Opinions on Hot water sources wanted

[muddstopper]

Dave, the pipe in the ground method is what we are trying now. We quickly discovered 2 major problems with the system. One, we used the flex pipe, similar to pex tubing. It is thin walled and prone to kinking. W buried 3ooft of the tubing below his garden. Ground temp 2ft depth is about 61deg. Problem number 2 is we used a heat exchanger out of a old airconditioning unit. This we mounted in the exsisting duct work to use the exsisting blower to recirculate the warm air thru the exchanger and back into the house. What we discovered was we could only get about a 1 or 2 degree increase in the water temperature between where it entered the exchanger and where it exited the exchanger. This meant we werent getting a very efficient heat exchange with our exchanger. So far, mold hasnt been an issue but I can see where with a good heat exchange it might become a issue. We also connected the solar water heater to the same heat exchanger with the hopes it would help heat the house this winter. Cant say yet how well that is going to work out but, I feel that if the exchanger doesnt do better heating than it did cooling, it not going to provide much benefit. We are currently looking for a bigger heat exchanger and are considering just building one out of copper. Its a work in progress that I hope we have figured out by the time I start building my retirement home.

 

[AHNC]

For cooling, I've thought about buried PVC pipes and a blower that draws in outside air, the air gets cooled by the ground temperature before entering the house. It seems like people who have tried similar methods cannot overcome the mold problems that occur when the outside air is cooled below the dew point somewhere in the pipe length. That would produce water laying in the pipes and the incoming air of course, carries mold and fungus spores.

People with under-the-house rock beds used to store heat have run into similar issues. It seems heat transfer with air is prone to this problem, even in normal AC ducting, so water-based systems may be a better choice.

My passive solar earth-bermed house is great for heating but if this summer hottest month on record stuff continues as normal, it will push me into finding a cooling solution of some sort. Evaporative cooling may not work very well here since our heat is usually accompanied by high humidity.

I just noticed your location. For you bermed home the heating, cooling and de-hu can be taken care of by a Fujitsu mini-split heat pump. Bangor Hydro and the local utility in your area are big fans of these.

On "passive air systems" I would recommend caution, not due to mold mildew but to fire. Back in the late 70's I was working on a house that was a kind of "double envelope" home was being built next door to the project I was working on. This place caught fire and with the passive air circulation the fire gained so quickly that there was almost nothing left by the time the fire dept got there. Building and fire regulations have probably caught up to this type building but with air circulation, keep fire in mind.

 

[dave1949]

I just noticed your location. For you bermed home the heating, cooling and de-hu can be taken care of by a Fujitsu mini-split heat pump. Bangor Hydro and the local utility in your area are big fans of these.

On "passive air systems" I would recommend caution, not due to mold mildew but to fire. Back in the late 70's I was working on a house that was a kind of "double envelope" home was being built next door to the project I was working on. This place caught fire and with the passive air circulation the fire gained so quickly that there was almost nothing left by the time the fire dept got there. Building and fire regulations have probably caught up to this type building but with air circulation, keep fire in mind.

Thanks for the input. No double envelope here, but worth remembering. I've heard good things about the mini-splits too, that's probably my best option assuming I can't find something less power-dependent. To get a more informed idea, I should probably have an HVAC guy come and look at my house.

 

[schweizer]

For cooling, I've thought about buried PVC pipes and a blower that draws in outside air, the air gets cooled by the ground temperature before entering the house. It seems like people who have tried similar methods cannot overcome the mold problems that occur when the outside air is cooled below the dew point somewhere in the pipe length.

We have exactly this "earth tube" system in our house. If you want to see how I did it, you can look at our website.
Earthtube Cooling
Unfortunately, we haven't tried it yet (see text on our website), so I can't give you hard data, but it should work fine. I write this with caution though: climate in Southern Oregon in summer very dry -- very low humidity. Very different than Maine. With our low humidity, we shouldn't reach dew point even cooling 90+ degrees down to ground temp, but I did drill holes in the bottom of the pipes every approx 10' and set the pipes on gravel for drainage if any condensation does happen. Now on the East Coast you have a totally different situation and airborne molds are not to be trifled with. Legionnaires Disease can be deadly. With good design this kind of cooling sure can work, but make sure the pipes are sloped with drainage points or sumps that dry out along the length.

Marcus

 

[muddstopper]

The Earth tube cooling looks like a interesting concept. I am not sure how well it would function in my area tho. Once you go down a couple of ft in the soil, you endup with moisture from ground water. Drilling holes to let water out just might let water seep in. Under a slap or buried under a crawl space might work, but I fear ground water might still become a problem. Use of a dehumidifier might be the answer, but I will ahve to research earth cooling more before trying it myself.