Roof coating vs. insulation? or?

slowjane CA/ Sunset 21July 30, 2014

Hi all,
Not sure this is the right forum - I'm surprised there isn't a roofing forum - so let me know if you think I should post elsewhere (this old house? i have no idea....usually i'm over in gardens)

I've got a garage work studio that we upgraded last summer. (I've posted around here before about the skylight - which as of yesterday is covered with a solar "hair net" style cover..)

The building is very very hot - the ceiling is hot to the touch, and seems to be radiating a lot of heat, though the SO blames the cracks around the garage door and says the heat is just heat rising in the room. ?

I've got three layers of shadecloth hung on the 2 car garage door which helps with that surface. My standalone a/c unit isn't able to cool it below 90' today....I work in this space every day so it is driving me nuts.

Some things I'm considering:
- blowing in insulation to the somewhat shallow sloped roof
- roof coatings to reflect heat like coatncool - no hoa so not a problem, but I just read that it's a controversial idea for asphalt shingles.
- obviously sealing up the cracks as best as I can between garage door and wall, below garage door. The room is drywalled and finished otherwise.

Any advice about how to rank the issues I'm facing? I'd love to hear opinions about what the biggest heat gain causes are, and how I should approach a holistic kind of program to make this building more efficient.

thanks much all.

-

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mike_home

It sounds like the garage has a shallow pitched roof and there is no attic separating the roof deck and your work area. Is this correct?

If this is the case, then my suggestion would be to add a finished ceiling to create an attic and then add insulation to the attic floor. You should also add ventilation to allow the hot air to escape.

The other option would be to spray foam the roof deck. My only concern would be trapping moisture between the foam and the roof deck. The application has to be correctly in order to avoid problems in the future.

I think it is a bad idea to put any coating on an asphalt shingle. Sealing any opening around the doors should be done but in my opinion the majority of the heat is coming through the roof.

    Bookmark   July 31, 2014 at 9:10AM
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jakethewonderdog

Ditto what Mike said.

You need to look at radiant heat barriers for the garage roof. I've used RMax (shiny side out) with an air gap between the RMax and the underside of the roof decking between the joists. The air gap needs to be vented at the ridge and the eves. Then use fiberglass for the remaining space between the joists.

This, of course, requires removing the drywall from the ceiling of the space to insulate it.

    Bookmark   July 31, 2014 at 9:39AM
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slowjane CA/ Sunset 21

I took a picture to clarify - it's got a low slope and this funny pitch on the garage door facing side. The ceiling inside is already finished - drywalled, mudded painting. The ceiling inside is sloped with the ceiling - though there is a larger "attic" at that steep pitch bit.

So really there isn't an attic which means I can't insulate it? Or is there still a way to cut a hole in the drywall and blow in insulation?

Also - would it help to have a vent in the ceiling/roof - at least to vent out the heat at the ceiling? I'm considering replacing the acrylic skylight with a vented one that at least I could open to let heat escape. But maybe a spinning vent would help? Or a vent just into the tiny attic part of the roof?

When we refinished the building my understanding with the contractor was that he would add insulation - it was just clapboard before, no drywall, no stucco. But at the end he denied that was the deal and I think he just got frustrated with the building and wanted to be done. ;( But now it may be too late to fix it?

Sorry I'm a huge newbie to large scale construction - I'm handy with a lot of things but don't have a grasp of roofing at all.

    Bookmark   July 31, 2014 at 12:33PM
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slowjane CA/ Sunset 21

and a picture of the inside slope - we also put in the door and the small window and the skylight....

    Bookmark   July 31, 2014 at 12:42PM
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slowjane CA/ Sunset 21

one other related question - if i were looking to have an expert come out and look at the building - what kind of expert should i be looking for? roof specialist? general contractor? seems like hvac folks install hvac systems and i need more general advice about how to fix/repair/improve energy efficiency. energy auditor? any suggestions appreciated!!!

    Bookmark   July 31, 2014 at 1:43PM
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mike_home

"When we refinished the building my understanding with the contractor was that he would add insulation - it was just clapboard before, no drywall, no stucco. But at the end he denied that was the deal and I think he just got frustrated with the building and wanted to be done."

Are you saying the contractor who finished the garage did not install any insulation in the ceiling or walls?

    Bookmark   July 31, 2014 at 2:43PM
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slowjane CA/ Sunset 21

yes.

    Bookmark   July 31, 2014 at 2:49PM
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slowjane CA/ Sunset 21

yes, that is what i'm saying. just to be clear. (not yes he installed insulation....)

*no insulation* - but i thought he was going to install it originally - he said at the last minute that there was no room for it - which maybe is true *now* based on how he installed the ceiling?

    Bookmark   July 31, 2014 at 5:07PM
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mike_home

If the walls are built with 2X4 studs then there is room is install R13 insulation batts. There was no excuse not to do that.

As for the ceiling, I assume the structure was built with 2X10 joists. It would not have been very difficult to install insulation batts from below and stable them into place. If there was very little room, then spray foam would have been a good solution. He should at least given you the option even if he wanted more money.

You need to bring in an insulation contractor and see what can be done. If your goal is to make the garage an working office, then it may be easier to remove the sheet rock, insulate, and finish the floors and ceiling.

    Bookmark   July 31, 2014 at 6:05PM
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slowjane CA/ Sunset 21

"There was no excuse not to do that. " yes, i agree. especially since it was in the contract. i got a bit bullied at the end because he got behind and stressed out...another thing would be to call him and try to make him fulfill the contract, but i'm afraid he would say it isn't possible (what he said last year, after he agreed to do it.)

removing the entire ceiling, installing all new drywall and finishing it seems really overwhelming and expensive and horrible since this ceiling is less than a year old (and i did all the finishing myself which was a lot of work)

thus my attempt to find another solution - like blown in insulation, venting, or roof coating. everyone agrees that these aren't real options and that removing the whole ceiling is the only way to insulate it?

one last gasp: would a vent in the pitch like my drawing help at all?

    Bookmark   July 31, 2014 at 7:33PM
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mike_home

Adding vents at each end will help move the hot air out. Perhaps the openings could be used to blow in insulation at in the peak portion of the roof.

    Bookmark   August 1, 2014 at 10:33AM
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saltidawg

Read Garry Trudeau's DOONESBURY comic stip in Sunday's paper. (8/3/2014)

    Bookmark   August 2, 2014 at 9:38AM
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ionized_gw

That is a very weird roof. You have to make your modifications with your climate in consideration. I'd talk to a local energy rater and have them look at your house while they are at it. They should know solutions compatible with your climate and will have eyes on it allowing them to make recommendations that will be the most economic. Check out resent.us. A good resource for reading up on this sort of thing is building science.com.

    Bookmark   August 2, 2014 at 11:41AM
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