Attic stairs

Insulating and air sealing the attic is of utmost importance here in the south. R-38 insulation is recommended in both flat and vaulted ceilings, but it won’t do much for the air infiltration/exfiltration that takes place between your attic and your living space. Blown cellulose does air seal slightly because of its weight, but it will not truly define the thermal envelope of your home. Top plates of walls, knee walls and HVAC penetrations are big culprits for energy loss, but one overlooked energy drain is the attic access. The photo below is of an uninsulated attic access taken with an infrared camera.

Many older homes here have a small (24”X24”) attic hatch that is often hidden away in a closet. These are relatively easy to deal with by weather stripping and gluing batt insulation to the attic side of the panel. If they are too light to fully compress the weather strip, adding another layer of drywall or plywood to the back side will help. The large pull down stair cases or “disappearing stairs” as architects like to call them can be tougher to deal with, but when properly sealed will make a tremendous difference.

Most builders or insulation companies will simply place an R-13 batt between the stairs and the cover panel. This makes little sense when you have an R-38 attic, but it is common. There are several commercial options available to seal and insulate the access that work very well, but some are rather expensive. An attic tent is good for providing an air tight seal, but has little R value. There are foam options that both air seal and insulate, but you want to be sure that what you install is tall enough on the attic side to hold back 13 inches of blown insulation (an insulation dam). If you are the least bit handy, building an attic “coffin” is the cheapest and easiest approach. One sheet of cheap plywood or OSB will do the job and you will find that it is much more rigid than the commercial options.

The coffin is a simple 5 sided box with a lift off lid. The weight of the top is heavy enough to compress the weather stripping and give a good seal. Be sure to make the sides of the box tall enough for the stairs to fold up in! This may sound like common sense, but it was my first mistake. Once you have sealed the attic hatch you can proceed with air sealing and insulating the remainder of the attic.