Experiences with radiant barrier in attics

Yes, I've done exactly what you are planning. I did it in a rental duplex I bought that had no attic insulation. Like an idiot I waited until June to do it and I also had to rewire the place before blowing in insulation. It was brutal putting the barrier up in the heat but once done it dropped the temp significantly. I was able to stay up there and rewire without overheating. That sold me on radiant barriers

I want to install a radiant barrier also. I know it won't help you but before I do it I will have some long term attic temp data vs ambient to compare with after I install it.

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Think one of the unintended consequences of adding it is increased heat load on the shingles and shortening their service life.

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A lot of insurance companies will not write insurance on a home with roof shingles 15+ years old. I have 30 year shingles that are 16 years old and it's been a bitch and expensive getting insurance. What's the point of 30 year shingles

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I want to install a radiant barrier also. I know it won't help you but before I do it I will have some long term attic temp data vs ambient to compare with after I install it.

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Any timeline? I’m super interested in what you’ll find, especially on the shingle temp/longevity front. Because I’m going back and forth on sealing vs radiant vs vent fans.

I did both. Radiant barrier is worth doing.

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Think one of the unintended consequences of adding it is increased heat load on the shingles

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If the barrier is tacked to the rafters it won't raise shingle temps. The 3 1/2" gap is enough to mitigate temp gain.

I plan on putting up some in the fall, adding insulation, and sealing the gaps around light fixtures, vents, etc. I will be putting in rafter vents too. The attic foil will be placed only between rafter vents and attic fan to allow ventilation. Attic fan will quickly remove any heat accumulation.

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Any timeline? I’m super interested in what you’ll find, especially on the shingle temp/longevity front. Because I’m going back and forth on sealing vs radiant vs vent fans.

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I guess it depends on how I end up defining "long term".

Ideally I would want several years of temp data to draw a solid conclusion but that's obviously too long. Also to this point I've only had one temp sensor in the attic and that's not enough information, so I'll be starting at day 1 whenever I do get started.

Maybe you can help with the planning. I was just going to start collecting as much data as I can and then figure out later how to interpret it. I was thinking I would put 4 probes around the attic just above the insulation, and 4 more in physical contact with the bottom of the roof decking. I considered putting some outside on top of the shingles but that would be a huge pain, and I figure measuring under the decking would be a good enough proxy. I will take some spot measurements outside to try to calibrate the temp differential as well as lag time to the under deck probe, and if it doesn't seem consistent then I might end up putting some up top later on if I really want to know the shingle temp.

So then how to massage, interpret, and use the data? I'm thinking I'll just chart the ambient, roof, and attic temps, and I'm hoping the pattern will be apparent. I'd expect to see clear peaks and troughs in roof temp lagging behind ambient, and then attic temps similarly lagging behind roof temp. Then lagging behind that I have my thermostat data which on the hottest days struggles to bring the indoor temp down until well past sundown.

I'm hoping to whittle it all down to a couple of values... one representing the amount of energy hitting the house (ambient temp over time), and another representing the amount of energy expended removing the heat that got inside (basically AC runtime). I have no idea what these formulas will look like at this point. A more direct set of values will be the temp differentials from the roof to the lower attic. And of course I will compare before vs. after a radiant barrier.

I also have powered attic vents which I can control and automate to add to the data. I'm really curious whether more heat is transferred from the roof to the insulation via convection or radiation.

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Cellular signal is definitely diminished. May have to deal with that separately.

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When we replaced the farm house roof with metal we went from 4 bars inside to zero. But turning on wifi calling allows calls and texts to come through fine.

(I have an Iphone, not sure of other brands do that...)

I've done about 75% of my roof. Doing it by yourself is sort of like making your bed while you are lying in it. It's doable, but a bit of a challenge. I have a pneumatic crown staple gun I bought for upholstery 10 years ago and I highly recommend it.

I'd be lying if I said I noticed a huge difference. I have had two roofing companies take a look and both confirmed my hip roof lacks sufficient ridge venting. Next step is turbines I believe.

In the fall, I will blow in more insulation. I'm angry I didn't get around to it this winter as planned.