Insulated, Enclosed, Unventilated Attic Question

[Joe Funderburk, CMI]

House is brand new with a tile roof. The roof sheathing was insulated with foam (which I have never seen). The soffits were completely insulated, and there was no other visible entrance point for ventilation. There was no ventilation at all to the attic that I could see. The ceilings were uninsulated.

Is this acceptable? I thought that attic ventilation was required at a rate of: 1 to 150 sq. ft.

Another question: won't the attic be hot as Hades if it's enclosed? How will the lack of ceiling insulation affect the living space?

And, how will the insulation on the sheathing affect leak detection???

This was my first tile roof structure. Is this the latest in building techniques and something unique to tile roofs?

Photos show insulated roof sheathing, insulated soffits, uninsulated ceiling.

[tdietrich1]

imho:

If the underside of the sheathing is insulated, then the attic has become part of the houses environmental envelope. So you wouldn't ventilate a room, you don't ventilate the attic space.

tom

[Bruce A. King]

That method is more common further north I believe.

I wonder what the r-value is of that expanding foam.

The construction of the tile roof and whatever they used under it and in the valleys should be high end quality on a house like that and leaks won't be a problem. If it leaks, it won't be noticeable until the tile sags about 15 years later?

Here is a link

http://www.buildingscience.com/docum...iew?searchterm=

[Brian E. Kelly]

I have seen fibergalss batts and cellulose sheets installed up next to the sheathing before Joe, but I have never seen the sprayed in foam. Neato.

[Marcel R. Cyr]

Becoming more and more popular up here mostly for inaccessible attics.

Provides an r-factor of around 6-7.

Marcel

http://www.pasprayfoam.com/Pa-Spray-...-ceilings.html

[Mark A. Timpani, CMI]

Yes, it is an acceptable practice in Tucson.

[Harold E. Miller]

http://www.jlconline.com/cgi-local/v...177f0000010565

Article in this months JLC on this subject of unvented attics. Good read.

[staylor5]

I think it provides r-6 or r-7 per inch. so a 2x6 would have about an r-30+. Althought I would imagine that baffles would help ventilation for the sheathing.

[Patrick J. Cloninger]

Joe,

I wish I could give you a good answer but all I can say is that in Knoxville, TN where I am tile roofs are vented the same as asphalt shingle roofs for the most part. I have inspected quite a few and have not seen any like the one you did.

[Joe Funderburk, CMI]

Found this in the '06 IRC:

"R806.4 Conditioned attic assemblies. Unvented conditioned
attic assemblies (spaces between the ceiling joists of the top
story and the roof rafters) are permitted under the following
conditions:
1. No interior vapor retarders are installed on the ceiling
side (attic floor) of the unvented attic assembly.

2. An air-impermeable insulation is applied in direct contact
to the underside/interior of the structural roof deck.
“Air-impermeable” shall be defined by ASTM E 283.
Exception: In Zones 2B and 3B, insulation is not
required to be air impermeable.

3. In the warm humid locations as defined in Section
N1101.2.1:
3.1. For asphalt roofing shingles: A 1-perm (5.7 ×
10-11 kg/s ⋅ m2 ⋅ Pa) or less vapor retarder (determined
using Procedure B of ASTM E 96) is
placed to the exterior of the structural roof deck;
that is, just above the roof structural sheathing.
3.2. For wood shingles and shakes: a minimum continuous
1/4-inch (6 mm) vented air space separates
the shingles/shakes and the roofing felt
placed over the structural sheathing.

4. In Zones 3 through 8 as defined in Section N1101.2, sufficient
insulation is installed to maintain the monthly
average temperature of the condensing surface above
45°F (7°C). The condensing surface is defined as either
the structural roof deck or the interior surface of an
air-impermeable insulation applied in direct contact with
the underside/interior of the structural roof deck.
“Air-impermeable” is quantitatively defined by ASTM
E 283. For calculation purposes, an interior temperature
of 68°F (20°C) is assumed. The exterior temperature is
assumed to be the monthly average outside temperature."

[Joe Funderburk, CMI]

Said this in my report: "The attic is called a "conditioned attic assembly". It is designed to be unvented. Air-impermeable foam insulation is applied in direct contact to the underside/interior of the structural roof deck approximately 6 inches thick. There is no ceiling insulation, in accordance with this construction technique. We cannot determine the R-value of conditioned attics and recommend that you consult with the builder or an insulation specialist to ascertain the efficiency rating."

My wife wonders why I spend so much time on the computer. Every time you think you know something, you run into something weird.

[tdietrich1]

My Motto:

"If you can't dazzle them with brilliance, baffle them with bull****".

[whandley]

Originally Posted by mtimpani

Yes, it is an acceptable practice in Tucson.

Hey Mark,

With your average summer temperature around 140-150F don't you need more than an R6 - R7 value?

[Brian T. Stevens]

That type of insulation is becoming more common here in Michigan where vaulted ceilings are being built. Venting is achieved by installing the chutes to the underside of the sheeting from soffit to peak and then the foam is sprayed in top of the chutes and the ceiling finnish material applied on top of that after it has cured. Tile roofs arn't that common here so I can't comment on how it might be vented however it may be vented in the same manner where you wouldn't see it from the interior of the attic.

Just what I know here.

Brian

[wforsyth]

That's the spray foam insulation I was talking about in the post about the copper pipe that looks like it has asbestos coating it. Same thing as here, or looks like it.