Insulation

From Antivist

The goal of thermal insulation used in building construction is to slow down heat transfer. The same materials are required to keep buildings cooler in hot climates, or warmer in cold climates; methods may be different because of the necessity to manage humidity buildup differently. Occupied buildings always need to evacuate humidity.

A well insulated building provides lower operational costs, greater conformity to environmental concerns, greater thermal comfort and often also greater soundproofing. There is no objective test or standard for thermal insulation. ASHRAE Standard 55 defines thermal comfort goals. The three means of Heat-transfer resistance reduce radiative, conductive and convective losses and gains. Local custom often determines the methods used to achieve comfort level goals.

In some climates, large thermal mass can be used to damp daily swings in temperature. Adobe, earth, stone, and concrete are poor insulators but serve the purpose of regulating indoor temperature by damping. If a house has an attic, indications that it is poorly insulated and poorly ventilated include the attic being oppressively, almost unbearably hot in the summer, and dew and frost forming on cold surfaces in the attic, such as on the underside of the roof sheathing, during the winter.

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), 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 but requires close attention to construction details in addition to the insulation.

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

Benefits

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.

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 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.