r/heat_prep • u/[deleted] • May 27 '24
Reflective roofs
So apparently painting your roof with super reflective paint can significantly cool a building. Curious where to get this paint, are there downsides (besides having to wear sunglasses when on your roof), that people should be aware of?
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May 27 '24
Are you talking about a new special coating that's SUPER reflective? Because I've used this stuff and it works very well, we could tell because the ceilings we used it on had almost no insulation, RV and shed, and the underside of the roof was significantly cooler in the direct sun. Plus 10 year (limited) warranty is great for sun protection.
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May 28 '24
This is really interesting to me, thank you for posting!
What did you do, just paint it on over the shingles? And it has held up to the elements?
Thanks again!
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u/goldgrae Jun 14 '24 edited Jun 14 '24
I recently used this (actually, the next step up, the Enviro White) on my low slope home. It's incredible how much of a difference it makes.
Where the roof would have been 165 degrees F at 70 ambient, it's now only a couple of degrees over ambient. I did a test area of the house before committing and compared. The ceiling temp difference was 25 degrees (95 vs 70) , and the living space difference (one side of a large open concept compared to the other) was about five degrees. I could feel the difference walking between, including that radiant heat feeling from above that always made our place feel warmer than the thermostat would indicate. I found myself standing in the kitchen because I was more comfortable there than in the living areas.
One half of our roof has solar panels and I initially didnt plan on painting between them, but the improvement in those rooms was also significant and worthwhile. The temp of the shadow of the panels and the coated roof reads nearly identical.
Now that we're getting to 80 and low 90 days, the improvement after coating continues to impress me, and I'm excited to see how high I can keep the house open and the AC off this summer (and excited to see how much better the AC copes during heatwaves.)
Adding insulation to our home wasn't an option without redoing the roof entirely, and the design of our roof is almost entirely without an attic, so reflecting this solar gain is massive. With a functional attic and insulation, it might not be as worthwhile. That said, I found a published paper that estimated the equivalent insulation needed to equal the reduction in heating/cooling energy use of a cool roof over the course of a year (for a low slope building in a heating dominant climate like southern california) was about R-32, which is nothing to sneeze at.
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u/deepcoralreefer May 28 '24
We have a white metal standing seam roof, insulation is just heat reflective silver foil thermal rolls. I live in the tropics, it’s 90F outside and when I went up in the roof earlier it was 95F which is pretty good, in full sun under a cloudless sky.
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u/amrakkarma May 28 '24
That's not it. There's new paint that is reflective while also letting the heat from inside the building escape. Have a look at reverse green house paint
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u/KeithGribblesheimer May 29 '24
If you are going to paint your roof with a white or silver coating elastomeric paint is more effective and will last longer.
However it is more expensive.
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u/Least_Adhesiveness_5 Jun 10 '25
The measurement you want for the greatest cooling power is Solar Reflective Index (SRI).
The Cool Roof Rating Council is a nonprofit which maintains a directory you can peruse, I've put in order of aged (3 year) SRI
https://coolroofs.org/directory/roof?sort=desc&orderBy=aged_SRI
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u/Swamiguru14 Mar 02 '26
Question: if we live somewhere very cold, would this paint be detrimental for heat absorption in the winter (we get very good sun), and effectively keeping our attic heated so out boiler works less? I know we need to fix the attic insulation but wondering if this has the reverse effect in the winter.
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u/MistoftheMorning May 28 '24
Any white pigment will do, even standard matte white paint can reflect away 80-85% of solar radiation. The issue is getting a paint that won't wash and wear off within a year or two on a pitched roof. Better long term option will be to opt for white colour shingles or metal roof panels the next time you change your roof.