I am planning on using 2 400 foot 8 inch diameter tubes buried 4 feet deep to cool/warm our 900 sq ft strawbale house. I am starting to get a little nervous about possible growth of fungus/mold growing in the tubes. Does anyone know if this is a real problem and if so, if there is some way to remedy it?

-- Doug Shutes (toadshutes@yahoo.com), May 17, 2000

Answers

No help here but is there information on strawbale houses on the net if so can you tell me were thanks Shaun

-- shaun&terri (shaun-terri@juno.con), May 17, 2000.

Hi,

Just a couple of thoughts. Air inlets well above ground to keep moisture levels down? Are you going to pressurize the air flow in any way (either negative or positive) to keep the air flowing? How are you filtering the inlet & exits? Are you going to use a 'thermal chimney' to pull the air through the house? More info would be appreciated.

j

-- j (jw_hsv@yahoo.com), May 17, 2000.

If you are afraid of the water moisture environment in the tubes, why not use a different fluid medium in the tubes (kinda like the cooling system of a car)? Is it glycol that I have heard used in such systems?

-- Mike O (olsonmr@yahoo.com), May 17, 2000.

When we put our house up about two yrs ago we did the cool tube thing, 6-200' loops of 4" drain tile. I cut a slot along the length of each tube. Drain tile has corregations. The slot was cut into the high spot on the corregations thus leaving the structural integrity in tact. When the tubes were installed the slots went to the bottom so the condensate would settle to the bottom and drain out thru the slots. BTW the slots were cut with a skill saw, setting the blade depth at about 1/8". At this point there is no fresh air inlet as both ends of the tubes terminate in the basement, one end in the shop area, the other end in the suction side of the "furnace" plenum. As we used it I monitored it with a sniff test to see if I could detect and moldy odors and I couldn't. So far, so good. Good luck

-- john leake (natlivent@pcpros.net), May 17, 2000.

I'm considering this too, mostly for summer cooling. But I see no way to prevent mold spore production just like happens in a/c evaporators and in forced air ductwork.

So, I'm considering a heat exchanger, i.e., somewhere in a room have a wall of these tubes cooled with underground air and altogether like a radiator. I'd blow air across these for the (cool) exchange. But I've read that forced air is expensive relative to pumping a liquid a low speed. So, maybe a geothermal loop with water or water antifreeze mix going to the indoor radiator (heat exchanger)? Don't know the effieciencies of any of this.

-- Charles Burandt (clb@watervalley.net), May 18, 2000.

I've gotten a fair amount of e-mail on my response so here's a little more info. The cool tubes are buried around the footing of the house at about 7' of depth at the south side and about 2' at the north side. We have a walkout basement with the entire north side exposed, thus the difference in elevation. Buried with the cool tubes is 1200' of 3/4" poly pipe which is a closed loop for a water loop. Both are beneath the drip line of the house because moist earth does a better job of transferring and dissipating heat. The cool tubes seem to work quite well and sustains an extended period of operation without getting appreciably warmer but I haven't done alot of scientific testing as yet. Theres more tweaking to do on the system. It'll need a bigger blower to move more air thru the ductwork.

As to the water loop, during the winter the loop is shut down. In the summer mode the same circulating pump that pumps water from the outdoor wood boiler is used and the water is directed to the air- water heat exchanger in the plenum. The heat exchanger is a homemade A-coil, made from two 80,000 btu heat exchangers, giving me a heat transfer capacity of up to 160,000 btu's. There are condensate troughs below the heat exchanger but not much condensate is generated due to the fact that most of the dehumidifying is done in the cool tubes---I think. Another option for those with new construction is burying a water loop beneath the septic drain field because it is always moist. Hope this helps.

-- john leake (natlivent@pcpros.net), May 18, 2000.

I have closed off the tubes I tried using, as the humid outside air would be saturated air coming out of the tubes, and eventually smelled musty. I`d say sucess would depend on climate.

-- Douglas Kalmer (sunart@netease.net), May 19, 2000.

Doug: Did you make any accomodations for getting rid of the water that would otherwise accumulate?

-- john leake (natlivent@pcpros.net), May 20, 2000.