In a typical multifamily building, which area would you air seal first?

In a typical multifamily building, which area would you air seal first?

• A. Roof
• B. Top of the building
• C. Exterior walls
• D. Basement

Answer: (B)

Air sealing from the top down is most effective because warm indoor air rises and tends to escape through gaps in the attic/ceiling area. Sealing the top of the building blocks the main pathway for heat loss and drafts, preventing conditioned air from leaking into the attic and then outside. This reduces overall energy loss and moisture migration, and it makes the remaining leakage paths, such as those in exterior walls or the basement, easier to address later. So, sealing the top first stops the largest leakage route and sets up a tighter envelope for the rest of the work.

Air sealing from the top down is most effective because warm indoor air rises and tends to escape through gaps in the attic/ceiling area. Sealing the top of the building blocks the main pathway for heat loss and drafts, preventing conditioned air from leaking into the attic and then outside. This reduces overall energy loss and moisture migration, and it makes the remaining leakage paths, such as those in exterior walls or the basement, easier to address later. So, sealing the top first stops the largest leakage route and sets up a tighter envelope for the rest of the work.