Fixing A Hot Shop, With Science

We know that pretty much everybody in the Northern hemisphere has had a hellish summer, and there’s little room for sympathy when someone busts out with, “Oh yeah? You think THAT’s hot? Well, lemme tell you…” But you’ve got to pity someone who lives in north Texas and has a steel Quonset hut for a shop. That’s got to be just stupidly hot.

But stupid hot can be solved — or at least mitigated — with a little smarts, which is what [Wesley Treat] brought to bear with this cleverly designed shop door heat shield. When it pushes past 42°C — sorry, that sounds nowhere near as apocalyptic as 108°F — the south-facing roll-up door of his shop becomes a giant frying pan, radiating heat into his shop that the air conditioner has trouble handling. His idea was to block that radiant heat with a folding barrier, but to make sure it would be worth the effort, he mocked up a few potential designs and took measurements of the performance of each. His experiments showed him that a layer of extruded polystyrene (XPS) foam insulation covered with reflective Mylar did better than just the foam or Mylar alone.

The finished heat shield is an enormous tri-fold plywood beast that snugs up against the door when things get toasty in the shop. There’s a huge difference in temperature between the metal door and the inside surface of the shield, which will hopefully keep the shop more comfortable. We imagine that the air between the door and the shield will still heat up, and convection could still distribute all that hot air into the shop. But at least he’s giving the AC a fighting chance.

In addition to great shop tips like this and his custom storage bins, [Wesley] is a talented signmaker. He’s pretty funny too — or maybe that’s just the heat talking.

42 thoughts on “Fixing A Hot Shop, With Science

    1. +1 to this

      Hanging a shade outside (with a reasonable air-gap so that it can shed heat to the air instead of the door) will be vastly more effective than trying to limit heat flow on the inside. It doesn’t need to be particularly thick as long as it blocks most of the light from passing through.

      The shaded door will heat only up to the outside 43C temperature (plus a tiny bit because the shade will radiate some heat towards it). And most importantly, the shade will shed the kilowatts of heat to the outside air instead of inside.

      The same applies to any kind of window shades and blinds. Having a nice mirror-finish blind on the inside of the window will be less effective than hanging “whatever” outside (although some people may object to the aesthetics, if you take “whatever” too literally).

    2. A shade is definitely a good idea.

      But this is simple and obviously suitable for his situation, where external modifications may not be allowed, impractical, or even actively unsafe on his building – have to work with what you have, and this looks to be a pretty good way to add some serious insulation value to the worst solar powered radiator in his shop in a way that should keep the landlord etc happy.

        1. It may be shitty renting laws, or simple utility and safety of the surrounding units and users – can’t pass the wide loads the unit 3 sheds down needs if there is a shade hanging out in the way all the time for instance.

          Sometimes a good idea just can’t be retrofitted, it needed to be designed in when the whole area was laid out and built.

    3. Yeah. Should have asked idk anybody in Texas with a trailer or an RV about this. Solutions exist. There’s all sorts of companies that build big metal shades to go over other buildings

      1. My father worked at a auto shop and the front end of the building was a Kwanzaa hut , in the summer time you couldn’t touch the metal it was so hot. One day my dad and his boss (the owner) set a water sprinkler about center up top the building and turned the water on. About 15 minutes was all it took and you could place your hand flat on the metal and it was cool to the touch. They only used it on the hottest of days because of the water bill in that county was silly high but with a bit of work and know how I’m sure a system could have been set up with a tank, pump and a means to recycle some of the water to be some what self-sufficient

      1. And I would rather get in to a white car during the Winter with seats so cold that the foam is stiff as a board, than get into a black vehicle in the Summer. YMMV

    1. Fixing it with any industrial solution probably isn’t gonna end well but so far those are the only solutions proffered. Man with technology is like an alcoholic with a barrel of wine

  1. Well, this building seems already really bright. I tried searching for the reflectance of the material used “Galvalume Plus” but it only said once, that this was above 65%.

    I saw a table showing different reflectance values, and I now think the mylar is more reflective mainly because of its surface roughness.

    We shouldn’t (and can’t) polish the garage door to make it more reflective, but I don’t think painting it will be that useful.

  2. Preventing heat absorption by a shade is best but may not practical to his needs. If he has to resort to blocking the heat after the face of the door has heated up then the best solution I can think of is to vent the heated air to the outside. Redesign the door to have a space between the face and the reflective insulation. This space will be closed to the interior of the shop. This may be done with stand-offs from the door’s ribs. The insulation will have to be flexible. Vents at the bottom and the top will allow cooler air to be drawn in from the outside through the lower vents. When the air heats up, it will rise to exit through the upper vents. The vents may be closed during winter to prevent loss of heat.

  3. Just seen he has a row up door. In my previous comment, my advice should work with a standard door but not with his door. The only way I can see how to make this work with a row up door is to box in the door. The vents would be through the wall. The insulation could be a reflective curtain or insulated door that can be raised. Basically building a vented vestibule.

    My bad for assuming he had a standard garage door. I commented after reading the article. By the time posted, my throttled internet connection had displayed the image of the door.

  4. I hate how AC was introduced as a ‘solution’ before any kind of moderately effective isolation or even some kind of shade outside. You know, cheapish, non-energy using measures which are easily installed.

    1. Yes, before AC we should have invented organic, self-reproducing, self-building carbon negative shade machines first. We could call them Terrestrial Reduced Energy Expender Savers, aka “TREES”.

  5. His design wasn’t a bad solution, he used a method to determine results, first one should realize just how nasty the situation he was in, he was literally getting radiantly baked (IE he was being heated by the door IR). So doing a quick test and having any conclusion what so ever should be considered a great result.

    Next the insulators need a radiant barrier on both sides, the reason is that it gets cold in the winter so his barrier can also keep his shop warmer in the winter and use less energy as a consequence.

    In all cases he will use less energy. In the end saving $4 a month might pay for the work within 2 years. Further the lack of extreme discomfort will probably help him get more done so it may be much sooner.

  6. Just as a general observation, it seems that in areas where the temperatures are reasonable warm during the winter (freezing only every few years, maybe 10°C as a regular lowest winter tempterature), buildings do not have well designed insulation. One will notice heat bridges and drafty spots easier in the winter, not so much in the summer with AC running. I observed this in some mediteranean, middle and far east areas, seems similar in Texas.
    Now that there was some infamous snow in Texas 2021, and a hot summer, whith even the best ACs making not much difference, people start to think about insulation.

    Here in Austria, you would hardly find a garage door seller that could afford not offering a fully insulated sliding door, and not many to take the uninsulated ones, even for workshops. Still many houses lack proper roof or attic insulation, but this is currently a hot topic (pun intended) for home owners to reduce heating costs in the upcoming winter – oil and especially gas prices are spiking (well, we stopped laughing about the gas and electricity price desaster in Texas Feb. 2021…)

  7. The roll up door is the main issue here. A more solid swing door would be much easier to insulate. Even my large 5 panel garage door that lifts is easier to insulate. Each of my 5 panels have foam glued to them and this helps a ton in Florida’s heat.

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