Remodel Attic Venting Question

[Bob Ozbirn]

This is a remodel in progress. The question is should the old roof be vented into the new attic space (holes cut in the old sheathing) or will the dead air space actually add more insulation value in the living space? The new roof is vented with soffit and ridge vents. The ceiling cavity below the old roof is insulated with R30 Batting.

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[Rick Cantrell]

Both attic spaces should/would normally be vented.
Old attic into new attic (or outside), new attic to outside.

[John Kogel]

I would not worry about venting, but I would like access for inspection.

I wish people would think to strip the shingles off before they build over old roofs like that.

[Brandon Whitmore]

Warm, moist air exiting living space may become trapped inside the original attic area if it's not vented- both attic spaces should be vented in my opinion.

[Jerry Peck]

It is as much of a fire fighting issue as anything. The firemen cannot cut a hole in the roof to gain access/venting of the attic of the original roof. Any fire within the original attic is not accessable to the firemen from the outside of the structure. I cannot recall how much of the original decking should be removed for this reason.

James,

That is correct. It for firefighters.

The original attic should have the minimum required access opening size, and since the new attic has more than 30" headroom in it, it too requires an attic access opening which meets minimum size.

- ATTIC ACCESS
- - R807.1 Attic access. Buildings with combustible ceiling or roof construction shall have an attic access opening to attic areas that exceed 30 square feet (2.8 m2) and have a vertical height of 30 inches (762 mm) or more.
- - The rough-framed opening shall not be less than 22 inches by 30 inches (559 mm by 762 mm) and shall be located in a hallway or other readily accessible location. A 30-inch (762 mm) minimum unobstructed headroom in the attic space shall be provided at some point above the access opening. See Section M1305.1.3 for access requirements where mechanical equipment is located in attics.

Now, regarding venting, the venting of the new attic space needs to meet the requirements of attic ventilation. I suspect that the original vents in the original roof are no longer serving any purpose, as such the new overhangs will need to provide the required soffit ventilation along with higher vent opening too - all of which is spelled out in the code.

[Bob Ozbirn]

Thanks guys, very useful information. I felt like the old attic should be opened up to allow air flow but the firefighter scenario had not occurred to me. Thanks for the advice.

Bob

[James Duffin]

How is the original roof/attic vented? If it was adequate and still functional then nothing has really changes as far as the first roof/attic is concerned.

[John Kogel]

How is the original roof/attic vented? If it was adequate and still functional then nothing has really changes as far as the first roof/attic is concerned.

The old roof sheathing is no longer a cool surface, so condensation is not a concern. If warm air leaks up from below, it will just dissipate slowly, not a problem.

A house I inspected on Monday had two attic hatches, the original into the old space and a new one into the addition.
It is typical to see at least one opening cut in the deck of the old roof, so that tradespeople can make the plumbing and cable connections. This house had such a small hole, I had to go up through both hatches to see the whole space.

[Jerry Peck]

Thanks guys, very useful information. I felt like the old attic should be opened up to allow air flow but the firefighter scenario had not occurred to me. Thanks for the advice.

Bob

Bob,

I will point out the obvious, but the code requirements for attic access openings and sizes still stand: If there is a fire ... the firefighters are not going to look around for the attic access, remove the access cover, and try and fit their ladder up into the access opening - nope ... they are going to use their fire axe and make their opening wherever they can easily and quickly get a view of the attic, and they will make the opening as large as they need, and as many as they need ... nonetheless, though, there is the code requirement for the attic access opening and it is for fire fighter access.

There is also a secondary reason for the attic access and it comes with a larger opening size (sometimes): when there is mechanical equipment in the attic (furnace, a/c, water heater, etc.) then the opening is required to be at least the minimum size, its location in relation to the equipment may be affected, and the opening is also required to be large enough for removal and replacement of the largest equipment in the attic (and not taking it out in pieces either, the whole thing, with the opening large enough for that).

Just wanted to cover all the bases.

I'm curious, why did you add such a high attic (steeply sloped roof)?

I'm not sure those purlin supports are going to do very well on the old roof like you have them.

[Bob Ozbirn]

Jerry,

It's not my house. I'm doing stage inspections for the owner. I spoke with the contractor today about the need for openings for firefighters and tradesmen into the various attic spaces. There are a number of issues including structural support issues. There is no equipment in either of the attic spaces and access hatches into the original attic space are still in place but no access from one to the other and that will be corrected.

Bob

[Larry Morrison]

I would say that the old roof needs vented to the new attic space.

The old roof is going to act like a vapor barrier above the insulation.

You say the insulation installed below is R-30 batt. Lots of moisture (and air) can come through and around batt insulation. I would say there is a very good possibility that there will be a lot of condensation forming on the cold underside of the old deck if not adequately ventilated. this is very similar to putting kraft face batts over existing insulation. a big no-no.

[Jerry McCarthy]

I would be a lot happier if I knew all those roof supports where landing on bearing walls? Not tearing the old roof off to make proper engineered connections is a big red flag to me. Also, why such a high roof profile?

Jerry

[Michael Avis]

I think others have handled the OP venting question thoroughly.

I wonder other things. Why are the kneewalls angled instead of plumb. This puts tremendous shear forces on the fasteners onto the plates on the original roof.

I see no straps or engineered connectors anywhere.

The collar ties at the top are completely ineffective structurally (they should be in the bottom 1/3 of the vertical span.

I too would like to know what those posts are bearing on.

Hope this isn't annoying, raising questions you may have already identified... As an old time framer I can't help it. I see these structural questions as just as, if not more important than the original venting topic.

[James Duffin]

I think others have handled the OP venting question thoroughly.

I wonder other things. Why are the kneewalls angled instead of plumb. This puts tremendous shear forces on the fasteners onto the plates on the original roof.

I see no straps or engineered connectors anywhere.

The collar ties at the top are completely ineffective structurally (they should be in the bottom 1/3 of the vertical span.

I too would like to know what those posts are bearing on.

Hope this isn't annoying, raising questions you may have already identified... As an old time framer I can't help it. I see these structural questions as just as, if not more important than the original venting topic.

It does look kinda rickety doesn't it!

[Rod Butler]

Cool roof addition but enough with the technical stuff. Why didn't they plan for a pool table up there?