Superinsulation

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) 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.

Superinsulation is one of the ancestors of the passive house approach. A related approach to efficient building design is 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 windows facing any particular direction
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.

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. Several houses, duplexes and condos based on Lo-Cal principles were built in Champaign-Urbana, Illinois in the 1970s^[1].

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".

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. Care should be exercised when adding a vapor barrier at a location other than on the "warm-side in winter" to prevent condensation and consequent mold and mildew. This may cause health problems for the occupants and damage existing structure. Many builders in northern Canada use a 1/3 to 2/3 approach, placing the vapor barrier no further out than 1/3 of the R-value of the insulated portion of the wall. This way, the vapor barrier will usually not fall below the dew point, and will minimize the possibility of condensation problems. With an internal room temperature of 20°C (68°F), the vapor barrier will then only reach the dew point for outside temperatures below −18°C (-1°F). An approved application of a building wrap on the outside of the insulation underneath the exterior siding helps keep the wind out, yet allows the wall assembly to dry to the exterior. Asphalt felt and other products are available for this purpose.

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 air barrier is more difficult and the house is left with less interior space. Another approach is to use the 1/3 to 2/3 method mentioned above — that is, to install a vapor retarder on the inside of the existing wall (if there isn't one there already) and add insulation and support structure to the inside. This way, utilities (power, telephone, cable, and plumbing) can be added in this new wall space without penetrating the air barrier. Polyethylene vapor barriers are risky except in very cold climates, because they limit the wall's ability to dry to the interior.

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.

Electric heaters are typically only used on the coldest winter nights when overall demand for electricity is low.

Notes

^ McCulley, M. (2008, November). Pioneering superinsulation and the Lo-Cal House: Design, construction, evaluation and conclusions. Paper presented at the 3rd Annual North American Passive House Conference, Duluth, MN

References

Computation and description of an outside insulation house: To build for tomorrow (translated from French)
Booth, Don, Sun/Earth Buffering and Superinsulation, 1983, ISBN 0-9604422-4-3
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

External links

[1] McCulley, M. (2008, November). Pioneering superinsulation and the Lo-Cal House: Design, construction, evaluation and conclusions. Paper presented at the 3rd Annual North American Passive House Conference, Duluth, MN

[1]