I need to insulate my ceiling.
The ceiling is 2by8 joists below a mostly flat roof with a slight pitch. It's a tarred rolled roof.
I was just going to use fiberglass batts and vapor barrier poly but my uncle said that moisture could build up in the ceiling causing mold/rot and I should have it spray foamed instead.
Is moisture enters the ceiling somehow from the roof, wouldn't it just exit the same way?
People use fiberglass batts in their walls and it doesn't cause moisture to build up. Why would the ceiling be any different?
Is he moronic or is this a serious concern?
I don't have money for spray foam.
It’s not insulated now? How is that possible?
Spray foam is well on it’s way to being banned and will be remembered as fondly as lead paint, aluminum wire, CPVC pipe, and asbestos.
>It’s not insulated now? How is that possible?
What?
It was an unfinished garage.
>Spray foam is well on it’s way to being banned and will be remembered as fondly as lead paint, aluminum wire, CPVC pipe, and asbestos.
Okay so what do I use instead?
>That's a ventilation problem and it has nothing to do with the type of insulation
I said the ceiling/roof is 2by8 joists. You can't really ventilate that.
Well then i guess your other option is a false ceiling like pic related
How is that my only other option?
There must be billions of buildings with low slope roofs with drywall on the joists? Do all of these buildings rot away from mold? I doubt it.
>Hence people are telling you that you need to vent it, moron.
LMFAO
So I need to put 25 fricking vents on my joist for each joist cavity?
This is unironically what you are saying right now.
you need to ventilate the room that's it, you could even do it by opening a window 3 times a day for 10 minutes, but installing a vent is usually the best solution
>you could even do it by opening a window 3 times a day for 10 minutes
Even in the winter?
This clearly isn't the right answer.
People with these types of roofs don't have this problem. Just admit you don't know the solution.
I'm not going according to code. I don't mind if it's slightly less energy efficient. I just don't want a moisture problem.
>Even in the winter?
man read this https://en.wikipedia.org/wiki/Heat_recovery_ventilation
https://en.wikipedia.org/wiki/Recuperator
welcome to the 21 century, we can ventilate without losing most of the heat, that will make your air healthy, get rid of the excess humidity and any air contaminants.
still you will need a vapor barrier as you have been told
answered already
these are correct. problem solved.
>solution: keep your window open in the winter
Yes, this makes sense.
If my pipes ever leak I guess I should just run a dehumidifier 24/7 instead of actually fixing the problem.
>solution: keep your window open in the winter
>you could even do it by opening a window 3 times a day for 10 minutes
???? No bugs in the winter to worry about, you're literally venting out humid air to keep condensation from building up.
It's obvious that you are not taking any advice from anyone here so the real advice is to call and pay an expert for this question rather than going on a japanese forum board for real life questions.
>It's obvious that you are not taking any advice from anyone here
Nobody here is giving an actual solution. Just band aid fixes.
>leak in your plumbing? Just put a towel there and run a dehumidifier lmao
>drywall unfinished? Just put some bedsheets up lmao
A finished apartment I am going to live in.
Nope.
Will you have full plumbing?
>It was an unfinished garage.
What is it going to be?
a cute studio apartment. No pets, credit score 750+, first and last months rent plus cleaning deposit plus application fee. Parking spot is an extra 120$ per month.
Rockwool
>Spray foam is well on it’s way to being banned
y
I don't know what he's specifically talking about but spray foam is absolute fricking garbage to work with after the fact, burring pipes, wires, etc, and should be banned in most residential applications for this reason alone. Next, you have the blowing agents used in most spray foam to be pretty fricking bad for the environment, then you have off gassing. Finally, it's all too often used as a catch all "fix" for moisture problems. "Oh you have moisture and stuff there? just spray foam it!" only to creature moisture sandwiches where all kinds of rot and mold problems can happen.
oh man people act super weird when i always point that that crap shouldnt be used for whatever weird shit as the fix it all
you forgot that if some of it gets uncured could be releasing shit slowly and the inhabitants could end developing weird allergies. but i think that one is fixed in the new stuff
IDK man I'm pretty fricking weird about stuff in general so I don't give a frick. Like, I won't use PEX in my own home because of microplastics and leaching. Won't use chipboard and MDF if I can absolutely help it. That kind of stuff. We're just poisoning ourselves for the convenience.
Out of curiosity, I needed to insulate my attic in my old ass house. I was looking into rigid foam insulation, since I found some that was about 4 inches thick and where I am, that's basically gonna hit the value. There an issue with solid foam that I should know about?
>rigid foam insulation
nta i am
why that one? at least in my country that is usually used when you need the insulation to be able to stand a load, ie is used in roofs, or in the basement bellow the concrete pour.
i always recommend fiber insulation if possible
Because I intensely dislike fiberglass, humidity is high in the attic due to my location, and the use of solid foam would mean that I could easily fill the attic, throw down a floor, and have a finished attic for storage and installation of utilities later, such as an HVAC unit. See, this house was built in the 20's, and has seen one modernization retrofit in the 90's, so while it hit code then, it doesn't hit code now. However, this house was built out of thick heart pine and is built up more than a modern stick house, so in terms of restoration potential, it's extremely high. I plan on completely redoing everything to modern standards and above code. Fiberglass would be easier, but for it to work, I'd have to build up the supports, or I could spend more and have the exact R value needed, followed by a floor that raises R-value further and adds storage. Potentially even an office or art room in the future. Basically, I'm hoping to add on some square footage doing this. No plumbing obviously, that's just asking from trouble, but a storage room and an upper office and crafts room would significantly raise value.
so you need a loaded structure, then i guess go for it. but at least in my country, rigid foam with structural capacity is very expensive compared with any other non structural insulations.
also, if you plan to prepare to use the attic in the future as habitable space, why not insulate the attic roof, you get another fully insulated area. I plan to do that myself
and there is rockwool, some plant bassed fibers, cotton based and other fibers, fiberglass is nasty
It is expensive. It's gonna be about 4,000 in total vs 1,800. However, one degrades over time, loses effectiveness, requires more wood to be installed, can house rodents if I'm unlucky (I live right next to a large chunk of forest about 140 acres in size, no neighbors,) and will eventually need to be replaced. The other is two and a half times more expensive for the R value, but will outlast me, is structural, and doesn't give a single shit about water, compression, or rodents if worse comes to worst. And yes, I plan on finishing the roof as well. I wanted to do some reflective foil, a baffle vent, more rigid, and some drywall, with the exception of some voids to allow for the running of some flex conduit for the incoming electrical rework since THHN in flex is usually about the same as Romex at this point, allows for easier replacement and upgrading, and gives defense against accidental wall intrusions, that will go into some specifically designed voids to mount the jackbox for termination, so I can then cover that with an insulated cover that rivets in with quick release tabs. Out of sight, out of mind, easy access for adjustment and repair later.
The only reason I can do this is because previous owners did absolutely NOTHING in the attic, so redoing everything proper is absolutely simpler than a normal retrofit. Starting from nothing is better than starting from wrong.
>moisture could build up in the ceiling
That's a ventilation problem and it has nothing to do with the type of insulation. All that matters is that you have enough air-movement in your attic.
havent said where you are lol!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
how old is the roof?
preferred method is cold roof where joists don't transfer heat. i.e. you put solid insulation sheets on top of the whole lot and then roof finish on top of that. you can buy steel roof sheets with insulation already bonded to the inside you just put it straight down on the deck.
>havent said where you are
Ohio.
>how old is the roof?
It was redone like 10 years ago, it's still in good condition.
>you put solid insulation sheets on top of the whole lot and then roof finish on top of that. you can buy steel roof sheets with insulation already bonded to the inside you just put it straight down on the deck.
I already have a roof. Why would I add a whole bunch of shit on top of my roof just to insulate my ceiling?
The vapor barrier stops condensation building up, it's standard building so there's nothing to worry about.
If your roof space doesn't vent that's a separate issue, usual response is a passive hood vent
why do people keep telling me to individually "vent" 25 or so 2by8 joist cavities?
You’re an annoying homosexual, I’m surprised your uncle even bothered to give you any helpful advice at all. Warm wet air rises to the top of an unconditioned space that has no venting. At night the moisture will condense on a surface thats lower than the dew point, like your insulation. Hence people are telling you that you need to vent it, moron. Come up with a solution, cut a hole in your roof and install a draft motor, cut a hole near the top of a wall and install a vent. Both easy and cheap. Or be an obstinate whiney homosexual like you are in this thread.
Ohio energy code requires R-38 insulation in a roof. In a 2x8 rafter cavity you can't get much more than maybe R-25 with fiberglass insulation. You could scab some 2x4's to the bottom of the 2x8's to make a 12" cavity which would get you to R-39 with fiberglass, or you could just put fiberglass in the existing roof and attach 2 or 3 inch rigid insulation on the ceiling.
>Ohio energy code requires R-38 insulation in a roof.
That high for a residential roof? What the frick?
Minnesota commercial buildings need to hit R-30.
So much misinformation and myths out there
The danger with a cold roof is that moisture from the INSIDE condensates on the roof when you heat the inside. You heat the air inside, it takes up moisture and if the hot moist air can reach the cold roof it will cool and condensate there and the joists get wet.
You just make sure that (1) the vapor barrier is air tight all the way. Tape the edges and don’t stab it with screws or nails or run conduit or whatever through it and (2) keep the humidity inside as low as reasonably possible by ventilating the room itself.
There’s no real way to ventilate the inside of the ceiling unless it’s a gable roof and you let the wind blow through it from below but that would beat the purpose of insulating it pretty much (because cold air would blow through the rockwool). Don’t get the cheapest vapor barrier available
> Is moisture enters the ceiling somehow from the roof, wouldn't it just exit the same way?
Yes but it shouldn’t. Water on the roof evaporates much easier into the outside air than into the roof because fricking wind. If liquid water comes in you have a roof leak. If you live in the tropics where the roof will be colder than the outside air in the morning, use vapor-closed on the cold side
t. rot inspector
Should I use rigid foam in the joist cavities against the osb on the roof?
and then spray foam the edges or something?
it's itchy bros.....
the new fiberglass batts arent itchy
Why are you living in a garage