Superinsulation

Superinsulation is an approach to building design, construction and retrofitting. A superinsulated house is intended to be heated predominately by intrinsic heat sources (waste heat generated by appliances and the body heat of the occupants), without passive solar or large amounts of thermal mass, and with very small amounts of backup heat. This has been demonstrated to work in very cold climates (notably Saskatchewan), but it requires close attention to construction details in addition to the insulation.

Some may consider that superinsulation is an alternative to Passive solar (although many building designs include features of both with special attention to preventing summer overheating). Superinsulation appears to be an ancestor 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
• Heat recovery ventilator to provide fresh air
• No large south-facing windows
• 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.

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 (often 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, if at least 2/3 of the total insulation is outside of the vapor barrier. 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.

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.

The use of electric heaters for backup heat may be environmentally questionable, 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.

References

Nisson, J. D. Ned; and Gautam Dutt, The Superinsulated Home Book, John Wiley & Sons, 1985 ISBN 047188734X, ISBN 0471813435

Marshall, Brian; and Robert Argue, The Super-Insulated Retrofit Book, Renewable Energy in Canada, 1981 ISBN 0920456456, ISBN 092045643X

Shurcliff, William A., Superinsulated houses: A survey of principles and practice, Brick House Pub. Co, 1981, 1982 ISBN 0931790255

Shurcliff, William A., Superinsulated Houses and Air-To-Air Heat Exchangers, Brick House Pub Co, 1988, ISBN 0931790735