Here’s one I’m doing this week. The foil backed insulation is on the drywall side of the roof.
If you’re doing a basement, you foam behind studs to break the bridge. One I did a few weeks ago.
If your doing an attic, you go over the joist or rafter ends
No idea. However, if the ceiling void is completely filled with closed cell spray foam then my understanding is there's no cavity for moist humid air to enter at all. I'll ask them about the thermal break.
No idea. However, if the ceiling void is completely filled with closed cell spray foam then my understanding is there's no cavity for moist humid air to enter at all. I'll ask them about the thermal break.
Doesn’t work like that. The joist gets cold and works like a cold beer bottle does on humidity. If that’s in contact with your drywall and condensation happens on both sides of the Vapor barrier.
In some houses you’ll see light ghost marks on the drywall where it’s fixed to the joist, telltales there is no thermal break — that’s caused by moisture from the inside the house. Another clue is when you paint over the area, blisters often appear in the paint.
None of the issues I've had currently have come from where the drywall is connected to anything above it. Paint blistering and stains are in void areas. I've asked them the question though. Also, there are zero issues in the winter, only the summer and only for a few days where the dew point is a bit odd.
This is a pretty big company, not a fly by night so I assume they know what they are doing.
Cover the beer bottle outside with a waterproof shield to stop humid air touching the glass and there won’t be any condensation there. Look at foam bottle cosies.
None of the issues I've had currently have come from where the drywall is connected to anything above it. Paint blistering and stains are in void areas. I've asked them the question though. Also, there are zero issues in the winter, only the summer and only for a few days where the dew point is a bit odd.
This is a pretty big company, not a fly by night so I assume they know what they are doing.
Cover the beer bottle outside with a waterproof shield to stop humid air touching the glass and there won’t be any condensation there. Look at foam bottle cosies.
While foam in the cavity evicts the humid air, it does nothing to the joist temp. Joist between plywood and drywall has no vapor barrier and no thermal break. I wouldnt be surprised if drywall gets some moisture there and that attracts dirt over time. To Mike's point, adding a thermal break below the joists kills this potential disappointment.
All of the above may not be a big deal if your ceiling joists are not solid lumber to the roof deck. Some are short trusses which gives you the break over most of the span. You'll find out what you have after the ceiling drops.
While foam in the cavity evicts the humid air, it does nothing to the joist temp. Joist between plywood and drywall has no vapor barrier and no thermal break. I wouldnt be surprised if drywall gets some moisture there and that attracts dirt over time. To Mike's point, adding a thermal break below the joists kills this potential disappointment.
All of the above may not be a big deal if your ceiling joists are not solid lumber to the roof deck. Some are short trusses which gives you the break over most of the span. You'll find out what you have after the ceiling drops.
If this was an issue now I'd be seeing the condensation along the joist lines but that's not and never has been the case. Got a response that this isn't going to be an issue with 5+ inches of foam in that cavity. Will see a bit more anyway when they tear down the ceiling.
If this was an issue now I'd be seeing the condensation along the joist lines but that's not and never has been the case. Got a response that this isn't going to be an issue with 5+ inches of foam in that cavity. Will see a bit more anyway when they tear down the ceiling.
It's all orders of magnitude. Right now, the cavity is the big issue. Fixing the cavity means the next weakest link tries to find a way to piss you off. Whether that link is a big problem or a non-issue is hard to predict ahead of time.
None of the issues I've had currently have come from where the drywall is connected to anything above it. Paint blistering and stains are in void areas. I've asked them the question though. Also, there are zero issues in the winter, only the summer and only for a few days where the dew point is a bit odd.
In the winter the issues can be tougher to detect as condensation freezes and the relative humidity is far lower above the ceiling. But the lumber does suck up moisture and that’s why you sometimes see mold or ghost lines on the ceiling.
This is a pretty big company, not a fly by night so I assume they know what they are doing.
Cover the beer bottle outside with a waterproof shield to stop humid air touching the glass and there won’t be any condensation there. Look at foam bottle cosies.
It's all orders of magnitude. Right now, the cavity is the big issue. Fixing the cavity means the next weakest link tries to find a way to piss you off. Whether that link is a big problem or a non-issue is hard to predict ahead of time.
I'll chat to them when they are here. If it's an issue (they see wet joists in the ceiling say) then they can add some materials and labour to the last part of the job which is the drywalling.
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