There is a measure for the amount of air leaks, or “infiltration” that passes through a building’s shell, and it can be determined by a blower door test. The test results for this measure of infiltration can sound rather abstract, but in fact, the amount of air that leaks or infiltrates a building’s shell has a significant impact on the energy performance of the building, as well as the indoor air quality. The benefit of a well-sealed building is that fresh air can be filtered and tempered through controlled intake and exhaust ducts and continuously delivered throughout the house to ensure a healthy indoor environment.

To achieve Passive House Certification, the blower door test result measuring the air infiltration through the building shell needs to be less than .6ACH @ 50 Pascals – which is a very low and difficult number to achieve. As a reference for this level of infiltration, the average new home that is built (with attention paid to air sealing) is typically 10 ACH. Passive House requires a 90% improvement on the air sealing of its certified buildings. We recently conducted a blower door test on our prototype and were pleased to see the test results were so low that the machine did not register the amount of air leaking into the building at the standard test pressure. The blower door technician did not have a small enough aperture on his fan to measure the tiny amount of air passing through!

The approach we used to achieve this level of air sealing on our building is based on planning the air barrier for the entire building from the foundation to the roof early on in the design process. We have also chosen durable construction materials for the air barrier, that are installed and sealed early on in the construction process. We find it much easier to seal the simple raw building elements before the many layers of insulation, utilities and finishes are installed, thus avoiding the complexities that happen later in the construction sequence.

The foundation: A plastic vapor barrier was installed on the inside of the foundation that is continuous, sealed at joints, and sealed to the SIPs.

Walls: The SIPs, which are considered air barriers unto themselves, are thoroughly sealed between the panels with both spray foam and tape. Because the panels are large, the number of joints between the panels is reduced.

Ceiling: The air sealing at the ceiling is created by adding a durable layer of o.s.b. to the underside of the trusses, which is then taped at the joints to ensure air tightness. We choose o.s.b. instead of plastic for this barrier because of its durability in the construction phase and over the long term.

Doors and Windows: The last and critical element of air sealing is at the openings for the windows and doors. In these locations we sealed the rough openings much like the joints between the panels with both foam and tape. In addition to sealing to the windows and doors, it is critical to choose windows and door products that are designed to have low infiltration rates as well. We find the European multi point lock hardware creates the best air seal for window and doors, and therefore have used these products on the prototype.

The structural insulated wall panel systems (SIPs) have many advantages when creating a well-insulated and air-sealed building shell that is cost effective to produce. The panels we chose to use on the prototype are 6-inch thick urethane panels, that are 4 feet wide by 24 feet long, factory manufactured and pre-cut by Winterpanel in Vermont. The most significant advantage of the SIPs is that they provide an uninterrupted thermal barrier for the shell that is also a durable and easily sealed air barrier.

The Passive House requirements for a building’s shell are very specific. To qualify for Passive House Certification, a building should not have any thermal bridges in the foundation or building shell, and the building, when complete, must meet strict air sealing requirements verified by a blower door test. The SIPs system has allowed the prototype’s construction to conform to these Passive House requirements, while still allowing for simple and cost effective construction.

The second advantage of the SIPs system has to do with the size of the panels and the ability to have them factory pre-cut to fit each building design. These benefits are maximized by utilizing our computer designs in the actual production of the construction components. By utilizing advanced three-dimensional computer models, we are able to coordinate all the expensive building shell components (including windows, SIPs and structural frame), and then incorporate the computer’s accuracy in the actual construction process. By putting emphasis on planning and leveraging that in the construction, we can improve the speed, accuracy, and quality of the site work.

One frequently asked question regarding SIPs panels is the environmental impact of the foam insulation used in the panels. The three standard foam types used in SIPs panels are urethane foam, and Expanded Poly Styrene (EPS). We choose to use urethane foam for the prototype’s panels because it has a higher R-value per inch, resulting in a thinner panel and a higher total R-value per unit cost. The criticism of this foam type is that the R-value decreases over time. The total aged R-value of the urethane, however, is still higher than the comparable EPS R-value per unit cost. While both foam options are considered green products according to the USGBC, it has been suggested that the EPS production is more environmentally friendly of the two foams. G•O Logic has used both foam types and considers their application on a case-by-case basis.

G•O Logic is currently building its 1500 Contemporary model home on a 4-acre site in Belfast, Maine, which will be completed in January.

With the launch of our website we’re offering a line of homes that prove great design, comfort, unparalleled energy performance and reasonable cost can coexist. We’re not here to throw around now-meaningless terms like “green” or “sustainable” to describe what we do. Let’s accept it: every new building on earth has an environmental cost, either initially or over the long term (or both, generally). Here in the frigid north a building can be made to produce more energy than it uses through the application of renewable technologies, but only at an enormous cost. Net-zero is possible and certainly worthy, but it’s affordable only to a very few. G•O Logic is out to show the most sensible approach to reducing energy use in buildings is to push the envelope on performance and at the same time keep costs affordable to the average homebuyer.

We’re in trouble, folks. I just read “Heat” by George Monbiot. In spite of years of official ignorance of the problem, it turns out climate change was and is happening, and the outlook is so dire it’s almost too depressing to think about. But as Mr. Monbiot is a true optimist he spells out a necessary path to survival in the next 30 years: reduce carbon emissions by 90%, nothing less. What does this mean for energy use in buildings? Again, we’re in trouble. Buildings gobble up around half of all the primary energy  used in the world (way more than cars and trucks do), but since heating oil has been so cheap historically we haven’t been too compelled to do anything about horribly wasteful buildings. Monbiot cites the German Passive House concept as a reasonable, proven method to reduce energy used for space heating in buildings by 90%, the same as his target. The passive house idea is catching on the the U.S. and we at G•O Logic are designing and modeling our homes to meet that standard.

Specifically what can we do? Create buildings that use the very least amount of energy possible for the various needs we humans have: staying warm, bathing with hot water, and watching episodes of Lost on wide-screen t.v.’s. What we as designers and builders can do is build a building that does such a good job of keeping out the cold we need nothing but the most minimal amount of electricity or firewood or body-heat to keep it warm; specify the most efficient water-heating appliances coupled with a solar-thermal system to cover half the annual domestic hot water load; remove the t.v. room from the floor plan and specify furniture with built-in chess boards. Who said architecture can’t be manipulative?

But don’t these homes cost a lot to build? What level of energy efficiency are we talking about at what cost? In the next series of posts  we’ll look at the numbers to see if this plan is affordable and and the reduction in energy use achievable.