Looking for natural cooling ideas

[stumpfield]

Since it's hot right now, I thought it's a good time to get cooling advice. I'm in the process of designing our rural home. We will be off-grid so we don't plan to have traditional compressor based air conditioning system. Prefer something not require any electricity at all. During the summer time (July-Sept), 100 degree is the norm here. However, at this elevation (~3000 feet), it cools off to the mid 60's at night. So, the average temperature is perfect if we can some how store the cool nights and release slowly during the day. Or store the heat during day and release slowly at night.

Base on what I have read so far, I know my design needs to have a lot of thermal mass. So, it will have a concrete slab foundation to act as a gaint heat sink and thick walls with lots of insulation.

-Should I dig into the hillside and build an earth shelter with only 1 wall to the south?
-Build deep down and live in the basement during the summer time?
-Bury pipes in the concrete foundation and run cold water through it during the summer?
-Incorporate a solar chimmey to promote air flow and create your own breeze?
-Minimize solar gain with the proper roof over-hang and orientation of the windows (minimize east/west wall exposure and no windows).

any other ideas? Thanks for your help

 

[EddieWalker]

I've always wondered about running cold water through the slab and what the results would be? Especially if you coiled it in the ground ten feet down to keep it nice and cool all the time.

Overseas in Asia, all the homes have very tall ceilings and lots and lots of windows that are kept open all day. There are doors on oposite ends of the building with long, wide, tall hallways between them. The doors are open all day long. Same with allot of the rooms in the house, they almost all have exterior doors that are kept open all day.

Every room has a fan, as do the porches and hallways. Air is always moving.

I never went in a home with airconditioning when I lived in Indonesia, or in any other countries along the equator. Most people thre just wont spend the money on it, and I'm talking about the upperclass people that associated with the embassy.

Eddie

 

[Highbeam]

Thermal mass isn't the same as really good insulation. Living inside a cooler isn't as good as living inside a concrete box buried in the ground so long as the ground temp is where you want to be. I would use your ideas 1,2, and 5. But also utilize ICF for concrete walls. The ground temperature a couple of feet down is supposed to be pretty constant year round as the average annual air temp. Burying your home to take advantage of this ground temperature will serve you in summer and winter.

My design struggle now is living on a slab vs. the desirable crawlspace. I like to be able to run ducting and wiring as needed through the crawl for future additions and changes in my rambler.

Non-electric cooling is tough. Water can be used as an evaporative cooler but you need to pump the water. Lotsof windows and taking advantage of thermal lift is needed to circulate the hot air out.

I share your temperature swings in my location where right now it may be 95 but tonight it will be 65. What I do is place my 350 watt fire fan on the floor just inside an opened screened slider and suck the inside air into the home while exhausting it out through the other open windows in the house. We can drop the whole house to 72 from 85 in less than an hour. Good thing too since I could never seep with that loud fan.

 

[dfkrug]

I built my house of concrete, using ICFs. I did not install A/C and
the recent heat wave (100+) has gotten the inside temps up to
only 77. IMO, all houses without major water table issues should
have basements, and ICF exterior wall construction from foundation
to roof. My total heating and cooling costs for 2000sf are about
equal to my old plant fiber house of 1100sf.

 

[dmccarty]

Stumpfield.

We built a semi passive solar house. I say semi because we we only have the living room and study on the south side of the house. We tried to get more rooms on that south side but it just would not fit into the design. And we where gong to put in solar hot water heating running radiant heating in the floor but the cost was to great to justify. We do have a heat pump for AC and heat but we heat primarily with a wood stove.

We do have a slab which is unusual here but that mass helps regulate the temperature in the house. The slab has one inch of rigid insulation on the edges and two inches on the base. One inch is about R7, two is about R14. We also have LOTS of big casement windows. The major living areas have at least one 8'x5' or 8'x6' casement window. The study, living room and bedrooms are on corners of the house which allow crosswind ventilation. We also have 2x6 walls with 1 inch of rigid insulation and brick. The walls are about 12 inches thick and we put something like R45 in the attic. If the outside temps are in the high 80s we can leave the AC off. At night the house temp has sunk to 71 which is cold. During the day it might hit 82ish when the outside temps hit the high 80s. We also have ceilings that are 10 feet tall. This helps get the hot air away from us and allowed us to fit in the taller windows. But we also ended up putting in doors that are 8 feet tall to match the scale of the windows. It really looks nice but it it was a bit more money to get the doors.

We do have a whole house attic fan which works but is somewhat noisy. However it will dump very quickly a lot of the humidity and heat out of the house. We installed exhaust fans in the baths that are really good quality and can run 24x7. In fact they are so quiet I wish I put them on a timer so we could set them to run for a set period of time. If I had to do it over we would have put these in the bedrooms, living room and study as well as the bathroom to move even more air. All the rooms also have good quality ceiling fans which help as well.

We bought the exhaust and attic fans at www.efi.org.

If you can berm the house that will help modertate the house temperature. We thought of running cold water through pipes in the slab, aka reverse radient heat but I am guessing this might cause condensation to form if the temperature differences and humidity is just right.

If we had more money we would have put a belvedere on the house. This would allow more light into the interior of the house and allowed heat to flow into and the up out of the house. We might do this with the add on we will do some day...

There is a PE name Lstiburek who has a website http://www.buildingscience.com/resources/walls/default.htm. I HIGHLY recommended his website and books. Many of our structural details are based on his designs. He has four books for different climates around the US. I would STRONGLY recommend the book that fits your climate.


Later,
Dan

 

[Tom_H]

In the southwest, thick adobe brick pueblo walls use thermal mass to absorb heat and release it at night. Even in the desert, they can be amazingly cool in the daytime. In Mariposa, you might not have the right kind of soil to use "rammed-earth technology" to build a similar structure. Rammed-earth technology requires the right kind of on-site clay. Forms are built; the clay is powdered and mixed with a small amount of portland cement and pigment of choice; 6" is lain and ram/packed at a time. Conduit is placed as these layers are tamped. Walls may be 18-24" thick and when the forms come off you have already finished interior and exterior walls. You could import the clay if necessary, or import heavy adobe brick.

I have never known of a house where the radiant floor heating equipment is used with cool water to cool a house. Condensation may be one problem, but heat rises and cold air stays low. Thus in winter the heat rises from floor to ceiling, but run in reverse, cold water would cool the floor yet do little with the hot air above. I have heard of one or two people trying to do the same concept by putting the tubes in masonry walls, but don't know how well it worked. I did hear of one guy who had this type wall with the tubes running to a big underground insulated reservoir. The walls transferred heat to the tubes, which carried it to the reservoir in the ground. On winter nights, the water brought heat back to the walls. In summer, water from the pipes in the wall could be diverted to an earth coupled heat transfer system.

Other thoughts: high ceilings, low overhangs, highly insulated roof, sod roof (requires heavy roof support, lead or copper waterproofed lining {lead would be illegal now}, and irrigation). I know it's exotic, but you're off the grid. I've seen lots of them in the Alps; The old Vikingsholm mansion at Emerald Bay in Tahoe has one. Also: big windows with house designed for cross ventilation along with propane powered stationary generator to power a couple of industrial sized whole house fans. Alternatively, hot days usually come from high sunlight, so what about solar photovoltaic panels on roof maximally positioned for this? When it's hot, you also have the sunshine to run the whole house fans, BUT photovoltaics = $$$. Another possibility is to run a long horizontal underground air shaft and use a big fan to draw cooled air through it and into the house. Just make sure no critters (especially black with a white stripe) get into the shaft.

You might surround the house with so many trees that they will grow up so dense as to leave the house in deep shade. Only drawback for you is by the time the trees grow up your greatgrandkids would be the ones to enjoy it.

Depending on where you are in Mariposa, you may not be able to dig into the ground if you are on that solid Sierra granite (unless you can afford to drill and blast big time) so it might pay to drill some small test soundings just to find out what's under the surface before you commit to an underground house or serious basement. (BTW, some guy here in the valley built an underground house. The entrance was this silly little pyramid on the surface. Wilton is a very desirable area, but when he decided to sell, it took 5 years to find a buyer for it and he got less than half of what he invested in it. So, be careful about getting too exotic for that reason. I live in a log house, which is rare here in the valley, but it is a desirable kind of exotic. Logs have good thermal mass and would be a perfect architecture and style for Mariposa.

 

[PineRidge]

You may want to check into monolithic construction techniques. I'm not talking about domes but using mass in the construction of the walls to keep the home hot or cold as needed.

 

[monkeymonk]

tom & stump

strawbale, Cobb as well. we have a cobb house/cabin at our other place and it stays cool all day in the summer.

It gets down to high 50s-mid60s at night and round 100 in the day. Where we are most the time (down the road) we keep all the windows open at night and round 8am we close the house down it stays round 10-15 degrees cooler than outside temp. Thick insulation and shades work for us.

I would build my lower story into the hillside if i was gonna do it again + go strawbale,timberframe,Slab. although living off grid i do have fantasys of having an ultra efficent A/C in one room all closed up........NAAAA

something tells me as well that cold water running through the slab would condensate?

We can do swamp coolers here in ca.

sounds like you got a major project ahead of you keep us informed. I quite often think of how i can make our house cooler living off grid and will soon be building again(next few years)

good luck

 

[dmccarty]

Stumpfield,

I can't believe I forgot this last night...

http://enertia.com/

The link is to a company here in NC that builds energy efficient homes. We looked at them but the house plans at the time did not fit what we wanted or could afford. I really liked the looks of the house but we wanted to be on one floor not multiple floors.

He uses 6x6 PT timbers to build the house. At the time I was researching the antiPT crowd was crowing and I was not going to have a house built with the old PT wood. Basically the houses are log cabins using the 6x6s. The houses have multiple floors to maximize passive heat gain in the winter and allow air flow in the house. The house has space to allows the air to flow from the lower to upper floors.

On the website the house on the right, first row, is the house we visited when it was being built. The builder who built the house we used to build our house. The house was origionally built without AC. We talked to the owners a few years after they had built the house and they had to go back and put in AC. The house worked to control the temperature but it did not beat the humidity. Which was one of my concerns. But if you live in an area of low humidity this system might work.

The lower floor is built into a hill side. The back and one side is bermed. The house has lots of mass due to the wood and it has a slab with radient heat on the first floor. If you want a multi story house he has some good ideas that might be of interest.

Our builder has built log cabins as well as the Enertia home. He said he would not by a kit. Enertia does sell the house as a kit for you to build. Our builder said they spent a lot of time just finding which piece goes where and then fitting it into place. The timbers had a plastic spline that fit between the wood to provide a air/water seal. That was time consuming to fit. Even on log cabin kits he said it was time consuming to find the part they needed compared to grabing a log and cutting to length.

We like the look of log homes but they have some issue we did not want to deal with. Enertia has some good ideas that could be used with other local materials. I just got a catalog that had evaporative mist coolers for livestock that can knock down the temperature up to 40 degrees. The question that popped into my head was how much water would I use to set up a mist system around the exterior of the house to lower the outside temp that could then be taken into the house? What would it cost power wise?

You also might search for resources in your state. NC State has a solar center at NCSU that has quite a bit of good information on energy efficient systems. Just a little thought and a small amout of money spent in the right place can really effect your energy use and comfort in the house. We heat with wood in the winter and until the temps go to the high 80s we don't use AC. We have been running a power bill of 90-100 dollars per month in a 2400 sf home. Now that the AC is on the bill will go to 150ish which is really good for our area. Our old home was half the size yet use as much power as our new home. And we are far more comfortable in the new house. Talking with other people including our builder I'm guessing that our power bill is quite a bit cheaper than what other people spend. The details in the house that lower the energy usage really are design details and materials that really don't cost much if anything. An example is the 28 inch roof overhangs we have to keep out the summer sun. It works. Its simple. It looks good. And it keeps water away from the walls.

Later,
Dan

 

[MarkV]

Here is an idea I read about years ago and thought would be fairly easy and relatively inexpensive. The idea was to dig a large trench about 6’ down where the ground temps stayed constant year round in the upper sixties. Then they installed metal culvert pipe, don’t recall the size, in a “U” shape beginning and terminating at the foundation wall. After backfilling and building the home a blower was installed on one side of the pipe to force house air through the pipe. The theory was to take the hot/cold house air and condition it in the pipe to closer that of the ground temps by moving it through the culvert pipe. I would think that the longer the culverts loop the more it would condition the air being moved through it.

We had good results at a weekend home by building a cupola in the center over the area our woodstove sets. The cupola is about 6’ by 8’ and has six awning windows that are operated by electric motors from a wall switch. In the winter it lets us vent off excess heat from the woodstove and in the summer acts like a chimney to draw heat out of the house when the windows are open on the lower floors.

MarkV