Has anyone heard of a pit dug next to the home (about 10X7) with a pipe from the outside air to the bottom of the pit, then a pipe going from the top of the pit to inside your home. The earth's temp is about 50 degrees, so the air is either heated or cooled (depending on the season). So if it's winter you only need to heat the home another 20 degrees, or if it's summer, you have free air conditioning. Possible problem: outgassing of radon or other poison from the earth into your home.

-- Evelyn Bergdoll (evandjim@klink.net), December 29, 1999

Answers

Evelyn, What I've seen done along those lines is a long trench(100ft+) about 3 feet deep with a large diameter pipe laid in and covered with the excavated earth. One end enters the home and has a low speed, low power ventilation fan running in it, the other end has a u-joint sticking out of the earth (with screening to prevent access to pests, insects,ect). I belive the way it works is that the fresh outside air is drawn into the pipe by the fan, but travels at a low speed through the pipe exchanging tempature differential with the earth(seeking equilibrium). The pipe is only open at the ends, so I would imagine the chances of radon gas getting into the home through the pipe are low, unless the pipe has a hole somewhere along its underground path and there is radon gas collecting in the ground in that location. I've never done this, mind you, but it's what I've seen. I imagine the underground run of pipe could be laid out in serpintine fashion, saving some digging labor by excavating a large square or rectangular area with a farm tractors bucket (rather than a single long trench dug by hand), but leave a few feet between runs of pipe so the air can exchage temp. with the ground, not with the temp of the air in other sections of the same pipe. Best of luck!! Glenn

-- Glenn Joseph (Ruadhain@hotmail.com), December 29, 1999.

How about circulating water through metal pipe rather than using air? The small pipe is easier to handle, install, maintain and also cheaper to buy. The trench is smaller in width, it will not cave in from the dirt covering the pipe and it's a better transfer of earth energy than the large air circulating system if installed properly. No outside fumes are moved into the house to contaminate the breathing air inside. Hydronic can be looped in a much smaller space and routed via a heat exchanger in circuit with your forced air furnace or hooked directly in the return line of a hot water boiler system. I doubt that it will help you very much and can in fact cost you money by "heating" the outside with your conventional furnace/heating appliance. It will take some engineering to determine if it's feasable or practical without a heat pump. email me if you want and i'll help all I can.

-- K.D. "hoot" Gibson (hoot@otbnet.com), December 29, 1999.

I've seen both of the above mentioned styles done of "This Old House" shows.

-- greenbeanman (greenbeanman@ourtownusa.net), December 30, 1999.

People that I have talked to that have done something like this have told me that you need lots more tubing than they ever thought at first. You would need many hundreds of feet of it, and 12" to 2 feet in diameter would be good. The pit idea wouldn't work because there isn't enough area in the walls of the pit--the dirt would warm up (or cool off, depending on the season) too quickly to do much good. Using some kind of tubing or culvert type of material buried 6 to 8 feet deep might work, but it would be basically warming or cooling the outside air coming into the house, to about 50 degrees (F), so it wouldn't really warm things up much in winter around here (Wisconsin, where it gets 20 to 40 degrees below zero with regularity). It apparently might work as a means of dehumidifying air coming into the house in the summer, though, if the pipes were arranged so that the moisture condensing on their walls from the fresh air traveling through them was allowed to drain out of the pipes. I have read a number of articles about this concept over the last 25 years, but can't put my hands on them at the moment. "Earthpipes" might be one term used for the concept.

-- Jim (jiminwis@yahoo.com), January 03, 2000.

I agree with what Jim says. Also, it's probably prohibitively expensive to install as much pipe as you'd need to make much difference in cooling (I've also heard concerns about fungal growth in the pipes in the summer)

As Jim says, a pipe supplying 50 degree air isn't going to make MY house warmer; it never gets that cold in the first place, and I like to keep the temp in the seventies

If, however, you have a conventional heat pump, you could greatly increase the heat pumps efficiency if you could direct the air from the buried pipe to the outdoor part of the heat pump. Heat pumps become EXTREMELY inefficient when the ambient temp gets down near or below freezing.

I have a ground source heat pump (uses the relatively warm ground temp to warm water which is used as a heat extraction source for the heat pump). This makes the heat pump about 400% efficient, compared with 100% efficiency in electric resistance heat.

-- jumpoff joe (jumpoff@echoweb.net), January 24, 2000.

This idea intrigues me. I live in Texas where the electric bills in July and August just about break me from running the a/c so much! I believe the ground temp is around 68º (I have a spring fed creek and have measured the temp at the spot where a spring is coming out of the ground). I own a backhoe and have LOTS of room (200+ acres), so those two factors in installing a system like this won't be a problem. PVC pipe is fairly cheap ~ even cheaper is that thin green stuff for septic lines. Or would it be better to circulate air from a root cellar/tornado shelter which we are planning on having anyway (a BIG one)? Maybe a combination of both systems?

Does anyone know of any websites where I can get more info on this?

-- Wingnut (wingnut@moment.net), January 25, 2001.