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Epitope
Nov 27, 2006



Grimey Drawer

A little more investigating, a little more theorizing, and getting my ducks in a row for propositioning more pros

I am backing out of the blower/thermal imager rabbit hole, at least for now. I did one last run before I stowed the fan and took down all the tape. Mostly it just confirmed that the rafter box thing "has issues," and that my foam and tape aren't very effective. There was plenty of frost accumulating behind tape, so Motronic is right that willy nilly trying to seal could go poorly. I think I learned some stuff though, so that's good right?

Here is the rafter box with the holes all taped up, blower running and microwave fan running too


Took out one piece of foam/tape, and cold air comes out fast enough i can easily feel the breeze



Then, after taking the tape down, I poked around looking at what I can see going on in there. There's a big enough gap I can stick a flashlight in there and get a decent view of things. Not able to get much in the way of photos, maybe I'll buy a borescope next. I think, though it's hard for me to know, I think I can see one of the original rafters that had it's rotten top cut away, and it's new sister behind it. I am pretty sure I can see the spray foam that they put in in 2015, as it matches the color from their photo. The light purple stuff. Here's that photo again:



(why is some yellow in there still, did they leave the previous foam in areas where it was still in reasonable condition?)
So, maybe this is my culprit air path? Not sure how to plug it. Do we need to cut drywall to get access for doing the plugging? Or remove the pipe and use the pipe's hole for access? Or, would just sealing around the pipe and outlets be sufficient?

Also while peering in there, I see something else that concerns me. The bottom of the rafter box has no wood just drywall, the sides are I believe rafters, and the top has plywood that sits on top of the rafters. The rafter in the back is the one that looks like it was chipped away to remove the rotten part. Above that chipped away part the plywood is dark/stained/(water damaged?). The rest looks like healthy raw plywood. So my concern is, did they frame the loft on top of roof decking? It kinda looks like they did. Is that bad? That seems bad to me. Decking needs to be replaced, and indeed just was replaced. Framing hopefully doesn't need replacing, or at least it's replacement is hopefully on a longer timescale. If that's what's going on, how big a deal is that? If they trimmed off the rotten decking that was under the roofing material, and now the remaining bit of plywood is acting as the loft wall sill plate or whatever you call it, how sketchy is that?

Here's a photo that you can't really see anything. This is putting my camera up against the hole where the pipe goes in. You can see the spray foam mass below, and some of it spattered up on the stained plywood decking.


Tezer posted:

quote:

Here's the current list for a GC, if we can find one who's worth a drat that doesn't just nope out immediately.
-Turn skylight to roof (need to decide how much eave, especially on the side)
-Seal the window that clearly leaks. Do we need to remove (replace with wall) that window too? Might depend on the foundation...
-Seal the attic corner
-Fix/seal the LED outlet wiring
-Seal the kitchen vent pipe through the rafter box. (Also verify the pipe itself is installed well)
-Extend the ridge vent so it connects and we have ridge vent along the entire roof

Except for removing the skylights, this is largely a 'while you are here' list on a larger project, and even the skylight one I wouldn't do unless it was a customer with an existing relationship. I know you need to get this done, just cautioning you that it's a really unattractive list. Small piddly items. It's a list made for a handyman, except handymen aren't really trained in air sealing. It's going to be a frustrating process to find someone (sounds like it already has actually) and I sympathize.

Do you (or anyone) know if I should provide a budget as I shop for contractors? Would a budget help me find someone? That is, can I make my list more attractive with dollars? Also, any idea of ballpark where that list will land? Is 50k optimistic?

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Tezer
Jul 9, 2001



Epitope posted:

(why is some yellow in there still, did they leave the previous foam in areas where it was still in reasonable condition?)

It's really annoying to remove spray foam, and literally impossible to remove it all without removing the material it's bonded too. They probably just left what they could.

quote:

Also while peering in there, I see something else that concerns me. The bottom of the rafter box has no wood just drywall, the sides are I believe rafters, and the top has plywood that sits on top of the rafters. The rafter in the back is the one that looks like it was chipped away to remove the rotten part. Above that chipped away part the plywood is dark/stained/(water damaged?). The rest looks like healthy raw plywood. So my concern is, did they frame the loft on top of roof decking? It kinda looks like they did. Is that bad? That seems bad to me. Decking needs to be replaced, and indeed just was replaced. Framing hopefully doesn't need replacing, or at least it's replacement is hopefully on a longer timescale. If that's what's going on, how big a deal is that? If they trimmed off the rotten decking that was under the roofing material, and now the remaining bit of plywood is acting as the loft wall sill plate or whatever you call it, how sketchy is that?

In the abstract, there is no problem building over the plywood decking. The new framing should have been properly blocked and fastened to the structure below. This is pretty common, especially when you're building an addition and you just frame over the existing roof and then cut into it once you're done (removing the shingles before framing, but not the plywood). I can't comment on how your particular loft was constructed, just noting that it's not unusual to see roof decking kicking around under a dormer/addition.

quote:

Do you (or anyone) know if I should provide a budget as I shop for contractors? Would a budget help me find someone? That is, can I make my list more attractive with dollars? Also, any idea of ballpark where that list will land? Is 50k optimistic?

Any contractor is going to have their own way of feeling out if a client is serious when it comes to money. You don't need to tell them your budget, just avoid saying things like 'affordable' and 'reasonable' which are secret code words that indicate you're a miser.

$50k is well more than enough for that list even for the people I work for, as long as stuff doesn't balloon (like, messing with the ridge vent doesn't turn into a roof replacement or something). I'd start conversations around removing the skylights since that is the largest 'real' project on the list, and talk about how it's part of general improvements you want to do regarding air sealing, etc. If you mention that you're fine with this being a fall project that will help, because everyone is busy and that way they know you won't fall out of the process when it becomes clear it won't happen in March. We are opening most client conversations by asking if they are OK with fall 2021 or spring 2022 and if they say no it really ends there.

Epitope
Nov 27, 2006



Grimey Drawer

Thanks again, you're helping me a lot

Epitope
Nov 27, 2006



Grimey Drawer

Good news, I am reasonably confident I have diagnosed most of this hot spot. Bad news, I still don't really know what to do about it, though I do have some things that might help and at least one hair brained idea.

Contractors-
We friend networked a custom builder who generously chatted for half an hour on the phone. He also offered to come look at some point. He more or less already said he wouldn't take the job though. I've called a few others and left messages and no call backs.

Some more things I found poking around-
-The microwave vent pipe through the rafter box is indeed not a single piece. There is a junction, and it's not taped (not surprising, there's no way to get in there to tape it). Maybe there's sealant (mastik?) but hard to have much confidence it's well sealed.

-I did another round of temporary sealing around the skylight and the rafter box. This round I used putty (er, "caulk cord") which I think is a bit more effective than tape and foam. It has a bit more impact on the surfaces (leaves more residue, rips off parts of the surface when you take it out), but I guess I'm feeling like getting more information is worth that cost. This time I also plugged the vent pipe (a sheet of plastic slid into a joint with ease). Before and after sealing, I looked at the roof† with the thermal camera. The vent pipe end outside the roof got cold, so I can tell that plugging worked. However yet again, the hot spot on the roof† did not go away. It is still like 30 degrees warmer than an adjacent piece of the same roof/siding

Putty plug and pipe cap

Hotspot


-Next I removed the ring-o-putty plug and build a blower box to draw air out of the rafter box in a targeted manner (vs blower window drawing air out of the whole house).

Blower Box


It is effective, with the blower running the roof hot spot cools down. As soon as you switch the blower off, the hot spot gets hot again, even if I plug the end of the blower. So, am I that poo poo at sealing? or is warm air getting in from somewhere else?

You may recall the interior wall outlet got cold when running the blower door/window. I tested more wall openings using my DIY smoke pen, while my helper switched the blower box on and off. With the blower running, smoke from the joint is drawn into the outlet for the range top, and also into the hole for the bathroom sink drain pipe. I had seen a possible cold spot at that outlet before when running the blower window, but in hindsight it makes sense it didn't get cooled much since it's so far interior. The plumbing holes had appeared to not cool at all, which threw me off the trail a bit, but I think the smoke is pretty conclusive.

Conclusions-
So, where does that leave us? There's this weird rafter box thing. Air can flow pretty easily from it to the "attic" (i.e. the small space between the insulation and the roof decking). The air can flow from there out of the structure through a "shed vent" (i.e. not a ridge vent cuz there's a wall above that section of roof). However the skylight is below, so there is no intake for outdoor air to the attic, so close to 100% of the make up of the flow is interior air.††
Before I started plugging there were large holes straight from the living space into that rafter box. However even plugging those holes doesn't cut off the rafter box from interior air- it is somewhat contiguous with the adjacent wall, which has numerous utility penetrations. Not to mention the inside of the wall is probably contiguous with the floor joist cavity, and that space is pretty much wide open. The downstairs is 99% finished but the boiler room has an unfinished section and some of the ceiling drywall is dropped below the floor joists for heater pipe runs and such. And there are numerous can lights down there.†
Another thing, I maintain my suspicion that there's an air path into the same (or next rafter bay over) attic space at the skylight/window//ceiling/wall junction.

Next steps-
1) Can these air paths be blocked?I don't think I can expect to seal all the penetrations to the wall/floor. Also, the rafter box might be a sufficient but not a necessary segment of the path. That is to say, the wall itself may have a path to the attic, independent of the rafter box. Here's what I think is going on.

Diagram of insulated rafter bays


If the rafter box and the rafter bay above the wall (marked with ???) had spray foam too, that might be a step closer. But I kinda doubt the bay above the interior wall does, it is also below the loft wall. I can't see how insulation could be added to either bay at this stage. Is there another way to block this path?

2) Improve roof ventilation
-The roof above the skylight does not have intake openings for air. To add an intake either the skylight must go, or a creative intake added above the skylight. I've taken a harder look at the skylight removal, and a question that arises is- can the existing framing (a corner made of 4 windows) support roof instead of skylight? Or does trying to add an eave take me back into "just tear the whole addition off and start over" territory?
-There's also the missing section of ridge vent, adding that would be easier I think, and might help the soffit frost.

3) Hair brained scheme
-It would be extremely easy to add a fan moving air out of the rafter box into the kitchen. It could be balanced such that air comes in from the attic rather than goes out to the attic. It could be on a switch, rheostat, even a sensor if we want. It could be quiet and out of view. I'm certain that there are many reasons this is a bad idea, and if Motronic were still in the thread he'd tell me about them. Anybody else want to disabuse me of this tactic? The down sides I see are increasing the heating bill, and complications for selling. I'm trying to imagine ways it could move air to create new and exciting problems, but I don't see any. Clearly I'm blinded by optimism. Help me out.

Elviscat
Jan 1, 2008

MESS WITH THE OWL GET DISEMBOWEL





Epitope posted:


2) Improve roof ventilation
-The roof above the skylight does not have intake openings for air. To add an intake either the skylight must go, or a creative intake added above the skylight. I've taken a harder look at the skylight removal, and a question that arises is- can the existing framing (a corner made of 4 windows) support roof instead of skylight? Or does trying to add an eave take me back into "just tear the whole addition off and start over" territory?
-There's also the missing section of ridge vent, adding that would be easier I think, and might help the soffit frost.

3) Hair brained scheme
-It would be extremely easy to add a fan moving air out of the rafter box into the kitchen. It could be balanced such that air comes in from the attic rather than goes out to the attic. It could be on a switch, rheostat, even a sensor if we want. It could be quiet and out of view. I'm certain that there are many reasons this is a bad idea, and if Motronic were still in the thread he'd tell me about them. Anybody else want to disabuse me of this tactic? The down sides I see are increasing the heating bill, and complications for selling. I'm trying to imagine ways it could move air to create new and exciting problems, but I don't see any. Clearly I'm blinded by optimism. Help me out.

This, at least I can answer.

2 removing the skylights is easy, skylights are just as heavy as normal roof with snow loads etc, it's just a matter of removing some drywall and roof decking and sistering on some new joists in their place (the blocking at the top and bottom of the windows should also be removed to promote airflow)

3 promoting the flow of outside air to the inside of your house is a bad idea.

While you have the ceiling ripped apart, have that rafter box ripped open too, see if there's a way to better seal it, or remove it entirely. It doesn't look like it's serving a structural purpose besides leaking air everywhere, and it's a remnant from a clearly poorly scabbed on addition.

Drywall is cheap, if you commit to ripping it apart to try and gain access to your leakage points the incremental costs of ripping out more drywall are low.

E: that boiler space, with all the heat it pumps out, and how quick the roof heats up, and all the utility penetrations, sounds like a likely culprit, and somewhere you can start carefully removing drywall with low risk, since you can just screw new stuff up and slap mud on it, it's a utility space who cares what it looks like?

Elviscat fucked around with this message at 03:10 on Feb 20, 2021

Epitope
Nov 27, 2006



Grimey Drawer

Haha, it's called save the rafters not remove them. Though it might be the only way to keep them safe... Maybe an engineer will answer the phone? I'd gamble a thousand on the chance I could get rid of the rafter box

I did think about taking away the drywall and plywood that makes up the box top and bottom. Quite a bit of effort and no guarantee it helps though

Elviscat
Jan 1, 2008

MESS WITH THE OWL GET DISEMBOWEL





Epitope posted:

Haha, it's called save the rafters not remove them. Though it might be the only way to keep them safe... Maybe an engineer will answer the phone? I'd gamble a thousand on the chance I could get rid of the rafter box

I did think about taking away the drywall and plywood that makes up the box top and bottom. Quite a bit of effort and no guarantee it helps though

It might just be that I hate your vestigial leaky colon of a rafter box, and would have taken a sawzall to them months ago in your shoes

FWIW, since they can't be load bearing because they're flying through your kitchen 2' from the ceiling, that's the sort of job a GC or carpenter can do under "general stick framing practices" (or words to that effect) and shouldn't require engineering evaluation.

I genuinely think that your best course of action is commiting to removing those awful ""skylights"" and tearing into the rest while you're at it, since the additional cost would be low, I've found it's rarely worth going through half-measures to try and fix a problem, when to truly correct it requires much more invasive measures, you end up doing the same job twice as many times and half as well.

That's just imo as a fellow homeowner, not a professional by any means.

Epitope
Nov 27, 2006



Grimey Drawer

Elviscat posted:

I hate your vestigial leaky colon

it's rarely worth going through half-measures to try and fix a problem, when to truly correct it requires much more invasive measures, you end up doing the same job twice as many times and half as well.

Haha yes, yes. I just wonder if that means a very big job. There's so many terrible choices, if there were only the one lovely addition I think I would be seriously considering removing it at this point. But there's three, plus other remodeling in the rest of the house.

Another one I just discovered this morning. A grundfos comfort system bypass valve. I think this means we're drinking from the 10 year old hot water tank that's never been flushed. Another ingenious boomer lux item to avoid the terrible inconvenience of ...having to run the tap for 20 seconds? I'd just take it out, but I worry it might also be preventing the pipes in the falling down insulation crawl space from freezing

devicenull
May 30, 2007



Grimey Drawer

Is there a ceiling you can get to where all those question marks are? I'd honestly just drill some holes in there and see wtf is up.

One suggestion for the skylight is to put some of this stuff over it. If that improves things, it's a pretty good indication that removing the skylight will help. Alternatively, try to pin up some heavy curtains, but that sounds pretty hard.

TBH I think that skylight is probably a part of your issue. Even if it is a pretty high end one, it still has an R value of around 3... wheras even a 2x4 bay filled with spray foam gives you an R12.

Epitope
Nov 27, 2006



Grimey Drawer

devicenull posted:

Is there a ceiling you can get to where all those question marks are? I'd honestly just drill some holes in there and see wtf is up.

Unfortunately not, they're both above and one's below a wall. I have opened what I can open to get a peek in places, but that one eludes me. If I buy a borescope I might try drilling a peep hole at the top of the bathroom wall. I'm guessing I might see a plywood wall top (it looks like there's plywood above other walls in this photo

) and don't feel too good about poking through that since I don't know how I'd patch the hole.
Another detail I can see, the kitchen side of the wall has plywood behind the sheet rock, but not flush- there's furring strips it looks like. Not sure what that's about. Also that reminds me, the wall above and below the rafter box are a couple inches off, so even if I removed the box there would still be a weird lip bevel thing.

I keep meaning to entirely block off the skylight, (or, now I kinda want to try drawing air out of it) but it's not a small job, and I haven't found the gumption yet. Also believe it or not I do try to do things besides abuse my house/self in my free time.

Epitope
Nov 27, 2006



Grimey Drawer

Called some more contractors, got some more no's.

But, I did get some more photos from 2015. Looks like the bay I labeled with ??? is indeed insulated. Which is great. Also the loft wall is more off-set from the interior wall below it than I thought. I'm still not sure exactly what is under the loft wall (maybe several generations of rafters...), and I feel I have pretty strong evidence that's where a lot of the air path is. Oh and I've been calling them rafters, but maybe they're technically joists (that's what the engineering sheet says).

Also, these photos confirm something I had suspected- that the skylights are just tacked on the the original roof edge. The box joist (aka rim board?) and maybe even the fascia board became part of the skylight frame. However they still protrude to the exterior of the siding, and they are now in free contact with interior air (the trim covering them was only ever just nailed up, and there's nothing else behind the trim but the framing, so no air seal). Seems jacked, but here we are. I did go ahead and put my little blower box in that skylight corner. When drawing air into the house, the piece of fascia board protruding out to the exterior cools down. So yes, there's some air leaking out the corner there. Maybe not much though, as the main hot spot doesn't visibly change. So the main air leak seems to be the rafter box.

Above skylight



Loft wall



Other end of skylight (less relevant I think)



Blower box



Next steps-
I just don't see any of this being fixed any time soon. The people we would want to do work are all busy or only do bigger projects. I feel that anyone who would take the job now is not someone we want. Replacing the skylights is only a half fix, and it requires huge redo of 5 year old parts (roof, insulation, framing). If we're doing that much it probably is worth doing more at the same time, and if we're replacing all that anyway what's the rush.

The question that remains for me is whether doing little things could help.
1- Extending the ridge vent so the frosty rafter bay has an air outlet
This would be the most, ah, legit?
2- Adding an air intake above the skylight
Possible, but risky and a bit wacky
3- Depressurizing the rafter box
Super easy but extremely wacky
4- Maybe someone could lop out drywall around the rafter box and the interior wall under it, then plug up the air path there.
I've been hunting for this person for a good while, and still coming up empty.

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Epitope
Nov 27, 2006



Grimey Drawer

Poking around some more in the interior wall -> rafter box path.

This pic again for orientation


Pulled the junction box behind the blank plate here:


Sticking my phone camera in there, looking up. The main wall cavity seems reasonable. The top is a 2x4, and the vapor barrier above the bathroom ceiling drywall is visible. The kitchen side is plywood, i guess to match the plane of the addition's wall?

Main wall cavity, looking up:


So, the kitchen side drywall is over that plywood sheet, but on furring strips. The next photo was taken using a mirror, to look up in the cavity between the drywall and the plywood. A rafter is visible, and lo, there's nothing behind it. I think the plywood maybe even continues up above the bottom of the rafter, though hard to say.

Furring cavity, looking up:


If i shine a light up in the furring cavity, and peer into the rafter box through the microwave pipe hole, i can see the light hitting the roof decking where the rafter is chipped away. Likewise, if i poke a light into the rafter box and point it down over the top of the chipped away rafter, the light is visible from the furring cavity. So, pretty clear that's an air path through the wall to the rafter box and roof. Also, even if the rafter box was completely removed, it looks like this path would remain contiguous with the roof micro attic (or whatever you call the roof vent space).

It wouldn't be trivial, but seems the drywall could be taken down, and the top of the furring cavity plugged. Maybe I could do that, but maybe since the scope of the job is more well defined, I could actually find someone?

Still, not sure that's everything:

Main wall cavity, looking left:


Here you can see the beam where the original exterior wall was (the beam is also visible at the edge of the looking up pic). The wall cavity space continues around the corner, behind the bathroom's exterior wall. It also looks like there's a gap between the beam and the top of the wall. I'd like to believe that's all fine, but maybe that's where the eave frost comes from (rather than from the same leak from the rafter box and then jumping across rafter bays). If that is a path, I am struggling to come up with a simple strategy to plug it.

Googling, i found this. Huh.
https://www.researchgate.net/figure/Cavity-in-the-demising-wall-is-connected-with-the-furring-space-in-the-exterior-wall_fig5_319317927

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