What was Urea-formaldehyde foam insulation known for before being banned?

Urea-formaldehyde foam insulation was commonly used in homes for insulation due to its effective thermal properties and its ability to fill gaps and voids in construction. It provided good insulation against heat transfer, which made it a popular choice during its peak use. Homebuilders and homeowners appreciated its advantages for temperature regulation within homes, and it was extensively utilized in residential construction.

However, this insulation became controversial and was ultimately banned due to health concerns linked to the formaldehyde gas it emits. Despite its effectiveness for insulation, the drawbacks, particularly the potential for releasing harmful volatile organic compounds, overshadowed its benefits. This context is crucial in understanding why option B is the correct answer, emphasizing the prevalence of urea-formaldehyde foam insulation before the recognition of its adverse effects.