Wall insulation became mandatory in US homes in 1965. The codes change and are upgraded as new information and products become available. Before then, builders insulated as needed or charged extra for it. Ninety percent of US houses remain underinsulated today.
Ancient Insulation
Many civilizations knew and appreciated the value of insulating their living environments.
- Egyptians. Built with thick heavy bricks. Cool during the day. Warm at night.
- Greeks. Used asbestos and air gaps in walls to resist heat.
- Romans. Wrapped water pipes in cork to prevent heat loss or gain.
- Vikings. Applied mud to seal cracks and joints in wood structures.
- Europeans. Hung tapestries to stop drafts.
Insulation Still Found in Houses
Homes built in the 1800s and 1900s were often insulated with whatever was available. Sawdust and shavings mixed with borax. Horsehair, newspapers, and rags stuffed around window frames. Most wall voids remained empty.
Purpose-made insulation became available in the late 1800s. Since then more options and inventions have appeared regularly.
Mineral Wool
Mineral wool insulation received a patent in 1880. It is made from lava rock and iron slag. Mineral wool is still popular today for its relatively high R-value and soundproofing capabilities. It was often wrapped in kraft paper to reduce dust and skin contact. Then nailed to the studs.
Asbestos
Asbestos insulation is one of the most popular products ever used because of its insulating and fire resistant qualities. By 1980 it was declared a health hazard and banned. After 100 years of use, approximately 50% of US homes still contain asbestos.
Insulating Lumber
Insulating lumber was developed in 1923 and promoted as providing more insulation value than regular wood. A combination of wood products and other natural fibers, it was used as sheathing and eventually for interior finishing. It was never used to fill wall cavities.
Cork
Cork has been used as insulation since Roman times. It is also a great sound suppressor. Originally intended to replace lath and plaster interior finish, it is still used for floors and walls—not to fill stud cavities.
Vermiculite
Vermiculite was used as loose-fill attic and wall insulation from 1951 to the 1970s. Until it was found to be contaminated with asbestos. It is no longer used as insulation in the US and Canada, but it is certified safe for use in other countries. About one million homes in North America still contain vermiculite.
Reflective Insulation
Reflective insulation was introduced in 1961. It laminated aluminum foil to kraft paper to reflect heat away from the house–especially from roofs. Reflective insulation is still used today–without the kraft paper.
Urea Formaldehyde Foam Insulation (UFFI)
In the late 1970s urea formaldehyde foam insulation was used in hundreds of thousands of North American homes. By 1982 it was classified as a “known human carcinogen” because of formaldehyde off-gassing. It also shrank–reducing its insulation value. UFFI is still used today for some applications.
Fiberglass
Fiberglass was created by accident in 1932. It is found in millions of houses around the world. It is still the most used insulation because of cost and availability. Older fiberglass is very itchy and the fibers become airborne easily–creating health problems.
Cellulose
Thomas Jefferson’s house was insulated with a form of cellulose in 1772. Cellulose insulation was popular in the 1970s. Demand waned over fire concerns but it has made a comeback with the addition of boric acid fire and pest retardant.
Health Concerns of Old Insulation
As noted above, many older insulations cause health problems. Most old insulation is benign until disturbed. When renovating a house, identify any exposed insulation and deal with it appropriately. Some jurisdictions require professional removal and disposal.
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