Super insulation is at the heart of the Passive House construction concept.
Is it possible we’ve been approaching heating our homes from completely the wrong angle? That’s what proponents of the Passive House believe. Those who follow the principles of this German construction concept say that instead of heating up our homes, we should be trying to keep them from losing their natural heat.
How do you do this? Through super insulation, active ventilation and superior building materials. The result is a home that claims to save up to 90 percent on heating and cooling energy use.
Think of it like your morning cup of coffee. You can keep it warm by leaving it on the hotplate, where it receives a constant supply of heat until you’re ready to drink it. Or, you can put it in a thermos mug, where it will stay hot for hours. In your home, you can either stay warm by turning on a heater, or by preventing the warm air inside from escaping through insulating your walls, doors and windows.
A Passive House is designed and built to be effectively airtight, using super insulation in walls, triple-glazed windows and thermal bridge free construction to prevent any heat escaping or intruding, depending on the season. The combination of these three building principals effectively eliminates any potential air leaks in the home, keeping the inside temperature at a constant level that never varies more than 10 degrees, no matter how frightful the weather is outside. Crucially, a Passive House has no need for a dedicated HVAC unit. It uses no external energy source to provide most of its heat.
Instead, a Passive House relies on passive solar gain and ambient heat given off by its occupants and electronic equipment. Combined with super insulation, that can provide enough heat to maintain a comfortable temperature throughout the home. Any additional need can be supplemented by energy generated from renewable resources. Solar-powered hot water, for instance, can power in-floor radiant heat for homes in particularly cold climates.
The other source of hot or cool air, depending on the season, comes from the Passive House’s ventilation system. An airtight home without a ventilation system could produce significant health hazards, so it’s essential to have fresh air enter courtesy of a specially designed ventilation system. That system also acts as a form of heat recovery.
According to the Passive House International Association, “A highly efficient heat recovery system is capable of transferring more than 75 percent of the perceivable warmth from the used, exhaust air to the fresh, incoming supply air. In this way, for example, 20° C exhaust air can bring the cold supply air on a 0° C day to at least 16° C, without the use of active heating. When it is too hot outside, warm ambient air can be cooled before it enters the home in much the same way.”
Cost and Energy Usage
Building a Passive House is estimated to be five to 20 percent more expensive than construction of a standard home. This incorporates building thicker walls for more insulation, paying for triple-paned windows and higher quality of building materials, and investing in a ventilation system. However, you don’t need to buy and install any HVAC system.
Because it does away with the need for an HVAC system, a Passive House uses less than 10 percent of the energy of a traditional home. The benefits here are clear—the house that can reduce its energy consumption by 90 percent is a game changer, and will do far more for the future of the planet than any amount of recycling or composting!
However, the construction of a Passive House relies on a delicate balance between insulation, ventilation and construction. To achieve this, calculations need to be precise in order to avoid any potential issues, so it’s important to use a builder certified in Passive House building. You should also have the project certified by the Passive House Institute.
Retrofit Your Existing House
The good news is that the Passive House concept can be applied to existing homes. It is entirely possible to retrofit your home to be a Passive House, or at the very least apply some of the principles of super insulation to your home to help cut down on the energy you use.
This farmhouse in the foothills of the Rocky Mountains in Idaho underwent a complete Passive House retrofit a few years ago and today uses 90 percent less heating energy and up to 70 percent less total energy than a standard new construction house.
This 1910 farmhouse is an impressive “green” building. It boasts triple-paned Krypton filled windows, 12 inches of super-dense insulation, a 93 percent efficient heat recovery ventilation system and a solar thermal heat storage system designed to provide extra heat during winters that can hit 10 degrees below freezing. Taking no energy from the grid, the combination of insulation, ventilation and solar power keep it at a comfortable temperature that is even throughout the home.
For so long, the idea of building green has always come with substantial upfront costs and the promise of long-term payoffs. The concept of a Passive House is one that costs about the same as a regular house but eliminates the monthly power bill. That is a significant, tangible saving that any homeowner will realize immediately. Not having to wait a decade or two to recoup on your investment is a pretty powerful selling point.
Jennifer Tuohy has 15 years’ experience in newspapers, magazines, marketing and online content, winning many awards. She writes on a variety of subjects, but her passion lies with technology, sustainability and the intersection of the two. She lives in Charleston, SC, where she contributes to numerous websites, edits two local newspapers, and renovates her dream home. To learn more about insulating your home as Jennifer talks about in this article, you can go to Home Depot's website. Read all of her MOTHER EARTH NEWS posts here.
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