Insulation conundrum in knee wall area

[monarda]

Had insulation work done on a  house a couple of years ago. Not satisfied with the work that contractor did. Ice dams and water leakage in the house. (This was a REALLY bad winter, but I think some might have been made worse by what they did.) Got an insurance claim for $2500 to cover interior damage. Talked to a lawyer, who said the dollar amount wouldn't be worth going after the first contractor, unless the cost to correct the problem was close to 10K. We are talking to insulators and roofers to figure out what to do.

The situation- a knee wall space can either be made into a conditioned space or a cold space. Currently it's a cold space. In order to make it into a cold space, cold air needs to be let in. Right now, that's through a vent through the roof shingles (see photo), that three different roofers said are not appropriate for this snowy climate. They work great in the summer, they said. So we need a different way to let cold air in. Through the siding? Asbestos shingles, but just one small hole could be cut with care. (probably needs to be done by us?)

Or we need to make it a conditioned space. If we'd do that, we need to apply several inches of spray foam to the underside of the roof deck.

We keep talking to contractors. We have yet to find contractors to agree on a plan. It's about 50-50 cold vs conditioned.

So I'm looking for more input.

We want minimal cost. We are trying to sell this house this spring. And do the right thing so the new owners don't have trouble.

[Fishindude]

Assume you are talking about a triangular shaped unoccupied attic space.   I see no point in insulating and heating an unused space, find a way to vent it.
Looks like it has a roof overhang & soffit.   Can you get some ventilation in thru the soffit?

[monarda]

The soffit was sealed off by the first contractors with spray foam. That's part of the problem.
That's why we were thinking about some kind of vent through the siding.

[bacchi]

Get a long drill bit and drill through the foam and soffits?

A vent/hole in the siding sounds like a really bad idea.

[Papa bear]

Soffits are usually where you bring in that air.  Drill holes through that or cut out rectangular openings and put on something to keep out critters.


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[TexasRunner]

That roof vent is a terrible design if you are in a snow area.  Exactly when you NEED the ventilation is when the vent will be blocked with snow.  I agree with the idea of drilling (Like, 1.5" holes every 3" with vent covers-  every 3 feet or so) and leaving the roof vent in place.

The other (easier) option is to tear out the knee wall and let the room run to the edge, and add spray foam as needed.  That fixes all the issues, and id you really want to ahve the knee wall inside, its much easier to add vents in the interior wall than in the soffit.

[robartsd]

In a snowy area, you really want the entire underside of the roof deck to be a cold space. This prevents heat from the inside melting snow on the roof that runs down to a cold space and freezes causing ice dams. Where did the ice dams form?

If the upper part of the roof is insulated on the underside to provide a conditioned space, I'd seriously consider making all of the underside of the roof a conditioned space and adding a heating system at the edge to prevent ice dams. Otherwise, you're likely to develop ice dams right over the wall where the roof transitions from conditioned space above to unconditioned space below.

If the entire underside of the roof is designed as cold space, I'd do what is needed to fix the venting so the cold space remains cold in winter. Drilling through the soffit and insulation sounds like a reasonable way to accomplish this to me.

[BudgetSlasher]

I would strongly argue for a cold (vented) roof. Snow is an insulator and no matter how much insulation is in your house, some will leak out. When it leaks out the snow act as an insulator and with the right conditions the shingles will be above melting point and some ice will melt run down the roof and encounter the portion of the roof above the eve/soffit which will be below freezing. An ice dam will form and then it is just a matter of time for the water to find its way inside.

My vote would be for removing the current vent that is part of the shingles by patching in some new shingles (though that might look strange when it comes time to sell) and cutting in some eve vents through.

However (and this is a BIG however) all of what I have just said requires that the air flow from the soffit/eve along the bottom of the roof deck (plywood) and out a ridge vent (or other venting system higher up). If you had a horrible contractor (which you seem to indicate) who spray foamed straight to the underside of the plywood there will be no air circulation under the roof. If there is no circulation you will eventually encounter the circumstances I described in the first paragraph, because the escaping heat will not be carried away by the flowing cold air outside of the insulation. Your vents under the shingles give easy entrance once the ice dam has formed over the cold even and the water starts to back-up.

If that is the case, I could brainstorm 3 ideas: 1)do what robartsd said (make it all conditioned and do heating wire over the cold eve), 2) dig out all of the insulation, restore air flow between upper and lower vents, and re-insulate properly, or 3) install a new cold roof over the existing roof deck. Perhaps others have more ideas if this is the case.

[monarda]

Lots of good ideas here. The roof is being replaced next week. (I didn't mention that, did I.... Sorry.)
For sure we're going to get rid of those vents under the shingles. But we need to decide a plan of action real soon.

But after that, I can see maybe boring holes with PVC pipe through the foam down to the soffit. Maybe PVC pipe can be pushed through if I sharpen the cut edge? And 2 ft lengths of pipe can be the vents? Seems like a mouse highway.

Or, if the roofer removes and replaces the roof deck in that area, we could more easily vent it then? He probably won't unless it's pretty rotted. But I should ask him how he's going to fill the cutout part of the roof deck where the shingle-vent is.

The problem is, we live 3 hours away from this house. And we don't have trusted contractors in that city.

Our trusted insulator here where we live cast his vote -  he said make it a hot roof with 5" spray foam and get rid of all the vents.

Tearing out the knee wall is not an option.

[Papa bear]

What is the rest of the attic space insulated with? Are the rafters insulated and drywalled?  Did they spray foam that or use baffles and fiberglass?  Basically, do you have a cold roof above that section or not?

Usually, when you’re redoing the roof, you would end up with a ridge vent and then vents in the soffits. Venting the soffits is what we recommended up thread. 

But if you have spray foamed the top 50% of the roof rafters, a ridge vent won’t do anything.  In that case, you’d have to look at other venting options just for your area behind the knee wall.   That is now getting beyond my knowledge of planning it out.  You may still end up with soffit vents and potentially a powered vent fan near the top of your unconditioned space.




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[monarda]

this might help

Yes- I am posting to look for other venting options behind the knee wall.
Or I need to make it a conditioned space.

[Papa bear]

Well yeah, I get that, about what I figured.  But do you have 2 separate cold zones? Or is it all connected with baffles?  That changes how you vent this thing.  If there are baffles, and the entire roof is connected, get a ridge vent and open up the soffits for vent.  Then roof over your old vents and close your gable vents.

If you have 3 “zones” because the rafters were spray foamed, then you have a more difficult situation. Can you get behind the knee wall and look to see what’s back there?  You should be able to see how it was insulated.


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[robartsd]

What is the rest of the attic space insulated with? Are the rafters insulated and drywalled?  Did they spray foam that or use baffles and fiberglass?  Basically, do you have a cold roof above that section or not?

Usually, when you’re redoing the roof, you would end up with a ridge vent and then vents in the soffits. Venting the soffits is what we recommended up thread. 

But if you have spray foamed the top 50% of the roof rafters, a ridge vent won’t do anything.  In that case, you’d have to look at other venting options just for your area behind the knee wall.   That is now getting beyond my knowledge of planning it out.  You may still end up with soffit vents and potentially a powered vent fan near the top of your unconditioned space.

Don't vent the area behind the knee wall if you cannot vent the roof deck higher up as well - this will cause ice dam at knee wall. You can have the higher part of the roof ventilated and the lower part of the roof warmed by insulation from a conditioned space if you provide heating to the eaves below the conditioned space; you cannot do the opposite.

I'm starting to think that BudgetSlasher's idea (3) of putting a new roof deck over the old makes sense. New 2x4 roof rafters directly above old rafters, cut through existing deck as needed to make secure connections, new roof deck on new rafters, ridge and soffit vent in each rafter bay.

[Fishindude]

Cut thru soffit and foam with a 3" or 4" hole saw drill on a long shaft if necessary, then install standard round metal vent caps on underside of soffit.     

[BudgetSlasher]

this might help

Yes- I am posting to look for other venting options behind the knee wall.
Or I need to make it a conditioned space.

If the knee wall is vented and that does not have a good channel through the area labeled "?? possible fiberglass" and passed the cellulose and out the gable vent (or some other way to ensure that roof area is cold). . .there will be melt on that section of the roof, which will freeze if you leave behind the knee wall un conditioned? (They make products like this https://www.homedepot.com/p/ADO-Products-Provent-14-in-x-4-ft-Rafter-Vent-UPV14480/100533902 and this https://www.homedepot.com/p/ADO-Products-Durovent-23-1-2-in-x-46-in-Rafter-Vent-with-Built-In-Baffle-10-Ctn-UDVB234610/202389935?MERCH=REC-_-PIPHorizontal2_rr-_-100533902-_-202389935-_-N meant to allow air to flow behind the insulation)

Did the sam bad contractor do the fiberglass and cellulose or have they been there along time? If not the venting may be fine (on just sealed off either on one end by spray foam or clogged by cellulose on the other).

I suggest 2 things: 1) A lot more research (these guys have some good papers https://www.buildingscience.com/) and knowing what you are going to do before you re-roof; re-roofing could give you a lot of options of how to address the issue (depending on what you want to spend).

If it were me (which it isn't) and if I were going to stay in the house (which you aren't) I would consider converting to a cold roof system, but the cost might be prohibitive.

[monarda]

Ah, I found the photo I was looking for. (why did it upload sideways? it's in correct orientation on my computer)
Just exactly what robartsd and budgetslasher said would happen, did last month.
At the top end of the area in question (circled in red) is the ice dam, at the top of the knee wall.

Talking through this is really helping.

The new roof deck would be best, but it will cost more than the market will support.  The house is going up for sale again - as soon as the roof and interior drywall repair is done. It was on the market in February, and we pulled it off with the ice dam damage. Hopefully back on the market in a couple of weeks.  We want to spend the minimum to get the best functional result.

Fiberglass?? area has been there for a long time. Cellulose was put in by the bad contractor in 2016.

Yeah, all the research has to happen this week and a decision made by Thursday.

Hole saw/soffit vent and some kind of vent channel through the fiberglass?? area might do it? (not sure about this)

The old roof shingles aren't in a noticeably worse condition over the fiberglass?? area, so maybe it's okay under there. But it's only been sealed off with spray foam below since 2016, so it WAS probably fine BEFORE the bad contractor did their work.

We are 3 hours away from all of this- but will probably go up and meet the roofers Weds or Thurs.
Making a list of things to check out in case we make a last minute call once we see it opened up.

If we have the roofers replace the bottom roof deck boards even in they don't need replacing, it'd provide easier access to do whatever we decide at the soffits....

And,I just found this idea, which might or might not be useful, depending on how things go
https://www.finehomebuilding.com/2016/06/29/rigid-foam-vent-baffles

[monarda]

Ah, a trustworthy contractor (recommended by realtor) FINALLY called us back and agrees with much of what's been suggested here. He'd looked at the house and we talked for quite a while. We're going to meet with him at the house  on Weds. or Thurs. this week and crawl into the different areas in question, making sure they are all vented properly.
He understands our goal to do the lowest cost option, whatever that is, so things are done right.

[monarda]

We met with the guy, added more fiberglass to the triangle back wall (R13) and now it's a moderately conditioned space.  The walls toward the heated spaces are all spray foamed, toward the outside (roof deck and triangle wall) all fiberglass.

All the roof vents are gone. The under-shingle vents are gone. The pan vents were supposed to be the exhaust for those, but they were funny. When the roofers took them off, they said there was spray foam sealing underneath and they weren't doing anything, anyway. Another point against those first contractors. There's now a ridge vent at the very top, so the upper attic is a cold space.