Urea-formaldehyde foam insulation (UFFI) has a medium R-value of three or four per inch, according to Conservation Services Group. For thicker insulation, multiply this value by its thickness. The R-value indicates the insulation's ability to resist heat coming through. Check local building codes before purchasing insulation to confirm it meets the requirements.
Carson Dunlop explains UFFI as a combination of formaldehyde, foaming agent and a propellant. It was often used to add insulation into the walls of existing structures. Immediately after mixing, it was sprayed into walls to expand and fill the entire space. The strong odor of formaldehyde during and after installation caused safety concerns. Formaldehyde gas slowly releases from UFFI over time, which happens quicker in higher temperatures and humidity levels.
UFFI was very common in the United States in the 1970s until it was banned from 1982 to 1983 under scrutiny for emitting formaldehyde fumes. However, those testing the problem had trouble finding UFFI homes with high levels of formaldehyde. The ban was lifted when there was no link established between UFFI and health issues. UFFI lost popularity and is no longer a common insulation.
If a homeowner finds UFFI, it is unlikely that it is still emitting formaldehyde. It commonly breaks apart into dust with age, so be careful when handling or removing UFFI.