roof insulation: "blown-in" vs. panels

Hi Brownstoners- We’re getting solar panels, and though Brooklyn Solar Works said the roof was good enough for them, it’s apparently 30 years old and we’re thinking better to give it a top-up now before the panels are installed since there’s an area on the entension below that needs to be repaired and the roofer will be out anyway. We also want to insulate the roof and while the roofer suggested blowing in insulation (he didn’t say with what) the contractor and architect are suggesting 4 x 8 flat panels of insulation and then another layer of tar paper (membrane?) on top. Any opinions on this? And idea of cost difference? Thanks!

winbrown

in General Discussion 3 years ago

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RobertGMarvin

in General Discussion 3 years ago

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“The panels won’t add any value with a vented cockloft”
Thanks Steve—I didn’t think of that, but it’s obvious in hindsight.

andriywww1990 | 3 years ago

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See what happens when we begin asking questions?

The trick in this business is not to have all the answers but to know what questions to ask. And who to ask-

kassie319 | 3 years ago

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I’d ask the architect if he’s ok with the additional load of the rigid panels which will need a a recovery board over the top of them (eg 1/2″ cement board) and the new membrane. I put a new membrane on my roof a few years back and a structural engineer friend told me it should be the last time I do that as there were already 4 old membranes on the roof.

andriywww1990 | 3 years ago

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Ok, so if you have to vent the cockloft to use blown in, why would you use both? The panels won’t add any value with a vented cockloft. Its one or the other.

We used 3″ think (i think 3) panels on a commercial roof. I have heard other roofers suggest panels as well in commercial and last night i would have said that MUST be the way to go. Then it dawned on me that panels were our only option as we did not have ceilings that can support blown in.

In most conversations i have heard, i hear people grumble about potential issues with blown in. Settling is a word that comes to mind. Without any first hand experience to go by, if it were my house, i would use the panels.

Make sure all parties know solar is going on that roof if you use the panels. The panels are not solid like wood but something like celotex with a little give and i have no idea how heavy solar is nor how wide the pads they rest on are (to disperse load) and how they secure all of this to the roof. You want to ask the question to be sure the panel will not give under the weight of the solar and allow the support for the solar to puncture the roof membrane. I know, the question sounds stupid, but when you have 2 or 3 different trades or specialists on a building, you cant assume they know that solar is going down. I assume if the architect is spearheading this entire thing, that person knows what they are doing and would not suggest panels if they did not think they can support the weight but just ask to be sure.

Always ask questions about things like this. With you being a homeowner, so long as you are not driving them crazy with questions all the time, they will think you are really smart for asking. If they cannot answer the question, that makes you smarter than them just for thinking about it. And when you are spending a lot of money do not accept these for an answer: ” i think” or “you should be ok”; people have KNOW. no guessing.

You could probably find the answer to the question i just posed on google and i might look later and report back. I did not look it up and state it here because i always speak from experience but more than that i want readers on here to learn how to “manage” their projects and the contractors the way pros do and that includes not assuming that others have thought of everything.

RobertGMarvin

in General Discussion 3 years ago

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FWIW I had insulation blown in back in the mid-70s. No problems so far. You do need to vent the cockloft to prevent condensation.

winbrown | 3 years ago

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Contractor said blown in insulation causes a bunch of problems down the line. Architect said it doesn’t insulate as well.

RobertGMarvin

in General Discussion 3 years ago

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Why not u I se both for a higher R value?