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Community and Q&A

Pretty Good steel building rehab?

Jim Coate | Posted in Energy Efficiency and Durability on

New to the group… I’m looking for ideas on how best to deal with an all metal building in terms of insulation and sealing/IAQ. Building is basically a clear span shell, ~45×85′ foot print, ranging maybe 12-15′ height low-slope roof, on a concrete block foundation raised 3′ above grade for flood protection. Walls and roof are corrugated metal with a nominal layer of maybe 1″ fiberglass and plastic on the inside, with various rips and holes, sandwiched between the metal panels and horizontal cross members when assembled. Floor is concrete slab, no insulation or barrier underneath that I know of. Built ~1984, located in central Virginia near Blue Ridge, so a very mixed climate. Motivation is that a new children’s museum will be moving into 2/3 of the space.

I’ve been assuming a box within approach, new studded walls supporting new ceilings (which avoids adding load to roof as solar panels have already used up much of the ‘spare’ load capacity), with typical drywall finish. In turn what type(s) of insulation, air gaps, barriers to get decent R-values on a tight budget and importantly avoid condensation in all the wrong places. Open to other approaches/finishes if appropriate, an “industrial” look is fine.

Looking in the archives, see suggestions that spray foam on back of metal panels seals it or also could warp the metal over time, or best to leave an air space behind metal then new wall structure inside (mouse heaven between?), or best to put all insulation on exterior with new cladding (vs solar panels already on roof), or … win the lottery and bulldoze it?

The concrete floor could be used as-is (folks are ready to paint a mini Appalachian Trail on it to connect the exhibits) so contemplating how much is lost if skip insulating over floor.

Planning on electric heat – cost is relatively low in Virginia as noted in recent blog and 12KW of solar PV already on the roof. Goal is heat pump(s), short term could be first season on resistive electric if desperate for budget reasons.

Existing roll-up doors would be replaced with retail type glass door/windows. Could make an entryway with second door if good energy reasons to do so.

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  1. Expert Member
    Zephyr7 | | #1

    This is similar to the types of buildings I usually work with commercially. Is your roof truss/bar joist or regular girders? If it’s a bar joist, we’ve successfully reinforced these by welding steel rods into the steel angle chords. You’ll need a structural engineer for that, but it will probably gain you enough support that you can at least hang lights and a drop ceiling if you want to avoid having to build an entirely new ceiling inside. I’d probably just spray the existing ceiling white, then hang strip lights and call it “modern industrial”. This has become popular, and it’s also fast and cheap!

    For ceiling insulation, if you aren’t reroofing, there is a type of fiberglass in sheets with plastic backing that is tensioned between the bar joists, support on metal tubes running perpendicular to the bar joists, and then stapled/taped together. It goes up fast and isn’t very expensive. Commerical insulation contractors should be familiar with the stuff.

    For the walls, you could just frame a non-structural wall, fill it with batts, then cover it with drywall. Metal buildings don’t have the same drying concerns as wood buildings in that the metal cladding is already an air/vapor barrier (check that the seals between panels are good though), but you don’t want it to stay wet either. Basically that means your insulation can dry ONLY in the direction AWAY from the metal wall regardless of what else you do. If you have block walls, then you’d insulate them the same as any other block wall.

    I’ve never tried spray foam, but I don’t know why it wouldn’t work. The only issue I could think of is if it failed to adhere.

    I wouldn’t worry too much about insulating the slab. That would probably be the worst place to insulate in terms of cost/benefit. I’d get the ceiling and walls in good shape first.


  2. Walter Ahlgrim | | #2

    Before you throw a lot of money at this building understand the breakeven point for the work you are considering is very long likely over 20 years.

    Does the museum own this building or have a long enough lease that this kind of investment could pay off?

    Affectively insulating a steel frame building on the inside is very difficult.

    I think the smart move may be to put as little money into this building as possible.


  3. Jim Coate | | #3

    I am the building owner - this has been my shop/storage space, I'd be moving my stuff into an uglier building nearby. I'm also a parent of 2 toddlers so motivated to see the museum happen. Our hope is the museum does well and grows into a larger space in the 5 year plan (perhaps my adjoining vacant lot :-) and then another tenant takes over this space. In 20 year plan, yeah, building might be replaced by then. Longer story but the "back" of the building is now the "front" along a new road with an open-field type of park across the new road which is soon to be redone as a much nicer city park/natural area leading up to a river. This would be the first step towards new life for the area. So... perhaps I should step back and ask what is the most economical way to provide decent occupant comfort (without risking mold growth inside walls)? And this may be the question Bill was answering as I read it.

  4. Joel Cheely | | #4

    How strict is code enforcement in your area? You are changing the occupancy class of the building to a "higher" occupancy. According to International Energy Code (which I see Virginia has adopted) you may have to bring building to current requirements. You may want to review with code official. You also may want to download COMcheck (a free energy software code check for commercial buildings) and see what you'll need to attain re: R values, etc.

  5. Jim Coate | | #5

    Thanks for the COMcheck info. From discussions with local building dept so far, scope of this project would be kept below their threshold. However for insulation I was initially thinking I'd be heading for better-than-current-code R values given my interests in green building. But now wondering if there is no good recipe for insulating when starting with an all metal building. :-(

  6. Expert Member
    Zephyr7 | | #6

    >>But now wondering if there is no good recipe for insulating when starting with an all metal building. >>:-(

    I’d start by air sealing things. Look for leaks between roof and walls, that’s a common spot for lots of leaks. Especially look around the ends of each bar joist. Spray foam is good here. Roof insulation can use the stretched fiberglass I mentioned earlier. Walls are more tricky and what you do depends on what you’re starting with.

    Close off those overhead doors too, those usually leak like crazy.

    You can reduce cooling needs by using a white roof, even painting the roof white. I’ve actually made measurements of this and it’s noticeable.

    Unfortunately, I don’t think commercial buildings have well known insulating strategies in the same way as the deep energy retrofits are for residential structures. You will be able to improve your building though, it is possible.


  7. Joel Cheely | | #7

    One approach I've seen on the roof is to add rigid insulation (usually polyiso) on top of the metal and install a single ply (TPO or EPDM) roof. The advantage is that you can achieve code insulation levels, stay dry while roofing and you'll have the benefit of a new roof. It also makes new roof penetrations easier.

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