Rarely, can you call someone or something ‘passive’ and have it come off as a compliment. Inactivity, especially in today’s society, comes off as just plain lazy in most circles. Oddly enough, adopting passive methods to power our homes just might ignite the fastest, most powerful sprint toward a net-zero building stock. Passive energy practices cut back on energy use by 80%, ease harmful emissions, reduce reliance on the grid, save heaps of money, and offer the population far healthier indoor air quality (IAQ).
The Passive House (or Passivhaus) concept dates back to a 1988 brainstorming session on energy efficiency between Bo Adamson of Lund University (Sweden) and Wolfgang Feist of Germany’s Institute of Housing and the Environment. Feist went on to create the Passivhaus-Institut in 1996 to promote and control Passive Building standards. Still, the idea of passive structures is not a new concept. Passive Homes were always the rage in areas such as Southern China and the norm during the Middle Ages in Iceland. It’s time to apply lessons from the past in a uniform manner and Passive House Institute U.S. (PHIUS) has done just that by setting and promoting standards (PHIUS+ 2015). The following Passive Building principles focus on meeting those rigorous standards for the ultimate energy-efficient structures:
Super Insulated, Air-Tight Construction: High levels of insulation allow a warm building to stay warm and a cool building to stay cool. A Passive Building incorporates insulation two to three times thicker than conventional construction methods. Heat is always trying to transfer its thermal energy to a cooler space or object, seeking thermal equilibrium. The better the insulation and the tighter the building envelope, the less opportunity there is for heat to pass in or out of the building. In that way, you can think of a Passive Building as a sort of thermos, capable of holding onto the temperature of its contents without use of a continuous, external power source.
Since a passive building must have a continuous thermal envelope, design must exclude thermal bridges. Also known as cold bridges, thermal bridges are less-insulated areas within the construction of the building that allow heat an escape or entrance route of lesser resistance. Some examples include eaves junctions, the areas around windows and doors, gaps between insulation boards, timber studs, and rafters that pass through the thermal envelope. Design and insulation must thwart these bridges in a Passive Building.
High Performance Windows and Doors: Passive buildings typically utilize triple-pane glass windows, which must be installed without creating a thermal bridge. The glazing of the glass should have a minimum g-value (or total solar transmittance) of 50% to help acquire heat from the sun during the winter. Many experts point to German-engineered windows as the cream of the crop, but the expense and shipping often prevent North American contractors from obtaining them. One of the reasons the European windows are so desired is that they can achieve a U-factor (measurement for rate of heat transfer) of .14, a passive house recommendation, rather than a requirement. If such windows are not an option, Passive Building designers can improvise by using a window with a higher U-factor and making up the difference in the building’s energy performance with more insulation.
Solar Orientation: A Passive House designer needs to take the home’s geographic area, annual weather data, and proximity to the Equator into consideration. Doing so opens orientation opportunities to utilize passive solar heat in the best ways possible. For example, when the long, front side of a building faces within 20 degrees of the South, the south-facing windows will bring passive solar heat into the home during the winter.
Balanced Ventilation and Moisture: With all the air-tight, insulated, energy-efficient goodness going on in a Passive Building, it’s important not to forget one matter such a set-up does not lend itself to: breathing! A sealed thermos has no need of a way to draw air inside, but your average human being certainly does. Stale air needs a way out and fresh air has to make its way in. PHIUS+ standards require a form of balanced heat- and moisture-recovery ventilation.
What sort of equipment offers that balance? As a leader in providing sustainable, energy-efficient solutions for structures of all sizes, Haglid Engineering recommends an Energy Recovery Ventilator or ERV for this balancing act. A high-efficiency ERV will precondition fresh outdoor air to room temperature while substantially reducing your energy bill, improving indoor air quality, and reducing the emissions that feed global warming. In other words, such units efficiently recover energy from stale air leaving the building and use it to warm room temperature in colder months and cool it during the warmer months. As moisture recovery is an important component in a Passive Building, the additional benefit of transferring latent heat is key. An effective ERV can offer precise control of the moisture in the air without dropping the temperature in the process.
Homes can be constructed as passive or retro-fitted. In addition to helping speed the transition to a more environment-friendly building stock, Passive Buildings offer unmatched comfort, superior indoor air quality, and energy bills that run from $0 to far lower than most folks are used to these days. Interested in learning more and understanding your options? Give Haglid Engineering a call for a real-world explanation of what a Passive Home or Building can do for you (888.989.8539).
We’re passionate about seeing Net-Zero become the global norm, and through our sister company, BPE, Inc., we have designed the HVAC equipment that can help achieve that goal.
Challenge
When it was built in 1977, the Saskatchewan Conservation House was one of the first completely energy efficient homes in North America. Our goal was to increase the energy and cost effectiveness of this passive house, which is nearly air tight, by improving the ventilation.
Solution
Haglid Engineering & Associates and its sister company, Building Performance Equipment (BPE), Inc.®, reduced energy requirements and provided the house with fresh indoor air via a BPE-XE-MIR 200. In addition, we installed high-efficiency lighting and upgraded the envelope.