When installing insulation with a vapor retarder, how many square feet of vent opening are needed per vent?

When installing insulation with a vapor retarder, it is essential to ensure proper ventilation to prevent moisture buildup in the attic or other enclosed spaces. The general guideline is to provide adequate vent openings to allow for a sufficient exchange of air.

The standard requirement is one square foot of vent opening for every 300 square feet of insulated ceiling area. This means that for every 300 square feet of insulation that contains a vapor retarder, at least one square foot of vent opening is needed. This ventilation helps to maintain an effective air barrier and prevents moisture accumulation, which can lead to mold growth and wood rot.

Thus, the correct response reflects this widely accepted practice within the building and insulation industry, ensuring that homes are both energy efficient and protected from potential damage due to humidity and moisture. The other options do not align with the accepted ratio, which is why they are not suitable for this requirement.