Exterior Insulation and Window Detail
What is a Passive House?
Recently, I had the pleasure of visiting a home in Westport, CT, owned by Mr. Doug McDonald. His home has been mentioned in the New York Times, and is a beautiful modern home that has been retrofitted to the Passive House standard. His home stays between 73 and 74 degrees no matter the season, achieved by air sealing the home almost perfectly, and adding 10 inches of insulation all the way around the exterior of the home.
Mr. McDonald’s home uses 90% less energy than the typical similar sized home. Since the home is super air tight and super-insulated, the heating and cooling needs are minimal, mostly supplied by the passive heat that cooking, electronics, and even people! Any additional heating or cooling is provided by a small mini-split system.
How Does a Passive House Work?
Air Sealing and Air Exchange
The main driving force behind making a Passive House so efficient is the almost total elimination of unwanted air infiltration. Doug’s home is Air Sealed with a rubberize membrane over the whole exterior concrete structure. This particular home only has three penetrations through the air-tight membrane in the whole house!!!
Because this home is very air tight, it requires mechanical ventilation. Doug’s home is ventilated with an ERV, which takes fresh air, filters it, and then brings it to bedrooms and living spaces while it replaces dirty air from the kitchen and bathrooms. This system captures 90% of the temperature of the exiting air to bring the incoming fresh air to proper temperature. It also helps eliminate indoor allergens, pollutants, or just plain old smells since it exchanges the air in the whole house a few times every hour.
Heating and Cooling
This home takes advantage of solar gain in the winter with nice big windows that face South. In the cold months, when there are 
no leaves on the trees surrounding the home, these windows let in lots of light which helps to heat the home. In the summer, the sun is blocked by deciduous trees, helping keep the home cool.
Also, as mentioned earlier, because of how air tight this home is, people and regular daily activities contribute to the heating of the home. Electronics, cooking, you, your children, and pets all contribute to the heating of this home. In the summer, or when you have many people walking around your home (like on this particular day of tours), opening a window is a simple way of adding some extra “air conditioning” (Actually, it’s just letting warm air escape from the home).
Additional heating, when necessary, is provided by 10 square feet of radiant floor heat in the main living area, with hot water provided by a solar water heater on the roof.
Can I Make My House a Passive House?
While most Passive Homes are built from the ground up, this particular home was even more special because it was a retrofit (no easy task to accomplish). Retrofitting almost any home to this high level is possible, but not always the most budget friendly. At AccuGreen Home Performance, we believe that striking a balance between your budget and the highest level of Home Performance is what we do best. Saving up to 50% on your total Energy cost is a very possible and a very real goal. Improving the comfort of your home with extensive air sealing, adding insulation, and proper ventilation is something that can be done within most budgets, leaving you and your family with a home that is more comfortable, healthier, and saves you money!
Contact Us today to find out how we can help you.
