Hello from Texas
 

Hello! I've been looking around for a few days at many good threads containing interesting projects and great advice. I've gots lots of learning to do.

After 20 years in software, I'm looking for something different. Rock star was my first choice but then I was introduced to the refrigeration cycle, which I find fascinating.

M.C. Pletcher's youtube channel has provided plenty of inspiration.

LINK REMOVED

I am skeptical of having the tools/smarts to build a tiny refrig system but I'm going to give it a go anyway.

Here in central Texas it is about 100 degrees for 300 days of the year (may be exaggerating a little I guess - the humidity is high as well). The house I live in has an asphalt roof and the attic gets to about 150 degrees. In effect, the attic is a solar oven. The problem is exacerbated by the fact the AC ducts are in the attic. For many years I've just ignored it, paying exorbitant bills in the summer but now I've begun to wonder if that could not be done better. A metal (aluminum or white) roof would be much better for example.

I've learned plenty from Matt Risinger's channel:

LINK REMOVED


Coming at these problems from a consumer's perspective, rather than a builder, has lead me to many similar conclusions.

* Keep the heat out first (radiant barriers) - don't invite it in with asphalt
* Seal the walls - don't just insulate them
* Condition your attic - don't just assume that allowing it to get hot is ok
* Use an variable speed AC - rather than one that is on or off

When the AC system (which we seldom use now) is replaced here (it is OLD and inefficient. I went out and measured the amps on it the other day ~25 @ 240v which equals approximately ... too damn much!) I'm likely to recommend a variable speed system that does not rely on the ducts in the attic. We have been using window units for the last 3 years and they have saved us at least 100 a month in the summer and we are cooler.

There is a small shed here and am using it to learn and test ideas. Even good old barn aluminum does a remarkably better job of keeping out the heat. Underneath the aluminum, on a 100 degree day, the roof gets to about 100 degrees where as before it was well above 160. _Of course_ that translates to a lower internal temp. The aluminium is not hot either (like the roof was) - it is emissive. Emissivity is a remarkable property I intend to investigate further.

Anyway, that's the skinny on who I am and where I'm coming from. Hopefully I'll meet you all on the flip side. Paul

Welcome to the site Paul. Sounds like you got some interesting projects to work on.

if you are saving that much using window units, just think how much more you could save by slapping something reflective on your roof. A 5 gallon bucket of cool-seal goes a long way.

Been there, done that. The problem that may occur is that in a metro area large amounts of carbon soot drift to earth staining the roof with a moderately hard to remove gray palor. Moving to a light colored shingle like Owens Corning "Amber" can lower the roof temperature down to about 125 in South Texas. Radiant barrier will get you down to about 110 - 115 in the attic with a good solar powered or electric ventilation roof fan.

Beyond that (if some spending is in the budget) a better solution will be a Gree Terra mini split heat pump. I have a 24,000 btu 21 SEER unit for the bottom floor (about 1100 sq ft with 23 foot vaulted ceiling), a 12,000 btu 25 SEER unit in the upstairs master bedroom with kitchenette and bathroom, and 6,000 btu window units in the downstairs bedrooms. The old 5 ton central ac was removed and all attic ducting is now gone also. All-electric home bill went for $200-300 per month with central to $100 to $200 with us running cooler temperatures than before in summer and warmer temps in winter.

They work so well I have bought two Gree 27 SEER 9,000 btu mini splits to replace the downstair window units 14 SEER. That is just to further lower monthly bills. We are already able to freze anyone out in summer or heat them to discomfort in winter, so when I install these later it will not be because we need more btu's.

Before I forget, welcome KazBach, fellow Texan!

We've seriously considered that - still considering it. We have a shingle roof which was just redone a couple years ago. (hail) We are still kicking ourselves for not installing a split-seam, still being pretty clueless about things then. Also, we have one east/south facing wall that we had siding redone - but did not well radiant barrier it (hardy board). So we were considering painting it with a radiant paint. The one troublesome room we have is behind this wall and upstairs.

It has been a surprisingly moderate August here in Texas - we have not turned on our central AC one time I believe. Having a large window unit (12k btu) does a remarkable job as 'a central AC' and uses about 1/6 the elect. It cools the central part of the house, which includes a loft and is located there so it naturally is more efficient than the central AC which has to scurry through the hot attic from the other side of the house. We are thinking of putting up with it (the one window unit) and getting a split-ac, with 2 internal heads, to augment it in the bedrooms.

I went out and checked the amp draw on the central ac. It leveled out at about 22 amps (240v) but spiked to better than 30.That really surprised me. When I finally got off my duff and really looked at the hvac here, I was honestly stunned at how inefficient it is.

When it turns on it makes a loud sound - 'probably' it could use a 'soft start'. A few years ago it actually blew the cap and caused an arc in the outside panel, melting it. It has been 'fixed' but it still causes me to flinch every time it turns on.

Anyways, cheers and Thank you.

We'd like to do a split seam roof (great for solar panels), along with a ridge vent (the gable vents are practically worthless), which will help a lot I hope and might allow us to avoid the internal radiant barrier. We'd also re-seal and blow insulation onto the attic floor.

If you are reading this and want to get an idea of how well a metal roof helps:
- pick up a cheap sheet of barn aluminium
- make a 1" frame for it as an air gap and for rigidity
- put it out in the sun on your (roof of all evil) asphalt roof

Here are my results using a laser temp on a 100 degree day
- better than 160 degrees without the alum.
- with it, less than 110.
- a fifty degree difference.
- interestingly you can set your hand on the alum - try that on the asphalt!

That whole exercise was an eye popper to me.


This is pretty much the exact route we intend to take. We will look into the Gree Terra. Those inverters are cool.

Reminds me of a (oldish but good) quote I found that really sunk in with me.

That's what we do with our window units. Kinda redneck - but hey, it works.

Mini-splits are modern versions of the same.



Great info sir, nice to meet you and thank you!

Just got a new roof myself. The white coating had extended the life of the failing shingles by about 5 years so I got my moneys worth. I went with Owens Corning Duration "Amber", a very light, but not white shingle. A metal roof was out of my current budget without blowing up other projects. "No dear, I will not keep the old water heater and downstairs window ac's just to give you a metal roof. They are at 'end of life'."

One more point I forgot to mention. When I put a white coating on the roof if dropped the surface temperature from 190 to 110, so that does work, and I agree that aluminum is crazy stuff with very little emissivity!

Don't worry about tools and smarts getting in the way of refrig system hacking. If you look around you will see that previously hapless idiots are able to wrestle success from a baffling pile of parts.

And they are here to help.

-AC_Hacker

Just so I'm clear, did you put the white coating on shingles?