I have a Chinese Govee temperature sensor above the fiberglass insulation in a mostly unventilated attic here in Florida. During a reroof there were periods of time when the attic was covered with
- concrete barrel tiles over hot mop tar paper
- modern peel-and-stick underlayment only
- clay barrel tiles (a medium-dark red/brown) over the modern underlayment
Weather conditions were reasonably consistent during these three time periods, i.e., hot and sunny.
Temps in the lower part of attic (only about 4′ high; probe on top of some fiberglass insulation above the finished ceiling) went from roughly 100 degrees underneath the old intact roof (concrete tiles) to 120-130 degrees under the peel-and-stick underlayment only (white in color, but apparently not very reflective), and back down to around 100 degrees underneath the new clay tiles over underlayment. Here’s a chart from the Govee app:
In late July, maybe the hottest time of year, the temps went up to a max of 115 degrees.
Speaking of Chinese tech, here’s an idea for an awning that can automatically deploy over a parked car:
(I hope that it checks the wind forecast and the actual wind and folds itself up automatically when necessary!)
We have a separate 1.5 ton A/C unit proudly made in the U.S. upstairs just for a small loft. The air handler is in the passively ventilated attic, and it runs all the time just to overcome the attic heat. An attic fan wouldn’t help, because it probably would just pull more sub-tropical humid air in and make everything moldy. We thought about putting in insulation under the roof itself, or moving to a climate where you don’t have to rely on it so much.
It has a ten year parts warranty, and of course the TXV failed after two–the part was covered, the labor was $1500. Ouch–new A/C shoppers, here’s a tip: consider trying to find a labor warranty at the time of purchase. Listen to your home inspector when she tells you the old one runs on R-22, even if it seems to be running OK. Don’t ask me how I know, $20K later.
Eichard Francis Burton remarked thst hot climates bred hot women. A/C breeds frigidity.
As evidenced by my hot wife from South Florida
Funny how china is moving from awning covered rickshaws to awning covered pavement melting cars. Can’t give up some traditions.
If you have an outdoor AC unit that is exposed to direct sunlight most of the day, you should either get one of these [1], or just head over to Home Depot and make one yourself. It is a no-brainer. I did this for my parents’ AC unit about three years ago, their unit faces the sun, and it made a big difference.
I actually discovered this by chance. We had cut down a tree, which left the unit exposed, and that summer, thanks to global warming and Greta Thunberg, I noticed the AC was working much harder. That was my clue, the sun baking it.
It is a shame HVAC installers don’t mention this, and even worse that government regulations don’t require it. These days they have strict R-value requirements or you will fail inspection, but something this simple is completely ignored.
[1] https://www.youtube.com/watch?v=juQVbAByneQ