Often, when we are talking to people about what we do, there’s a pause and then, “You build what?” It’s easy to reply, “an energy efficient home” but it doesn’t really get at the heart of what building passive or super efficient means and we want everyone to know because we believe that building in this way is just one way to make an impact on our environment for the better!
Here are some details of home building we consider/ implement for a passive or super efficient home:
Conditioned Spaces: the size and density and where a home is geographically located is investigated to determine how much energy the heating/cooling/ventilation system would have to use per year. To determine this, we look at Peak Heating and Cooling loads. Peak heating is how much heat your system needs to put out on the coldest day of the year in the location of the home. Peak cooling then is the opposite. We build with dense packed cellulose insulation and do a rigorous amount of air sealing to keep the peak loads at a minimum. We want our homes to basically maintain a comfortable temperature of approx. 74F throughout the year which for the customer, results in lower energy bills.
Energy Sources: We want our homes to be significantly less consumptive than a standard home. To do this, we consider, how many people will live in the home and how the home will be used; what appliances will be in the home, what type of bulbs for lighting, the hot water heater and the Energy Recovery Ventilator Unit. We design the windows to provide solar gain in the winter when it’s needed and avoid window placement in areas where summer heat gain would be greatest. We evaluate the quality of everything making up the home because it’s these materials and fixtures that play a significant role in the energy performance of the home.
Air Tightness: By using the right materials and well developed building practices that prevent air and vapor from penetrating or leaking through the envelope (your homes shell) you can have a comfortable and healthy home. To do this, homes are blower door tested, which is an interesting and informative part of the build. The house, once the windows, doors, siding, roofing, and insulation are installed, is closed up and pressurized using a fan placed in a doorway. As the fan runs, the amount of air that escapes the home is measured, through software, and the output is generated in cubic feet per minute at 50 pascals of pressure per square foot. FUN FACT: Pascal: a pressure of one newton per square meter or in S.I.: one kilogram per meter per second squared.
Lets just break that down a little: the number generated from the blower door is the number of times the air volume changes in a house over an hour at 50 pascals of pressure. PHIUS (The U.S. Chapter) requires homes to meet 0.06cfm50 per ft2 to be considered passive. The lower the number, the tighter the home! Some City and County Building departments will also have their own standard for air tightness as well. For example, in the City of Fort Collins a homes air tightness “shall not exceed 3.0 ACH50 (air changes/hour at 50Pascals of pressure) for either gas or electric heated homes” https://www.fcgov.com/building/files/cfc-sfd-air-tightness-testing-protocol-v4.2.pdf?1588951497 This is an important and incredibly useful tool in determining the energy efficiency of a home!
Whew! you’ve made it through that lengthy interpretation of what makes a passive home, passive. By building thoughtfully, we create homes that make an impact in human health, building health and environmental health.