Dropped ceilings & sealing

If your home has a dropped ceiling (soffit) inspect it for possible air leaks. Dropped ceilings are a common cause of energy inefficiency and air leakage.

They often involve hidden air cavities where the air travels till the kitchen or other rooms, causing higher air leakage than other more visible sources. Solving problems with dropped ceilings provide very important energy savings.

The air infiltration

Wind pressure may easily cause air to travel through eave vents into the air cavities associated to dropped ceilings and from there to the kitchen or other rooms. Common insulation will not stop air penetration: cellulose, fiberglass and other fibrous insulation boards aren’t air barriers and will not prevent air leakage...

Recessed light fixtures or other weak elements in the dropped ceiling are also part of the air leakage chain. That's why sealing the soffit is so important...

What's behind the insulation

Ceiling Dropped Ceiling according to EERE

The image on left (from US DOE) shows the layers and steps associated to the insulation and sealing of the dropped ceiling: 1) the air barrier application, 2) the insulation layer over the air barrier and 3) the caulking of gaps and edges...

Image: EERE/DOE

Applying air barriers (and insulation)

Insulation per se doesn't solve possible air leakage sources in dropped ceilings. That's the air barrier's (plywood, drywall...) function.

So, when assessing your situation, put aside your attic insulation to see if an air barrier exists over the dropped ceiling.

And if doesn't, the solution is to cover the whole area with a proper air barrier: usually a piece of rigid foam polyurethane or other foam board, or a sheet good (plywood, drywall...) or reflective foil insulation (in moderate and hot climates).

Glue the air barrier in place, carefully, and cover it again with the insulation layer (that's also the ideal time to reassess or to add new insulation to the attic).

Sealing dropped ceiling gaps

All edges - involving the dropped ceiling and the air barrier and the insulation - should be carefully caulked. Any gap should be caulked.

Use a good foam or a polyurethane or silicone based caulk. Possible recessed light fixtures should also be conveniently caulked. See: Caulking Electric