Spring Issue: Design Strategies, Do's & Don'ts from Architect Peter Pfeiffer, FAIA

With the conventional home building industry in free fall, you’ve suddenly decided to jump on the green building bandwagon. You want to differentiate yourself as a builder, embrace eco-friendly tactics and build high-performance homes. And you want to do all this while switching from site building to a building system to keep your staffing lean. Wonderful! But before you simply assemble a laundry list of sustainable building materials for your clients to choose from, take a long look at the homes you’ve already built. The lessons for how to best to improve your building methods in your local climate can be found in the homes you’ve already built, says Architect Peter Pfeiffer, FAIA, partner in Barley-Pfeiffer Architects (Austin, TX) and one of the leading specialists in sustainable design.

Think Home As A System
Pfeiffer, who has been in the design business for three decades, says that homes he worked on more than 27 years ago have provided important lessons. “Don’t assume just because you haven’t gotten any callbacks that there haven’t been any problems,” says Pfeiffer.

Thermal insulation, tighter building and the overuse of forced-air heating and cooling systems has changed how homes perform. Call it the law of unintended consequences, but our home’s various systems (HVAC, lighting, plumbing) are often fighting each other and creating bad indoor air quality in the process.
If you want to offer high-performance homes, you need to look beyond the gee whiz green gadgetry to how your homes operate. “A house is a system. Often one component—such as a power attic fan—can affect another seemingly unrelated feature, such as mold growth under a bathroom vanity,” explains Pfeiffer.

The concept of a home operating as a system—once referred to by old timers as “the building sciences”—has been lost in the past two decades of the building boom, when housing became a simple commodity and total square footage was king. “We’ve become such a wealthy, disposable society, I think some of that same thinking crept into home building. We were creating disposable housing,” Pfeiffer adds. His tips for builders looking to change that follow.

90/10 Rule
Don’t rush the design process. “A full 90% of opportunities to achieve a high performance or green home come in the first 10% of the design process,” says Pfeiffer. “A plan is simply not just a pretty picture. It’s a solution to a whole matrix of problems, challenges, opportunities and client desires.”

The Big Four Failures
In most of today’s new home construction, the primary culprits of poor energy efficiency are infiltration of outside air, improper orientation, excessive solar heat gain and (to a lesser extent) appliances and light fixtures that produce humidity and heat gain, such as top-loading washing machines and halogen or incandescent light bulbs. (He recommends the front-loading, energy-efficient washing machines.)

Passive Solar 101
Bring a compass to the building site. Passive solar orientation involves placing the home with the long sides facing south and north to minimize summer solar gain and allow for some winter solar heat gain. Orient streets in a new subdivision to run from east to west as much as possible, giving the majority of building lots either a north- or south-facing front and rear. Take advantage of prevailing breezes during different times of the year. Refer to the NOAA website for climate information and check with a local airport for even more data.

Be Climate Specific
Every region should employ different sustainable design strategies that reflect the region’s climate, material availability and building practices.

Don’t Design By Building Code
The building code is a guide to the absolute minimum to preserve the health and safety of the homeowners—it’s not a design tool. For example, having a ventilated attic is not wise in humid climates, even though many building codes call for it. (Humidity infiltrates the living space below.) Sealing the attic and ventilating a continuous air space immediately below the roof decking (not the attic), is a better configuration.

Employ Awnings, Porches, Large Eaves
Use awnings, porches and eaves as a buffer against the summer sun as well as to protect windows, doors and exterior walls from the elements. For roof overhang and window sizing, use the Pilkington Sun Angle Calculator (SAC). You can get five for $25.

Protect Against Infiltration
Thirty-pound ASTM building felt in conjunction with commercial-grade building wrap that is well taped makes for a good weather barrier system. “You want to create a raincoat underneath the wall cladding because all siding and cladding leaks, eventually,” Pfeiffer says. Keep humidity from infiltrating the wall cavity by installing a moisture and vapor retardant on the warm (or more humid) side of the wall. In the North, this is the inside surface; in the South, this is the outside surface of exterior walls. But be careful about the vapor retardant placement—even in “Northern” cities where air conditioning is used during many months of the year—lest you create problems. Also, do not use vapor barriers on the inside surface of exterior walls, including vinyl wall coverings, in buildings where air conditioning is used for a significant part of the year. Improperly placed vapor barriers can trap moisture in the walls, leading to serious mold issues. “A wonderful advantage of spray foam cavity insulation systems is that the vapor barrier placement becomes less of an issue than with traditional fiberglass insulation products,” he says.

Improving Exteriors
Make sure all flashing is installed shingle style, meaning the upper piece overlaps the lower piece. Employ a “water table,” a band at the base of the building that sheds water and prevents capillary absorption of water into the framing or sheathing at the base of the building.

HVAC Strategies
With proper windows and shading, most homes should require no more than one ton of cooling capacity for every 650 sq.ft. of living area; 850 to 1,000 sq.ft. per ton should be the goal of a well-designed home. Only use sealed ducts to move conditioned air. Leaky ducts rob energy efficiency and can cause depressurization of a home. Depressurization brings in outside air and humidity, which can cause mold growth.

Ducts with a slick interior surface—such as metal—are best for delivering clean air and for staying clean. Unlined return air wall chases are not effective nor are open return air plenums above dropped ceilings and using floor joist cavities.

Be Better Than Batt
Spray polyurethane foam insulation, such as Demilec or Bio-Based Foam, is preferred over fiberglass batts, since batts don’t stop water vapor. Structural insulated panels (SIPs) are great for creating a tight envelope. Wet-blown, borate-based cellulose wall cavity insulation is also good (when used in conjunction with good air sealing practices) in reducing infiltration. Cellulose from recycled cardboard and paper is very green; this material makes good use of post-consumer recycled products and the borates are a natural insect repellent.

Passive Cooling Strategies
Proper orientation that minimizes exposure to the afternoon sun is key. Use light-colored roofing materials in most climates since dark roofs absorb non-beneficial heat. Shade all the east-, south- and especially west-facing windows from the spring, summer and fall sun. Low-e windows are not a substitute for proper shading and solar control; a proper-size overhang does a much more effective job.

Use Radiant Barrier On Roof Deck
A radiant barrier on the underside of the roof deck, such as LP’s Tech Shield, will substantially reduce heat gain through the roof, reducing A/C bills, enhancing occupant comfort and reducing A/C loads. “Radiant barriers do not lead to the deterioration of roof shingles, contrary to some myths from 20 years ago,” Pfeiffer says.

Lighting & Electrical Tips
Avoid recessed can lighting (even the so-called airtight ones) that puncture the thermal envelope of the building. These are counter-productive to reducing infiltration of outside air. For the same reason, try to avoid placing light switches and electrical boxes on exterior walls.

Become familiar with the new types of fluorescent lamps, especially the thin T2, T5 and T8 type. The light quality is superior and you can get a wide range of color correctness. Fluorescents put out very little heat and last much longer than incandescent and halogen lamps. Halogen lamps produce a lot of glare and heat that the air conditioner will have to fight.

Run To Daylight
Proper day lighting, especially indirect daylight from high windows, can make for substantial energy savings and an enhanced indoor environment. Clerestory windows work well, and if operable, can be used to naturally siphon heat out of the space below in the spring and fall.

Green Plumbing
Water heater placement is important. Isolate gas units from the indoor air of the home and provide them with their own source of combustion air directly from the outside; sealed combustion units are ideal. Thoughtful placement—close to bathrooms and the kitchen—can also negate the need for energy wasting circulating pumps and still ensure quick hot water to the points of first need in a home (usually the master bath).

Insulate all water lines, even the cold water line. Uninsulated cold water lines (including A/C system condensate lines) are susceptible to condensation, setting up conditions for mold growth and inviting insects into wall and ceiling cavities.

Healthy Indoor Air Strategies
Avoid chemical treatments for termites. They don’t last, lead to occupant health problems and pollute the underlying ground water. Use Termi Mesh, a physical barrier, instead. It’s about one-and-a-half times the cost of standard chemical treatments, but it is permanent. (Chemicals only last about five years.)

Use low-VOC (Volatile Organic Compounds) latex paints on the interior. Unroll carpeting outside in a covered area at least two days before installation to let it “off gas,” before installing. Install outside venting exhaust fans in all bathrooms, kitchens and other rooms where there may be a lot of internal moisture generation—but be careful not to draw so much air out that you create negative pressure. Electronic timer switches are preferable, since they are quiet, reasonably priced and last longer than the wind-up ones.
Finally, keep in mind that this is a far from comprehensive list of options. Pfeiffer says not to use all his suggestions verbatim. Instead, investigate locally appropriate strategies and use your creativity. "The great thing about green building is its flexibility," Pfeiffer says.

Peter L. Pfeiffer, FAIA, of Barley & Pfeiffer Architects, earned his “F” in the FAIA in 2004. The College of Fellows within AIA extends the invitation to only a handful of architects each year. Pfeiffer was singled out for mainstreaming green building. Pfeiffer is available for consultation on sustainable projects: 512-476-8580, or visit Barley-Pfeiffer Architects.