The Ins & Outs of a Passive House
My name is Michael Carrier and I am the owner and CEO of Alpenglow Building & Design located in Durango Colorado. My firm has been in business for 18 years and has been focused on true design-build where the designers and architects in the office collaborate with estimators and project managers to see projects through from initial
design and budgeting and actual construction.
As a team, we have had a focus on sustainability and energy efficiency since our humble beginnings. We liked to use reclaimed wood and steel, quality insulation and tight windows and doors. This has allowed us to decrease the amount of embodied energy in a project which translates into less waste and a more efficient use of resources.
We had a turning point 4 years ago when a client came to us and wanted to build a passive house (PH) and we quickly did the training and research to move forward. Like most, we assumed that passive house meant a passive solar house. While PH use passive solar, it is only one of many criteria for achieving a passive envelope in a structure. We learned that high-performance houses like PH are healthier, more comfortable, more durable and easier on the planet through drastically lowering carbon emissions through very low energy needs.
As an overview, PH utilizes a very rigid criteria to accomplish the goal of reducing energy needs by up to 90% within a building. These criterial are as follow:
- Airtight construction controls the transfer of air, heat and moisture into and through the building envelope. Doors and windows need to be air-tight as well to complete the system.
- Thermal bridge-free construction eliminate the typical bridging that rob buildings of energy, comfort and durability. Visualize a standard 2×6 framed wall with plywood and siding on the outside and drywall and paint on the inside. Every single 2×6 is a thermal bridge where outside moisture and temperature is in direct contact with the interior finished wall. Energy moves inside and out through this continuous area of contact.
- Continuous insulation values that are appropriate to the climate that you live in is next on the list. Here in southwest Colorado, we have cold winters and hot summers and the temperature can swing 45 degrees in one day. The translates to R-65 walls and R-95 roof assemblies. This insulation is continuous as well throughout the entire floor, walls and roof.
- Triple-pane windows are essential to the PH. A window with three panes of glass is thermal broken, keeping with our rule of eliminating thermal bridges. These highperformance units let passive heat inside during the winter when the sun is low and keep out the harsh direct summer rays when the sum in more overhead. They also do not bleed energy or heat up from the exterior in the warm months.
- Because these structures are so tight and efficient, a ventilation system in required in the form of an ERV or energy recovery ventilator. These magic boxes continuously exhaust stale air from the building and exchange this for fresh outdoor air effectively keeping out all allergens, pollen or contaminants all the while keeping the heating or cooling energy in the house. They also provide humidity control which is a huge benefit in our very dry climate.
All the above principles translate into a building that uses up to 90% less energy than a building of the same size built to the current building code. As well, these structures are healthier to live in as well as more comfortable. Imagine a house with no drafts in the middle of winter and a temperature that only changes 3-5 degrees all year long. In a sense, PH is building science that proves that buildings behave similar to ecosystems where changes to one part of the system can have big impacts in other areas.
Obviously there are big differences between ecology and building science in that ecosystems are wildly complex, but buildings? We are finding that they need not be perceived this way. They are in fact not so complex and are predictable and manipulatable given a correct knowledge of building science. This is a new and appropriate way to look at the structures that we inhabit.
Obviously there are some costs associated with this type of building and the premium is in the range of 7-12% of standard square foot construction costs. But heating and cooling systems can be either eliminated or greatly downsized in a PH and a building that is this efficient will save money every year for its life thus the full payback is easily obtainable.
To date, Alpenglow has completed 3 passive house projects in La Plata County and currently has the 4th in design which will be constructed this summer. Visit our website to see some of our passive houses.