HELP - insulating a Florida addition
R. A. Glidewell
air-conditioned, addition in Florida.
It is one large (34x36) space, spanned by attic trusses, and divided by
partitions into three rooms.
The attic trusses form a 12-wide storage room on the 5' tall "second
floor." I do not plan to air-condition this storage area, but would liek
to keep it from getting too hot. The roof is asphalt shingle with GAF
Cobra ridge vent running its full length.
The walls will get the standard (for Florida concrete-block
construction) 1" reflective foam board behind the drywall. But where
should the rest of the insulation go?
If it would work, I would like to use those foam channels to direct air
from the eaves, up under the roof , and out the ridge vent, and have
insulation only under those channels, i.e. insulating the underside of
the roof. The "attic area would then be an un-air-conditioned area
between the first floor drywall ceiling and the roof insulation. This
might keep the attic room from getting too hot. But would it make the
first floor hard to air-condition?
The other alternative I can see would be to insulate the ceiling of the
first floor and also the walls and ceiling of the attic storage room -
otherwise the attic would get very hot.
Any thoughts are appreciated.
Richard Glidewell
thunder
<r...@glidewell.net> wrote:
Unless you want to be cooling your attic, your insulation wants to
be in the ceiling. There are other ways to cool you attic.
Radient barriers and ventilation work effectively. You may want to
look at the following link.
http://www.ci.austin.tx.us/greenbuilder/glfs_radiantbarrier.htm
Erik Deckers
> I do not plan to air-condition this storage area, but would liek
> to keep it from getting too hot. The roof is asphalt shingle with GAF
> Cobra ridge vent running its full length.
That's going to be part of your problem there: using dark shingles in a hot
climate. You'll be fighting that problem until the end of time, unless you
put reflective insulation or radiant barrier under the roof. Just staple it
to the bottom of the rafters (leave 3 - 6" gaps at the top and bottom for
air circulation) to accomplish that.
> The walls will get the standard (for Florida concrete-block
> construction) 1" reflective foam board behind the drywall. But where
> should the rest of the insulation go?
The foil on the foam board should point outside, and there should be a 1"
air gap between the foil and the exterior sheathing. If you can't do that,
turn the foam around so the foil is pointing toward the inside, and have an
air gap between the foil and the rest of the insulation.
You can actually skip the reflective foam board and use the same reflective
insulation I mentioned above, and then use your regular insulation. Again,
just install it so there is a 1" air gap between the foil and the exterior
sheathing for the best results.
> If it would work, I would like to use those foam channels to direct air
> from the eaves, up under the roof , and out the ridge vent, and have
> insulation only under those channels, i.e. insulating the underside of
> the roof. The "attic area would then be an un-air-conditioned area
> between the first floor drywall ceiling and the roof insulation. This
> might keep the attic room from getting too hot. But would it make the
> first floor hard to air-condition?
Using the reflective insulation on the bottom of the rafters will serve as
the air channel. If you don't want to put it on the bottom of your rafters,
you can actually install it BETWEEN the rafters. This will still accomplish
the same thing as the foam channels. However, doing it this way will solve
two problems: 1) Reducing incoming heat; 2) Spending money on the channels.
If you don't stop the incoming heat, it will be harder to cool the first
floor than if you did stop it. Use reflective insulation on the attic walls
to help reduce heat too. By doing this, your first floor will be MUCH
easier and cheaper to cool.
Erik Deckers
WE International, Inc.
both...@nospam.we-intl.com