Insulation help for my garage with pics

-
4spdragtop

4spdragtop

FABO Gold Member
FABO Gold Member
Joined
Aug 28, 2009
Messages
39,595
Reaction score
22,925
Location
Ontario Parts Unknown
I tried searching for the thread I started a while back but couldnt find it. I was at TimbrMart today and bought some "Silverboard" styrofoam to insulate my overhead garage door, and thought maybe I would use that to insulate the ceiling in my garage. Here is the issues, my rafters are currently open and would like to keep it that way as I put crap and stuff up there all the time(see pics LOL) I was thinking of insulating the actual angled part of the trusses instead of the flat horizontal 2 by's. I have been told if I put insulation up tight to the plywood sheating condensation will build up and rot the boards. Below I have listed options.

1. What do you guys think if I put use "silverboard" and put it up similar to the way you would drywall, just put it up on the angled trusses?? The "R" value on the "silverboard" is approx 5-6....nothing great but better than nothing.

2. Use "moore vents" and then insulation between the angled rafters.

3. Do what pettybludart mentioned earlier and I could staple poly or vapour barrier to the horizontal part of the rafters, and simply take it down and restaple when I need to get up there.

Im not sure of what would be best, but my soffits are NON vented, so I have to make sure that the roof sheating can "breathe", so that means drilling small holes every other rafter in the soffit to make sure it can breathe.

Garage is only 500sq ft, so it wont take long to do I hope.
Sorry for being so wordy, just trying to give as much info as possible.
 

Attachments

  • DSCF0299 (Medium).JPG
    121.7 KB · Views: 1,910
  • DSCF0300 (Medium).JPG
    157.4 KB · Views: 2,009
  • DSCF0301 (Medium).JPG
    85.7 KB · Views: 1,918
  • DSCF0302 (Medium).JPG
    81.3 KB · Views: 1,846
  • DSCF0304 (Medium).JPG
    111.3 KB · Views: 1,873
  • DSCF0307 (Medium).JPG
    58.1 KB · Views: 1,840
That foil board would be ok, but you need to make sure that you Tuck tape all the seams, and caulk the edges. You should Tuck tape that door too.
Nice job on the door, by the way.

If you had any more crap in the rafters, you wouldn't need insulation :bootysha:
 
Looks like your bottom chords need more webbing.I think I would address that before I put any more weight on it.Silverboard is cheap and works good-don't forget the Red Green duct tape.I would use screws with plastic stars-or nails with stars
 
Yeah the door isnt done yet, but I planned on tuck-tape on the seams. The garage is only 500 sq ft, so I use up every sq ft I gots!!
Don, I know the boards need more support. Are you saying to "silverboard" on the angled boards?? If so, I should still drill holes in the soffit though right so the roof can "breathe"

Thanks!!
 
If you drill holes in the soffits, bees, wasps, etc will LOVE it. Cut a hole and use a push-in round vent. Or replace the aluminum that's there with perforated stuff.

I do not know how to insulate between the rafters and avoid moisture problems. I'm sure there's a way.

If you would like to spend a small fortune, put about 1/2" plywood decking on top of the rafters, then batts of insulation between them, then staple some plastic sheeting to the bottoms of the rafters, then put some "whatever" up against the bottoms of the rafters. Garage attic is not heated. Put a plywood lift-out panel in there, or fold-down steps. I have the fold-down stairs and they're nice because you can get bigger stuff up in the attic.
 
Thanks fourspeed, I really dont want to be crawling up in there, my fat *** would probably get wedged!! I want to insulate, but keep my rafters for storage.
Thanks for the tip on the soffit vents!!
 
I think I would just go with a flat ceiling,but I would put a 2x4 in the center from the ridge to the bottom chord.then take a 2x4 from the bottom-on a 45,back up to the rafter,from there a 2x4 on a 45 back down to the bottom chord.When finished you should have a center post and an inverted W in the truss.Do this to every truss and you wiil strengthen your roof x 10 I usually drill the soffit with a 2" barrel bit,you can buy inserts at Lowes or home depot,Good luck,If you have a question just let me know. I see!You are trying to insulate just your rafters-you have got a job ahead of you.Make sure that you drill your ridge board too.If you dont the air will pocket at the ridge,and will not circulate.You will still need the webbing,maybe you can get your girlfriend in the rafters and you can cut insulation for her?eh?
 
Thanks again guys, hey lilcuda, I just signed up to the garage forum!! Pretty cool little site, just like here but for garages. Some of those garages are mausoleums!! Here is some advice a member there gave me...sounds like a good idea to me.

quote}I insulated a building once by attaching 1 X 4 to the bottom of the trusses running in the direction of the lower truss member, then cut the foam to drop in between trusses like a drop in ceiling. They will then lift out for access to the attic.
 
lilcuda said:
I recommend logging on to the Garage Journal Forum and asking the question there. Lots of smart people there talking about every aspect of garages. Here's the link to the Heating & A/C section
Click to expand...

WHAT? Do you mean that there are people smarter than us, and that Steve should probably listen to them over us?

Makes sense.
 
Garage Journal is a great site! You can insulate the top part of your rafters just below the roof (at an angle). You just have to leave a space for air to pass through.
In Australia they insulate the ceiling and the roof to stop heat from getting into the house. Will work the same to keep it in. Just make sure you leave an air space. The same idea as putting in your insulation stops by the soffits.

As for tape on the garage door, you can use the red tuck tape, sticks like **** to a blanket. But I would recommend silver foil tape. Works the same as tuck tape but is more esthetically pleasing to the eye.

I am a sheet metal mechanic and we use it all the time. I have even seen it used on a 68 barracuda to simulate the top piece of the trunk trim. You would be surprised with a little thin black pinstripe how good it looks from 5 feet away!

Good luck with the garage.

Dorian
 
The key to insulating the rafter cavity with fiberglass (or rigid foam insul) is to fill the cavity completely with insulation, without compressing it. You do want the air pockets to be maintained within the insulation. If you fill the cavity completely, then ventilation is not required at the eaves. The key to stopping the moisture is to have a continuous vapor barrier on the warm side to stop the warm moist air from getting into the wall and condensating. Condensation occurs as soon as the moisture in the warm air travels through the wall and reaches the dewpoint, which is approximately half way through the wall.

If you don't completely fill the cavity with insul then you will need ventilation at the eaves and the vapor barrier.

If your using the ridgid foam insulation the sheets already have a vapor barrier so taping the joints is definately needed. Be careful with the foam types of insulation because most of them are required to be cover with sheetrock because they are highly flammable. Some types are listed for use without being covered with sheetrock just check the labels on the sheets. Also I think fiberglass is a lot cheaper.

Hope this helps...
 
Thanks Dorian and Joethedog!
Dorian, I shoulda waited to tape!! Dang!! I had a roll of the tuck tape and 3/4 done already. Oh well. Good idea though, I still may use the silver foil, but $$ pending. I couldnt believe the "silverboard" was $30 for a 4x8 sheet 1 1/2" thick. So $120 already spent on the overhead door!! Jeez!!

Joe, are you saying that if I completely fill the hole in the angled part of the rafters and vapor barrier the bottom side of the angled truss that there wont be any moisture? I always thought you had to have a gap with ventilation between the insulation and the "outisde"??

Whats your input as to doing what the guy from "garage journal" said? Basically making a t-bar ceiling with 1"x4" and dropping in rigid board?? If I went this route I was thinking of cheaping out with the 3/4" silverboard as its $12 for a 4x8 sheet.

Thanks for the responses and looking forward to more!
 
That's what all the experts have told me. If you fill the cavity, and vapor barrier no ventilation is required. I know it sounds wierd, but if you stop the warm moist interior air from getting into the wall and condensating then there's nothing to ventilate. If you think about it, you don't ventilate the walls, they're filled with insul, and vapor barrier. It's all about the interior moisture, not the exterior moisture. The exterior moisture is kept out by the roof, and the siding assemblies, tar paper, tyvek, shingles, siding, cualking, etc...

If I wanted to insulate the ceiling of my shop I would sheetrock the ceiling, installed unfaced fiberglass insul above, and ventilate the attic space. Install the insul as you sheetrock. Just lay it on top. Or you can have a insulation complany come in and install blow in insulation which is just ground up fiberglass. they'll probably blow in about 12 inches, and it would cover everything, very efficient. No warm side vapor barrier would be needed because any moisture that got through from the warm side is ventilated out through the attic vents. If you still want to be able to store stuff above install an attic access ladder from Lowes,or Home depot, the kind that folds down. Be careful not to put to much up there because the trusses weren't design to carry a strorage load. Also don't forget the walls, no sense doing the ceiling if you don't do the walls. Doors, windows? You want to create a complete thermal envelope. Then you'll be toasty warm when your workin' on the toys...
 
4spdragtop said:
are you saying that if I completely fill the hole in the angled part of the rafters and vapor barrier the bottom side of the angled truss that there wont be any moisture? I always thought you had to have a gap with ventilation between the insulation and the "outisde"??

Thanks for the responses and looking forward to more!
Click to expand...


I know this topic is a few months old, but did you get it figured out? We do commercial engineering design here at work and although I'm a mechanical designer the architectural guy is in the office next door so I may be able to help you out. To do what you're thinking of just picture what a cathedral ceiling looks like - it's insulated exactly the same as the walls are ...roof sheathing-batt insulation-vapour barrier-interior finish
 
I spoke too soon, just spoke with the expert and there IS an air space between the roof and the insulation. I still have some suggestions for you if you haven't already taken care of this
 
I would put Stro vents in every 3rd truss. Use bat insulation to fill in the gap area left over from the vents.Put R13 in the ceiling Poly it then add what ever to the underside. R13 isnt thick so it shouldnt be sticing up causing problems with stuff in the rafters....Remember you need air flow and dont put any insulation in tight...........I did this for a living along time ago...........Door looks good......Edd BTW.........If the bat insulation bugs you , glove mask and then a cool shower for a bit then to hot.......Keep the pours open to get rid of the insulation........Hot water opens them......JM2C
 
No I still havent attacked this project yet, I temporarily stapled up some poly on the bottom of the trusses fro now.
 
that'll help keep some of your heat in.

I gotta say one thing that you probably already know first ...you need to be careful how much weight you put up on those 2x4s or you run the risk of throwing one more piece up there and having the whole works coming down on you - especially if there's any snow load on the roof.

with regards to your insulation plans, most of what you were thinking will work for you and some ideas are more efficient than others. the thing here is if you break some of the cardinal rules you run the risk of either causing other issues or just wasting your money because you'll defeat the purpose of what you're trying to accomplish.

if you go with your original plan of just throwing the rigid insulation up against the roof sheathing your problem won't be moisture (as long as you tape the seams). the problem will be ice damming on the outside of the roof ...see all those icicles hanging off the eaves? Roofs are different than walls in areas where we get snow. You need to keep the roof itself cold, meaning as close to the same temperature on the inside as on the outside, this is done by maintaining an air space between the insulation and the roof. this air space must be vented so the air will flow. You can accomplish that by fixing your rigid insulation to the trusses and not the sheathing, but as stated before you will need to vent the soffit. In the case of cathedral ceilings (essentially what you have) a ridge vent is used at the peak ...you could probably get away with just using a gable vent at each end of your garage.

follow me so far?
 
4spdragtop said:
I tried searching for the thread I started a while back but couldnt find it. I was at TimbrMart today and bought some "Silverboard" styrofoam to insulate my overhead garage door, and thought maybe I would use that to insulate the ceiling in my garage. Here is the issues, my rafters are currently open and would like to keep it that way as I put crap and stuff up there all the time(see pics LOL) I was thinking of insulating the actual angled part of the trusses instead of the flat horizontal 2 by's. I have been told if I put insulation up tight to the plywood sheating condensation will build up and rot the boards. Below I have listed options.

1. What do you guys think if I put use "silverboard" and put it up similar to the way you would drywall, just put it up on the angled trusses?? The "R" value on the "silverboard" is approx 5-6....nothing great but better than nothing.

2. Use "moore vents" and then insulation between the angled rafters.

3. Do what pettybludart mentioned earlier and I could staple poly or vapour barrier to the horizontal part of the rafters, and simply take it down and restaple when I need to get up there.

Im not sure of what would be best, but my soffits are NON vented, so I have to make sure that the roof sheating can "breathe", so that means drilling small holes every other rafter in the soffit to make sure it can breathe.

Garage is only 500sq ft, so it wont take long to do I hope.
Sorry for being so wordy, just trying to give as much info as possible.
Click to expand...



You might want to add some x -braces between the boards that run across. I see one one of the board twisted all ready( the one that has the red wire). If they go then the roof might come down. I would add the every 3 feet or so.
 
JoeTheDog said:
The key to insulating the rafter cavity with fiberglass (or rigid foam insul) is to fill the cavity completely with insulation, without compressing it. You do want the air pockets to be maintained within the insulation. If you fill the cavity completely, then ventilation is not required at the eaves. The key to stopping the moisture is to have a continuous vapor barrier on the warm side to stop the warm moist air from getting into the wall and condensating. Condensation occurs as soon as the moisture in the warm air travels through the wall and reaches the dewpoint, which is approximately half way through the wall.

If you don't completely fill the cavity with insul then you will need ventilation at the eaves and the vapor barrier.

If your using the ridgid foam insulation the sheets already have a vapor barrier so taping the joints is definately needed. Be careful with the foam types of insulation because most of them are required to be cover with sheetrock because they are highly flammable. Some types are listed for use without being covered with sheetrock just check the labels on the sheets. Also I think fiberglass is a lot cheaper.

Hope this helps...
Click to expand...

Yep...that's it...did insulation work for years when I was younger.
 
You must log in or register to reply here.
-

Back
Top