Even if you aren’t planning to build a Passive House – a home with extremely low energy use heated by the sun and waste heat produced by people and devices in the house – there is a lot to be learned from these homes that can be applied to building any house, such as the modern example above, Plan 497-29.
Air Sealing Though most people have been attuned to the importance of insulation in a house for many years, and many of us know the effect on comfort and utility bills a drafty window or door can have, few know how much air flows through a traditional house. Air enters a home in many places, and though these drafts might not be possible to feel, like a drafty door, they add up. Air can flow right through many insulation materials, so a rigorous approach to air sealing needs to come before insulating. The techniques used vary depending on region and construction type. Suffice to say here, it is something with which you and your builder should be concerned. No house should be built these days without several blower door tests done during construction to help detect weak spots in the air sealing.
Insulation My dad always says “A little’s good, a lot’s better”. Though this saying doesn’t apply to nearly as many situations as he seems to think, it applies to insulation. As building costs go, adding insulation gets you the most bang for your buck. Again, the type of insulation used will vary, but you should choose the R-value of your walls, and not just the paint color – if you want to save on utility bills. A Passive House is also mindful of thermal bridging. Most houses are built with wood, which, though not a great conductor of heat, can still allow heat to move right out of your house. A plan that minimizes this either with rigid foam sheets or advanced framing techniques is often worth the investment.
Orientation As I described in “Control Costs Before You Build” the orientation of your home should be considered to take advantage of the free energy the sun provides. A Passive House is oriented so that windows allow winter sunlight deep into the house, but shades those windows so that the high summer sun doesn’t increase the cooling load unnecessarily. The side of the house that will be exposed more to winds should feature smaller windows and have evergreen trees planted so as to buffet the house from wind that draws heat from the house.
System sizing Here is a consideration that will actually save you money up front. If you followed steps 1-3 you will have created a house that needs heating and cooling equipment sized to the reduced loads the house will have. Though you will need energy modeling done to determine the potential savings, a Passive House can often remain comfortable indoors throughout the year with no air conditioner and minimal space heating.
Fresh Air A Passive House is sealed so well that it includes devices designed to fill the home with fresh air without losing heat in the process. Indoor air has been found by the EPA to be 2-5 times more polluted than outdoor air, so the air sealing from step 1 can create a sicker home if you are not mindful of the need for fresh air. Your builder and energy consultant should work together to determine if an energy recovery ventilator should be added to your house, but this may also be an addition that can allow other systems to be downsized.
To see a collection of energy efficient house plans click here. For more information about Passive House standards click here.