Ceiling Insulation Questions...

[Everyday]

I'm getting ready to insulate and drywall my garage ceiling. I'm going to use the blow in cellulose insulation from Lowes. It's less than half the price of fiberglass batts so it seems like a good way to go.

The question I have is, do I need to put a vapor barrier against the trusses before drywalling and insulating? I have vented soffit and ridge vent and I plan to eventually install central heating and AC.

I'll probably try to insulate and drywall the side walls in the spring which I know will need a vapor barrier since its going directly against the metal siding of the pole barn. The ceiling is the only one that has me stumped.

Anyone done this? If so, how did it go?

 

[Graham08]

I did not install a vapor barrier when I did my ceiling and had no problems, but the building has been kept heated since new.

I did install some styrofoam "chutes" at the eaves to keep the blown in insulation away from the vented soffits and allow air to enter the attic from the soffit vents. I think I got them at Lowe's.

 

[Everyday]

I was planning to use the "chutes" as you described them to keep the insulation from blowing into the soffits.

Heating and cooling the space is a whole other issue for me. Trying to determine if a ductless or ducted system is right for me. In any case, if I have a vapor barrier below the concrete and I'll put one on the walls it would make sense to put one on the ceiling. But again, just not sure.

 

[rburke65]

My answer would be...I have never seen insulation that was labled "For Ceilings Only" because it lacked a vapor barrier, so yes I would be putting up a vapor barrier. My 2 cents.

 

[boiler7904]

I'd look at using a foil backed gypsum board for the ceiling. The foil backing acts as the vapor barrier.

USG Foil Backed Sheetrock

 

[Everyday]

Foil backed insulation, that's a good idea. Adds a little more fire protection too. I'll check it out. Do they have that stuff at Lowes and Home Depot?

 

[lt1nut]

IF you plan on ever heating a space it must have a vapor barrier on the heated side of the building envelope. Reasoning is that you do not want any moisture to transfer into the dew point range/temperature. IF that is allowed to happen the moisture will drop out of suspension (from the air) and collect on the top of the ceiling material or in the insulation. Ever been in a tent when it was cold outside and had water droplets form on the inside of the tent ceiling/walls?

In all honesty, visqueen(sp?)/plastic is very cheap, staples for attaching it to the trusses even more so.

 

[Snowbound]

lt1nut is right on. Use the vapour barrier in ALL heated spaces! You know how a cold beer bottle sweats on a warm day? Well think of that cold attic space against your new warm drywall on the ceiling. That drywall will be ruined in a few years from all the condensation/frost building up on it.

The poly is pennies compared to drywall. Get a roll of that red Tuck tape to seal the joints and some poly boxes for the outlets and light boxes. Tape and seal everything!

I just finished my ceiling today. PM me if you have any questions.

Brian

 

[Graham08]

Wow. Never seen vapor barrier on a ceiling, and I've spent my share of time in attics when I worked for an electrician. Something to keep in mind for the shop at the new house...

 

[rancherbill]

It all depends on your location.

Here, in Canada, they are required. You do not want moisture going through the drywall and condensing in the insulation.

Go talk to a local store that has qualified people and ask, or phone a drywalling company and pull the old "Do you have a minute? I have a dumb question" routine.

 

[SUPERFORD]

here in VA, neither the architect, the building contractor, the insulation company, nor the county building inspection office called for vapor barrier in either the walls or the attic of my garage.

the insulation company went as far as to say that it was a BAD idea when using sprayed cellulose or spray foam.

maybe it's different with fiberglass?

 

[Everyday]

Thanks for all the input. My initial thought was to just staple plastic sheet/rolls to the trusses. I have to admit that I never thought of taping the electric boxes though. Obviously I would have taped the seems just to keep things neat. 2400 sq ft garage with 14 foot ceilings, looks like I'm renting a scissor lift!!!

 

[rburke65]

Anything that you can do to keep the heated air in the garage and not have it escape into the attic.

 

[boiler7904]

Foil backed insulation, that's a good idea. Adds a little more fire protection too. I'll check it out. Do they have that stuff at Lowes and Home Depot?

You could use faced insulation but the foil backed gypsum board would be more continuous.

Home Depot and Lowes probably don't have foil backed gypsum board but you could get it through a local drywall supply house.

 

[boiler7904]

here in VA, neither the architect, the building contractor, the insulation company, nor the county building inspection office called for vapor barrier in either the walls or the attic of my garage.

the insulation company went as far as to say that it was a BAD idea when using sprayed cellulose or spray foam.

maybe it's different with fiberglass?

Closed cell foams act as a vapor barrier.

 

[boiler7904]

Thanks for all the input. My initial thought was to just staple plastic sheet/rolls to the trusses. I have to admit that I never thought of taping the electric boxes though. Obviously I would have taped the seems just to keep things neat. 2400 sq ft garage with 14 foot ceilings, looks like I'm renting a scissor lift!!!

If you're installing a vapor barrier, every penetration needs to be sealed otherwise the vapor barrier is not contiguous and therefore not useful. It actually starts to do the opposite of it's intended purpose and trap moisture near the opening.

 

[5wndwcpe]

Thanks for all the input. My initial thought was to just staple plastic sheet/rolls to the trusses. I have to admit that I never thought of taping the electric boxes though. Obviously I would have taped the seems just to keep things neat. 2400 sq ft garage with 14 foot ceilings, looks like I'm renting a scissor lift!!!

Before renting, consider buying a scissor lift. I bought a one man JGL for $2000 for my shop build and honestly couldn't imagine going up and down a ladder every time I ran a circuit or did any of the overhead work for that matter (16' ceilings). Even if I sold it for $1500 when I'm done with it, it's still far cheaper than renting.

 

[lt1nut]

You don't say where you live so I went to your business link and it says it's in Philly. I assumed it was a cold area from your post when you mentioned heating ducts. Different areas of the country approach vapor transmission differently, if you are really interested in it pick up the book on insulation techniques that is published but the Taunton Press (Fine Homebuilding).

What it amounts to is that you want the vapor barrier towards the predominantly hot side of the building envelope. In the northern states that is the interior side, in the (far?) southern states that is on the exterior side. The reason for this is that warmer air has the capacity to hold more moisture (grains of water) per give cubic measurement than cold air does. Another way of stating this is that cold air is "denser".

I assume that Philly is considered a cold climate as there are more heating days than cooling days. I recommend sealing up any "hole" in the vapor barrier/drywall/insulation with caulk, tape, and/or expanding foam.

 

[Everyday]

Sealing up any holes in the vapor barrier appears to be the key. The question I have is how close can I run the plastic to the recessed lighting fixtures yet still seal it up? They are safe for contact with insulation but plastic is a whole other story.

 

[tfi racing]

If the fixtures are rated for direct contact with insulation,poly will be safe also.Up here they sell poly "buckets" to use with pot lights and such,a lot easier than trying to seal them other wise.