Best way to insulate a brand new build metal building for a/c use indoors?
Hi, I have read a few forums sections about insulation, but I can’t find anything about how it is best to insulate a brand new build metal building (Zone 9 South Texas) to allow for a/c use indoors. This will be a hobby shop, the big drive in door will seldom ever be opened. I am so confused on getting the best insulating values for this all metal framed building. I also do not want spray foam in this building, but I am confused as to the best way to go about insulating from the roof and down the sidewalls of the building.
Can someone please help me so that I am not so confused about all of this? We are in the planning stages now and hope to start concrete foundation and electrical going to the build area at the same time. I would like electrical wires to be accessible indoors if my husband needs to add another plug or anything else for that matter. I don’t think hiding it behind insulation is a good idea, which is another reason I do not want spray foam insulation. I can’t imagine trying to remove that stuff if we have a problem down the road.
So, I would like to know the best way to insulate while the building is being built, not after the building has already been built, as we are still in the planning stage.
Thanks to anyone who is not so confused as I am. 🙂
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Replies
First off, look up the concept of thermal bridging.
Now understand that mostly in homebuilding, we're looking at wood being the thermal bridge between fields of insulation. The wood conducts heat about 3-5 times as much as the insulation.
Steel will will conduct heat approximately 400 times as well as wood.
Thermal bridging is a lot of the game here. Putting insulation in between metal studs or stud-like things is going to be mostly useless. You could put insulation all-the-way-outside the steel, or all-the-way-inside the steel. Most of the advice focuses on exterior continuous insulation strategies. https://www.buildingscience.com/documents/insights/bsi-001-the-perfect-wall
Just keep in mind: Any time you have a steel fastener, even a tiny one, which bypasses the insulation and reaches outside air, you've created a sizable thermal bridge; With a big enough thermal bridge the ability of outside air to carry heat away becomes the limiting factor. Plastic fasteners of some sort are likely to be very helpful here. So is thermal-bridge-resistant design, like offsetting panels so that steel structural elements don't come into direct contact with each other.
AIr sealing is important and can be somewhat difficult with metal structures; Often you see spray foam used for this.
See also https://www.greenbuildingadvisor.com/article/insulating-pole-barn
Thank you Burninate for your response. I have read about putting the insulation on the outside before the metal cladding went onto the building but it did not explain it as well as the article you linked to regarding the perfect wall. Now I understand that far better.
I have already been looking into insulation in numerous places for our building online but I had not called anyone at the time I posted this question. So, I contacted LTH Metal Buildings company who does metal buildings and insulation. When I told the gentleman who answered what the plans were he said, you want to get as close to R30 as possible and I can do that for you. This is exactly what I wanted, R30 in walls and possibly higher in the roof of our building.
This company designs the insulation to your specific building, but he is going to give me a prelim quote until I can get the actual stamped certified plans for the building and give him the info he is looking for. He needs width and depth of girts and purlins, and how far apart they are spaced on the walls, and roof for an exact insulation design. I think they are 4 feet apart but not positive as of now.
The only other problem I have is seeing if the builder will actually put it in for me after they put the frame up and before they clad it. Hopefully it will be all okay in that arena. Thanks again for all of the info. It helped me to finally connect the dots of all I had been reading about the last couple of months.
Connie
Thermal bridging of metal fasteners is not an issue. I actually showed this mathematically several months ago in another thread on this forum. The likely thermal losses for an entire wall due to fasteners is something less than 10 BTU per hour. The total losses due to metal fasteners is so low as to be essentially immeasurable in any normal structure.
Thermal bridging due to studs IS a BIG issue though. Your best option here may be a layer of rigid foam on the interior of the building. You want to put your insulation in in a way that the steel structure itself doesn’t provide a thermal bypass to “cancel out” your insulating efforts.
For electrical wiring, I’d suggest using EMT conduit. This will provide some physical protection to the wires, and will allow for future changes since you can pull extra wires through conduit relatively easily. You can run the conduit on the surface and not worry about issues accessing the cabling in the future.
Bill
Thank you Zephyr7 for your response. I think the outcome of what I found today on insulation will be the perfect scenario to add the electrical with the conduit and ability to get to it later if needed. I think the plans for this building are finally getting ready to complete.
Connie
Update:
I've contacted a couple of companies regarding insulation for our new building and have not heard back from anyone as of yet. The build will be starting soon because the concrete will be started this coming week. We should have concrete full completed in the next two weeks. I am hoping we get some info on insulation because we have already decided what insulated doors to buy, and the a/c unit. We just need to nail down the decision on which products to use for insulating the building. Yay, we break ground tomorrow (Monday).