# Ceiling insulation in shed/home.



## TNbear23 (May 31, 2014)

Ok,I am in desperate need of advice. We have a 16 x 30 shed, it has a metal roof and siding, framing is wood. When it was built the builder installed bubble wrap (not sure what it is really called) under the metal roof and siding. There is no plywood/osb. We were told this would act as a vapor barrier. Well here's the problem, we live in an area that gets cold and heat is needed. We installed bat insulation between the rafters and studs. All was good until winter, now we have a water problem, condensation. After some research we purchased foam board to install as a solution. Nope, that's not working. I have looked all over the web for an answer. Some say leave a 1" air gap, others say don't. We do not have the typical vents in the back and front you see in most sheds, nor do we have a ridge vent. Our shed was a custom on site build. We have a peak roof and would hate to lose the interior height by having to install a drop ceiling. I am so frustrated, as of now we will have to replace all the ceiling insulation because it has gotten wet, which is going to be expensive. If we don't come up with a way to fix this we are afraid our only option will be to remove the metal roof, install decking and reinstall the roof, neither of us is comfortable (knowledgeable) to do this. Help.


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## jwal10 (Jun 5, 2010)

You need roof ventilation. This is why I always tell people to put plywood on, heavy roofing felt, then metal roofing. Leave a 2" gap at peak in the plywood, then the roof vent ridge cap. Did you leave the air gap when you put up rigid insulation? Wouldn't do any good unless you have vents. Problem with no attic is air movement and not letting all the heated air out. Need eave vents, gap and ventilation to stop condensation....James


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## MattB4 (Jan 3, 2016)

You probably need to go to spray on foam insulation. You will also want some form of ventilation for your structure if you have a bathroom and kitchen. Through wall fans are available.


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## Steve_S (Feb 25, 2015)

Sorry to say this but it's likely occurred to you already. You bought a "shed" designed without the intention of being heated. I live in an area that swings from extreme heat to cold, moist to dry and tin is common. The tin will condense water and leach it into your insulation. A proper roof with heating inside, would provide an airspace between roof decking and tin with either black paper or roof membrane / underlayment. Alternately, battens on top of the rafters with StyroVents between the rafters can create the air channel as well BUT does not protect the insulation under it... and wet insulation has no insulation value.

Here is my roof, 2x8 Rafters, 5/8-T&G Roofdeck, Underlayment wrap, 2x4 battens in parallel over the rafters with 1x4 cross battens with the tin attached to those.

Pic#1 Battens and Cross Battens laid out over the Roofing Underlayment.
Pic#2 3" Air intake Channel (eaves/soffit side) 
Pic#3 underside of air channel
Pic#4 Finished underside with std soffit & tall facia. (Facia is 12" in this install)


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## Fishindude (May 19, 2015)

That bubble wrap is "bare minimum" stuff to keep the underside of an un-insulated, unheated shed from sweating and dripping in summer.

Here is how I would handle a building like that.

1. Install a plywood, OSB or metal ceiling on underside / bottom cords of trusses creating a flat ceiling in this building. This assumes you have conventional trusses, rather than cathederal or scissor type trusses.

2. Place plenty of blow in or fiberglass insulation directly atop the new flat ceiling.

3. Ventilate the attic space above ceiling with vents in the gable ends or a continuous ridge vent.

Now you have a cool / vented attic space with an insulated / heated work space below, just like you would build a house.


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## TNbear23 (May 31, 2014)

Fishindude said:


> That bubble wrap is "bare minimum" stuff to keep the underside of an un-insulated, unheated shed from sweating and dripping in summer.
> 
> Here is how I would handle a building like that.
> 
> ...


We have what I guess would be considered cathederal, so we would have to create something to attach the OSB to. Not real sure how to go about this and keep as much ceiling height as possible. We are beginning to think this maybe our best option. I believe there must be a solution, a lot of people are converting sheds into homes.


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## Steve_S (Feb 25, 2015)

Photo's of the existing framing would be helpful. Is it 2x4, 2x6 or ? More info you can provide will result in better / more complete answers or suggestions.


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## Fishindude (May 19, 2015)

OK, you have a cathedral ceiling, probably a couple issues, but here is how you are supposed to do it:

1. Assuming your rafter / joists are 16" or 24" on center running up / down the slope. For discussion purposes, let's just assume the rafters are 2x8's.
2. Install rolls of kraft faced 6" insulation between and stapled to the underside of joists, kraft facing towards interior. 
3. 6" Insulation with 8" joists will leave approx. 1.5" gap between top of the fiberglass insulation and underside of the roof decking. This will be the vented attic space.
4. Install a plywood, OSB or metal ceiling on underside of insulation anchored to underside of roof joists. This is your finished ceiling and will provide a good tight separation between the warm and the cool space.
5. Roof needs soffit venting to allow air into the gap between joists and they make carboard baffles you nail between joists to assure that insulation doesn't block the flow of air.
6. Then you need a continuous ridge vent to allow the air to escape from the gap between joists. Essentially you have created an small shallow, cold vented attic between each pair of joists.

Just do an internet search for "insulating a cathedral ceiling" and you can see numerous illustrations, showing how to do it.


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