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Maine Passivhaus Comes of Age

by: Paul Kando

The world's first passive solar houses, built by researchers and tinkerers decades ago, had shed-roofs, massive floors and walls to store heat, and large south-facing windows to collect solar energy. Looks were unimportant; the point was that houses built differently performed better. Likewise, early passivhaus (PH) structures, designed to reduce energy consumption by over 90%, emphasized their technical features - the more obvious the better to explain how and why they worked. With new inventions, function often trumps other considerations.

Hotopp-Gorrell House
photo credit: Paul Kando

In later phases of development the new adapts to market demands. Car buyers begin to question the need for a carriage-look. Engineers develop sleek, aerodynamic designs. Soon the horseless carriage morphs into an automobile with its own distinctive appearance. In the PH case, designers used to please clients displace researchers and computer programs get tweaked to consider attractiveness, not just performance. "But they look alien - German, Austrian, Swedish" -- some complain. If so, that's proof that PH is at home in surroundings for which it was designed - until recently mostly European.

A PH can look like you want it to look. Drive by Robin and Ken's house, for example. You will see an elegantly simple house at home in its Western Mountains surroundings. Inside the visitor is greeted by a beautiful interior. Nothing looks odd, you feel right at home. Like its European cousins, this Maine PH has come of age. It doesn't look like it uses 90% less energy - it just does. What makes it work is mostly hidden. Neither the thicker walls, nor the super high performance windows hit you in the face. If anything the triple glass, argon filled, casement and fixed windows are more practical and attractive than their conventional double-hung cousins. And, to me, a more massive, thicker wall suggests substance, security and permanence. Next to this house a conventionally built counterpart would look like it was made of cardboard.

The house rests on a concrete slab insulated from below to an R-value of 63. The super-insulated double-stud walls are R-57, and the blown-cellulose insulated roof ranges in R-value from R-85 to R-135. Choosing windows for energy efficiency is a challenge, since the more windows block heat loss, the more they also block incoming sunshine. Every window therefore represents a compromise. There are two kinds of PH-rated windows in this home: high solar gain U-0.16, (R-6.33) models, and U-0.11, (R-9.43) units that maximize resistance to heat loss.

A typical Maine house this size would use up to 1,000 gallons of heating oil, costing about $3,800 this past winter. Ken and Robin paid only $230 to heat their house, for electricity and less than half a cord of firewood. Water heating cost another $80 -- the house has a heat-pipe type solar water heating system with 60 evacuated tubes on the roof.

Passive houses like this one outperform their conventionally built counterparts in comfort, energy efficiency and operating cost. But how does the cost of such a house compare to conventional houses? -- The true cost of a house is the sum of mortgage payments, taxes, insurance, maintenance and the cost of energy. If the house is far from job and essential services, the cost of transportation must also be added. Any one of these costs can make a house expensive or a bargain to live in. Taxes, insurance and transportation costs depend on location, not on how your house was built. Mortgage payments, on the other hand, are affected by everything you need to finance. The cost of energy is another matter. In a conventionally built house it is an annual extra cost paid on top of other expenses. In a PH, since maximum energy efficiency is built into the structure, energy is mostly financed through the mortgage. Therefore, while a PH may cost a fraction more to construct than a conventional lookalike, the total cost of living in it will be far lower. Put another way, someone building a PH can more than afford to pay any extra up-front cost without affecting the overall cost of living in the home. As a product of the information age, a PH is first built virtually, by computer simulation, before ground is broken and it is performance-tested upon completion. Costly mistakes in the field are thus avoided. Furthermore, insulation is cheap and quality workmanship shouldn't cost extra.

How much of a PH can you afford? -- If , for instance, it reduces energy costs by $400 per month and you finance it by a 4.01% fixed rate 30 year mortgage, those savings will cover the monthly cost of an additional $65,941 in mortgage principal without raising your monthly cost of living. Unless you have a castle with a moat in mind, no PH construction cost-premium will even approach $65,000. My bottom line: building anything less efficient than a passive house makes no economic sense. Robin and Ken can attest to that.