Cheapest was to insulate a concrete flat roof?

I have solid precast poured concrete garage with a flat roof. The problem is, by 3pm that this has heated up and starts baking like an oven. What would be the cheapest way to insulate it? Has anyone else ever dealt with something like this?

  1. 3 weeks ago
    Anonymous

    Is it already painted white? If that doesn't work you're looking at building something that creates dead air and shade, which is pretty much going to be a second roof.

    • 3 weeks ago
      Anonymous

      Yeah, it's already white. Second roof you say? Walls are also solid concrete so you sure that will work? Kinda always been hesitant to do anyhting because I am not 100% what will work.

      • 3 weeks ago
        Anonymous

        People who build with shipping containers in the desert often make little awning roofs to make their structures inhabitable. Might be a good place to start researching.

        If you live in a place that doesn't get much wind, you might try some sort of "shade sail" a few inches above your roof.

      • 3 weeks ago
        Anonymous

        Silver paint, 99% reflectivity is worth a lot more than 80%.

    • 3 weeks ago
      Anonymous

      I should add that the roof itself is not white, on the walls. The roof is unpainted concrete.

      • 3 weeks ago
        Anonymous

        Well paint the roof. They almost certainly have paint specifically for that purpose.

        • 3 weeks ago
          Anonymous

          What decrease in temp should I expect? I am thinking about what I should do if I am still not happy with the temperature decrease... Internal insulation? The ceiling is a little low already

        • 3 weeks ago
          Anonymous

          Is it already painted white? If that doesn't work you're looking at building something that creates dead air and shade, which is pretty much going to be a second roof.

          Okay, just did some research, turns out they sell special “roof cooling” paints… Does anyone if these are gimmicks or not?

          • 3 weeks ago
            Anonymous

            Example product:
            https://leroymerlin.co.za/roof-raint-exterior-low-sheen-plascon-nuroof-cool-white-20l-81416861?refSrc=24238&nosto=nosto-page-product2

  2. 3 weeks ago
    Anonymous

    Does it not have a rubber roof membrane? Most flat roofs I've seen have an insulating foam layer between the rubber and the concrete

    • 3 weeks ago
      Anonymous

      No, solid concrete.

      • 3 weeks ago
        Anonymous

        >didn't put a layer of insulation between concrete pours

  3. 3 weeks ago
    Anonymous

    obviously a moat is the answer

  4. 3 weeks ago
    Anonymous

    get a second roof over it, people who live in RV trailers and shipping containers will tell you what a difference it makes not to have direct sunlight on your roof surface. If there are reasons that's not possible, the next best solution is an insulated air gap at the ceiling. like, get some wood-concrete glue, glue some lumber across the bottom of the roof then attach bubble foil or foam board across it. This will leave an air pocket that will trap the radiant heat. I've seen this used in old metal buildings that didn't have any insulation at all and it made a huge difference in minimizing summer time heat

  5. 3 weeks ago
    Anonymous

    If your problem is warm in summer and cold in winter I'd just use some ethene-based styrofoam and plaster it or some shit.

    If your problem is heat and sun you could get some solar-absorbing collectors, either for electricity or heat.

  6. 3 weeks ago
    Anonymous

    Roof-mounted polyisocyanurate insulation board. R-3 per inch. Your problem is "easy". Chances are the old roof would need to come off in order to put down the insulation board because it needs to be epoxy applied to the concrete deck. There are mechanical fasteners made for this, but you're taking a huge risk of the concrete is old and shitty (i.e. breaking big chunks off driving fasteners through it). You can loose lay it with insulation board and membrane, but you would need ballast in the form of gravel or pavers to hold the fucker down. Local code might prohibit this as well if you live in a very high wind zone or hurricane zone.
    >Oh, it's solid concrete
    If you have a water proofing system like Tectum as the base, epoxy down polyiso, fully adhered membrane over the top. This is not a DIY application unless you want to spend 800 bucks on a two part epoxy spray backpack rig.

  7. 3 weeks ago
    Anonymous

    you could try attaching rigid foam insulation to the ceiling, or install ceiling joists so you can hang fiberglass or blow-in cellulose insulation within the joist bays

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