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
All *my* ex-s live in 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
We used to have “Elephant Ear” plants around the outside unit for shade. Greta’s bambi deer ate them to the roots. 🙁
@Trust No. 1: I had a metal (white reflective) roof put on my FL home in 2017, along w/ 3-inches of a rigid insulation-board underneath the metal roof panels. I think it was 12 squares (1200 sf?) total including detached 2-car garage. Total cost in 2017 was $17,500. Good work by a 4-man Mexican crew. Certainly double that price today, and those Mexicans are probably doing some other kind of work in some other place.
@George A. & Trust: Good idea! Thanks for sharing. My 4-ton central AC condensor faces east. Gets the strong FL sun from 8:00am – 12:00N. My 2.5-ton 3-head split system faces south, and is in the sun from 10:00am – 3:00pm.
Both AC systems installed in 2018 at total price of $13,500. A full 10-yr parts & labor warranty at $900 each. And the contractor has fully honored it 1x on each unit so far.
On the other hand, the same contractor would not cover a (external) condensation pump replacement on my 87-y/o father’s 4-ton AC system (installed 2023 for $5500). The pump is not a direct part of the condensor or air handler. I can accept that, but they charged him $600 to install a $60 pump (Amazon price). I called to complain and they offered a $100 credit off next service.
I wish we could have just put a window unit in my office for 1/10 of the price, with no 100′ runs of coolant line that needs to be evac-ed each time the POS breaks down–and the air handler would be in conditioned space, but my despotic fourth-reich HOA would never let that happen. The Platinum Level installers wouldn’t budge on the labor warranty–pandemic shortages.
I was up to 3AM last night cleaning up a water leak from the ad-hoc portable dehumifier we use because the whole house one is broken after 1 year, and we’ve been waiting for a year for the mfg to replace it. Probably made-in-the-USA by immigrants, instead of in China like the portable dehumidifier by proud patriots. 🙂
Phil:
What were humidity levels in all three scenarios ?