Insulating ceiling joists before drywall
I have a detached garage that I am about to drywall. I have insulated the walls but I am wondering what the best way to insulate the ceiling is.
The bottom chord of the trusses define the ceiling. Since the pitch of the roof is low I would like to insulate it before drywalling if possible because it seems like it would be much easier. The space is clear except for some can lights which I can insulate around.
Thanks in advance for any help.
Replies
Kev-
What about 'insulating as you go'. Basically, put up a few sheets of sheetrock then get on a ladder and throw some bats in. Start with sheets along the eaves and work towards the middle. Then, for the last few bats, you're only in the attic a short while and you're only workign in the area with the greatest clearance. Will there be attic access?
You could also do blown-in insulation - you'd have to be in the attic for all that.
You can also hold insulation in place between joists/truss cords using spring clips - basically a thin piece of metal slightly longer than the truss spacing. Just push it up to hold the bats in place. The only drawback is the small air space created by the arch of the spring between the bottom of the bat and top of the sheet rock.
Also, don't forget to create a channel for ventilation at the eaves.
Have fun!
Jason
You could fasten netting loosely on top of the trusses (so it can easily bulge upward) and blow cel in from the bottom.
Thanks for the suggestions. I guess I just need to start. I like the idea of putting in batts as I install drywall. That should be pretty simple. I was not planning on adding attic access right away though; I figured I would cut a hole when I need one :). I am not aware of any code that requires access but I haven't actively checked it out either.
The spring clips sound the way to go for me.
FHB had an article on air tight attic schuttles some time ago. Might find it in tier archieves.
I would install the vent baffels at the eave walls and the build the acces hatch. Hang the 5/8" f/c drywall with glues and screws,finish, and then call someone for blown cellulose insulation. Cellulose maybe a little more expensive, but air movement within the insulation drops to near zero. You end up with a much better job overall.
FHB also did a insulation comparison article you may want to read b/f you make up you mind. JLC or FHB (CRS) one also did an article on fiberglass insulation detailing that is a must read if you decide to go that route.
Dave
"...the small air space created by the arch of the spring between the bottom of the bat and top of the sheet rock."Why is this air space a problem?I'm trying to plan a similar insulation job, in a subroof coming out of the side of the house and over a kitchen. I expect furring strips fastened to joists (both metal), so I figure I'll hang bats on the furring strips which will be 16oc. My only issue is covering recessed can lights (ic-rated air-tight), R-38 will be about 11", so I'll have the height. And given opinion here that FG is POS, I'll be using a cotton alternative.Since such subroofs can be a source of air leaks between the floors of the house, I plan to spray polyurethane foam on the inside of the roof to close air leaks.My impression is that there are no easy solutions with these roofs....
I am no expert but I think that air spaces between insulation and walls or ceilings are bad because they can create convenction loops and air movement.
Around here fiberglass is used to insulate floors (access from crawlspace). I believe the metal wires have been banned, though I'm not sure why. What is used instead is thin poly twine stapled to the bottom of the joists. The same thing would work well for your application. Stick the batt in the bay, zig-zag and staple the twine to hold it, install drywall. Be done in no time.
First of all batts must be above the ceiling line instead of the rock carring the weight "wet" during finishing and texturing. If you have say 24 inches on center and used 5/8s fire code it would hold it unless you used a blown texture that holds 40 gallons of water per 1000 per sg ft. An orange peel would hold hardly anything and smooth would just be paint that does soak in two coats wetting the rock all the way to the back side. The most common compromise is to insulate after the finish and final texture or paint is completed , letting the rock dry back out before loading it . The most common mistake is to staple insulation to the bottom of the joice line creating loose rock that also tends to sag. If you do decide to insulate before hand , make sure the insulation is "above the level line of rocking and the staples are what is holding the weight of the insulation. The face of joices or studs belong to the drywall alone.
Secondly any uninhabited attic space needs an access of 24 "x 30 ".
Tim Mooney