rot and decease.

What can be done to overcome these weaknesses of wood as a building material?

Protect against natural causes of deterioration –  coat or impregnate wood with protective agents.

Drying – is one of the most effective ways to prevent degradation of wood and to improve its performance.  Wood can be dried in air or in a dry kiln.  However, while kiln drying has many advantages, such as killing off staining or wood destroying fungi or insects, it is also energy intensive.

Wood building materials

Natural timber

Roundwood – wood supplied in log form

Sawn Timber – wood is cut from logs into different shapes and sizes.

However, as discussed above, building with century old trees as they did in the past, is no longer an option.  As young trees don’t have the properties of old ones, modern timber in its solid form has only limited building potential.

Engineered wood

In comes engineered wood.  Engineered wood (sometimes referred to as composite) is comprised of wood veneers, lumber, panels, fibers or strands bound together with an adhesive.  It has emerged from the realization that we can use the fiber, which is the basis of wood, to its best advantage by chopping the wood up and gluing it back together, stronger and with improved properties.  Engineered wood products mean that wood can now be used where once the only option were steel or concrete.

Structural Applications: Structural Composite Lumber (SCL)

is a family of engineered wood products used for structural applications.  SCL products are made by layering either veneers, strands or flakes with adhesives:

Cross-laminated timber (CLT) –  a wood panel product with characteristics similar to a pre-cast concrete panel.  Layers of timber are glued together with the grain alternating at 90 degree angles for each layer, which improves the structural properties of wood by distributing the along-the-grain strength of wood in both directions.

Clulam (short for “glued laminated” timber) – a single large, strong, structural member manufactured from smaller pieces, finger-jointed into continuous lengths.

Laminated Veneer Lumber (LVL) – manufactured by bonding together rotary peeled or sliced thin wood veneers under heat and pressure.  Comparable in strength to solid timber, concrete and steel.

Oriented Strand Boards (OSB) – a structural panel product produced by bonding together thin wood strands with adhesive.  For dimensional stability, the grain direction in the outer layers is at the right angle to the grain direction in inner layers.

Plywood- an assemblage of wood veneers bonded together to produce a flat sheet.  The most common product consists of at least 3 plies, with the grain in the alternate plies running at right angles.

I-Beams – high-strength, long-span structural beams.  I-Beams are economical to produce, because they are made from a combination of wood products: the top and bottom flanges – which make the distinct ‘I’ shape, – are made from material with a high tension strength, such as LVL or even solid timber.  The vertical web serves to transmit stress, which requires a material with good shear properties, such as structural plywood or OSB.

Interior Applications:

Decorative Wood Veneers – produced by slicing a large piece of wood log into thin slices or veneers.  The way the veneer is cut will determine the appearance of the grain.  Veneer then are pressed to a substrate, such as MDF, particleboard and plywood.

Medium Density Fibreboard (MDF) – a reconstituted wood panel product manufactured from wood fibers, as opposed to veneers or particles, and is denser than plywood and particleboard.  MDF has an even density throughout and is smooth on both sides.  MDF is primarily used for internal use applications due to poor moisture resistance.

Particle Board - a reconstituted wood panel product manufactured from wood particles, or wood flakes, or strands.  A mat of individual wood particles is coated in adhesive resin and pressed together into a finished panel.  As the wood fibers in the particles are randomly oriented, the finished panel has uniform properties in each direction.  It is mostly used for furniture, veneer substrates and cupboards.

The main concern with engineered woods, is that the adhesives can changes the properties, rendering them much less friendly to the indoor air quality than natural wood.

Looking into the future

The industrial revolution gave us concrete and steel and allowed us to indulge in huge, terrifically complex structures.  Now, the carbon revolution compels us to factor sustainability into our thinking about what and how we build.  This will bring wood back as a key building material.  

For this to happen sooner rather than later, changes in both building codes and building professionals’ attitudes have to happen.  In the meantime, these are a few considerations that may speed up the acceptance of wood as a major construction material:

• Developments in wood science and building technologies create many new uses for wood.
• Climate change.  The climate change is likely to make insect infestation problems worse, as has already been happening in Colorado with the mountain pine beetle epidemic.  The trees so affected, need to be harvested before they rot releasing CO₂  back into the atmosphere.  This is where composite products such as CLT, made from small pieces, will come to the rescue.
• Architects need to design for large wood panels and convince the industry to supply them.  Engineered LVLs that fit this purpose already exist, and they come out of the manufacturing process in enormous sheet, yet, as there is no demand, suppliers chop them into smaller sizes.  These products open doors to larger structures built of wood.  In fact, the technology to build multi-storey wood structures of up to 20 or 30 levels using engineered timber products is already here.

As the economy is slowly but surely turning green, as the society begins to accept the necessity of sustainable way of life, we will have to learn how to meet our needs using only renewable resources.  And this is why wood must come back.

A typical basement, in winter, is like having an air conditioner running under your floorboards. In summer, it’s akin to living above a swamp, with damp foundation walls and floors, sweaty pipes, musty odors, and many-legged creatures scurrying about.

There are two ways to solve these problems, according to Larry Janesky, home energy audit expert and president of Dr. Energy Saver: insulate the basement “ceiling” or insulate the basement walls. Deciding which is best for you and your home is best left to an energy expert, but it’s helpful to understand your options.

Option one: Insulating the basement “ceiling”

When most homeowners (and many builders) think about basement insulation, they think about stuffing fluffy pink stuff between the overhead joists (framing) in the basement. It doesn’t do much, but it makes people feel better that there’s some sort of thermal barrier between them and the basement. Many people don’t bother with insulation here at all because of all the obstacles to installing it: air ducts, electrical cables, plumbing, bridging, and light fixtures. In addition, fiberglass bats are notorious for soaking up condensation, sagging out of position, and allowing air to pass through them.

Nevertheless, there are times when insulating the basement ceiling makes sense. They include:

• You want to keep the basement as cool as possible because it’s being used to age wine or store root veggies.
• You are on a tight budget and the basement ceiling (overhead joists) are relatively unobstructed by ducts, electrical junction boxes, and plumbing valves. Homes with hydronic heat usually have fewer overhead obstructions.
•  You have no other space than the basement to store volatile liquids, such as paints, cleaners, and solvents, and want to eliminate air movement to the rest of the house
•  Your HVAC equipment and heat/AC delivery system are not located in the basement and the space is only used for storage.

If you do choose to insulate the basement ceiling, ask your energy conservation contractor about using a two-part, closed-cell spray foam insulation. Advantages include a higher R-value than fiberglass, moisture-resistance, and superior air sealing capabilities. Foam insulation can quickly and efficiently seal gaps between the perimeter (rim) joists and the foundation, too. It can also seal around obstacles, such as ducts and bridging, quickly and easily without cutting and fitting. Keep in mind, however, that all occupants (including pets!) will have to vacate the house during the installation and while the foam cures, typically 24 hours. Spray foam must also be treated with a fire-retardant coating. Here is more detailed information explaining the best types of insulation for a basement.

Option two: Insulating foundation walls

In many cases, insulating the interior face of foundation walls is the best way to eliminate cold floors and to improve your home’s overall energy efficiency. In effect, the basement becomes a tempered, or “semi-conditioned,” space that is much closer to the temperature and humidity levels of the rest of the home’s habitable spaces. In addition to warmer floors in winter, benefits to this approach include less heat loss from basement HVAC equipment and heat delivery systems, the elimination of condensation that normally plagues basements in summer, and a far more useful basement.

Insulating foundation walls instead of the basement ceiling makes sense if:

• You want to use the space for doing laundry, as a workshop, playroom, or craft area.
• You want to eventually convert the basement to habitable space.
• You require access to overhead mechanicals or want to use the joist bays for storage.
• Volatile products are stored outside the home.

There are many ways to insulate foundation walls, but the preferred method is to use rigid insulation boards (expanded polystyrene, extruded polystyrene, or polyisocyanurate). They can be installed directly to the interior of foundation walls, across framed walls, or placed in steel tracks, offset from the walls. Some insulation board products, such as Total Basement Finishing System’s Basement to Beautiful™ insulated wall panels, are fabricated with integral steel studs and pre-cut channels for running electrical cables. These water-resistant panels provide R-13 on walls and create a vapor barrier when installed. They can be covered with a waterproof, mold-resistant wallboard when you’re ready to convert the basement to living space.

Spray foam insulation may also be used to insulate foundation walls. This approach has some advantages when your foundation walls are irregular, such as when a foundation was built of stone. But it is not particularly attractive and will also need to be coated with a flame-retardant finish.

Regardless of which insulation you choose, it is important to take steps to eliminate moisture from accumulating in the basement. Exterior grading, gutter systems, interior perimeter drains, sump pumps, and dehumidifiers may all play a role in ensuring a dry basement.  Other energy-smart steps include insulating and air sealing the rim joists as discussed above, providing outside combustion air to your furnace or boiler, and upgrading to insulated windows and doors. If interested in learning more about basement energy efficiency I recommend reading this Department of Energy article.

There are a few green building standards competing for the industry’s attention in the US: USGBC’s LEED, the Green Building Initiative’s Green Globes, the International Living Future Institute’s Living building challenge, the Passive House (aka Passivhaus).  And now, there is also the Active house.

Active Houses is energy efficient and uses only renewable resources.  The indoor climate of the Active House is designed to be comfortable and healthy, and the home itself is designed to interact positively with the local environment.

Active House is a very new concept, it was first conceived in 2011, at a conference in Brussels, although the movement itself started in Copenhagen, Denmark.  Since then, quite a few Active Houses were built in Europe.  And just this year, the first two prototype houses were built in North America, one in the US, and one in Canada.

Active House key principles are:

Energy:

• a building that is energy efficient and easy to operate
• a building that substantially exceeds the statutory minimum in terms of energy efficiency
• a building that exploits a variety of renewable energy sources integrated in the overall design

Environment :

• a building that exerts the minimum impact on environmental and cultural resources
• a building that avoids ecological damage
• a building that is constructed of materials with focus on re-use.

Comfort:

• a building with an indoor climate that promotes health, comfort and sense of well-being
• a building that ensures good indoor air quality, adequate thermal climate and appropriate visual and acoustical comfort
• a building with an indoor climate that is easy for occupants to control and at the same time encourages responsible environmental behavior

The Active House concept is promoted by the Active House Alliance, which is a non-profit association registered in Belgium.  The Alliance’s ambition is to create a “viable, independent and internationally influential principle for new buildings which would provide healthier and more comfortable lives for their residents without impacting negatively on the climate and the environment”.

The Active House Alliance issues the Principles, the Specificaiton and the Guidelines to help design teams to meet the Active House standards.

The Principles provides an overview of the vision, thinking and principles behind an Active House.

The Specification provides the insight and knowledge for the technical specifications and design concept for an Active House.  The Specification is process-oriented and provides guidance on how to achieve the performance levels described in the technical specifications.  It also gives some advice on the holistic approach to the design process (biodiversity, local culture and location).  The specification, now in its 2^nd edition, is comprised of the shared knowledge and experience of the Members of the Alliance, using an open source model.

The Guidelines address the process of planning the construction of an Active House.

Case Study – Active House USA

The very first Active House in the US was just finished in Webster Groves, MO.  Webster Groves is located in a mixed humid climate region.  A house built there has to meet both warm and cold climate efficiency needs, making it the ideal location for a prototype house.

Most Active Houses built in Europe showcase modern designs.  However, because the Active House USA is located in a historic part of town, it was designed to “blend harmoniously with the historic homes in the surrounding area so it has the look and all the charm but outperforms them by far”.  Although the house represents top of the line construction technology, it is still appraised on point for the average new home construction in this highly coveted, historic neighborhood of Webster Groves, MO.

Active House USA was designed using the Active House Specifications developed by the Active House Alliance and built for certification in four North American Sustainable building standards: Energy Star, EPA Indoor, Building America Builder’s Challenge, and ANSI ICC-700 (aka The National Green Building Standard).  By meeting and exceeding these existing metrics and certifications, the Active House USA prototype aims to prove itself and to help develop standards for future Active Houses in North America.

Since this is the prototype, the homeowner has agreed to allow the University of Missouri’s Center for Sustainable Energy to monitor energy consumption and indoor air quality for the first year of residence.  The research team will analyze the data and share it with the Belgium-based Active House Alliance and their UK-based contract-engineering firm, Grontmij, who will do the final commissioning of this Active House prototype.  The data and information will also be shared with the NAHB’s Home Innovation Research Center, the certifying body for the ANSI ICC-70 standard.

On March 8 and 9, 2013 the final open house for Active House USA was held.  Close to 2,000 people (!) came on these two days to see the house and to speak directly with the design and construction team.

Key Principles: Energy – Environment – Comfort

The stated goal of the design team was: “… to provide the homeowner with a cost-effective, and easy to operate and maintain living space, that creates a healthier and more comfortable lives for their occupants without impacting the climate.”

Throughout all phases of design and construction, the Active House USA design team specified energy efficient materials, design techniques and building practices with emphasis on renewable resources.

Active House USA is a very healthy house.  It takes advantage of solar orientation, natural cross-ventilation and natural lighting in every room.

Solar orientation* in particular, was a key to successful performance planning for the Active House USA.  A well-designed and properly oriented house capitalizes on solar heat gain in the winter and deflects unwanted heat in the summer.  This simple consideration can significantly reduce a house’s energy use, it is free and will last for the entire life of the building.  Proper solar orientation can also provide glare-free natural light throughout the house.

*Solar orientation refers to orienting the design of the house in relation to the natural path of the sun.

The interior layout of the house is open and airy, which will maximize daylight throughout the house.  The house makes extensive use of vertical light, using sun tunnels and skylights, which makes daylighting even more effective as it provides a higher percentage of light with less glare.  American architects worked with the engineers from the Active House Network in Denmark to maximize the effectiveness of the lighting design.

As a result, there is less need for artificial lighting, thus lower energy costs. Furthermore, less artificial lighting generates less heat, which in turn further decreases the demand for air conditioning in summer.

Issues with the Active House standard

Without a doubt, the Active House USA is a very important project for the green building movement in the US.  However, some in the design community expressed reservations about certain green design claims of the Active House.

A look at Active Houses built to date, shows beautiful homes with a lot of skylights and windows.  The problem is that a lot of windows and skylights greatly reduces the overall performance of the building envelope.  The level of wall insulation in the Active House USA is barely above building code for the northern parts of the country (R-25 for walls, and R-45 for roof).

As far as the fully renewable energy goal, the Active House USA has solar panels on the roof, however, the other source of energy is gas.  The gas heating is described as “a clean, low cost, domestic energy source, which provides an opportunity to broaden energy resources for the customer”.  Still, many would say that this is greenwashing, and that the use of gas does not qualify the house to be called Net Zero energy.

Nevertheless, Active House has the potential to become a popular way of building, as it is much healthier and energy efficient than conventional homes.

1. Cost Efficiency - One of the biggest downfalls solar power generation has had to face in the past is the cost of implementing such structures. For residential areas, the cost could range between $45,000 to $65,000 before subsidies and/or tax credits. If you finance the project, the monthly payments usually surpass your current electric bill savings and could take you up to 10 years to pay it off. Essentially, you would have to live in your home for more than 10 years before you begin to feel the benefits of the installation.

However, technologies are being developed regularly in order to reduce the cost of these installations. The goal is to drive the cost down so that photovoltaic power can become a reality for everyone and not just the upper-class citizens who can afford the installation. If people could see the immediate benefits of building a solar alternative, they would be more inclined to invest in the project.

2. Little by Little - Some coal-based power plants are adding small 20Mhr panels a piece at a time as they can afford to do so. Although this doesn’t sound like a vast amount of power considering many of these plants generate one-gigawatt hour and up, every little contribution helps. Eventually, the solar array will be large enough to surpass the methods of coal, oil, and even nuclear generation. If the cost of panels could be decreased, these companies would invest in building larger units as time goes on. Since there is no real material that goes into creating solar-based power, these companies would save hundreds of billions of dollars across the country in coal alone.

3. Innovation through Demand - You see the effects of innovation through the demand of a particular good every day. Each year, mobile phone units are created to be better than the one before. The competition is fierce in this market and each version surpasses its predecessor. This is because it is demanded by the consumers. If the demand was equally as strong in photovoltaic technologies, manufacturers would be hard pressed to develop cost effective methods in order to stay ahead of the game. Although the market for solar power on a global scale is gaining traction, such as the DESERTEC project in North Africa, the advancements aren’t nearly as forthcoming as they would be 4.1 billion people demanded it as they do their smartphones. One sure-fire way to drive that demand is by reducing the cost to the consumers.

Set aside that solar power generation leaves a miniscule carbon footprint behind. Overlook the headlines starting with, “Green Energy.” But consider the ramifications as a whole of the benefits solar arrays can provide to communities. It is a source of power that will only dissipate when the Sun does. Our star will produce power for the next several billion years, why not tap it to improve our way of life?

This is a guest post by Liz Nelson from WhiteFence.com. She is a freelance writer and blogger from Houston.

Therein lies the dilemma inherent in renewable energy advocacy: while a renewable energy lobbyist or advocate may pursue a completely logical, economical, and tactical energy policy (for example: let’s build all new power plants with renewable energy since it requires no fuel input, and thus lowers our fuel imports), their logic is usually confounded with environmentalism and so it loses strength and efficacy. The result is a rejection of the renewable energy proponent’s ideas and logic.

Personally, I’ve found it quite challenging to make the distinction between being an environmentalist and believing in the benefits of renewable energy. Yet, this delineation is so utterly important, because in the field of renewable energy activism, one immediately loses half the audience if labeled an environmentalist.

Almost daily, I must field the incessant, but still cumbersome question: “You’re an environmentalist, right?”

No, not really at all. I’m a political philosopher. I’m an economist. I like logic. I believe in humanity. I believe in social progress. I’m a futurist, a forward thinker. I examine the present in the light of the past, and looking towards the future (to paraphrase Keynes). Sure I believe in some forms of renewable energy, but think other supposed renewable energies (ahem, corn-ethanol) are usurping the term for their own benefit; and in fact, use more energy than they create.

I have no problem acknowledging the importance of fossil fuels to the world economy.

Yes, I believe fossil fuels could become irrelevant one day. No, I don’t think renewable energy can completely replace conventional energy right now. But yes, I do think more and more people should be involved in energy decisions, thought processes, innovations, explorations. The more people involved, the better chance for creating new, innovative renewable energy.

When attempting to explain to my family, close friends, or other acquaintances what I do (which albeit is difficult because presently I work in several somewhat divergent fields), almost immediately I’m labeled an ‘environmentalist’.

This is usually how it goes:”So what are you doing right now; what is it that you do?” My typical reply: “Well, for example, last week I attended a conference discussing the technological innovations behind battery storage, in order for us to harness and use more renewable energy. Renewable energy is basically energy derived from the earth that does not require a constant input including solar energy, wind energy, or geothermal energy—though others certainly exist.”

The response: “Oh okay, I get it. So you’re an environmentalist.” “No”, I say, “I’m simply a logical thinker focused on the best, most holistic solutions for societies around the world. By using energy more efficiently, and deriving it more directly, we as mankind are moving forward. Renewable energy is not environmentalism; it is logical human progress.”

The most ironic part is that this thought actually comes from a self-preserving, almost selfish, prescience: I’d like my grandchildren to breathe clean air. I’m actually concerned about the extension of my bloodline more than the environment.

The simplest way I can describe what I do is to declare that I work in energy awareness. The more people I can convince to examine their own energy use, or investigate renewable energy technology, and the highly beneficial part they personally can play in the subject, the more successful I will be. I’m sort of a renewable energy lobbyist without the paycheck. There are several I.O.U.s out there that someday I may collect, if one day I’m associated with the progenitor of such efforts.

Renewable energy is logical energy because once built and installed, it requires very little human input or raw material input. In other words, no coal, oil, natural gas, or uranium needs to be trucked to a solar or geothermal power plant after it is built. This allows us to use our computer technology to very effectively monitor and control energy within localities; this will ultimately increase energy efficiency dramatically.

If, for instance, a computer system is in charge of controlling a solar energy power plant, it can precisely dispatch electricity across the grid as required; it can store excess energy in batteries, steam, molten salt, hydro-pumps, or fly wheels, as needed. That stored energy can then be dispatched when it is needed.

On the other hand, a conventional power plant such as a nuclear reactor, must run 24/365 at full capacity, wasting as much as 75% of all the energy it has created; or a coal power plant which is largely at the mercy of human error, takes many hours to power up and down; and therefore, cannot respond to actual societal needs.

To me, the former renewable energy technology is a significant step forward for human civilization. Though it may be shortsighted to immediately convert all power plants around the world to renewable energy, (since the technology keeps getting better (Moore’s Law), it does make sense to carefully begin implementing the technology within reason.

The Merriam-Webster’s definition of environmentalism is this: “a theory that views environment rather than heredity as the important factor in the development and especially the cultural and intellectual development of an individual or group; advocacy of the preservation, restoration, or improvement of the natural environment; especially the movement to control pollution.” This brings up one more important point: renewable energy lobbyists must back away from arguing within a “carbon frame”, or arguing in favor of renewable energy in order to stymie the negative effects of carbon emissions. Arguing in this frame lays the game wide open for manipulation by advocates of “lower carbon emission” energies such as nuclear and natural gas.

I suppose I am guilty of having an emotional tie to renewable energy. I’d like my children and grandchildren to inherit a life similar to mine. I feel very fortunate to have been given a beautiful, luscious, hospitable planet.

I believe in space exploration but think colonization of another planet is far away. I think logically about the earth’s resources. Sure, I care about the environment but that comes after my first two core beliefs: I believe in humanity and progress. Conventional energies are no longer progressive, though at one point they were. Humanity must begin to bind together to coherently create new energies. This collective exploration and implementation must begin now.

Picture Sources:  James Provost & Pacific Northwest National Laboratory

Do buildings designed for high performance function as intended?  Do energy savings, improved occupants’ productivity and comfort materialize as promised?  Green buildings offer a lot of benefits, but building owners and tenants increasingly want proof that these benefits are actually achieved.

This is where post-occupancy evaluation (POE) comes in.  The objective of POE is to learn whether the building is performing as designed and whether it meets the occupants’ needs as intended.

POE originated in the 1960s, as a part of a movement to apply scientific approach to architecture and to explore the new-found connection between behavioral sciences and design.  Designers saw POE as a tool to test their hypotheses as they tried to use design to change people’s behavior and relationship with the built environment.  It was used to evaluate building systems as well as occupants’ responses to those systems.  After the peak of popularity in the 1970s and early ’80s, the use of POE declined, until the sustainability movement reclaimed it.  Today, building owners rather than building designers are driving POE.  For a building owner it is one thing to read in a study that green buildings on average perform 25-30% better, or that they command higher rents and occupancy rates, but it is another to be able to verify that their own building does so.

At the same time, growing popularity of building ratings, as well as the increase in local and state disclosure ordinances requiring building owners to publicly disclose actual energy consumption, makes POE almost a necessity.

This means that there will be pressure on building designers to incorporate features that will allow building owners to operate the building to design specifications.  Buildings will need to have feedback systems to help facility managers and occupants understand how their choices affect the building’s performance.  In this task, “smart” buildings have an enormous potential, as they can use the data they are constantly generating to engage users’ by providing real-time, visually appealing and easy to understand performance feedback via dashboards.

The classic POE involves surveys, targeted interviews, focus groups, and direct observation of the building and its occupants.

POE of the occupants’ comfort typically focuses on the work environment, elements such as lighting, acoustics, thermal comfort, privacy, and convenience.  POE of the building performance, also called “building performance evaluation”, focuses on energy and water use, and even financial performance.  In “smart” buildings, POE will include quantitative testing and measurements of building conditions, such as illuminance and temperature.  Depending on the interests and needs of the building owner, other sources of information, such as utility bills, maintenance records, and financial statements, might also be analyzed.

POE can range from one person walking through with a notepad and doing some interviews, to a team of environmental psychologists, sociologists, cultural anthropologists, architects, and engineers collecting data and conducting in-depth focus groups and extensive surveys.

Usually, POE is undertaken after the building systems are commissioned and fine-tuned so that occupant reactions are not distracted by technical problems with equipment.  However, it might also be beneficial to use POE-style occupant surveys as a part of a commissioning process.

LEED and POE

Green and high-performance buildings are especially good candidates for POE, as it allows to document the results of using innovative technologies and materials that might so far have limited or no track record.

POE creates hard evidence that green building advocates can use to make their case to skeptical clients, owners, investors, or tenants.  With data on the table, the conversations evolves from the argument that “this is the right thing to do” to using facts to demonstrate how green design meets clients’ financial or other critical interests.

POE is an important tool for supporting the LEED rating system.  Many of LEED requirements are normative, that is, they are based on theory, but largely haven’t yet been validated by practice.  There is a lot of interest in seeing whether LEED-certified and other green buildings really deliver on their promises.

The 2012 update to LEED has a newly created “Performance” category which includes two LEED credits: “Reconcile Projected and Actual Energy Performance” and “Occupant Experience Survey”.  This development shows that, as the green building market matures, LEED guidelines adjust accordingly.  LEED seeks to serve both the energy reduction goals and occupants’ comfort and wellbeing.  In this, POE has become a valuable tool which allows to measure satisfaction and integrate occupant comfort with energy performance.

The rating system that is currently best suited to incorporate POE is LEED for Existing Building Operations and Maintenance (LEED-EBOM)

LEED-EBOM (Existing Buildings – Operations and Maintenance)

LEED-EBOM is the fastest growing of the LEED Rating System.  It sets performance standards for the operation of existing buildings that are not undergoing major renovations.  It is different from the other LEED rating systems in that it documents the actual building performance, rather than an estimated performance based on design.

The first time the building goes through the certification is called the initial certification.  The initial certification happens in two phases:

1. Establishment period – assess the building, do cost-benefit analysis, select credits to pursue
2. Performance Period (PP) – implement new policies and building changes, as well as track ongoing building performance.

All buildings, even those that were LEED-certified for Design and Construction, must go through the initial certification.

A successful LEED-EBOM certification requires a collaboration from a variety of stakeholders: building owners, property and facility managers, general contractors, vendors and tenants.  This team will set up policies, procedures and targets to achieve for the certification.  This process is normally facilitated by a LEED AP specializing in EBOM.

LEED-EBOM is also the only LEED rating system that requires re-certification.  Re-certification verifies that the building has been operated and maintained in accordance with the standards achieved during the initial certification, or, ideally, that its performance has improved over time.  Buildings must get re-certified at least every 5 years, although more frequent re-certification is encouraged.  Once a building receives the initial EBOM certification, the re-certification process begins.  There is no fee to re-certify, and it should be fairly easy, since all the policies and procedures are already in place.  During the re-certification, a building performance evaluation is conducted in the form of audits, surveys and testing to track the on-going performance of policies established during the initial certification.  This evaluation may open up the opportunity to increase the building’s certification level.

Looking into the future: LEED and POE

Benefits of POE work well with the priorities of green buildings.  In the short term, POE can suggest adjustments to improve performance and occupants’ experience.  In the long term, designers and their clients can use the feedback to improve the design of subsequent projects.

As the performance evaluation tools are perfected and commoditized, they will inevitably become more widely used.  When they are more widely used, the great flow of information will serve to improve our understanding of how buildings work.  Incorporating POE into LEED will help to ascertain that our buildings are serving their intended functions.  Shouldn’t that be a prerequisite for green buildings?

In some cases, however, building owners purchase or manage facilities built before the 1980s. With these buildings, there is a good probability that asbestos products such as drywall, insulation and tiles are present. Owners then face special challenges when having construction work done on their buildings.

Before hiring renovation crews for potentially asbestos-disturbing tasks, these building managers are required to perform asbestos inspections. Federal regulations mandate these surveys for all public schools and most government buildings, as well as for all older buildings that are set for demolition or renovation. By identifying and acting on any potential hazards, owners can avoid Clean Air Act violations and major risks to their workers’ health.

Non-Construction Related Asbestos Management Surveys

Property owners not planning construction in the near future can conduct these surveys on their own schedule – or not at all. However, even when asbestos management surveys are optional, owners should still consider regular testing. This simple process is a major step in protecting the general health and well-being of the building’s occupants.

If asbestos is present and friable (loose), the building’s occupants are at risk for a number of serious conditions, including mesothelioma and lung cancer. Initial prognosis for someone exposed to asbestos, may not come for 30- 50 years. During this latency period, anyone who inhaled asbestos may develop these illnesses at any time. Asbestos management is one of the only proven ways to help prevent people from developing these conditions.

Surveys help building owners identify all the asbestos-containing materials on their property, then determine which ones are imminent health hazards. Inspectors also can provide suggestions for remedial action for these products; in most cases, owners can choose between removal and encapsulation. The inspection crews can make recommendations based on the location and condition of the asbestos-containing materials.

Additionally, asbestos surveys provide documentation of non-friable asbestos products that may become a threat in the future. If the property was to change hands, these surveys can help the future owners make environmentally conscious construction decisions.

Scheduling Asbestos Surveys

Before scheduling an asbestos management survey, building owners should check the credentials of the company they plan to hire. The surveys should only be done by accredited asbestos management companies, and all inspectors should have up-to-date licenses.

Owners should evacuate the building during the survey, since inspectors may take samples of the fibers. To provide the most accurate results, surveyors should review the following details before the survey:

• Site layout
• Building specifications
• Future building plans
• Past asbestos inspection history

Depending on the type of asbestos and its condition, surveyors should inspect an asbestos-containing building every six to 12 months. If any construction work occurs, inspectors should perform another follow-up inspection to ensure the safety of the building’s residents. The diseases, such as pleural mesothelioma, that can arise from asbestos exposure are serious; therefore all precautions should be taken to prevent such exposure.

Every house is unique and foundation-type is one distinct difference between them.  A home typically has a crawl space, basement or a concrete slab foundation.  In this three part article series author Joe Provey explains how foundation-type should be taken into consideration when upgrading a home’s energy efficiency. Joe’s first article explains how a home with a crawl space foundation can increase their energy efficiency.
Save energy with the bonus of controlling excess humidity and improving home air quality!

Like it or not, your crawl space and living space are joined at the hip. Holes for wiring and pipes, plumbing chases, leaky heating ducts, gaps in subflooring, ensure that your living space and your crawl space communicate freely! It is no surprise that the U.S. Department of Energy recommends you insulate your crawl space. Insulation in the floor joists is typically inadequate to offer much of a barrier. To make matters worse, the laws of physics actually cause the air in your crawl space to be pulled up into your living areas. As warm air rises in the upper levels of your home, it creates a draw on the lower areas. As much as 40 percent of the air in your crawl space eventually mixes with the air inside your home.

This creates a whole series of problems, ranging from energy loss to breathing unhealthy air. In summer, cool air is lost to the crawl space. In addition, excess humidity from the crawl space causes your air conditioner to work harder and use more electricity than it should. In winter, cold air entering through the crawl space makes your floors cold and first level rooms drafty. Heating bills climb. Winter and summer, you’re apt to be breathing unhealthy air laden with allergens and soil gases.

There are five steps you can take to turn a crawl space into a clean, healthy, energy-efficient part of your home. Here they are roughly in the order you should tackle them:

1. Seal and insulate rim joists
The first framing member attached to a foundation is called the sill plate. It lays flat atop the home’s foundation wall and is fastened to it with J-bolts or by some other mechanical means. Because the top of the foundation is often uneven, there may be gaps under the plate. In new construction, a gasket helps to solve this problem, but in older homes it is a major cause of air leakage. The second framing member is the rim joist. It rests on edge upon the sill plate and provides a way to secure floor joists. Subflooring is installed over the rim and floor joists. Air leakage may occur at the joints between the sill plate and rim joist as well as between the rim joist and subfloor. In addition, the R value of the rim joist (its ability to stop conductive heat loss) is only 1.88 – about the R value of a single pane window with a storm window in place.

To stop energy loss from the framing assembly that rests upon your foundation wall, seal all joints with a bead of closed-cell foam insulation. Then install rigid foam board insulation against the rim joists wherever possible. For example, cut the board insulation to snuggly fit between the floor joists and between the sill plate and subfloor. Then press it against the rim joists. If the fit is loose, fill the gaps with spray foam insulation.

2. Seal ducts that run through crawl space

Heating and cooling ducts often reside in the crawl space. Typically fabricated from sheet metal, they’re used to distribute warm or cool air to the rooms of your home. Unfortunately, ducts typically leak a large percent of the air they carry. This means your HVAC equipment must work overtime and that your energy bills are higher than they need to be.

To stop energy loss from ducts, seal all metal-to-metal joints and holes with mastic sealant or with metal tape. Do not use duct tape because it will eventually fail. Seal joints between the subfloor and ducts with spray foam insulation. If you do not plan on insulating the walls of your crawl space, consider insulating the ducts with duct wrap. Duct wrap is fiberglass product with a foil vapor barrier to the outside. Be sure to seal all seams with aluminum duct tape. Otherwise, air leaks will allow moist air to penetrate the wrap. In summer, that moisture is likely to condense on the cooler ducts and wet the fiberglass – and wet fiberglass is ineffective as an insulator.

3. Insulate walls

The above- and below-grade portions of your crawl space wall will lose heat in winter, so you will save energy and be more comfortable by installing wall insulation. Rigid foam boards can be adhered to or mechanically fastened to either block, stone or concrete walls. They are waterproof and will not support the growth of mold. The recommended R value depends upon where you live. Check with D.O.E. recommendations or with local building department officials for recommendations in your area.

4. Encapsulate

A continuous vapor barrier that covers both floor and walls adds another layer of insulation by sealing out air leaks. It will also help control moisture and stop soil gases from infiltrating your home. For a vapor barrier to be effective in the long term, it must be durable. If interested in taking on this project yourself I recommend this great guide that explains how to install a vapor barrier.

If your crawl space is susceptible to water infiltration, install drainage matting before installing any liner. It will allow water to drain toward either a drainage pit (no pump) or to a sump basin and sump pump for discharge. Here is a great resource explaining in detail what needs to be done to fix crawl space water leaks.

5. Dehumidify

If you’ve opted for encapsulation, install a dehumidifier in your crawl space to dry out framing and flooring that has long been exposed to excess humidity as well as to ensure against excess humidity on an ongoing basis. Lower humidity in your newly conditioned crawl space will translate to lower cooling costs and greater comfort in warm weather.

An investment in any or all of the above will make your home more energy efficient and improve the comfort level and health of family members. In addition, controlling moisture levels protects your home from structural damage due to rot, corrosion, termite infestation and can give your home extra storage space.

Interested in learning more about crawl spaces? This very informative crawl space learning center can educate you on this often overlooked part of a home.

Interested in learning how to make your basement more energy efficient? Check out Joe’s next article on the CleanEdison about Insulation your Basement.

Have any other tips to help make your crawl space more energy efficient? I would love to hear about them in the comments below!

“In the day”, I was sent to Siemens Photovoltaic Cell manufacturing plant in Santa Barbara to visit with the Southern California Edison customer, document the manufacturing process and take some pictures for my bosses presentation.  It has been years since then and the United States, the once leader in cell manufacturing, has given way to others overseas (~four(4) cell manufacturers remain in U.S.).  As a result, a manufacturing goal of 100% “Made in the United States” cannot be achieved for photovoltaic (PV) modules with mono-crystalline cells at cost effective prices.  Never the less, other quantifiable goals like USGBC LEED Material Resource Credits can be achieved.

Various products can claim to be as much as 80% made in the United States and anywhere from $1.80 to $4.50/Watt installed (including but not limited to, additional structural systems like; racking, ballast, lagging or wood lattice).  Using a goal to be the “Greenest” possible without additional expense, the owners of EcoGym Worldwide set out to design a PV System that met some of these goals.  Seeking the guidance of A Solar Studio, a small 2-3 man studio in Naperville who’s principal has been involved with PV off and on for the past twenty years, they learned they could achieve some of these goals using the Solon Sol quick 295.

Ecogym’s solar renewable system was designed for a flat roof commercial tenant space approximately 10,000 square feet, few obstructions in the roof, 5 air handling units and a 4′-6″ south facing parapet.  The system is is expected to produce 7.93 kW of AC power  each solar hour per day and has been designed for a future second phase development if needed.  Yellowlite, Inc., a regional solar installer located in Cleveland, Ohio was selected as general contractor and installer.  Solon Corporation is a subsidiary of Solon Group located in Tucson, AZ provided the modules for the system.

The Solon Solquick 295 module is largely manufactured in the United States. The critical monolithic rack (perhaps 60% by weight) is made in Minnesota where it is then shipped to Arizona for assembly and testing prior to shipment.  They are a fixed tilt (~9°), ballasted, non framed rack.  The 295W modules are connected in series and provide designers with a low profile tilt thereby reducing wind loads significantly and with no snow drift issues caused by the array.  In addition to the interconnection ties and cinder blocks used for ballasting, the A Solar Studio design team required an additional 5 positive connections on both the east and west sides of the arrays.  These connections are lagged through the roof reducing uplift most prominent in the winter months of northern Illinois.

The net metering process was very simple by comparison to other utilities in the northern Illinois area. The City of Naperville has its own municipal utility where it gets a large portion of its electricity from renewable resources west of the community in the form of wind turbines. Its net metering process consists of a one (1) sheet application submitted at the time of permitting with no other communication exchanges needed unless a copy of the application is not available on-site when final inspection is conducted.

A look at today’s architecture and design magazines, or at new construction projects in NYC, confirms that the current material of choice is glass.  Floor-to-ceiling windows, 360° views, natural daylight, connecting inside to the outside are the design vocabulary du jour.  Glass, and lots of it, is intended to convey modernity, sophistication, and, increasingly, green design.

The first glass was made about 2,000 years ago.  It was used to seal off small apertures made to let in light.  However, it was not until many centuries later that the use of glass in buildings became widespread.  Still, window sizes were constrained by practical considerations: impact on the load-bearing capacity of the walls, material limitations, energy conservation requirements, expense.  In the 20^th century, the development of structural steel, and later reinforced concrete, allowed to transfer bearing loads from the exterior walls to interior columns.  At the same time, glass came in increasingly bigger unbroken sheets.

The International Style in architecture, made simple glass façades and huge opens spaces synonymous with modernity.  In the late 1940s, double-pane glass with thermal insulation was created.  Windows were becoming bigger and bigger, until eventually the entire exterior skin of a building was made of glass – it was called the curtain-wall.  Lever House, built in 1952, was the first curtain-wall building in New York.  By 1970s, coated, laminated glass, and other innovative glass products were created.  Today, fully-glazed office buildings are ubiquitous, and in residential buildings, especially on the higher end, panoramic, huge, often floor-to-ceiling windows became a requisite amenity.

What is it that makes glass so appealing to architects and building owners? 

Aesthetics: A successfully designed glass building looks sleek, simple and modern.  It is in harmony with the environment.  On the outside, it disappears against the sky, reflects and blends with the surroundings.  On the inside, natural daylight, views, openness, make the inhabitants feel connected to the outside, not confined in a box.

Ease of design and construction: Most, although not all, of heavily glazed façades are curtain walls.  The entire curtain-wall glazing system is engineered and manufactured offsite, essentially outsourcing the entire façade design to a curtain-wall manufacturer.  Even a traditional structural wall with inset windows requires less design effort, as glass itself becomes the main design element.

Glass as a green material?

Today, big windows are often presented as a part of a building’s sustainable design solution.  Glass is billed as a green feature.

Green design criteria emphasizes resource efficiency, well-being and safety of building occupants, and energy efficiency.

Does glass meet the green design criteria?

Resource-Efficiency:

• Glass is a resource efficient material which is made of abundant natural raw material such as sand and glass waste (cullets).
• Glass is 100% recyclable, it can be recycled in close loop over and over again.
• Glass recycling saves energy as cullets melt at a lower temperature than raw materials.
• Glass is very durable, short of breaking, it ages better in an urban environment than most building “skin” materials.

 Well-being and safety of building occupants:

• Glass brings in the natural daylight.  Daylight increases light levels and provides good color rendition.
• A study commissioned by the USGBC confirmed that daylighting improves office workers’ productivity, students’ performance, and brings increases in retail sales.
• Daylight has physiological and psychological benefits, and it positively impacts the immune system health.
• Well-designed glazing system combined with effective interior design can distribute daylight deeply into the building and minimize glare, thus maximizing the number of building occupants who benefit from daylighting.

 Energy Efficiency:

• Glass has high thermal conductivity, which means it has poor insulation qualities (for comparison, thermal conductivity of glass =1 W/(m.K), while insulating materials have <0.065 W/(m.K)).  This means that glass has high U-factor*.
• Glass, even the most technically advanced, has R-value** (insulation) below the cheapest legally allowed conventional wall assembly.  Most typical office buildings don’t even approach a third of that.
• Inefficient windows are responsible for up to 15% of a home’s heating and cooling losses according to the U.S. Department of Energy.
• Glazing needs to be no more than 25% (± 5%) of the total area of the building envelope in order to get the full benefit of natural daylight, according to data from the University of Oregon’s research on high performance envelopes (subscription only).  Beyond that percentage, glazing does not contribute more daylight, and starts to create a net energy loss.  ASHRAE 90.1-2007 energy code already specifies the amount of glazing that can be installed in commercial buildings.  Its prescriptive performance path sets a maximum glazing area at 40%.  To exceed that glazing percent, the building owner and the architect would have to show that a building will use less energy than it would with 40% glazed façade.

*U-factor – heat transfer coefficient that describes how well a building element conducts heat.  U-factor is generally only used to express the insulating value of windows (the smaller is the U-factor, the better are insulating properties)

**R-value = 1/U – measure of thermal resistance (insulation).  The higher is the R-value, the better is the insulating quality of an assembly.

Based on this assessment, it is not yet possible to apply a green material label to glass.  While it scores top marks on resource efficiency and occupants’ well-being, it does not score well on energy efficiency.

However, developments in glass technology combined with design solutions intended to maximize glass performance are working to mitigate this limitation.

Design solutions for maximizing glass performance

Sustainable building design seeks to gain the most solar heat possible in the winter, and minimize heat gains in the summer.  A successful design solution will take into account the climate, identify the most effective building footprint and orientation, and select the appropriate glass and framing options.

Climate: 

In cold climates, the most important energy consideration is heat loss, therefore the U-factor becomes the main concern.  Architects and builders should select glazing systems with low U-values and high R-values.  In warm and sunny climates, the most important energy consideration is solar heat gain, therefore a product with low SHGC (solar heat gain coefficient) that transmits less solar heat into the building is approprate.

Building footprint and orientation: 

Energy modeling exercise done by the engineering firm Arup for Environmental Business News (subscription only), showed that square building shape is the most economical.  On elongated buildings, which have larger façade area, the impact of increasing the percentage of glazing is greater.

With elongated building shape, building orientation plays a big role: when the longer façade faces east-west, the annual energy consumption can be up to 9.4% higher than when the longer façade faces north-south (depending on the type and percentage of glazing).

Glass Selection: 

To help architects and builders navigate product offerings, National Fenestration Rating Council offers, besides Energy Star, a comprehensive rating system with specifications in five categories:

1. U-factor – heat transfer coefficient
2. Solar heat gain coefficient (SHGC)
3. Visible light transmittance (VT)
4. Air leakage
5. Condensation resistance.

Glass selection becomes one of the most important decisions in creating a green glazing solution.  These are the most common types of glass products:

Insulated glazing (IG)

Most typical are double-pane windows.  Two window panes are separated by an airspace and sealed around the perimeter.  In the US, the airspace between the two glass panes is ¼” or ½” in most models.  Triple-pane windows are now becoming more common in the highest-performance buildings.  Triple glazing increases insulating properties of glass, but the extra glass panel correspondingly increases the risk of seal failure.  Also, due to weight considerations, glass and frame material choices are currently limited.  While triple-glazed windows offer superior insulation, they sacrifice passive heating opportunities in the winter.

For better efficiency, the airspace between glass panes can be gas-filled with argon or krypton.  An alternative is vacuum glazing, where panes are separated by a vacuum instead of inert gas.  Another energy efficient option is warm-edge glazing, where the spacer either incorporates a thermal break or is constructed from a low-conductivity material, as opposed to typical aluminum.

Low-E glazing

Low-E glass uses microscopically thin transparent coating of silver or tin oxide to allow short-wavelength sunlight to pass through, while blocking long-wavelength heat radiation, thus lowering the U-factor.  Low-E glass costs about 10% – 15% more, and can reduce heat flow by 30% – 50%.  The type and positioning of the Low-E coating affects the glazing performance and durability.  The problem with Low-E glass is that the sunlight it reflects contributes to the “heat island” effect outside of the building.

Spectrally selective glazing

One of the most common solutions to reducing the solar heat gain (lower the SHGC) is by using tinted glass.  The problem is that it blocks most of the visible light as well.  For this reason, spectrally selective clear glazing is more popular today, it selectively blocks out the solar spectrum outside of the visible band.

Dynamic glazing

Dynamic glass responds to changing light and heat conditions.  There are three types of dynamic glass:

Photochromic – when exposed to sunlight, photochromic glass darkens or becomes opaque, but it doesn’t control heat gain and may darken more in the winter when the sun’s rays are more direct.

Thermochromic – blocks out sunlight in response to rising heat, but the inability to control the glass’s response is a major disadvantage.

Electrochromic – is the most promising technology, in which the glazing is tinted on demand by supplying a low-voltage current.  These “smart” windows can be controlled by the homeowner or a building-management system.  In a clear state, electrochromic glass also blocks more UV light than typical Low-E glass.  When fully tinted, it blocks most wavelengths of visible light, protecting artwork and furnishings from fading in sunlight.  Electrochromic glass is expensive, but the costs have gone down significantly just in the last couple of years.

Frit on the glazing panels

Frit is a screen-printing pattern that serves to block heat gain while still allowing fairly good visibility through the glass.  There exist both translucent and opaque frits.  However, while frits are effective in reducing solar heat gain, they are not helpful with poor insulation qualities of the glass.  Therefore, they are best used in temperate climates.

Photovoltaic glass (PVG)

Solar-powered window is an insulated window with integrated photovoltaics.  A layer of transparent solid-state solar cells, at most three microns thick, is added to conventional glass.  It turns around 12% of the solar energy received into low-carbon electricity.  The current application of PV glass technology is mainly used power the building, and not yet even the whole building.  However, as technology develops, it has the potential to turn buildings into energy generators, not only supplying their own energy needs, but exporting the energy into the grid.  One of the manufacturers of this technology, estimates that it adds no more that 10% to the overall cost of the façade.

Framing: 

Energy-efficiency of glass cannot be discussed without discussing energy-efficiency of framing.  In fact, in today’s glass products the frame almost always perform worse than the glass.  Selecting the appropriate framing material will make a big difference in windows’ performance.

Aluminum is the most common frame material, but it is highly conductive, which causes high heat loss and cold interior temperatures in the edge-of-glass region during the winter. The result is a band of condensation or frost at the bottom of the glazing unit.

Wood frames are energy efficient, and can be obtained from a sustainable supplier.  However, they are expensive and need regular maintenance to avoid water or moisture damage.

Fibreglass frames are energy-efficient, low-maintenance and can be painted and repaired, but are expensive.

PVC frames, also known as uPVC, are made of vinyl and are not expensive.  They are energy efficient, low maintenance, and have very good moisture resistance, but once their original exterior finish fades or chips, they cannot be repainted or repaired.

Looking into the Future

Technological developments will continue to improve the energy-efficiency and performance of glass.  The development of new materials and new structural concepts will continue to perfect curtain-wall and window manufacturing techniques.  Developments in silicone chemistry will continue to enhance sealing and insulation materials.  With the maturing of PV technology, glazing will increasingly take on the energy supply role.

In short, the windows and the frames will become increasingly high-tech.

However, hopefully, the architects will also turn their attention to the simpler options: fine-tuning window placement to maximize passive solar design and maintain daylight; accounting for local climate and site conditions; finding the optimal glass to wall ratio for the specific needs of the project; seeking quality, rather than quantity of views.  These are basically free, if you take time to do them.