Indoor Air Pollution has many sources

These days, energy costs and environmental concerns being what they are, there is a great emphasis on building tight, well insulated, homes. To increase the energy efficiency of the home builders blanket the house with layers of thick insulation. And decrease the amount of air that infiltrates the home from the outside by covering it in house wrap. We go to great lengths to build green homes that are, in essence, as close to air tight bubbles as we can make them. But is this a healthy way to build? After all, if a house can’t breath, the people within it probably will struggle as well.

In fact, indoor air pollution has increased as homes have become more energy efficient and better insulated and many people suffer illness as a result. Indoor air pollution can be ten times worse than outdoor air pollution. Billions are spent annually to remedy the health costs of indoor air pollution.  What do we mean by air pollution? It’s more than just stale air and cooking smells. Indoor air pollution consists of chemical gases from building materials, mold spores, mildew, pollen, oxides including carbon dioxide and monoxide, and radon just to name a few. If these contaminants can’t escape into the great outdoors, they will stay in the home, there for the inhabitants to breath over and over again.

What then to do?

At Trilogy we take a multi-disciplined approach to improving the air quality within our homes. It is well known that Trilogy builds exceptionally well insulated homes. Structural Insulating Panels are used in many of hour homes to dramatically increase the energy efficiency of wall systems. Knowing that tight homes needed to find a way to breath, we have experimented over the years with various combinations of technologies. Now, all Trilogy homes include air quality improvement systems. Whole house humidifiers tied to air circulation and ventilation systems bring in fresh air and eject stale air constantly. As fresh air is brought in from the outside, it is humidified and purified as stale used air is ejected. Heat exchange systems insure that cold air is passively warmed before it enters the house. And that hot air is cooled before it enters the house.

So not only is Trilogy building the most energy efficient, tightest homes in the industry. It is also building homes that breath in pure clean air. The result is exceptional indoor air quality.

With the multitude of residential building technologies available, it only makes sense that the optimized home might take advantage of more than one. Though the majority of residences in this country are built using conventional framing technologies (dimensional 2×4 and 2×6 lumber for walls as an example) other structural technologies are available and have become increasingly popular. This article begins a series on how multiple building technologies combine seamlessly to form superior and environmentally sustainable structures.

The residence we affectionately call Caleb’s Journey combines conventional framing, structural insulating panels, and post and beam to create a fully modern and highly sustainable home with timeless design.

Structural Insulating Panels (SIPS) form the super insulated walls of the structure. They come precut from the SIP factory.

SIPs form the walls

First, we stand the SIP Panels.

Setting the SIP in place

And then we add the post and beam structural members.

Post and Beam roof trusses are milled and assembled.

The roof trusses are supported by log posts and by the SIP walls. The combination provides extraordinary structural integrity.

Creating a room that looks like this when finished. Reclaimed redwood covers the ceilings.

Interior walls are conventionally framed

Conventional framing is used for the interior walls and some roof transition areas. SIP panels are also used on the roof.

The end result is a home that combines the energy efficiency of SIPs, the structural integrity and beauty of Post and Beam, and the flexibility of conventional framing. For more photos of Caleb’s Journey, a true hybrid home, visit the photo gallery.

Wendy Koch, USA TODAY

USA TODAY

Just how tough is the passive house standard that’s starting to catch on in the United States? I put my own new green house to the test.

My house, nearing completion in Falls Church, Va., wasn’t designed to meet the rigorous passive standard, which focuses solely on energy efficiency, but rather the top rating of a more general program by the U.S. Green Building Council. Yet it has many of the same features of certified passive homes, so I figured: why not try?

After all, my project has high-performance windows by Serious Mate rials, a well-insulated and sealed exterior (we used structural in sulated panels or SIPS) and ultra-efficient appliances and lighting (only LEDs and compact fluorescent lamps.) Really, how hard could it be?

John Semmelhack, a passive house expert in Charlottesville, Va., who runs the Think Little consul ting firm and advised on how to make a Waldorf school meet the passive standard, agreed to do a preliminary analysis of my project for this story. I anxiously awaited his results.

He let me down gently. “While the house is going to be a very energy efficient house, it’s not going to meet the Passive House standard,” he wrote in an e-mail that reported his findings. He explained them in a phone interview.

“The biggest problem by far is your windows,” he said. My house simply has too many of them, and the large south-facing windows don’t capture enough solar energy because of their glazing and less-than-optimal siting. (To get the perfect southern angle, the house would have needed to sit diagnally on the lot, which would look odd.)

Windows absorb more solar power if the glass has a high “solar heat gain coefficient” or SHGC. But since we have a shady lot and the U.S. government’s Energy Star program doesn’t recommend high SHGC windows for the Mid-Atlantic region, we didn’t request such glazing.

The second biggest issue, Semmelhack said, is the home’s geometry. It’s not a simple cube. My L-shaped home opens to a south-facing courtyard, so it’s more spread out than a colonial or a foursquare, which is an easier shape to make energy efficient. Its top floor also overhangs the main level in both the front and back, which looks cool but creates potential thermal breaks.

Semmelhack said the home’s foundation, walls and windows could also have benefited from a bit more insulation, but he said we didn’t miss the mark by much.

He said the Mid-Atlantic is a tricky place to do a passive home, because “we get a little bit of Maine and a little bit of Florida.” Homes certified by the Passive House Institute US, a private Illinois-based group, need to have annual heating or cooling loads be low 4,750 British thermal units per square foot of interior finished space, which is about 10 times less than many regular new homes.

Semmelhack figured my heating load was about twice the passive standard while my cooling load was about 30% higher. My home’s overall energy use was about 20% higher than the standard’s maximum of 38,000 Btu per square foot of interior finished space per year. He said we could opt for a slightly more efficient Rinnai tank less water heater, but the conventional Carrier Infinity heating and cooling system we selected is just fine. “It’s about as good as you can get,” he said, noting its 95% efficiency rating.

The passive standard also requires homes be virtually air tight, limiting the air changes per hour (at 50 pascals) to 0.60, which is a fraction of what the Energy Star program al lows.

I don’t know yet how well my house will fare on this measure, because we haven’t done our final blower door test. But my builder, Arjay West of West Properties, did preliminary checks before enclosing the walls in drywall and tried to address any thermal breaks. Since my house isn’t a simple cube, though, sealing it is more of a challenge. We’ll keep you posted on our progress.

Source: USA Today

OSB SIPs

Structural Insulating Panels (SIPs) are a composite building material consisting of a panel of insulating material, usually foam, sandwiched between two wooden layers. The wood can be oriented strand board (OSB) or plywood. Sometimes more exotic materials, such as sheet metal or concrete board, are substituted for the wooden layers. SIPs replace several components found in conventionally framed buildings including studs, joists and insulation. SIPs are most commonly used to construct exterior walls and roofs but may have other applications, such as insulated ceilings beneath conventionally framed roof truss systems.

Structural Insulating Panels have a history dating back to the 1940s when structural wall panels were first invented. Over the years the technologies and materials incorporated in SIPs have improved. In addition, computerized CNC cutting machines allow SIP panels to be factory manufactured and then cut to the exact size needed for construction, providing a certain level of prefabrication not seen in conventional construction.

Panels for Walls and Roofs

Homes using SIP panel construction tend to have a very tight envelope. Air infiltration, or draftiness, is eliminated and the walls themselves have a very high insulating quality. SIPs may cost more than conventional framing, but because they bring extreme energy efficiency to buildings, they lower operating costs. SIP panels are often combined with post and beam construction where the panels drape the frame creating an extremely durable and energy efficient structure. Trilogy Partners utilizes SIP panels in all of its Timber Frame and Post and Beam homes.