Insulated, Enclosed, Unventilated Attic Question

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.

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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.


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

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.:slight_smile:

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

Provides an r-factor of around 6-7.


Yes, it is an acceptable practice in Tucson.

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

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.

**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.

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

  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
    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."

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.

My Motto:

“If you can’t dazzle them with brilliance, baffle them with bull****”.


Hey Mark,

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

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.


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.

Joe, I worry about the use of spray foam insulation such as this. I understand the comments about the insulating factor and the attic being treated as living space however I cannot help but wonder…what about condensation. As this is a newer practice I believe that time will tell and it will do so at someones expense.

What if leaks is a great question too, if the foam is closed cell then it should contain any water leaking in allowing the wood to rot before any indications of a problem are visible.

Word it well and CYA!

I am pretty sure it is not closed cell. In fact, it is good at dealing with roof leaks because it doesn’t “hide” them----it just leaks straight through (making finding the leak behind easier) and supposedly is “good-as-new” when it drys out. There is only going to be condensation if there is air movement. Because there is NO air movement with this type of insulation, condensation isn’t “theoretically” possible. It puts the dishes away when it is done too:D :smiley:

My thoughts (okay… “guess” too). As the roof sheathing is insulated, for all intents and purposes there is no attic. Any windows?

See, that’s what I was thinking. It’s not an attic right unless they put the ceiling/flooring in, insulated or not. That space, that would be considered the attic, is not enclosed, therefore does not exist.

The insulation on the roof sheathing is all that is necessary for the entire space.

Does any of that make sense, or did I stay up too late again?:shock: