Cool roof coating over asphalt shingles? (OT)

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Ken M

Mountain climber

Los Angeles, Ca

Oct 18, 2018 - 08:57pm PT

I have done a lot of research on this issue for the last decade, and it's surprising whats out there.

The specific solution that you ask about is definitely controversial, although it clearly is ok for flat roofs of asphalt rolls. In fact, NYC has a program to do this to all commercial buildings.

This is done a lot in Scottsdale/Az. Interesting to look at Sat pictures of the city.

However, there may be a much simpler process----Behr makes a paint specifically designed and recommended for asphalt shingles

https://www.homedepot.com/p/BEHR-1-gal-White-Reflective-Flat-Multi-Surface-Roof-Paint-06501/100164524?MERCH=REC-_-PIPHorizontal2_rr-_-204177723-_-100164524-_-N

There are also a couple of sites of guys who wanted a "try", without spending a lot of money. So what they did was whip up a batch of WHITEWASH, for less than $25 for the whole roof, just as a trial

https://www.builditsolar.com/Projects/Cooling/WhiteRoofExperiment/WhiteRoof.htm

Ken M

Mountain climber

Los Angeles, Ca

Oct 18, 2018 - 09:05pm PT

Here is a nice summary from Yale:

https://e360.yale.edu/features/urban-heat-can-white-roofs-help-cool-the-worlds-warming-cities

Bad Climber

Trad climber

The Lawless Border Regions

Topic Author's Reply - Oct 19, 2018 - 06:23am PT

@JLP -- Yeah, minor thread drift there. My current old-skool double wide is a '73 with a super low pitch metal roof. Spray foam has been great, but I'm not looking to foam the shingles, just add reflectivity if I can do so safely and cheaply enough. New place gets LOTS of sun while the old place has mega shade. Even with the shade, the white + insulation helped a lot. It was amazing to be up on the roof pre-foam job. The metal would get freakin' hot! Now cool as cucumber, baby.

Thanks Ken et al. Super interesting. Can't wait to read it. I've been really into energy efficient homes for a long time and wanted to build a straw bale years ago but not being contractor, the hassles seemed too much at the time.

For Bishop, we hit double wide gold!

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toejahm

Trad climber

Chatsworth, CA

Oct 19, 2018 - 06:26am PT

Hello bad,
High-density spray foam with a polyurethane walking surface is what I believe you're considering. There are a ton of upsides, most already mentioned. The downsides are; maintenance every five years with UV and heat taking a toll on the finished surface. The finished surface is very undulating and lastly how do you tie into head walls, eaves, fascia, confined rakes without substantial modifications to your flashings. Spray foam use to be the product of choice, but commercial systems have switched, some time ago, to TPO roofs. There is a home in Calico canyon RR near the craft bouldering parking area that utilizes the roofing system you're thinking about, maybe someone here knows the owner.
Peace,
kenny
p.s. best advice is talk to the manufacturer and a preferred installer. Most if not all of the foam systems require specific installers, otherwise No Warranty.

Bad Climber

Trad climber

The Lawless Border Regions

Topic Author's Reply - Oct 19, 2018 - 06:39am PT

@Kenny and xCon:

Good points, but as I tried to clarify--no foamy on this roof. The crew who did the old double wide added a flashing damn all the way around then laid down a sealing coat which had to thoroughly dry. Then they laid down about 2" of the foam, then a couple of coats over that with some small gravel, which apparently discourages birds from pecking at the surface, which I guess is a thing. Manufacturer said we could probably go quite few years before any re-coating would be needed and that some maintenance like that would make the roof last indefinitely. Wasn't a cheap job. $$$

@Ken M: That Behr stuff looks like the bomb. I figured SOMEONE had to be making a paint for the job. I contacted Henry directly and they said NO to the use of any of their products on shingles.

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Chaz

Trad climber

greater Boss Angeles area

Oct 19, 2018 - 07:49am PT

They paint the shingles on these things and the buildings around them.

I don't know exactly what they use, but it comes out of a can and is applied just like paint.

jbaker

Trad climber

Redwood City, CA

Oct 19, 2018 - 10:34am PT

I've used the Behr reflective paint on a flat roof. It made a small but noticeable different in max temps. I think it would have made more difference if the house hadn't otherwise been poorly insulated with a lot of air movement (it was a redwood cabin built by hand in the 20s). It is a cheap and easy enough solution to give it try. If it doesn't work, you're only out a few bucks and an hour or two of labor.

Bad Climber

Trad climber

The Lawless Border Regions

Topic Author's Reply - Oct 19, 2018 - 11:01am PT

Hey, Chaz, that red roof is neat. It seems the Behr is reasonably priced. Key seems to be priming first. I'll prolly give it a shot in the spring.

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