Passive House, Little Compton, RI

by Bruce on May 13, 2011

The House: A small weekend getaway for a family of 6, it sports a sleeping loft accessed by a ladder that leads through a hatch in the floor.  It’s hip, comfortable, quiet and full of light–and definitely doesn’t require the wearing of a hair shirt.

Passive House specifications hail from Germany and Austria; there are more than 15,000 such buildings across Europe.  The basic premise:  every BTU is sacred, and keeping them inside in the winter and outside in the summer is the house’s primary job.  During the cool and cold months, most of the heat in a Passive House is generated by solar gain and the lights, appliances, and bodies of its occupants; the result is that a PH uses 10% of the energy of a standard-built, code-compliant house.

Why I Like It:  Unlike some “green” houses that rely on complex and ultimately perishable gizmos like ground-source heat pumps and solar panels, the bulk of a Passive House’s magic comes through dumb technology like lots of insulation and extreme attention to thermal bridging and air sealing.  One crucial gizmo is an heat-recovery ventilator, a not-very-complicated machine that conquers the challenge of an airtight building by stripping heat from the stale air it expels and adding it to the incoming fresh air.

The Economics:  Architect Matt O’Malia designs and builds Passive Houses in Maine and presents the following analysis:  “Because a Passive House’s energy demand for space heating has been reduced by 90%, the resulting heat required to keep the build at 70 degrees is very low, which allows its heating system to be drastically simplified to a small amount of electric baseboard controlled by a thermostat in each room. The cost to install this simplified heating system is about $500, replacing the standard system of a boiler, radiant slab, pumps, fuel tanks, chimney and manifolds, saving around $15,000. The significant financial savings resulting from minimizing the heating system is reinvested in the building-shell improvements: walls at R49, foundation at R70, roof at R80 and triple glazed R8 windows and doors. The cost of these improvements is about $30,000. When the cost of the heating system is subtracted from the building shell improvements, the first cost increase for building a Passive House is about $15,000, or 7% of the total construction cost. The combination of these improvements, in conjunction with heat-recovery ventilation, results in a home with energy costs for space heating at less than $300 per year, with energy costs savings over 30 years of $170,000 (including inflation)–which is nearly equal to the original cost of construction.”

Contacts:  The architects behind the Little Compton house are ZeroEnergy Design. Matt O’Malia’s firm is G-O Logic Homes.

Homeowners’ POV: For a blow-by-blow of what it’s been like to have a Passive House built, visit Hilary and Pierre’s blog.

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