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jsahara24
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# Posted: 7 Apr 2021 13:42
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This is not for my cabin but I frequent this forum and respect everyone's opinion so I wanted to get your take...
I recently purchased a farm with an old stone farmhouse. The roof was old so today I am getting it replaced. The main house roof replacement is going typical, with a lot of the plywood being replaced but all is well/expected.....
The issue is on an addition added on about 30 years ago. Its a single story room (~20x34) and was built with exposed rafters, then 1x6 T&G pine boards on top of the rafters. On top of the pine boards is 1" thick foam insulation. Directly on top of the insulation is shingles.
Inside we had noticed some water staining throughout the ceiling, with active leaking during rain storms. I had originally assumed it was just old shingles, but now I'm thinking it is a combination of condensation and old shingles. There is a wood stove in the room and with the undersized insulation, no tarpaper or air space I have to imagine moisture has no way to get out......
My roofer is talking to his supplier about the best way to resolve this. In my head we are going to at a minimum have to add purlins and then plywood, then tar paper and shingles.......but will that let it breath with the purlins cutting off the flow to the ridge?
Perhaps I should switch to a metal roof for this situation to let the corrugations aid in venting?
I have another issue that this room ties into the main house very close to a window, so going up with an extra set of rafters isn't really an easy option...
I'll track down a picture of the house and post it...Just wondering if anyone has dealt with a situation like this and could offer some advice....
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jsahara24
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# Posted: 7 Apr 2021 13:49 - Edited by: jsahara24
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Couple pictures I found......i'm at work now, the roofer is going to wrap up the main house roof while we figure out the best way to handle the addition....Thanks
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Brettny
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# Posted: 7 Apr 2021 14:43
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Metal roof will make the problem worse, plywood and shingles are just going to have the same issue. You need the proper amount of insulation under any roof. R6-7, 1in of foam board isnt going to cut it.
Removing or moving that window and adding alot more foam board may be the only option. You also cant really get proper venting with only one gabel end open.
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jsahara24
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# Posted: 7 Apr 2021 15:40
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Quoting: Brettny Metal roof will make the problem worse, plywood and shingles are just going to have the same issue. You need the proper amount of insulation under any roof. R6-7, 1in of foam board isnt going to cut it.
I know you are correct....but I'm hoping to figure out a reasonable way to resolve this that doesn't cost 10k and then the roof....
This winter I used the woodstove to heat that room and it was consistently warmer than the rest of the house, I was trying to move warm air out of that room and into the other sections of the house which everyone knows isn't easy when you're dealing with small door openings....
I was thinking if I could get the roof vented by adding 2x4 strips on top of the existing rafters (running directly on top of the rafters). Which would create an air space between the insulation and the plywood.....Then sheath it with plywood, then tar paper/shingles.....Add soffit and ridge vents....
Wouldn't that leave the issue being poorly insulated, instead of a condensation catastrophe? Or do you think the lack of insulation is going to continue to cause condensation?
As for venting the gable side that ties into the main house, I don't see any possible fix for that even if I had unlimited money....which I don't by the way! haha....
Thanks
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ICC
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# Posted: 7 Apr 2021 18:34 - Edited by: ICC
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Once the old shingles are torn off how much space is there between the roof deck and that window. The real solution is to apply layers of XPS or polyiso foam sheets and sheath the top with OSB or plywood. Polyiso has more R-value per inch. The required thickness of foam to avoid all possible condensation issues varies with the climate zone. Info is online or the roofer should have access to that info if they know what they are doing. Enough foam = no need to ventilate anything.
Nail the shingles to that top sheathing. The foam panels will need covering around the eves and rake. No need to do anything inside that room. The top plywood is screwed down to the existing rafters through the foam using HeadLok screws. That does take careful measuring but we've done it.
Or if that T&G is not run-of-the mill 1x6 but is actually 5/4 or thicker the screws can be fastened into that, if the screw lengths are just right. Done that too.
If the clearance from roof to window is tight perhaps only the trim needs to be modified.
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gcrank1
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# Posted: 7 Apr 2021 19:03
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What sheet product over the 1st deck is recommended before the insul?
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ICC
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# Posted: 7 Apr 2021 19:57 - Edited by: ICC
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Stagger the panel edge seams in the layers of foam panels and there is no special product needed over the base layer of sheathing.
https://www.finehomebuilding.com/pdf/021224084.pdf
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jsahara24
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# Posted: 7 Apr 2021 21:54
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Quoting: ICC Once the old shingles are torn off how much space is there between the roof deck and that window.
The ridge is right at the bottom of the window....pic attached....
I got home from work and checked everything out. The foam board depth is to my first knuckle, so 1" appears correct. On top of the foam board is tarpaper and then shingles. The foam board (where we opened the roof up anyway) has mold growing. Pic attached.
I am going to go read that PDF, thank you for the advice. Seems like that window isn't going to be able to stay there with either venting the roof or providing the necessary foam insulation to avoid venting.
Only good news is that the wall with the window is wood framed. So I'm thinking adding two windows on either side and removing the one in the middle seems like the direction I need to go.
IMG_20210407_2136557.jpg
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IMG_20210407_2137522.jpg
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ICC
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# Posted: 7 Apr 2021 22:17 - Edited by: ICC
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Quoting: jsahara24 So I'm thinking adding two windows on either side and removing the one in the middle seems like the direction I need to go.
That would seem to make the most sense and give the best roof and insulation combination.
The HeadLok screws come in a variety of lengths. We would buy them by the bucket
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gcrank1
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# Posted: 7 Apr 2021 22:27
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Yeah, a good roof is way more important than saving an old window.
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Brettny
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# Posted: 8 Apr 2021 06:13
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That window is alreaty way to close to the top of the roof to properly flash it. It does look like it's on a load supporting wall so moving it up 16+in may be an issue.
Venting or insulating cathedral ceilings that alreaty have a interior done be becomes very expensive prety quick.
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jsahara24
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# Posted: 8 Apr 2021 08:29
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It is definitely a load bearing wall, not sure if the header is touching the top plate or if there is room to go up. My best guess until I open up the wall is I will need to close that window in. I suppose I don't need to immediately add windows on that wall to get this roof wrapped up, but it would definitely be nice.
I think I need to decide whether I want to insulate and vent the roof, or do the unvented roof like specified in the PDF above. Still waiting to hear back from the roofer on his opinion, and then it looks like i'm going to be taking some time off of work to get this taken care of.....
Thanks again for all the advice!
Jason
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NorthRick
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# Posted: 8 Apr 2021 16:45
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If it were me, I'd strip the roof down to the T&G boards you can see from the inside. If those are in good shape I'd cover the entire roof with water and ice shield. That won't let moisture from the room to get into the roof in the first place.
Fix your window issue and add whatever amount foam board insulation you want and then sheath over that with plywood/osb. Add the roofing of your choice and properly flash were the roof abuts the wall.
I think most of your issues are from having shingles nailed to foam board. I'm pretty sure none of the manufacturers would say that's acceptable.
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gcrank1
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# Posted: 8 Apr 2021 19:02
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I dont like the idea of no waterproof layer on top of the 1st deck either. It just isnt the way I do things now, I start making laps and overlaps from the bottom up on everything that is getting closed in. Murphy has taught me a lot.
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Brettny
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# Posted: 9 Apr 2021 08:16 - Edited by: Brettny
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Quoting: NorthRick If it were me, I'd strip the roof down to the T&G boards you can see from the inside. If those are in good shape I'd cover the entire roof with water and ice shield. That won't let moisture from the room to get into the roof in the first place
It's not always about letting moisture in. In this case it's about warm air condensing on a cold surface. The air sealing your achieving with ice and water shield can be done with foam board and allow for less warm/cold air transfer. By useing the proper amount of foam you eventually allow no heat transfer thus no warm air escaping to condense any where.
Theres a whole science behind cathedral ceiling insulating and how to do it properly. I think part of the issue your going to have is the finished interior and exposed rafters. They do look nice but wont easily or cheaply allow for proper insulation. When you dont have proper Insulation you get mold...like you have.
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jsahara24
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# Posted: 9 Apr 2021 08:43
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So yesterday the roofers finished up the main house roof, along with the porches....I had them strip all the shingles off the rec room roof while the dumpster is still here and expose the foam board.....I tarped it last night as we have some rain in the forecast over the next couple days.....by the way I live in central/eastern PA near the Appalachian trail, zone 5 per the PDF link above.
I am working today but I think tonight I'm going to remove the trim for the window in question is see if I have any room to raise the header and window up, or if it has to go.....Thankfully I found a bunch of extra siding in the barn, so I should be able to patch that back together no matter what direction I go....
Based on the PDF I need R20 to keep the heat transfer from occurring and eliminating the condensation issue...The existing foam board doesn't have any of the joints taped or anything, so I'm sure that isn't helping either....
Doing some research it appears that Polyiso insulation gives you an R value of 6.5 or 6.8 per inch....So 3" would give me ~R20....That along with 1/2" plywood would raise the roof up 2.5" from its current height....so not as much as I originally thought....
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ICC
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# Posted: 9 Apr 2021 09:55
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Polyiso very good; best R-value per inch. More cost than XPS though. Easy to tape the seams with the foil facings on the poyiso. With sufficient thickness as per the climate tables the condensation problem is removed.
In some locations the work that is about to be done would be looked at as a major reconstruction and would require the new work to meet the latest building code. Climate zone 5 calls for more than R-20; maybe as much as R38 or 49. Is updating to present code a factor or is more energy savings for your own satisfaction a factor?
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Brettny
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# Posted: 9 Apr 2021 09:55
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Zone 5 would be r30 minimum.
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jsahara24
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# Posted: 9 Apr 2021 10:45
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The image below is from the PDF above. That says R20 will stop the condensation issue, but maybe I'm missing something.....Did the code change over the last 10 years? Or is R20 what's necessary to stop condensation, but more is recommended?
I am very rural and don't need to deal with any permitting agencies.....My goal with this project is to provide a roof that is not going to condensate, and allow the shingles to serve there expected lifetime without early degradation.
I am looking at the price of polyiso and I can see this getting very expensive which unfortunately has to be a factor in this decision, especially after I am paying for a new roof as well this week.....
I have a wood stove in this room, and this winter it was typically 5* warmer than the rest of the house....Maybe not relevant in everyone's eyes, but anything I do is going to be a major improvement over the rest of the house..... it is a 140 year old house...
Thanks for your advice!
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ICC
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# Posted: 9 Apr 2021 11:35
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Yes, virtually anything you do will be an improvement. You may want to see about a ventilation system that can move air from that room into the rest of the house through ductwork if at all possible.
Quoting: jsahara24 Or is R20 what's necessary to stop condensation, but more is recommended?
R20 satisfies the science of dew point temperatures and condensation. For energy saving more is listed as required. Mostly because most people burn fossil fuel nat gas or oil. Wood is renewable but still has to be burned. There are different views on that.
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ICC
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# Posted: 9 Apr 2021 11:37 - Edited by: ICC
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That 2009 code has been superseded by 2015 and 2018. States do lag behind a version or two usually. The code R-values for energy conservation became higher in later versions in many areas but dew point / condensation science should be the same.
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Brettny
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# Posted: 9 Apr 2021 12:10
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Hunter pannels near Middletown NY sells scratch and dent pallets for very cheap. Very cheap meaning less than $100 for 4'x8x4'
You have a wood stove in that room so even with no Insulation it's going to be warmer. Blow the cold air to the warm air, not the other way around. By moving hot air your cooling it and its alot harder to move hot air down than it is to move cold air from the rest of the house into that room.
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jsahara24
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# Posted: 9 Apr 2021 13:33 - Edited by: jsahara24
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Quoting: Brettny Hunter pannels near Middletown NY sells scratch and dent pallets for very cheap. Very cheap meaning less than $100 for 4'x8x4'
That sounds very reasonable, thanks for the tip.....
The room with the wood stove is connected to the kitchen with a typical doorway opening, along with a window they removed and left open and finished....So I have been putting a fan in the window opening and blowing it towards the stove...Its definitely helping to heat up the kitchen but to get into the next room is a single doorway opening and I haven't been able to get the heat into that room yet.....Maybe one of the doorway corner fans or something would help....from there the stairs take you upstairs so heat would naturally want to rise if I could get it there.....
As for adding duct work, the house has oil fired hot water baseboard heaters downstairs and radiators upstairs...So that would certainly be a pain but I would love to get central air, I was thinking it would be easier to go with a couple mini-splits but that is going to be a couple years down the road anyway.....
Thanks!
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Brettny
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# Posted: 9 Apr 2021 13:39
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Try putting a fan in the doorway at floor level. You may also need a fan in the other doorway at floor level.
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jsahara24
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# Posted: 9 Apr 2021 13:56
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Quoting: ICC R20 satisfies the science of dew point temperatures and condensation. For energy saving more is listed as required. Mostly because most people burn fossil fuel nat gas or oil. Wood is renewable but still has to be burned. There are different views on that.
Thanks, that was my understanding as well....I'm not going to touch the fossil fuel topic except to say we have ~100 acres of woods for free firewood collection and I'm planning on continuing to burn it....
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gcrank1
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# Posted: 9 Apr 2021 13:56
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How about putting an opening in the peak of that cath ceiling to that upstairs. Have good sized reversible? fan there.
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jsahara24
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# Posted: 9 Apr 2021 13:59
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Quoting: Brettny Try putting a fan in the doorway at floor level. You may also need a fan in the other doorway at floor level.
Thanks, I'll give it a try..
I should have mentioned that the room off the kitchen with the stairs also has a big fireplace.....I've always thought of fireplaces as more of an aesthetic thing instead of a heater.....I haven't fired it up yet, and have it blocked off so it doesn't pull heat out of the house.... maybe a wood insert or similar will be in future...
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jsahara24
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# Posted: 9 Apr 2021 14:01
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Quoting: gcrank1 How about putting an opening in the peak of that cath ceiling to that upstairs. Have good sized reversible? fan there.
Not sure that I'm following, the cathedral ceiling room does have a ceiling fan that I run to push the heat down.....But the stairs to the upstairs is in the room on the other side of the kitchen with the fireplace....
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gcrank1
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# Posted: 9 Apr 2021 14:29
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With an fanned opening into the old house from your addition peak you can suck cooler air from the old to new or hot air in the new room peak into the old. Imo it would set up a circulatory air flow mixing and better stabilizing the air temps between old and new. Guess it would be into your stairwell? Still, to me that would be way better than walking around a box fan at floor level of the only doorway into the addition.
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jsahara24
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# Posted: 9 Apr 2021 14:38
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Quoting: gcrank1 With an fanned opening into the old house from your addition peak you can suck cooler air from the old to new or hot air in the new room peak into the old. Imo it would set up a circulatory air flow mixing and better stabilizing the air temps between old and new. Guess it would be into your stairwell? Still, to me that would be way better than walking around a box fan at floor level of the only doorway into the addition.
Got it....Certainly something to consider....getting an old farmhouse to regulate temps is a difficult thing......I need to get the upstairs on its own tstat b/c I hate sleeping in hot temps, but that makes the downstairs cold....The wood stove is helping but still have some stuff to work out for sure.....
I knew this place was going to be a money pit, but its a beautiful property at a fair price so I jumped in.....It also has a ~32'x65' bank barn that I am also working on so I have no shortage of projects that's for sure...
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