My shop is old stick built with aluminum corrugated siding and roof. The radiant heat inside in the hot months is almost unbearable. The walls have roll insulation in them but ceiling has nothing. At one point I had plastic stapled to the bottom side of the trusses and it was much better but that old plastic deteriorated so I took it down. I don't want to put a ceiling in it and cover up access to the wiring plus it would be too low IMO. I was considering putting lath strips up half way in the trusses so I could insulate above those but that's the hard way. Lately I've been thinking to just use roll insulation between the rafters right below the underside of the metal. I looked at metal building insulation rolls with the white plastic one side and reflective on the other that is R8 value and that's acceptable. I will condition the space to some extent once it's insulated. What is y'all's opinions on the best path for ease of installation, cost effectiveness, and the best R value for this job? Shop is 28' x 48' and rafters are 24" O/C mostly. There is no ridge vent, but there is 3 whirlybirds and an exhaust fan at the rear.
Old Shop Insulation Guidance Needed
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RatLabGuy
You look like a monkey and smell like one too
- Joined
- May 18, 2005
- Location
- Churchville, MD
The best solution is going to be spray foam insulation but your wallet may disagree
Not doing spray foam and I don't think it would be good over the wood anyway. Can't afford it anyway so that's out
skyhighZJ
Gov retirement < needs to live
- Joined
- May 31, 2012
- Location
- Aberdeen, NC.
There are loads of ads on FBMP for foam board (mostly 4x8x2.5) with or without foil. That would be the route I’d go. Press it up between the trusses and figure out a way to secure it to the rafters. Roof purlins would give you a bit of an air gap to the aluminum roofing for moisture issues.
- Joined
- Mar 24, 2005
- Location
- Stanley, NC
Id do spray foam. Yes it costs more, but anything else is a compromise. It will do exactly what you need and be worth it in the long run.
The problem with spray foam is that when the roof eventually gets a leak it will trap the water inside that foam against the roof and the purlins. It will pool and find a way out via gravity and it will not be where the leak is so you will have to rip it out to figure out where the leak is.
I also vote for foam board; get expanded polystyrene with the foil layer and point it at the metal roof. The air gap will make it work as an effective radiant heat barrier.
- Joined
- Mar 24, 2005
- Location
- Stanley, NC
- Joined
- Mar 13, 2005
- Location
- Raleigh, NC
My professional opinion: don't do closed cell polyurethane.
RatLabGuy
You look like a monkey and smell like one too
- Joined
- May 18, 2005
- Location
- Churchville, MD
I don't see how any tightly coupled, well installed insulation won't have the same problem, except almost anything else will allow it to make a much larger pool before you see it.
- Joined
- Mar 13, 2005
- Location
- Raleigh, NC
XPS will have slightly higher r value per inch. It's also slightly less likely to absorb water, but that shouldn't matter for your use case. Either would be fine, though. There are also wrapped batts (fiberglass or polyethylene) that might be worth considering. Board would be a pretty easy install assuming the dimensions work. Can foam them in place and use a couple pieces of furring to hold the panels in place.
- Joined
- Mar 13, 2005
- Location
- Raleigh, NC
Closed cell polyurethane will trap vapor between the insulation and the metal roof and rot out the purlins. Bad choice.
I did use the XPS Board to make an attic door enclosure to stop loss through it and it works great. It was actually a little harder to cut and work with than I thought it would be. But this was my original thought to use this product. I would like a reflective side to point upwards if it's made that way.
skyhighZJ
Gov retirement < needs to live
- Joined
- May 31, 2012
- Location
- Aberdeen, NC.
untchabl
I like rocks
- Joined
- Mar 30, 2009
- Location
- Bear Creek, NC 27207
Banded System | Bay Insulation Systems
Long-Tab Banded System Long-Tab Banded (LTB) filled-cavity insulation is a popular and cost-effective method for insulating metal building roofs and walls. The long-tab banded system involves using laminated insulation with extra-long facing tabs as well as metal banding for support. The...
bayinsulation.com
I put this in my new pole barn shop and we used it in our old pole barn shop with no issues. They can make it to whatever width you need, our old shop had odd spacing on the trusses. My new shop has 22" between most purlins except 2 are 16" spacing. They made exactly what I needed. You can also order the rolls to whatever length you need.
Just having the ceiling insulated in my new shop has made a big difference in comfort.