The kitchen of my house has a cathedral ceiling. The room is cold in the
winter and hot in the summer. The house was built in the late 70s and I'm
reasonably certain, there is little if any insulation between the ceiling
sheet rock and the roof. I can't get into the area between the ceiling and
roof to inspect. Any frost or light snow on the kitchen roof melts quickly
whereas all the other areas of the house with a flat ceiling and 13 inches
of cellulose above, do not. I would like to insulate the ceiling from the
inside and then install either a suspended ceiling about 8 foot from the
floor. I'm looking for suggestions.
John, a flat ceiling is fine. You can install a drywall suspended
grid, this is the same type system as a commercial drop ceiling
with slightly wider faces made to screw drywall to. You would
need to do the insulating before installing the gyp. You might
want to consider a more decorative approach as long as you have
the cathedral height. Look through this Trim Tex site for some
especially the drywall art section:
look for the gallery section and the videos
Keep the whole world singing . . . .
You can insulate the ceiling and then any which way "drop" a ceiling.
One of the important factors in this consideration would be to provide
adequate ventitlation between the roof deck and insulation as to allow moist
air out. This would include any of these: metal roof vent, "cora ridge"
vent, gable end vent, and also some "bird hole vents" and or strip venting
to provide a flow in at the lower rake of the roof. Descriptions of these
are readily available by searching roof ventilation.
I think a cathedral ceiling is a nice feature and I would hate to give that
up. I would explore other possibilities such as removing the existing
drywall to install better insulation and maintain air flow or at the very
least look into blown-in insulation. After that I would install an
additional layer of drywall with a radiant foil in between drywall layers.
I would also install a suspended paddle fan to keep heat from accumulating
up there. Perhaps for the summer a small exhaust fan at the peak would help
with the heat load or locate an A/C return vent up high.
On Sun, 7 Dec 2008 12:01:58 -0500, "John Grabowski"
This is a very good point. My garage building (steel, fully
insulated) can be 80 degrees at the peak, and 55 at the floor. It
really amazed me as to how much heat was trapped above head level.
In my case we installed ceiling fans to move the heat from the high
peak into the working area. Major difference, totally changed the wayt
we heat the building.
Radiant foil between two layers of drywall is useless. In order for
foil to be a radiant barrier, it must face an air space (and not face
up, where dust would accumulate against it). If you have no air
space, then the heat will simply conduct through the radiant barrier,
it won't be a barrier at all.
Do you have any ceiling light fixtures in the kitchen? If so, you could
turn off the power and remove the light fixture. This should let you see
around the electrical box to see if there is insulation behind the
You may also be able to measure up next to the electrical box to see how
deep the rafters are. Standard R30 fiberglass insulation would need at
least 2x12 joists (11-1/4" deep), though foam insulation may not need as
This doesn't offer any "solution" to the problem, but at least you would
know what is currently there.
Cathedral ceilings are nice, to keep it restud over drywall on the
studs then use foamboard, Polyisocyanutate Dow foilfaced is R 7.2 per
inch with radiant barrier, its the highest R value insulation you can
get. with 2x4 you will ger R 25.2, but thats not enough,2x6 will get
you R 39.6, Finish anyway you want I use T&G pine planking
I agree with this approach, with a slight variation and added details.
1 - if you have recessed lights in that ceiling, rip them out and seal
up the holes. Recessed lights in cathedral ceilings should be illegal.
They're a huge energy waster and worse, they are responsible for more
moisture entry into the cavity than any amount of permeability of the
ceiling material. If you do that, and close up any other holes in the
ceiling, moisture will not be an issue in there.
2 - for optimal insulation, fill the cavities with dense packed
cellulose. Forget what they're saying about ventilating under the roof
deck. If you seal the holes, you don't need to worry about that. The
only place moisture will get in the ceiling cavity during the winter
is from indoors. You'll have less ice damming and better insulation
all around if you just forget about it and seal up the cavity. For a
typical 2x8 rafter, you'll get about R-25 insulation from the dense
3 - Affix the foil faced polyiso board directly to the existing
ceiling, 2" thick, taped at the seams Then, attach nailers over that,
perpendicular to the original rafters. This will give you a high
quality thermal break to minimize thermal bridging through the 2x4's.
The foil faced polyiso board is also a complete vapor retarder, so
this further ensures no moisture will get in the cavity. This will add
R-15, bringing you up to R-40.
4 - If you want to go the extra mile, fill in the space between the
2x4's with another 1 1/2 of polyiso board, giving you another ~R10.
Stagger the seams with the layer below, which again reduces any chance
of moisture getting through the layers. Add sheetrock below, attached
to the 2x4's.
If you're afraid of filling the primary cavity because of the
ventilation propaganda, leave it as is, but do the rest of the steps.
But now you're going to want a total of 6+ inches of polyiso board in
order to get sufficient insulation. This will be much more of a pain
Keep in mind that sheetrock is pretty cheap and easy to work with (for
a pro), so don't be afraid to rip it out to get at the underside of
the roof deck above. Another option besides the above one is to rip
the ceiling out, then spray high density polyurethane directly to the
roof deck above. Fill the cavities and seal up all the way down to the
soffits. This will provide a complete vapor barrier and excellent
insulation. No ventilation required or desired. when you're all done,
this solution may be less expensive than the previous ones because
it's just a couple steps - rip out ceiling, spray foam, replace
For more details on roofs, venting, etc., consult:
You'll hear a lot of arguments about venting. Venting is needed when a
structure is poorly built and it needs venting to remove the moisture
carried by the warm, humid interior air leaking into the cavity. This
warm air then cools, and when it does, the moisture condenses and rots
out the roof. If you seal up the ceiling so that moisture can't get in
there, the problem goes away. During the winter, when moisture is the
big issue, the moisture must come from the inside. The outside air
during the winter contains very little water, and will tend to
dessicate the roof assembly rather than add to the moisture.
During the summer, people will argue that venting is required to cool
the roof. But the amount of cooling provided by venting in the normal
fashion is vastly too small to actually be useful. Even a properly
vented roof, with continuous strip vents at the soffits and large
ridge vent provides minimal cooling, so that argument is bogus as
well. The worst are the nominal vents that most people add - those
2"-3" holes drilled in the soffits and filled with "vents". The free
area (amount of space open to allow air flow) is so tiny as to be
totally worthless. Worse, during the winter, south facing walls heat
up and the warm air from the walls will travel up and into the soffit
vents. This then warms the roof, melting the snow and leads to ice
dams. Current building practices are a series of band aids applied to
fix other problems. If it were done right in the first place, with
proper consideration for the physics involved, these problems would go
A short addition to my previous long posting:
An example of dense packed cellulose being used in a cathedral
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.