Houses without Heating Systems, part one

Posted Wednesday, August 3, 2011 in Sustainable Maine

Houses without Heating Systems, part one

Schematic of the most important components of a passive solar house.

Credit: International Passive House

by Paul Kando

The average Maine family spent 5 percent of its net income on energy in 1998. By 2008 energy’s share has increased to over 20 percent. And by 2018 the forecast is over 40 percent. Factor in rising health-care costs and the family in 2018 will have less than 25 percent of its income left for all other expenses, like housing, food, clothing, education, etc.  

How is all that energy used? In Maine about 40 percent goes to heat homes. Another 50 percentis guzzled up by cars. And the remaining 10 percent goes for electricity. In addition to fuel for our vehicles, eight out of 10 Maine houses rely on oil for winter heating. This makes for a near-total dependency on imported oil, the cost of which is simply removed from Maine’s economy. This is hardly sustainable. To avoid climate catastrophe due to human-caused global warming, we must cut energy consumption by about 60 percent across the board. 

The irony is that much of the energy we “use” is actually wasted. Based on the international Human Development Index (HDI), the United States has a standard of living roughly on par with other developed countries, such as Germany, Italy, France and England. Yet to achieve a similar HDI, the Unites States, alone among countries, per capita consumes more than twice the energy. In other words we are wasting over half the energy we use for no benefit whatsoever. There are no energy alternatives sufficient to cover such wastefulness. But there is enough renewable energy for mankind to live comfortably if we all cut out the waste. There is between 2 and 4 kWh per square meter of earth surface per year of renewable energy available wherever people live.

The easiest place to cut energy waste is in buildings, where proven, off-the-shelf technology can reduce consumption by as much as 90 percent while improving comfort. Passive house (PH) is an integrated building concept whose goal is to ensure the highest level of comfort using the least amount of energy. Measurements in over 32,000 homes and other buildings in all climates show that fuel consumption of PH is 75 percent to 90percent lower than of comparable ordinary buildings. Their efficient ventilation system doubles as a heating system. No need for a costly boiler or furnace, separate ducts, piping, fans and pumps. Needless to say, using fresh ventilation air for heating will only work in buildings with a minimal heating load.

A PH uses less than 1.5 liters of heating oil per square meter (m2; about 0.039 gallon per square foot) of living space per year – far less than a typical low-energy building and about 1/15th of what the typical Maine house uses. (Similar energy savings have been demonstrated in buildings that require cooling.) Passive houses use energy sources internal to the building. Residents' body heat, waste heat from appliances and solar heat entering the building are captured and redistributed by heat-recovery ventilation. Special windows and a highly insulated building shell keep winter warmth in and summer heat out. The ventilation system supplies a constant stream of fresh air, removing excess moisture and providing superior air quality without unpleasant drafts. A highly efficient heat-recovery unit captures heat contained in the exhaust air and transfers it to the incoming fresh air. 

Appropriate building components ensure consistently high energy savings even as they increase indoor comfort. Compared with a standard double pane, a passive house window reduces heat loss by over 70 percent. Insulation saves up to 90 percent of the heat lost through an external wall. An efficient heat-recovery system reduces ventilation heat losses by 75 to 95 percent. Renewable energy can cost-effectively meet the remaining energy demand, turning a PH into a zero-energy structure. An energy-balance calculation helps determine the level of insulation required in a given building in a given climate.

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