Green Building Library
Weatherization Tips

How to Baffle Heat Producing Fixtures in Dropped Ceilings

  • Some electrical devices located in attics, generate lots of heat when operating. If you pile insulation on top of a heat producing fixture (HPF), it could get hot enough to start a fire. Before blowing insulation into an attic, place baffles around all HPFs.
  • Recessed lights and ventilations fans are often mounted in ceilings and soffits that drop below the level of the main ceiling. this is common in kitchens and bathrooms. Three methods to baffle these fixtures are shown below.

Baffles

Baffles should be made from a solid, flame resistant material. Wide metal flashing makes a great baffle (except for use around wiring). It's easy to bend, can be fastened with staples and cuts easily with a utility knife. In some areas, fiberglass insulation batts can be used for baffles. Treated cardboard, sometimes used to baffle attic vents, is not acceptable for baffling HPFs. Baffles must be firmly attached to something in the ceiling structure, such as the ceiling joists, rafers or roof sheathing.

 

Clearance Between HPFs and Insulation

Baffles prevent overheating by maintaining the proper clearance between the fixture and the insulation. The "Three, Four, Twenty-four Rule" is an easy way to remember the proper clearance for HPFs in dropped soffits. Try not to baffle too large an area, because the additional uninsulated area will increase heat loss.

Clearance of HPF

3"

At least 3 in.—but not more than 4 in.—clearance between the HPF and the baffle.

4"

Baffles should have an open top that extends 4 in. above the final level of insulation. This makes it easier to keep insulation from falling into the baffle.

24"

The top of the baffle may be closed and covered with insulation, if there's 24 in. between the top of the fixture and the baffle.

 

Deep Soffits

If the distance between the top of the HPF and the top of the soffit is at least 24 in., you can place a flat cover over the top of the soffit. The cover material can be flashing, gypsum board (drywall) or plywood.

 

Shallow Soffits

If the soffit is shallower, you must baffle the HPF.

For accessible areas, place the baffle down into the soffit. The baffle should be tall enough to stand 4 in. above the finished level of the insulation.

 

Inaccessible Areas

For inaccessible areas, install the baffle at the top of the soffit so the baffle's top is 4 in. above the finished level of the insulation.

Tools

  • utility knife
  • hammer stapler
  • gloves

 

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© Copyright 1993 Iris Communications, Inc.

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Tubular Foam

Deep Soffits

Fiberglass

Shallow Soffits

Inaccessible Areas