Anyone have experience or knowledge of earth tubes?
I've done a lot of research on them and know how to set the system up as far as the buried tubes go, what kind of tubes to use, sizing the system, etc ... but I'm uncertain how to connect it all into my home for dispersion. Do I just do a general venting to the whole house or vent to individual rooms? Do I have one pipe that comes in and then branch off to different zones like in a traditional AC system? I'm not sure why I can't get my head around all this.
Our house is a mix of rock, cob, and timber frame with a central clear story "spine" that has operable windows for air flow. We get a good breeze through the house already but summers are brutal with over 30 days of 100+ degree weather so added cooling is necessary in some form.
Personally, I'm venting mine right into my thermal mass, to cool it down. I think that is the most useful thing to do with it. Air temperature is less of what makes a house comfortable than temperature stability of thermal mass. As it leaves the mass, it'll disperse through the house, but not till the mass has absorbed what it can first.
I'm also running mine underground, but my intake is from the coolest area I can find.
I think the questions you have can vary based on other dynamics or factors that play into your specific situation. Like how many square ft. is your home, do you have a centralized point of ducting to distribute air for cooling, how well does your house hold cool air, and how long will your tubes run under ground? All these factors change the dynamics to maximize efficiency. For example, I think its a 6" corrugated tube on average, reaches maximum temperature exchange at 300 ft in length at a given CFM. A smaller tube would change the available surface area to exchange temperature, so a change in length and or CFM may be necessary to compensate regarding maximum efficiency.
The best placement for the air exchange will also have a few factors, like where is the best location for the most even distribution or air collection regarding cooling for intake and exit. Since your focus is cooling, you will want both intake and exit up high, with the inlet of cool air centered for best distribution unless you already have individual ducting set up as part of your heating system. Im guessing you don't need to do individualized ducting for this application, unless those rooms are to be up high within your structure, and are to remain closed off.
Along the ideas of individual ducting, just having multiple runs of the same size tubing in ground, can alow you to draw all intakes from the highest source where heat will gather at like peaks, then alow you to distribute that cool air evenly to various parts of your house at say mid level, where that cool air can fall down evenly around your house.
Of course the layout of your house may limit what you can do for implementation regarding aesthetics, but sometimes creativity can help solve these issues.
Where are you located?
That will help us to understand your issue better.
In Australia I have used a cooling tower which replicates the middle eastern designs.
It is tall and draws air through the house creating a slow current of air that works well
John Daley Bendigo, Australia
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We are located in the central plains states in the US. Winters get below freezing for most of 2 to 3 months and in summers reach over 100F for up to six weeks or so. Fall and spring are temperate. Our land is wooded with lots of tall trees and shade. The earth tubes will be under a pond, ten feet below grade, for part of their 250' length. We were planning three 8" tubes with an air inflow tower downhill from the house.
The house is rock, timber frame, and cob so it retains heat well and stays cool-ish. It is one story and around 36' x 55' with a central clear story running the length of the house. The center of the house is the living spaces while the bedrooms are on either end. The end closest to where the tubes are running has a basement room (it is our storm cellar for tornados and my office with a root cellar attached) where we thought would be perfect to bring the tubes into intially but two of the bedrooms are on the other end of the house and on the west side (sunny). We could run the tubes under the living space to those rooms or we could run them separately around the house underground to the other bedrooms.
Heating isn't a big issue as we have a masonry heater and radiant floor heating plus lots of heat sink/mass that warms up in the sun. I'm an architect so I designed it to be passive solar for the most part but even that doesn't cut it in our summer heat.
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