Reducing energy consumption (AC's) in hot climates

mekrob · Expert Joined: Dec 09, 2005 Posts: 2663

So I was thinking about living in hot climates and what that does to your energy bill. I was wondering and thinking about ways to reduce energy consumption if you were to build a house from scratch. One of the ways I was thinking about that I'd like some input on goes something like this.

We all know that hot air travels up, cold air down. So say you're in a hot climate but energy is not that cheap nor available at demand (hey, aren't we heading to this place?) What I was thinking was if you were to have the ceiling of each room tilted just slightly (or more if possible). You'd have to imagine a house or building with at least two rooms per side.

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Like so.

This way you're able to turn the ceilings into little V's, except with angle very high (175 degrees, at least). This way, you have a support beam in the middle to help prevent a collapse. Now the hot air will rise up to the ceiling as usual. But currently, the air at any point at the ceiling is about the same as any other. But with the tilt being directed towards the outside of the house, the hot air will rise again towards that direction. Here, you could have a little ventilation shaft that allows the air to go out, but a screen would prevent bugs from coming in, and of course this can be closed during rain, etc.

I'm thinking that the climate would have to be very hot, at least 100 F for this to be possible. Of course, this wouldn't make it 70 degrees, or even below 90. But it would prevent the hot air from being kept inside the home and thus regulate temperatures better.

So would having a ceiling that is not level cause a major problem with the stability of the above floors/roof (it wouldn't bend in the middle of the room, but at the wall between two rooms in a house)? Or would this possibly work to some degree?
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timmac · Heavy Crude Joined: Mar 27, 2008 Posts: 136

What climate are you talking about, dry or humid, here in the southwest like Vegas, you can use a swamp cooler verses a a/c unit, its a low electric usage and could use a solar panel for this type of unit, building the walls the way you have mention dont work here because its hot every where, 110 degrees in the shade, shade trees are the best bet to help keep house cooler and no windows facing south, if you are not living in a hot climate now, moving to a hot climate can be hard, I have been here for 21 years and still can not stand the heat.. Under ground house's are great in the desert, they stay cool all summer long, no a/c or swamp cooler,, check Vegas out in Augest and see if you can stand the heat before you make the move...

kpeavey · Expert Joined: Oct 04, 2004 Posts: 1131

GeoJAP

I live in Central Texas, where it can get up to 100-105 for 30-40 days straight sometimes in the summer. I have two experiences I can share with you.

One person I used to know built a house out in the country, about 30 miles east of Austin. It is a wooden, three and a half story house, that is open all the way through the middle of it. There are stairs and balconies in the house, that lead to rooms off to the side of the central open area. It is not very wide, but very tall. It has no air conditioning and uses solar panels. It is completely off the grid. It is designed to carry the hot air up and through the house in the summer. Does it work? Yes, as well as it can, but it's no ice box.

Another was a house that I built out in the country and no longer live in. It was a conventional 2400 square foot home, which had bare concrete floors, 9-10 foot ceilings, ceiling fans and an extremely tall roof and roof peak. This house would stay amazingly cool in the summer without AC. I think it was because the roof angle was so high, and the attic had so much volume, that it did a great job of buffering the inside of the house from the sun's energy. We had no shade trees in this location either. The cool concrete floors, lots of windows and 9-10 foot ceilings also really helped to keep air moving through the house. It was a very breezy, cool house. It was a little big for my tastes now, but I miss it as it was a very well designed house.

TreeFarmer · Heavy Crude Joined: Jun 26, 2007 Posts: 301

Just a general observation here. A well insulated house takes quite some time to warm up on a hot day. If you have a location with cool nights and hot days such a house can be opened up at night to take advantage of the cooling and then kept closed up during the day.

While this is no panacea it will often keep a house very comfortable until say 2 or 3pm. After that it may start to get warm insiade the house but being able to go over half the day with no AC is not bad.

Personally, when it comes to lowering AC costs, or even not needing one nothing beats a good design for your location.

Most likely, if I ever build another house, it will be out of the styrofoam blocks that you fill with concrete and if is in a hot location, it will have wide eaves so that the summer sun never hits the walls of the house except in very early morning and late afternoon.

TF

Ludi

I live in Central Texas and we don't use AC in the house. On the very hottest days we close the windows in the morning, to trap the cool air, as TreeFarmer mentioned. The house stays a few degrees cooler than the outside, though still rather hot. Our house is poorly insulated, with cheap windows.

Here's some links:

http://www.builditsolar.com/Projects/Cooling/passive_cooling.htm

http://www.azsolarcenter.com/technology/pas-3.html
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Roy

When our A/C unit failed last June, we decided to forgo the repair and do without,.

Last summer was one of the hottest on record here, with a stretch of what seemed like weeks of temps near 100.

We do have an attic fan. What we would do is similar to what Ludi described. Keep the house closed during the day, and as soon as the sun went down, open up the house, and crank up the attic fan.

That would draw cooler air into the house and usually get the temp down to the low 70's inside by about 10 pm.

In the morning, shut the windows, lower the blinds, and wait.

By about 4 pm, the inside temp of the house would creep from 73ish to about 84ish.

Not too bad if you're dressed properly and acclimated. Then the sun goes down, and do it all over again.

My electric bill last summer was approximately half what it was the summer before when I was still using the a/c.

Most guests complain and guffaw when we tell them we don't have a/c.

The way I see it is that eventually, electricity will become very expensive, and air conditioning will be seen as a luxury rather than a necessity, as it once was.

You're on the right track in looking at ways to get along without it.

Of course, large shade trees, awnings, and house orientation can also make a difference.

skyemoor

What you are referring to is a solar chimney. This has long been a practice, though relatively recently abandoned with the advent of A/C. George Washington used one in his Mount Vernon home in the form of a vented cupola to draw out hot air at the top of the house. Indeed, that is the primary purpose of the cupolas you see on the ridgelines of older buildings.

There are many variations in design.

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3aidlillahi · Intermediate Crude Joined: Mar 25, 2008 Posts: 601

Hey, Mekrob's new name here.

Thanks. I'm looking into ways for sustainable "urban" living (more like condensed rural) so that second design from the above post is just what I was looking for. But time constraints due to the failing US economy could mean I have to build only a home for myself, so either way, this was a lot of help with plenty of details and advice.

TreeFarmer · Heavy Crude Joined: Jun 26, 2007 Posts: 301

Does anyone know how much energy a small window unit AC uses? If solar keeps getting cheaper the day may soon come where you can run a small window unit with a few solar panels and keep a well insulated house very comfortable throughout the day.

TF

Tyler_JC

http://www.walmart.com/catalog/product.do?product_id=4456965

This particular unit produces 10,000 BTU (or 2.93kWh) worth of cooling.

Divide that by three to find the electricity use.

So if you keep the thing running for 10 hours a day for 100 days in the summer time...that's 1 megawatt hour of electricity just for that one unit, which can only cool is mid-sized room.

That can cost you anywhere between $100 to $200 depending on your location.

Add in a few more rooms and it starts to become a serious drag on the budget.
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TreeFarmer · Heavy Crude Joined: Jun 26, 2007 Posts: 301

In a well insulated and well designed house I bet that would keep 1000+ sq ft cool.

That is the point I was getting at, with a well designed house your AC bill does not have to be onerous.

Four years ago we built a new house here in PA that is 2350 sq ft (single story) with a full basement that we also heat. We moved into this house from a 1500 sq ft house built in 1967 with a 1000 sq ft basement that we only partially heated. The 1967 house had decent insulation and newer double-pane windows so it was not a total energy hog.

The heating bill in the new house was 20% less than in the old house. Of course that is the result of better insulation and a more efficient furnace. I'm betting the majority of it is due to the insulation, we have 6" walls with blown in cellulose.

TF

skyemoor

rockdoc123 · Light Sweet Crude Joined: May 16, 2005 Posts: 1671

this all seems very climate dependant too me. I live in a place that has cold winters and hot summers. You can't have a house that "breathes" naturally to cool it in the summer as it is impossible to insulate it in the winter. What you can do which is cheaper and more energy efficient than AC is install an electric exhaust fan in your attic or invest in a window reverse circulation fan. I used both in the house we previously lived in and they worked quite well. The attic circulation fan you might turn on for an hour or so just as the sun goes down and it basically evacuates all of the heat that builds up and rises in the house. If you need a quick fix nothing beats one of these reverse circulation fans. Basically you fit the fan into a window where it is perfectly sealed (they come with a expandable frame that fits most window spaces, open a door to let in the cooler air and turn on the fan. It take about a half hour to an hour to fully change out the air in a fairly large home as I remember.
Alternatively if you live in a hot/humid country I think learning from the Spanish settlers is key. They built large haciendas that took advantage of breathable walls (adobe) and natural flow through circulation with large shaded courtyards etc. I've sat in several such courtyards and homes in Mexico and Colombia in 90+ temperatures and it has been quite pleasant.

skyemoor