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Hot, sunny climate with little insulation and AC unit on the roof. How can we permie this?

 
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I've been following and encouraging a user who recently bought land in California: https://permies.com/t/40/214583/permaculture-sites/finally-land

He mentioned this:

The whole neighborhood up there is like this: thin walls, effectively no insulation,  not adobe or cob is what I'm getting at.

And this:

Every house has at least one AC unit on top (on the roof, in the sun.) ...  (Our friends said this is the fourth time the AC has gone out.  Good for the AC repair shop, bad for everybody else?)


I tossed out the first crazy idea I had for at least getting some shade on that AC, and then I thought that there are lots of creative people here on permies and maybe we could come up with a permie-perfect-practical solution for what I consider an undesirable design.

For the record, I do *not* have AC - generally don't need it in my climate. However, my parents did and my sisters still do where they live in Ontario.

My first crazy idea:
1: Get a really good anchor plate for something like a flagpole or weather vane. Adjust the top of it to hold a large sun/market umbrella. Adjust it's mechanism so you can pull a string to raise it, tie off the string to hold it open, and release the string if it's not needed/high winds expected.

My second crazy idea:
2: Salvage 2-4 of those old triangular antenna towers that it used to seem like every house used to have. Grow plants up them that will cover the roof and the AC unit. Pictures would help. Since they need fast help, put the largest pot that will fit inside the triangle up near the top and outfit it with drip irrigation +/- make it a wicking type pot and plant pole beans. They'll grow fast and provide fairly quick shade if you plant enough of them. Plant something that will naturally grow that tall in the ground for the future.

Can anyone else think up some crazy ideas for shading the AC? It may not make a huge difference, but my understanding from my sisters, and my father did this as well, is that finding a way to shade the AC unit with plants did improve its efficiency.

Of course, finding ways to insulate the whole house would make a huge difference also, but that could be a much more expensive project.
 
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I would put a sprinkler system that mists or sprinkles the A/C unit during the hottest part of the day.

I would grow lots of vines on the south side of the house to offer some shade there.
 
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Every house has at least one AC unit on top (on the roof, in the sun.)



I wonder if what looks like roof top ac units are really 'swamp coolers'? I thought they were still used a lot in the southwest.
https://en.m.wikipedia.org/wiki/Evaporative_cooler
 
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If they are running swamp coolers (evaporative systems) they need to have no obstructions by plants to get the best air flow.
Refrigerated air I don't know, and anything I say after this involves swamp coolers, as I have repaired hundreds of them, my parents had rentals and I was on the maintenance crew from an early age.

I spent most of my life in NM and fought the coolers on the roof thing all along. Makes zero sense to me. I put them on the ground, with the output into the house low, and opened something up high, and got MUCH better results.

It comes down, as far as I can see, to builders being "used to" building with heating systems and wanting to run ductwork they way they are familiar with, and that puts the AC on the roof, as it has to be outside, gets the ducts in the right place.

When I built the clerestory on my last home, my dad, who is a construction guy, insisted on framing in an AC point at the highest part. I gave in and let him frame it, then covered it. Never opened it up. As soon as the first window was opened it was obvious to him that an AC up there would be a waste of time. He hadn't thought about it. That's just "How it's done" and he was sure he was saving me from making a bad mistake, and I appreciated that. But we never opened it up.  "It's not designed the way you are used to" is hard to get through a construction guy's head.

So that's why it's up there, and why you can't put plants over it.
 
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Anne's suggestion is a great application of low tech to a high-tech weakness. It's been around a while...when I was a kid my grandparents had central AC installed on their house, a burnt adobe ranch with (at the time) no roof insulation. In Tucson, where summers can be brutal. The unit was on a small slab at the east end of the house.

The first thing my grandfather did was to plant a fast-growing chinaberry tree on that end of the house. Then he put a swamp cooler next to the AC unit and set it up so that the fan on the evaporator coil pulled air from the box. That way, the AC ran more efficiently and didn't have to work as hard to cool the house. The tree shaded that entire area and kept the ambient temperature down, and then the evaporative cooler lowered it even more.

Obviously, this won't work on a roof, but cooling the air that the air conditioner needs will help, and this setup avoids mineral deposits on the heat exchanger fins.
 
Pearl Sutton
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Insulation would help a lot, as would thermal mass. I'd check for air leaks, make sure it's sealed up well, and see if there's a place that the AC hits hard that can have a thermal mass of cinder blocks or something. A fake fireplace made of landscaping blocks, right where the AC hits, would stabilize it quite a bit.
 
gardener
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For me, the permie thing is to be able to survive without the AC, and relying on this just for increased comfort.
Also, since he is going to use the machine, doing it in a way that makes it last long, using its waste for something useful and make it stack functions with other parts of the house system.

Let me elaborate.

- If California is something like Andalousia (it is), then it has cool nights and cool winters. So, it pays to have some heat mass. In old houses that's thick walls. In newer houses it can be a wall or a concrete floor that captures heat in winter and is shaded in summer. Another less intrusive heat accumulation is to keep the heat in an underground pool: geothermic AC.
Shading is vital. So it is controled ventilation. When the air is good, it's nice to have the option to make it temperate the house, and when it is bad, the option to reduce it to the minimum. There are a few ways to do this, but I prefer the ventilation chimneys (they don't work always, but the maintenance is null).
Also, favor furniture with good heat mass: wooden and earthen are good, metalic are not.

It also pays to have good insulation, especially in the roof. In a flat roof, you can reduce a few degrees the temperature just by pouring a layer of white small stones. Even if his walls are thin, insulation plates can be installed in the outside.

- As they've already said, placing the compressor unit where it is cooler, makes it work less. The best place is the eastern wall, shaded by trees.

- The AC unit creates condensation water and releases heat. Use it. The water is easy: any plant would gladly receive it, or it can be sprinkled for cooling. The heat is trickier, but maybe you have something that you'd like to dehydrate, or you have clothes that you want to dry fast.

- Having the AC irrigate the same plant that is shading the intake is stacking functions.
 
Jay Angler
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Abraham Palma wrote:Another less intrusive heat accumulation is to keep the heat in an underground pool: geothermic AC.


I just want to be sure I understand.  "underground pool" just means the heat is "collected" in a place - not that you actually are using an underground tank of water to "keep the heat"?
Water being the thermal hog that it is, and if land was limited, as a crazy and expensive idea, burying an insulated tank of water and heating it with summer attic heat, would be an interesting experiment in number crunching to see if it was any more useful than collecting heat in dirt/rock. I know that one concern about using pipes in the ground to cool/heat buildings is that if there isn't sufficient summer/winter differences in the environment, the efficiency gradually decreases because the soil is so slow to reset itself.  Heat can move around much faster in water can't it? We plant our septic tanks, why not an "air conditioner tank"?

There are two (at least) important parts to the problem:
1. What Pearl said: "this is how it's always been done" inertia in the building industry.
2. Buildings being built without attention to the real climate they are situated in because power to artificially fix the problem was too cheap and prolific to be bothered fixing it with simple, passive, intelligent design!

However, we saw what a war did to people relying on Natural Gas in Europe last year. I didn't hear of people dying, but I do understand that it increased people's stress levels which can have long-term health repercussions.

This subject in a wider sense has been in my local news lately. We had a "bad" heat wave in 2009. People died. There was a big study and recommendations made. It was ignored. Even bigger "heat dome" in 2021. More people died. The government's promised to subsidize the cost of air-conditioners for people at risk - air conditioners *increase* the ambient temperature of the neighborhood, not to mention the noise factor. And they require the person to be able to pay for the increased electricity costs. But will the recommendations of decreasing hard-scape and increasing tree coverage ever happen?  

I do not know what exact community I was quoting when my brain started imagining crazy ways to help with cooling. I don't *know* if the air-conditioner in question is or is not what is called a "swamp cooler" - I'm not aware of those being used much in Canada. That doesn't mean that there wouldn't be places appropriate for their use, but it comes back to treating the whole country as if it's got exactly the same climate... (sigh... no, we don't!) which gets badly caught up in the part of the problem of "that's how we always do it."

If we *really* want to permify the community I took the example from, we'd go in the fall and plant a thousand trees. If it's an HOA there'd be "words"!

 
pollinator
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Certainly, beefing up the insulation would be tops: It is not very expensive and works to heat or cool the house.
Has someone mentioned placing the AC unit low to the ground on the shaded side of the house? This is what I have in zone 4b Wisconsin, and it works really well... or is this too obvious.
Before we use the AC, we often run the fan from the basement during the day. That might not work in hot zones, but in Wisconsin, our basement is quite a lot colder in the Spring and Summer, so we can get a cool breeze by bringing air from the basement.
 
Abraham Palma
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Hi, Jay.
There are many ways of doing it. An underground pool is just one way. I guess it doubles as a water reservoir. These are the tanks: https://darcoinc.com/thermal-storage/ The advantage of this system is its large flow of energy. The drawback is the price. I've seen only large projects like schools installing this option.

Other systems just run water pipes through the ground, as you suggests (which is cheaper). Or make use of natural warm water.
https://www.epa.gov/rhc/geothermal-heating-and-cooling-technologies

The idea is that instead of throwing the heat to the environment which is too hot, the HVAC uses the thermal mass underground as a heat sink (or heat source, in winter).
 
Jay Angler
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Abraham Palma wrote:

The advantage of this system is its large flow of energy. The drawback is the price. I've seen only large projects like schools installing this option.

On the scale shown in the link, that's understandable. However, there's someone on South Vancouver Island who uses smaller, vertical, well-insulated tanks on a lower level of his house to store hot water for house heating. I think he gets enough solar gain even in the winter that he's not having to store *all* his heat in one season and hold it until winter. "Smaller" is relative. They'd be in the order of 6 feet tall from the picture I saw, and close to that or larger in diameter and I think he had at least 3 of them.

The question would be, would a system like that keep a 1500 square foot house, cool in California heat wave temperatures? Cool to me would be 75F - that's another huge bone I'd like humans to smarten up about. Yes, I wouldn't be happy coping with 95 F day and night. But why would I want to spend my summer at 68F??? It's SUMMER! It's *supposed* to be hot! I hated working in Ontario and feeling like I'd get to work and immediately have to cover my pretty summer dress with a sweater! Often the issue is air movement rather than temperature, and our failure to design buildings with the seasons in mind!
 
Abraham Palma
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The question would be, would a system like that keep a 1500 square foot house, cool in California heat wave temperatures?



I see where you go and I completely agree. As I said in my first comment, the house should be liveable without AC, and AC is just for a little extra comfort. Here we have nights over 27ºC and high humidity, that's something you can't sleep unless you use a wet clothe and a fan. And that's pretty uncomfortable too. Having an AC running at 28ºC (or the DRY setting) and a simple fan just makes it enough for a good sleep. No need for more cooling. Except that some people feel the urge to set it at 21ºC.
Why? Maybe cause they can. I mean, it shows that they can, that they don't mind the cost for they've earned so much money and they are so hard workers that they deserve now this treat.

If a typical McMansion is going to run the AC non stop either way, well it may as well save some energy using one if these tricks. That will also show not only that they can, but they do care for the planet. And hopefully they will burn less energy.
Or maybe it's a small hotel. These bussinesses are usually very conscious of the cost of climatisation
 
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One thing I would consider is a 'safari roof', it sits above an existing roof with 2 layers of roof battens, crossed,  with sisalation between them.
The extra roof is screwed to the top batten.
Air can flow under, and the base roof is shaded.
I have dropped the original roof temps from 78 deg. C to 38.
 
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I agree with Abraham.

The first thing is "despoiling" of AC users. I knew people who call 25C hot and 15C freezing. They would be unhappy.
I have noticed that most population in California brought with them from the east of Rockies: intolerance to heat, lack of knowledge and experience how to deal and build with heat, desire to have green lawns and acceptance of $600 monthly electric bill for AC.

The second problem is complete lack of thermal mass and simple window shutters. I have never seen so many houses so cheaply and badly built and sold at outrageous prices as here. Everything is built of flammable materials of course so can be nicely incinerated with the next massive fire.
When these problems are solved then using occasional AC on very warm and humid nights would make sense.
Right now it's 40C here, but the sky got cleared and yesterday's humidity left. The breeze is nice, the night should be cool.
 
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Keeping shade on an A/C unit is important for its proper function.  My thought is to make a trellis and grow some vines up so that the A/C will be shaded.  Make sure to keep the area around the A/C open enough for maintenance.

Eric
 
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My garage-shop is 1,800 square feet. It's located in Eastern Washington where it, often, hits 114 (recorded 124 once) and, in the winter, 20 below.  I'm way grown up, so slower finishing some projects. One being getting rock up on the ceiling and walls.  I do have 6" insulation on the walls and 3-1/2" on the ceiling, with a target of about 16" overhead.

Entering the shop, the first thing you notice is, it's about 15 degrees different than whatever is going on outside. Even without air or heat running.  Even the uninsulated, unrocked auto bay is a bit different (better), in the winter.

For our poorly insulated house, we bought roll down blinds that latch at the bottom.  They make the difference between the heat pump keeping up and lagging way behind, in the hot of the day.  They work so well, I've thought about extending the deck railing up and tying it to the house, so I could create a large frame to accommodate, say, six inch wide strips of material extending from the deck rail to the house, to shade the majority of the west end of the upper portion of the house (the lower section has cedar boards shielding the lower portion of the west end).

The north and east sides of the house have backfill on the lower floor. The dirt, up against the concrete block walls [and the lack of direct sunlight in the hot of the day] contribute to the comfort in the basement.

Just moving the air from the basement to the upper floor makes improves the over all comfort in the home (see the reference to tunnel cooling, using the mass of earth, below).  

Clearly, blocking sunlight and wind changes the game dramatically, whether by shading or insulation.

As most know, just stepping out of the sun into the shade makes a huge difference in how hot you get. Accordingly, I, years back, built a lean to over our heat pump. It helped a little, just like parking our car in the shaded, hot garage does (if I leave it out, I have to get about a mile down the road before the AC becomes noticeable. Even if the garage is the same temp outside, just being in the shade maked a huge difference - the car is putting out cool air before I hit the end of the block).

From these things, it's obvious anything one can do to get shade, or if they can add insulation, they'll be better off for it.



From there, there is that countries where hot is the norm use tunnels they run air through to cool buildings.  They MAY have to contend with condensation in the underground tunnels/pipes (mold).   At any rate, we know holes in the ground make for some decent root cellars, so there is value in that, when it's possible to take advantage of it.
 
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I don't have tons of specific experience with this exact situation, but am in a cob house where it gets to 100F in the summer (so far).

basic permie idea: Shade !    get shade over the house, or at least the AC unit.  Some kind of tent, sail, tarp, second roof, something.  You could have something up there tomorrow.  Even one of those sun roof things the vendors use at farmers markets.

basic builders idea: get someone in there and insulate the roof.

basic gardeners idea: grow plants to create shade on the south and top of the house.
 
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Jay Angler wrote:

Of course, finding ways to insulate the whole house would make a huge difference also, but that could be a much more expensive project.



I'm not sure how expensive it would be to get this happening, but I think it would be considerably less expensive once you had the process down.  

Make your own natural insulation:  



Flame proof and eco friendly!

 
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