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Thread: Keeping a garage warm: What would you do next?

  1. #46
    Join Date
    Jan 2004
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    Lewiston, Idaho
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    28,504
    Augusto,

    When I finished the interior of my shop, I installed the insulation dams in the eves before I put the sheetrock on the ceiling and the plywood on the walls.

    IIRC it cost me just over $300 to have R-38 fiberglass blown into the 740 square foot ceiling. I checked with the local HD. I couldn't do it that cheaply.

    My shop is heated with NG Lennox 75,000 btu gas furnace. I have R-19 in the walls of the shop and 1 10' insulated garage door, 3 4'x3' thermopane windows and 1 36" insulated steel walk-thru door. It isn't expensive to heat my shop. I typically set it for 58ºF. When I want to work, I go out set the thermostat for 64º and go back in for another cup of coffee. When I come out the shop is warm.
    Last edited by Ken Fitzgerald; 12-17-2009 at 10:45 PM.
    Ken

    So much to learn, so little time.....

  2. #47
    Quote Originally Posted by Ken Fitzgerald View Post
    IIRC it cost me just over $300 to have R-38 fiberglass blown into the 740 square foot ceiling. I checked with the local HD. I couldn't do it that cheaply.
    Now you are just rubbing it in, Ken

    I think the cheapest I can find here is an online offer at HD for 0.99sf of blown in; but only for R19. I can still do it cheaper myself with fiberglass batts and achive an R30.

  3. #48
    Join Date
    May 2009
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    Boston
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    1,740
    I think HD had r30 for 10 bucks a roll.

  4. #49
    Quote Originally Posted by Eric Gustafson View Post
    I thought the 1978 study was interesting because they artificially elevated interior humidity to 35% and held it there. Hardly a normal condition, yet ordinary paint did better than expected. Unless you run a humidifier 24/7 or are in a area with a unusually high water table, do you really get internal humidities that high?
    I live in the Canadian prairies. (Saskatoon, Saskatchewan) Winters are cold and _dry_. So yes, we do like to keep humidity close to 40%, but at -40 I drop the humidity to about 30% to keep too much frost from forming on the windows.

    35% humidity doesn't seem unusual at all. Health Canada recommends 30-50% for interior humidity.

    Quote Originally Posted by Doug Swanson View Post
    +1....and nobody wants to admit that vapor barriers are bad (building codes) because then you would could have a huge liability to contend with...my brother is in that line of work and it is a sticky issue to address in the codes...
    Depends on where you live. Around here vapour barriers are an absolute necessity in winter otherwise the vapour in warm interior air would condense in the wall cavity. When there is a 110F temperature differential between inside and outside, you need the barrier. Summer times aren't particularly moist, so the barrier is still fine then.


    As for the original question, I'd start with airtightness, then ceiling, then walls. Make sure you've got the vapour barrier boxes around your electrical outlets, or at least the gaskets under the faceplates. I had R30 fiberglass blown in to the ceiling for cheaper than buying batts at HD. The walls are R12 batts. I'd prefer more but they're only 2x4 walls.
    Last edited by Chris Friesen; 12-21-2009 at 12:43 AM.

  5. #50

    About the space between the joists

    Quote Originally Posted by Augusto Orosco View Post
    I got into the attic tonight to double check... the joists are 32" OC. Is that standard? I guess the original builder was cheap

    This is probably a silly question, but I have no clue: For batts/rolls, should I get the 15" wide or the 16" wide ones, assuming that I need two batts side to side to fill up one cavitiy? The exact space in between joists is 30.5". Two of the 15" sound too short, but two of the 16" would be 1.5" too wide, and am concerced about compressing the insulation and loosing R value
    This question got lost in the thread... but it has become more relevant now because I have the opportunity of buying 15" wide rolls at a large discount. Can I use two 15" wide batts side by side, or would it be too short (given the 30.5" space between joists). Would two 16" batts be too wide? What has been your experience?

  6. #51
    Join Date
    Jun 2009
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    My math says use one of each and you will be very close...
    I drink, therefore I am.

  7. #52
    Quote Originally Posted by Mike Cruz View Post
    My math says use one of each and you will be very close...
    I know, just as close as with two 15" (but on the wider side, which might be better). I am just trying to make my life simpler and save some money: I can buy the 15" ones for about half the price per sf than the 16" ones right now.

  8. #53
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    I would think that two 15's, being a little shy would make your insulation efforts ineffective. Two 16's, and you have pointed out would be squeeshed in a bit too tightly. I think a 15 and a 16 would be your best bet. Of course, money comes into play. Just think of it as getting 25% off the whole job instead of 50% off by getting all 15". Hope that helps.
    I drink, therefore I am.

  9. #54
    Quote Originally Posted by Mike Cruz View Post
    I would think that two 15's, being a little shy would make your insulation efforts ineffective. Two 16's, and you have pointed out would be squeeshed in a bit too tightly. I think a 15 and a 16 would be your best bet. Of course, money comes into play. Just think of it as getting 25% off the whole job instead of 50% off by getting all 15". Hope that helps.
    Thanks, Mike. You are probably correct. Probably better snug than loose.

    Now, does insulation is measured like dimensional wood? (i.e. 16" is not really 16, but say, 15.25"?). I can't measure it directly at the store because they are all packed, and the employees look at me funny when I ask that question

  10. #55
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    The only help I could give you there is that if you figure that normal insulation is made for studs that are 16" oc. So, that would make the space between them, what, 14.5? See what it says on the packaging and compare. Oh, and tell the folks at the Borg what you are trying to accomplish. I would imagine they would carefully open a package of each so you could measure.
    I drink, therefore I am.

  11. #56
    Join Date
    Aug 2009
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    In the 20 years I have been a general contractor it seems the industry has changed its view on vapor barriers several times. I have worried that any job I did in the past will haunt me later. Often it is the same subcontractor that tells me what we did last time was wrong!

    I think there is no need for extra vapor barrier here. If you use kraft faced insulation put it towards the heated space. If you have some sort of vapor barrier don't use faced insulation over that. I think as leaky as a garage is it isn't a concern, especially if you open the garage door often.

    My insulation has a $350 minimum and doing a garage ceiling would fall under that catagory. They buy such huge quanities of material that I can't touch it by doing it my self.

    I'll bet the 15" and the 16" batts are the same size. The 16'' material is made to fit between to studs or joists so they probrably measure 14 1/2".

    If you are 32" oc then it will measure 30 1/2" so you might not make it. You could do it with the 16" and leave the space and then blanket another layer perpendicular to the joists but that may be out of the budget for now. If the 16" stuff you mention is actually 16 the squishing it in isn't going to cause a problem. Or maybe you could get both sizes and one of each will do the job.

    For the walls later I would check with a pro because there are other options than batts and blown in.

  12. #57
    Quote Originally Posted by Doug Carpenter View Post
    If you are 32" oc then it will measure 30 1/2" so you might not make it. ... maybe you could get both sizes and one of each will do the job.
    I decided to follow Doug and Mike's suggestion and go with a 15" / 16" combination, but once I got to the store, they had a lot of 15" R30 but no 16" rolls or batts to be found . Since the 15" rolls were so cheap per sqf compared to the rest I took the risk and bought enough for the full job (they do measure exactly 15").

    Late last night I was able to cover about 40% of the attic in less than two hours (not as hard as I was expecting, even with cutting around electrical boxes). Two 15" rolls side by side seem to fill the space between joists well. I'll see how it works once the job if finished. I saved a good deal of money, so I could still find a way to make make them fit tighter if needed (such as placing a roll of 15" R19 on top, right in the middle where the two R30s meet)

  13. #58
    Join Date
    May 2008
    Location
    Boston Area
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    Agusto,
    If you consult your building department and indicate that you are adding heat to a space in MA, the AHJ will require you to have a building permit and meet the state energy code for the building envelope. This will be way more costly than you now imagine. The best solution would be to fill the ceiling joist space with faced batts to fit the depth of the ceiling joists. Tape the joints, joining the batts (15" to 16") and staple the kraft face to the inside of the joists close to the ceiling to seal as best as you are going to get without removing the ceiling sheetrock. Lay another layer of unfaced R-30 across the top of the joists. Make sure the soffit vents are not blocked. Pick up some owens-corning raft-r-vent shims if you have soffit style vents and gable vents. This will keep the space above the insulation ventilated and cold to prevent mold growth on the underside of your roof. If the floor is in good condition, consider sealing it with a quality epoxy sealer. With the floor sealed, other that you sweating hard over the workbench, the moisture from internal sources in a garage environment are pretty negligible. Best of luck with the project.

  14. #59
    Quote Originally Posted by Rick Metcalf View Post
    Agusto,
    If you consult your building department and indicate that you are adding heat to a space in MA, the AHJ will require you to have a building permit and meet the state energy code for the building envelope. This will be way more costly than you now imagine. The best solution would be to fill the ceiling joist space with faced batts to fit the depth of the ceiling joists. Tape the joints, joining the batts (15" to 16") and staple the kraft face to the inside of the joists close to the ceiling to seal as best as you are going to get without removing the ceiling sheetrock. Lay another layer of unfaced R-30 across the top of the joists. Make sure the soffit vents are not blocked. Pick up some owens-corning raft-r-vent shims if you have soffit style vents and gable vents. This will keep the space above the insulation ventilated and cold to prevent mold growth on the underside of your roof. If the floor is in good condition, consider sealing it with a quality epoxy sealer. With the floor sealed, other that you sweating hard over the workbench, the moisture from internal sources in a garage environment are pretty negligible. Best of luck with the project.
    Hi Rick,

    I spoke to the town building inspector early this week before proceeding. I explained that the garage was previously unheated, but now I have a 240v heater that I am planning to use 2-3 times a week for a few hours each time. He said that given that description, fiberglass insulation with no vapor barrier was fine (I actually mentioned that I was planning on using kraft faced batts, he said it wasn't necessary) and that I could go ahead; just make sure to leave them short enougth so the soffit vents are not blocked.

  15. Quote Originally Posted by Augusto Orosco View Post
    It's a 2 car attached garage with 8' ceilings and about 500sf of total area. The garage walls are sheetrocked, but with no insulation (with the exception of the wall that is shared with the house). The ceiling is also sheetrocked, but the attic on top is not insulated. The two garage doors span most of the longest wall and are already insulated with a 1.75” thick rigid foam in between the metal sheets (pre-installed by the manufacturer).


    I got in on this topic late and I see you have already moved forward with fiberglass bats. But maybe my experience with my garage will help out down the road when you tackle the walls.

    My garage is the same setup...one insulated, commom wall with the house. I chose to use blowin cellulose. It took my wife and I a couple of afternoons to get it done but it has made a huge difference in the temps.

    Here are some pics from the project.

    http://www.crenshawweb.com/texastele/ttp03.htm#insul

    I built side extensions for the hopper out of OSB and when we got ready to blow the attic, we built a pen in the floor out of old plastic shelving that allowed us to break open 10 or so blocks of cellulose and just shovel it into the hopper with a snow shovel...it went very quickly and was easy to do.

    The walls were a bit tougher...you have to vent the space to let air out as insulation goes in...I started with 1.5" holes...just large enough for the nozzel, but ended up opening them up to 2.5" to let the blow back exit the wall cavities. I'm going to let them settle over the winter, top them off and fill the holes next spring.

    I just got a new digital weather station for Christmas so I'll be able to see what the inside/outside difference is. I can say, it's very noticable with it insullated.

    Peace,
    Mark
    "Thought that is no longer limited brings experience that is no longer limited" Marianne Williamson.

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