We have a finished attic. Typical kind, I think, side walls slope down to
about 3-4 feet from the floor, then become vertical.
Behind the vertical part of the walls is storage space. There is a door on
each wall giving access to that space. The walls have fiberglass insulation
on them, but the doors don't.
Since the door feel noticably warmer than the walls on a hot day, I'd like
to put some insulation on the door. Any suggestions on how I might attach
First, you need to define what is the insulated envelope of the attic.
In your case, it sounds like the insulated envelope runs down the
sloped roof to the knee walls (that's what the 3-4 foot high walls are
called), and then would need to run under the floor of the storage
area. The idea is that you have a unbroken surface of insulation across
the entire roof. In your case, as you have identified, you need
insulation in the doors to the storage area. Also, if you are *really*
doing it right, you should have weatherstripping on the doors,
insulation under the floor in the storage areas, and technically, you
should ventilate the storage area and essentially make it be part of
the outside. Assuming you have eave vents, they should open up into
this storage area and then have a path above the sloped roof insulation
all the way to a ridge vent. This is admittedly a lot of work to
accomplish all of this.
An alternate way is to make the insulated envelope be the entire
underside of the roof deck. Continue to run the insulation down the
sloped part of the roof in the storage areas. In addition to keeping
the heat from getting through the door to the storage area, it will
also keep the storage area itself more comfortable, if that matters to
you, such as if you have items stored there that are sensitive to heat
or cold. But the tradeoff to this is that you are also paying to
heat/cool that storage area, which may not make any sense to if all you
are storing there is the Christmas decorations that you get out once a
year. Also a lot of work to do this.
Of course, just putting some rigid insulation panels on the back of the
door with take about 15 minutes, not counting the trip to the hardware
store, and will cost you about 10 bucks, and may be adequate. Make
sure you use panels that are fire rated, which I think are the foil
backed panels. Plain pink or blue rigid insulation must be covered by
a fire rated covering such as drywall.
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