Superinsulation
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Superinsulation is an approach to building design, construction, and retrofitting. A superinsulated house is intended to be heated predominantly by intrinsic heat sources (waste heat generated by appliances and the body heat of the occupants), without using passive solar building design techniques or large amounts of thermal mass, and with very small amounts of backup heat. This has been demonstrated to work in very cold climates but requires close attention to construction details in addition to the insulation.
Some may consider that superinsulation is an alternative to passive solar design (although many building designs include features of both with special attention to preventing summer overheating). Superinsulation is one of the ancestors of the passive house approach. A related approach to efficient building design may be zero energy building
There is no set definition of superinsulation, but superinsulated buildings typically include:
- Very thick insulation (typically R40 walls and R60 roof)
- Detailed insulation where walls meet roofs, foundations, and other walls
- Airtight construction, especially around doors and windows
- a heat recovery ventilator to provide fresh air
- No large N-facing windows (or s-facing in the Southern Hemisphere)
- No large amounts of thermal mass
- No active or passive solar heat (but may have solar water heating)
- No conventional heating system, just a small backup heater
Nisson & Dutt (1985) suggest that a house might be described as "superinsulated" if the cost of space heating is lower than the cost of water heating.
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[edit] History
The term "superinsulation" was coined by Wayne Schick at the University of Illinois at Urbana-Champaign. In 1976 he was part of a team that developed a design called the "Lo-Cal" house, using computer simulations based on the climate of Madison, Wisconsin. The house was never built, but some of its design features influenced later builders.
In 1978 the "Saskatchewan House" was built in Regina, Saskatchewan by a group of several Canadian government agencies. It was the first house to publicly demonstrate the value of superinsulation and generated a lot of attention. It originally included some experimental evacuated-tube solar panels, but they were not needed and were later removed.
In 1979 the "Leger House" was built by Eugene Leger in East Pepperell, Massachusetts. It had a more conventional appearance than the "Saskatchewan House", and also received extensive publicity.
Publicity from the "Saskatchewan House" and the "Leger House" influenced other builders, and many superinsulated houses were built over the next few years, but interest declined as energy prices fell. Many US builders now use more insulation than will fit in a traditional 2x4 stud wall (either using 2x6 studs or by adding rigid foam to the outside of the wall), but few would qualify as "superinsulated".
[edit] Retrofits
It is possible to retrofit superinsulation to an existing older house. The easiest way is to build new exterior walls that allow more space for insulation. A vapor barrier can be installed on the outside of the original framing. Window and door openings must be rebuilt to accommodate the thicker walls.
Interior retrofits are possible where the owner wants to preserve the old exterior siding, or where setback requirements don't leave space for an exterior retrofit. Sealing the vapor barrier is more difficult and the house is left with less interior space.
[edit] Costs and benefits
In new construction, the cost of the extra insulation and wall framing is offset by not requiring a dedicated central heating system. The cost of a superinsulation retrofit may need to be balanced against the future cost of heating fuel (which can be expected to fluctuate from year to year due to supply problems, natural disasters or geopolitical events).
A superinsulated house takes longer to cool in the event of an extended power failure during cold weather, for example after a severe ice storm disrupts electric transmission. Adverse weather may hamper efforts to restore power, leading to outages lasting a week or more. When deprived of their continuous supply of electricity (either for heat directly, or to operate gas-fired furnaces), conventional houses cool more rapidly during cold weather, and may be at greater risk of costly damage due to freezing water pipes. Residents who use supplemental heating methods without proper care during such episodes, or at any other time, may subject themselves to risk of fire or carbon monoxide poisoning.
The use of electric heaters for backup heat may be environmentally questionable (unless the house is located where electricity is produced by clean technologies such as hydro or nuclear), but they are typically only used on the coldest winter nights when overall demand for electricity is low.
Straw-bale construction may be especially compatible with superinsulation, due to the thickness of the bales, but only if combined with the other construction details listed above.
Structural insulated panels (SIPs) are also ideal for superinsulated construction. They are a very simple and affordable way to create the needed R-values.
Earth-sheltered housing such as Earthships are often superinsulated by their very nature.
[edit] See also
[edit] References
- Computation and description of an outside insulation house: To build for tomorrow (translated from French)
- Nisson, J. D. Ned; and Gautam Dutt, The Superinsulated Home Book, John Wiley & Sons, 1985 ISBN 0-471-88734-X, ISBN 0-471-81343-5
- Marshall, Brian; and Robert Argue, The Super-Insulated Retrofit Book, Renewable Energy in Canada, 1981 ISBN 0-920456-45-6, ISBN 0-920456-43-X
- Shurcliff, William A., Superinsulated houses: A survey of principles and practice, Brick House Pub. Co, 1981, 1982 ISBN 0-931790-25-5
- Shurcliff, William A., Superinsulated Houses and Air-To-Air Heat Exchangers, Brick House Pub Co, 1988, ISBN 0-931790-73-5
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