Jason_InfinityRoofer said:

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All the minerals in your water (that aren't present in rain water) will be corroding the shingles. It just doesn't seem ideal. To be fair, it's the same way I feel about misting the HVAC system. It just corrodes and ages the item way faster.

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I didn't think of this, but it's a great point. My neighbor and I just put up a shared fence a few months ago and you can see the differential coloring of the hard SA water from the sprinkler systems starting to show up while the cedar weathers. I would imagine your roof would tend to show some pretty good streaking since there will be funneled runoff and tons of evaporative deposits due to the repeated application.

Hodor said:

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Here's my off-the-wall answer:
If I were in your situation, I'd install solar panels.

Your roof would be shaded by them, and you'd pick up the extra electricity benefit. I'm guessing they'd be more money than the spray foam quote, but you'd get the palpable ROI (I'm not going to speculate whether that ROI is higher than spray foaming would be, just that you could see the actual number every month.)

I lived in a house for a dozen years or so that had a tile roof. It bugged me when I noticed after moving in, that there was no radiant barrier, given the price of the house. BUT, the attic was cooler than any house I'd lived in (until now, a 1-year-old custom build with spray foam). Not sure if it was the air gap under the tiles, or insulation quality of the tile material, but it was definitely noticeable. I wonder if having solar panels shade the roof would be the next best thing?

Has anyone here used a laser temp gun or similar to measure the temp of the roof sheathing under solar panels, compared to bare roof areas?

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This got me thinking, and I finally remembered to take some Infrared pictures yesterday.

34 year old house. Comp roof with solar panels on the East, South and West slopes. No real shade from trees. No radiant barrier. Three powered attic fans and (WAY) insufficient inlet vents.

There is a noticeable about 20 degree difference from the shade of the panels. Picture order is South, East, West

Was around 230pm













Attic was not terrible to be in, but I had the stairs open and was near the fan, which liked having the stairway opening to draw from. Pure subjective opinion, but it was a little bit cooler......Was that the shade from the panels? No idea. But the IR shows they do provide some cooling.

If anyone has requests for some different images or information let me know. Happy to provide what I can.

Thanks! That's what I was thinking you'd see.

I didn't consider the fact that you're not going to have panels on the entire roof, so obviously the shading effect isn't going to be as much as I'd hoped, but there's certainly less heat gain thanks to the panels. Of course, that looks like a BIG roof, so the difference may be insignificant.

Not huge really. 2200 to 2300 sf house. Looks bigger Iin the drone picture.

You could get better/more evn coverage in some simpler roof designs. But that is pretty typical around here for both the roof design and solar install.

Clearly a double roof is the correct answer here.

Aggietaco said:

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Clearly a double roof is the correct answer here.

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Out million dollar idea! Really big patio umbrellas!

Baylor beat us to the punch, tarps.

Jabin said:

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Quote:

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If you want to try newer tech, GAF makes hip ridge vents. You will certainly have enough of that to make the numbers work.

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Thanks, Jason. You had previously suggested those to me. I mentioned them to 2 or 3 roofers where I live and they had never heard of them, even though at least one was GAF certified! They were very skeptical, especially about the ability of those types of vents to prevent rain from leaking in. Every roofer I talked to here recommended instead that I seal up my existing ridge vents and replace them with 2-3 wind turbines.

I'm somewhat skeptical of those recommendations, however, because in looking at the data, that number of turbines would not be sufficient to adequately vent my attic either. In these hot days the wind barely blows, further reducing the turbine effectiveness. The local roofers seemed to be recommending the turbines and the number simply because that's what they typically install on a house the size of mine.

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I can tell you that every time I pull up to my house, my wind turbines are going what seems like full blast regardless of wind speed. It takes very little wind to get those things to move. Don't let the big windmills make you think otherwise.

Now, whether they're effective in cooling YOUR attic is a different issue but they do move.