I was thinking that you could run all the electricity in the ceiling and avoid "puncturing" the vapor barrier.Bödde said:
Then I'm wondering what happens if you nail the panel directly onto the rafters with the plastic on the outside, there will be a LOT of small holes for all the nails in the plastic.
Aha, yes, that was a good thought.BBJB said:
Those I've asked about the puncture issue, which also applies to moisture barriers in bathrooms (though it is obviously more sensitive there), say there's no danger because you "clamp" the board/roofing material against the stud - thus keeping it sufficiently tight.
I'm just afraid you'll create problems with the plastic inside between the layers. The pros (i.e., not me) talk about the condensation point and where it occurs, among other things, depending on how much insulation you have in the wall/ceiling.
The role of the plastic is to stop the moisture before it gets into the construction.
Your planned construction with the plastic inside the insulation may not matter at all, but double-check to be sure.
Like the previous writer, I'm also wondering about the depth of the air gap. There might not be a mathematically perfect solution that fits all houses, but an old carpenter I asked, who also works with building maintenance, said that "it should be a 3 cm air gap, neither more nor less". His argument was that it (obviously) shouldn't be too little ventilation, but not too much either. The air carries moisture that the construction can't handle if the gap is too deep. Therefore, according to him, 3 cm was perfect.
It wouldn't hurt to double-check this as well
Regarding the air gap, I've talked to 2 carpenters and they always go with a 22mm air gap, so I hope that will suffice.Bödde said:Aha, yes, that was a good thought. Those I've asked about the puncture problem, which also applies to moisture barriers in bathrooms (though there it's obviously more sensitive), say there’s no danger as you "clamp" the board/roofing material against the stud—and thus keep it sufficiently tight. I'm just afraid you might create issues with the plastic inside between layers. The pros (i.e., not me) talk about the dew point and where it occurs, among other things, depending on how much insulation you have in the wall/ceiling. The plastic’s role is to stop the moisture before it gets into the construction. Your planned build with the plastic inside the insulation might not matter at all, but double-check to be safe. Like the previous writer, I'm also pondering the depth of the air gap. There might not be a mathematically perfect fit for all houses, but an old carpenter I asked, who also works with building preservation, said "it should be a 3 cm air gap, neither more nor less." His argument was that there should obviously not be too little ventilation, but not too much either. The air carries moisture that the construction can't handle if the gap is too deep. Therefore, according to him, 3 cm was ideal. It doesn't hurt to double-check this too
Then I read in a DIY guide about the plastic a bit into the insulation, where they indicated you can have it up to 70mm in if you have 300mm of insulation. So it should work with 45mm in with 140 insulation?
But I will try to double-check this with the carpenters too.
One thing I wonder is how you should finish with the plastic against the gables? Is it enough to lay overlapping plastic inside the drywall, or must it be clamped with the studs that we’re building on the gable (45mm)?
Best regards, Jonny
Was over talking to one of the carpenters yesterday.
He strongly recommended using plastic in the walls if we have it in the ceiling.
One thing I hadn't thought of was that the ridge should be able to release air. Will need to drill some holes along the ridge board.
Then it will be up on the roof this summer to try to make some kind of cover over these holes with roofing felt to be on the safe side.
Then we could run the vapor barrier 1/3 into the insulation.
Regards, Jonny
He strongly recommended using plastic in the walls if we have it in the ceiling.
One thing I hadn't thought of was that the ridge should be able to release air. Will need to drill some holes along the ridge board.
Then it will be up on the roof this summer to try to make some kind of cover over these holes with roofing felt to be on the safe side.
Then we could run the vapor barrier 1/3 into the insulation.
Regards, Jonny
Is ridge ventilation necessary? Some claim that it can lead to too much ventilation, drawing in moist air, and that perhaps ventilation should be limited instead.
You already have channels from one attic to another. If more ventilation is needed, isn't it possible to have adjustable ventilation outlets at the gable peaks, possibly enhanced with a small duct fan? That way, the ventilation can be somewhat regulated. And maybe control the fan(s) with a humidity sensor if needed.
You already have channels from one attic to another. If more ventilation is needed, isn't it possible to have adjustable ventilation outlets at the gable peaks, possibly enhanced with a small duct fan? That way, the ventilation can be somewhat regulated. And maybe control the fan(s) with a humidity sensor if needed.
Oh.
I actually don't know how to do it.
I was thinking of drilling about two 16mm holes between each rafter at the ridge, I've nailed up ventinock plastic ventilation on the ridge so that it can't "rain" into these holes.
I'll test with that, and if it doesn't work, I'll have to close these air holes.
What do you mean by gable ventilation?
Leave a little at the top with the insulation and run ventilation from gable to gable at the ridge?
I actually don't know how to do it.
I was thinking of drilling about two 16mm holes between each rafter at the ridge, I've nailed up ventinock plastic ventilation on the ridge so that it can't "rain" into these holes.
I'll test with that, and if it doesn't work, I'll have to close these air holes.
What do you mean by gable ventilation?
Leave a little at the top with the insulation and run ventilation from gable to gable at the ridge?
When I was almost finished writing my post, everything suddenly disappeared, so I'm trying again.
As I mentioned, I am an amateur planning a similar project for this upcoming spring.
Ridge ventilation is certainly very effective, it creates a kind of chimney effect and the suction is more evenly distributed with holes in the sheathing between the rafters.
It's just that I am strongly against making holes at the top of the roof, even if there are rain covers that you have already installed. Someone who can is welcome to try to convince me that I am wrong, but it feels like I don't have control over what will happen in, say, 15-30 years.
My rafters are very similar to yours (38 degrees), except that I screwed and glued a plywood reinforcement in the triangle at the top. That's where I'm considering making holes, about 80-100 mm, just to allow air flow between the gable peaks. But I need to measure a bit more accurately, unfortunately, the object is 230 km away.
I am not going to insulate all the way up to the ridge but will leave room for free air flow.
Yes, I mentioned "adjustable ventilation outlets," I don't even know if such things exist. What I was thinking of were ventilation grilles, say with a 100 mm connection, where a duct fan can be mounted if needed, maybe one at each gable. I will at least prepare the wiring for fans and also for some form of moisture sensor.
The natural ventilation is probably significantly worse with my intended ventilation, the question is really how much is needed, as many scholars debate this. There are many threads about air gaps, mostly under "Roof and Attic" or "Insulation."
And then I discovered that the company Ventotek has a solution with sensors and fans, though more comprehensive (and more expensive?). It's found, among others, in the thread "Dilemma regarding attic ventilation." Unfortunately, I don't master the technique to fetch the thread here (retiree, you know).
But regardless of which path you choose regarding the ventilation, I look forward to hearing about your experiences when it comes to the continued work with foam board (screwing, gluing, etc.).
As I mentioned, I am an amateur planning a similar project for this upcoming spring.
Ridge ventilation is certainly very effective, it creates a kind of chimney effect and the suction is more evenly distributed with holes in the sheathing between the rafters.
It's just that I am strongly against making holes at the top of the roof, even if there are rain covers that you have already installed. Someone who can is welcome to try to convince me that I am wrong, but it feels like I don't have control over what will happen in, say, 15-30 years.
My rafters are very similar to yours (38 degrees), except that I screwed and glued a plywood reinforcement in the triangle at the top. That's where I'm considering making holes, about 80-100 mm, just to allow air flow between the gable peaks. But I need to measure a bit more accurately, unfortunately, the object is 230 km away.
I am not going to insulate all the way up to the ridge but will leave room for free air flow.
Yes, I mentioned "adjustable ventilation outlets," I don't even know if such things exist. What I was thinking of were ventilation grilles, say with a 100 mm connection, where a duct fan can be mounted if needed, maybe one at each gable. I will at least prepare the wiring for fans and also for some form of moisture sensor.
The natural ventilation is probably significantly worse with my intended ventilation, the question is really how much is needed, as many scholars debate this. There are many threads about air gaps, mostly under "Roof and Attic" or "Insulation."
And then I discovered that the company Ventotek has a solution with sensors and fans, though more comprehensive (and more expensive?). It's found, among others, in the thread "Dilemma regarding attic ventilation." Unfortunately, I don't master the technique to fetch the thread here (retiree, you know).
But regardless of which path you choose regarding the ventilation, I look forward to hearing about your experiences when it comes to the continued work with foam board (screwing, gluing, etc.).
Many houses have uninsulated attic spaces and a small attic above the "cape beam," just like the one you will get. I also have part of my house like that. Gable and ridge vents are the simplest way to manage ventilation. You don't want holes in the ridge, and it's not needed in this construction. As I understand it, it's only if you insulate the entire roof from eave to ridge that ridge ventilation may be necessary. If you live in a windy area and the house is oriented north-south, it might be enough with just eave ventilation. The same goes for the air gap. If, like me, you live in a windy area (Skåne), 22mm is more than enough.
Regarding whether or not plastic is needed, I would say that with light insulation and all hygroscopic materials, it works without it, because the whole wall/roof gets slightly warmed, thus preventing condensation. With thick insulation and non-hygroscopic materials, plastic is necessary. In your case, I highly recommend the plastic.
Personally, I think it's foolish to have cold drafty spaces. It's much better to insulate from the gable eave to the ridge. Normally, it should also be simpler. However, when it comes to renovating older houses, it's not always practical or sensible to do.
Regarding whether or not plastic is needed, I would say that with light insulation and all hygroscopic materials, it works without it, because the whole wall/roof gets slightly warmed, thus preventing condensation. With thick insulation and non-hygroscopic materials, plastic is necessary. In your case, I highly recommend the plastic.
Personally, I think it's foolish to have cold drafty spaces. It's much better to insulate from the gable eave to the ridge. Normally, it should also be simpler. However, when it comes to renovating older houses, it's not always practical or sensible to do.
Yes.