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ASK THE INSPECTOR: Stop air leakage into attic from pot lights

QUESTION: We read your column in the Free Press and would like some information about attic insulation. We had an energy evaluation done last fall and the inspector found there was air leakage in the kitchen pot lights that extend up into the attic. He said there were cone-shaped covers available to seal them off so no air would be drawn up into the attic.

Could you please advise me where to get them and also how to install them so they don't overheat? I appreciate any information you can give me.

-- Ed St. Laurent

ANSWER: Air leakage into attics around ceiling pot lights, especially in older homes, is a common problem that can cause significant condensation and leakage. There may be several ways of providing a relatively safe way of covering and insulating these lights, but there are some concerns with any retrofit of this type. Some of these methods will be discussed, but the true repair may require replacement of the entire light fixtures.

Air-sealing any component that extends through a portion of the "building envelope" can be tricky, but especially pot lights, due to the large amount of heat these units produce. This heat not only can cause an issue with warming the air above the light in the attic, causing condensation, but it can also be a safety hazard.

Some types of insulation and wood framing in attics are combustible and may come into contact with an older pot-light housing protruding through the ceiling. These lights can produce a sufficient amount of heat to create a fire hazard from the hot metal housing surrounding the light. Care must be taken to prevent any combustible material from sitting direct against this housing, which includes polyethylene sheathing and possibly the cone-shaped covers that your energy evaluator recommended.

One way to prevent this fire hazard from occurring is to install a small box around the light housing out of non-combustible material. While drywall is sometimes used for this purpose, I would not recommend it due to its tendency to fall apart when it becomes damp. This could happen in an attic environment unless an excellent air/vapour barrier is installed under sufficient insulation.

Still, the heat that may accumulate in this box could still cause deterioration. A better solution may be a plywood or OSB box lined with non-combustible material such as metal sheathing or other insulation materials with an aluminum skin. This would provide a good moisture-resistant material that can be easily covered with an air/vapour barrier and insulation and would provide protection from the heat of the light.

Care should be taken to build the non-combustible box large enough to provide sufficient air space around the light housing to prevent overheating of the box. A gap of several centimetres between the box and the housing in all directions is ideal. This box should be installed so it does not touch the housing or the metal light fixture at all, and should be sealed to the drywall or plaster ceiling to prevent movement. Once in place, the box needs to be air-sealed and insulated.

Several methods are available for this job, depending on existing insulation in the attic and access to the area above. The most conventional method for insulation of a light box in an attic is to cover it with six-millimetre polyethylene sheathing, which should be sealed to the other air/vapour barrier underneath the existing insulation with acoustical sealant or other caulking. Once sealed and in place, it could be covered with insulation similar to that already in your attic. This insulation could be blown-in fibreglass, mineral fibre, cellulose or batts of fibreglass. Adding more of the existing material may provide adequate protection from heat loss, but better alternatives are available.

One possibility is to encase the new box with rigid polystyrene insulation. This may be a good choice due to the ability to cut this rigid material to exactly the same dimensions as the light protection box. Gluing this material directly to the plywood sheathing on the exterior of the box will prevent it from moving, and overlapping the seams with a second layer of rigid foam will prevent any voids. Once installed, this material can be covered with polyethylene sheathing, or it may only need to be caulked to the existing poly if high-density expanded polystyrene is used, which may have a sufficient air/vapour barrier rating alone.

The final option for insulating and air-sealing the new light-box cover is the easiest, but may be the least cost-effective. Covering the light boxes with blown polyurethane foam will provide the best seal and a high insulation value with minimal thickness. This can be accomplished with a few small canisters commonly available at the local building centre if there are only a couple of lights, but will be too costly if there are several lights. In that case, hiring a professional foam-insulation contractor to insulate and seal these lights will be required.

Unfortunately, it may be difficult to access the area above your pot lights if they are near the eaves or if you have sloped ceilings. Also, working in attics can be a difficult process. If you have had little trouble with your lights and no evidence of condensation, you will have to decide if the cost and effort required to seal these lights will be equal to the gain from the lack of air leakage in this area.

Finally, newer pot lights are made with specifically designed boxes already installed, for use in insulated ceilings. Installation of these units, with lower-temperature compact fluorescent bulbs, may be the best solution of all.

Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the president of the Canadian Association of Home & Property Inspectors -- Manitoba (www.cahpi.mb.ca). Questions can be emailed to the address below. Ari can be reached at (204) 291-5358 or check out his website at www.trainedeye.ca

trainedeye@iname.com