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Thread: More Garage Insulation Questions

  1. #1
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    More Garage Insulation Questions

    I just moved to a new house where I'm putting together a woodworking shop in the garage. It's a three car garage which has drywall on the ceiling without insulation, open studs on the outside walls and uninsulated steel doors. I know insulating garages has been covered in previous threads and I've read them. But things are always changing and I still have some questions:

    - Would it be better for me to install fiberglass bats in the ceiling myself or have someone blow insulation in the ceiling?

    - Should I use drywall or OSB to cover the walls after I've installed fiberglass insulation? I used OSB in my previous garage and I really liked it. I was expecting OSB to be much more expensive than drywall these days, but based on what I'm seeing online, it appears drywall is only slightly less expensive. Or am I reading that wrong?

    - I'm not impressed with the garage door insulation kits I'm seeing. The insulating panels are puny thin with very low R-ratings. I was thinking 2" think pink foam panels would work well. Looks like those are almost $50.00 for 4'x8' sheets. That would get expensive with one two-car garage door and and other 1-car garage door, but if it works well, maybe it's worthwhile?

    I live in the Colorado Springs area where it can get below zero in the winter. Summers aren't really a problem. An insulated garage door would help when the sun is hitting it in the summer, but it's rarely too hot to work outside here.

    Thanks!

  2. #2
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    You can probably rent the machine and blow the insulation in yourself. When I built my cabin I put walkway down the middle of the attic, had my wife throw the bales of cellulose in the machine and I ran the hose. Got a little dusty but saved a bunch.
    Confidence: The feeling you experience before you fully understand the situation

  3. #3
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    Lowes rents the machine here. It does settle a lot, so blow it way thicker than you think you need it.

  4. #4
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    I had not thought of renting a machine to blow in the ceiling insulation myself. Thank you for the suggestion. Is doing that better than fiberglass bats because it's easier or because it's more effective insulation?

  5. #5
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    You blow in one layer as thick as you want. With bats you should put in two layers perpendicular to each other to avoid gaps. Don't forget to put "chutes" into the roof truss cavities for proper ventilation. Also, does the ceiling have a vapor barrier? You'll need one.
    Confidence: The feeling you experience before you fully understand the situation

  6. #6
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    Obviously your results will vary, but I'm seeing ~$16 a sheet for OSB vs $10 a sheet for drywall. One thing that's nice about drywall unmodified is that it's white and reflects light. Also if this garage is attached to your house you might be required to use drywall, 5/8 fireblock. Even if you're not, it's probably a good idea. OSB is going to burn a lot quicker than drywall, which has suspended water in it.

    As for garage door insulation you're probably right, but almost all doors and windows have low R values. It's still useful, and even an increase from none to some can be very useful. The utility also tends to drop off exponentially as the R value climbs. The only advantage I've seen to the kits is precut vs DIY. If you've got a bandsaw that can do an excellent job of making precise cuts in extruded insulation, though it's messy.

    All that having been said, the standard seals on garage doors are abysmal and it doesn't seem to be a problem anybody is trying to solve. So having a high R value on a garage door is sorta defeated by the seals.

    This goes doubly if you vent your dust collector outside like I do. When I turn it on, all the unconditioned air gets sucked in from outside. That having been said, it take a while to start effecting internal temperatures, and I'd rather all the fine dust be outside, than run through a filter.

  7. #7
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    If the garage door is a typical sectional door that rolls up tracks (rather than a tilt-up or California door), you will probably have to bevel the edges of 2" foam to provide clearance when the sections make the turn in the track. Easy enough to work out with a couple of scraps and some double sided tape.

    Blown-in insulation, installed correctly, makes it easier to fill the odd sized and shaped spaces that are common in attic spaces. You can do it with batts but it's usually more work. If you are going to do any wiring up there, do it before you insulate. As others have mentioned, you will likely need baffles to maintain ventilation assuming you have eave and ridge vents.

    Definitely check code in your area regarding OSB vs. sheetrock. In my area, fire code sheetrock is required at least on the wall that is shared with the house and all penetrations in that wall have to be fire blocked.
    --I had my patience tested. I'm negative--

  8. #8
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    For any kind of attic insulation, I put a 1" foam end on the space between the trusses over the outside of the wall, with a breathing baffle over it stapled to the roof sheathing, and foam it in place.

  9. #9
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    Quote Originally Posted by Paul F Franklin View Post
    If the garage door is a typical sectional door that rolls up tracks (rather than a tilt-up or California door), you will probably have to bevel the edges of 2" foam to provide clearance when the sections make the turn in the track. Easy enough to work out with a couple of scraps and some double sided tape.

    Blown-in insulation, installed correctly, makes it easier to fill the odd sized and shaped spaces that are common in attic spaces. You can do it with batts but it's usually more work. If you are going to do any wiring up there, do it before you insulate. As others have mentioned, you will likely need baffles to maintain ventilation assuming you have eave and ridge vents.

    Definitely check code in your area regarding OSB vs. sheetrock. In my area, fire code sheetrock is required at least on the wall that is shared with the house and all penetrations in that wall have to be fire blocked.
    My doors are the sectional doors on tracks. They're pretty new, so the seals are in good shape. I suppose it can't hurt to install extra seals.

    I'm recalling my real estate agent said he could recommend people to blow in insulation pretty reasonably. I should give him a call. (That guy knows everyone!)

    The parts of the garage that share a wall with the house already have fire code drywall.

    I'm also working on installing 120 and 220 outlets so I'll be sure to finish that before I insulate. Although, I was thinking I could insulate the garage doors.

    Thanks for the information, everyone.

  10. #10
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    My new shop walls will be drywall because it's cost effective and honestly, I'm not really worried about damage or hanging things up. In all the years I've been woodworking, it's been very rare for me to "whack" a wall with something. For hanging things, a French cleat system eliminates the concerns for solid support. I'm also not one who likes to randomly hang things up anyway as I prefer to keep things in closed storage like drawers and cabinets. If your garage space connects to the home, there are fire regulations you must follow for the walls and ceiling relative to fire rating and that includes 5/8" fire rated drywall anyway.

    For wall insulation, I think that Rockwool is a better choice at this point than typical fiberglass batts. For the ceiling that already has drywall, blowing in fiberglass or if you prefer, cellulose is going to be a better solution for insulation properties unless the space above has to be floored for storage. If so, then higher density batt/roll material that can fit under said flooring without compression may have to be employed and it may require blocking up the height to meet the typical R38 minimum for a ceiling in a residential situation.

    Yes, the pink/green/silver 2" foam R10 sheeting is pricy right now...it's made from oil...but it's still about the best product for insulation panels. You can also use the white styrofoam stuff, but it's not as efficient as the higher density foam. What you also might consider is keeping the smaller door as the one you open for access and building an insulated false wall to box in the larger doors. Bent's Woodworking as well as Woodwhisperer have used this in their respective shops. You still have access for material/projects/tools, but gain more wall space and reduce noise this way.
    --

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  11. #11
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    Quote Originally Posted by Jim Becker View Post
    My new shop walls will be drywall because it's cost effective and honestly, I'm not really worried about damage or hanging things up. In all the years I've been woodworking, it's been very rare for me to "whack" a wall with something. For hanging things, a French cleat system eliminates the concerns for solid support. I'm also not one who likes to randomly hang things up anyway as I prefer to keep things in closed storage like drawers and cabinets. If your garage space connects to the home, there are fire regulations you must follow for the walls and ceiling relative to fire rating and that includes 5/8" fire rated drywall anyway.

    For wall insulation, I think that Rockwool is a better choice at this point than typical fiberglass batts. For the ceiling that already has drywall, blowing in fiberglass or if you prefer, cellulose is going to be a better solution for insulation properties unless the space above has to be floored for storage. If so, then higher density batt/roll material that can fit under said flooring without compression may have to be employed and it may require blocking up the height to meet the typical R38 minimum for a ceiling in a residential situation.

    Yes, the pink/green/silver 2" foam R10 sheeting is pricy right now...it's made from oil...but it's still about the best product for insulation panels. You can also use the white styrofoam stuff, but it's not as efficient as the higher density foam. What you also might consider is keeping the smaller door as the one you open for access and building an insulated false wall to box in the larger doors. Bent's Woodworking as well as Woodwhisperer have used this in their respective shops. You still have access for material/projects/tools, but gain more wall space and reduce noise this way.
    Thanks, Jim. I always appreciate your input.

    I've seen The Wood Whisperer's wall he built in front of his garage door. However, I still have to park cars in my garage. I know, it seems blasphemous, but we get some serious hail storms where I live. We've already lost multiple vehicles to hail and dont want that to happen again.

    Yeah, looks like drywall is the most practical option. Does all of it have to fire code, or just the stuff on the walls shared with the house? I know codes vary a lot, but I'm thinking that one is likely consistent everywhere.

  12. #12
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    I believe that the fire rated material requirement is only for walls shared with the living space, but it's best to consult with your local building/zoning officer to be sure you are following their requirements which may vary from actual code.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  13. #13
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    When was the house built? Make sure the mud sill is properly bolted down while the wall is open. Will you have to nail the osb as a shear wall? If you need a shear wall OSB is a no brainer.
    Some claim a company, with voluume discounts, can blow in insulation for less cost then you can buy it for. Rockwool can be left exposed until you get time to cover it up.
    Bill D

  14. #14
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    I believe you have to isolate the house attic too. You can run the shared wall drywall to the peak or do the whole ceiling in the garage. At my house they did the whole ceiling and at my cabin they went to the peak.
    Confidence: The feeling you experience before you fully understand the situation

  15. #15
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    Quote Originally Posted by Bill Dufour View Post
    When was the house built? Make sure the mud sill is properly bolted down while the wall is open. Will you have to nail the osb as a shear wall? If you need a shear wall OSB is a no brainer.
    Some claim a company, with voluume discounts, can blow in insulation for less cost then you can buy it for. Rockwool can be left exposed until you get time to cover it up.
    Bill D
    House was built in 2019.

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