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Will adding plywood over exposed joists and insulation in attic impact home insulation?
Posted on 1/31/25 at 8:51 am
Posted on 1/31/25 at 8:51 am
I have a huge attic, but probably 3/4ths of it are just exposed joists with pink insulation between them. Insulation doesn't stick up above joists, so adding plywood won't compress it at all, which I read wouldn't be good.
I would like to have more storage space and I'd love a bit more insulation. Will plywood make any difference in the latter? My assumption was minimal.
Any other issues with this I need to be worried about? Should I leave small gaps between the plywood sheets for moisture reasons?
I would like to have more storage space and I'd love a bit more insulation. Will plywood make any difference in the latter? My assumption was minimal.
Any other issues with this I need to be worried about? Should I leave small gaps between the plywood sheets for moisture reasons?
4
Posted on 1/31/25 at 8:55 am to CatfishJohn
So no blown in insulation, just laid between the joists?
Posted on 1/31/25 at 8:57 am to calcotron
Looks like this:
Posted on 1/31/25 at 9:00 am to CatfishJohn
So, you just want to deck the attic? It shouldn't be a problem. I would leave a little gap (1/4") between boards if you're worried about moisture. It's an attic deck. It's doesn't need to be air tight or visually perfect.
Just watch it around any ventilation for stove hood vents and clothes drier.
Just watch it around any ventilation for stove hood vents and clothes drier.
Posted on 1/31/25 at 9:02 am to CatfishJohn
Blanket insulation, or any insulation for that matter is compromised if it is compressed. Leaving it "fluffy" is the best way to insulate.
So no, simply placing some plywood over the joists so you can use that area for storage should have no impact on the insulation doing its job.
It's no different that insulating an outside wall and covering it with sheetrock.
So no, simply placing some plywood over the joists so you can use that area for storage should have no impact on the insulation doing its job.
It's no different that insulating an outside wall and covering it with sheetrock.
Posted on 1/31/25 at 9:03 am to CatfishJohn
think of it like this:
the physical insulation isn't what insulates, it's the air that is trapped or not allowed to flow through which actually insulates. It's more important to make sure you have a) full cavities and b) be as sealed as possible to not allow any air movement through.
this kind of explains it:
https://www.energyvanguard.com/blog/compressed-fiberglass-insulation-really-so-bad/
edit to add on this comment:
correct, just for clarification, i mean sealed with regard to the conditioned space.
the physical insulation isn't what insulates, it's the air that is trapped or not allowed to flow through which actually insulates. It's more important to make sure you have a) full cavities and b) be as sealed as possible to not allow any air movement through.
this kind of explains it:
https://www.energyvanguard.com/blog/compressed-fiberglass-insulation-really-so-bad/
edit to add on this comment:
quote:
It's an attic deck. It's doesn't need to be air tight or visually perfect.
correct, just for clarification, i mean sealed with regard to the conditioned space.
This post was edited on 1/31/25 at 9:05 am
Posted on 1/31/25 at 9:05 am to gumbo2176
quote:
So no, simply placing some plywood over the joists so you can use that area for storage should have no impact on the insulation doing its job.
It's no different that insulating an outside wall and covering it with sheetrock.
Would it actually help the insulation? I assume a little bit?
Posted on 1/31/25 at 9:07 am to CoachChappy
quote:
It's doesn't need to be air tight or visually perfect.
I give no shits what it looks like. As far as sealed, I just read some horror stories online about moisture and it's important to leave gaps (like 1") between boards.
I'm trying to decide if I want to deal with this. If it not only gives me more storage, but also helps insulation a bit, I'm more likely to be motivated to deal with it. I'll have to cut the damn boards to get them up there.
Posted on 1/31/25 at 9:14 am to CatfishJohn
quote:
Would it actually help the insulation? I assume a little bit?
I think you'd likely gain some upgrade in comfort if heat and cold is kept at a minimum from even reaching the insulation in that area and is contained more so in just the actual attic space.
How much more---------------I don't know. Guess you'd have to have an expert in the field answer that question.
Posted on 1/31/25 at 9:15 am to CatfishJohn
if you're just throwing plywood on top and screwing down, there will be some gaps. if you're having that much moisture, you've got bigger issues.
where moisture would come from is if warm humid attic air is directly against the back of the ceiling sheetrock or light fixtures where the sheetrock is cooler and creates condensation. but man, even that you'd have to have your house an ice box.
where moisture would come from is if warm humid attic air is directly against the back of the ceiling sheetrock or light fixtures where the sheetrock is cooler and creates condensation. but man, even that you'd have to have your house an ice box.
Posted on 1/31/25 at 9:18 am to Coon
Posted on 1/31/25 at 9:33 am to Coon
quote:
if you're just throwing plywood on top and screwing down, there will be some gaps. if you're having that much moisture, you've got bigger issues.
I just left an 1/8" gap between sheets and I've never had any moisture issues.
I'd hate to have a 1" gap between sheets. Seems like something would always be falling and getting lost in that crack.
Posted on 1/31/25 at 9:39 am to Shexter
quote:
I just left an 1/8" gap between sheets and I've never had any moisture issues.
I'd hate to have a 1" gap between sheets. Seems like something would always be falling and getting lost in that crack.
Yeah that was just one thing I read online. I was thinking 0.5", but may do what you did.
Posted on 1/31/25 at 10:22 am to CatfishJohn
I wouldn't worry about gapping for moisture too much. Not going to hurt to leave a gap here and there though.
You may consider strapping the joists up with something like a 2x4 on edge for extra insulation room if possible. Going perpendicular to the joists with the strapping will give a a bit of thermal break through to your ceiling. Unless you have 2x8 or better ceiling joists then your insulation really isn't great. You may want to blow in extra insulation at some point in the rest of the attic and then at least the storage area will already be done.
There, I just turned your simple storage project into a full insulation job. Don't forget to install vent baffles at the eves!
You may consider strapping the joists up with something like a 2x4 on edge for extra insulation room if possible. Going perpendicular to the joists with the strapping will give a a bit of thermal break through to your ceiling. Unless you have 2x8 or better ceiling joists then your insulation really isn't great. You may want to blow in extra insulation at some point in the rest of the attic and then at least the storage area will already be done.
There, I just turned your simple storage project into a full insulation job. Don't forget to install vent baffles at the eves!
Posted on 1/31/25 at 1:34 pm to Turnblad85
as an aside you might check the load tables for the spans of the ceiling joists in question. should be OK, but you never know.
Posted on 1/31/25 at 11:46 pm to CatfishJohn
As long as you don’t push down any insulation, you won’t have any problem at all. If anything, a layer of plywood would add a little more insulating value.
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