I plan on building an air tight passive solar home soon and will be incorperating an air to air heat exchanger. It has been brought to my attention that a system has been developed in Europe that burries a plastic channel in the ground below the frost line preheating the incoming air in the winter using the grounds heat. This system would also be used for the summer air conditioning. Aparently the plastic channel is mold resistant and I would assume is installed with a slight slope to drain the condensation. Any information on this subject would be appreaceated. Your fine magazine may want to do a little reaserch on this. The only direction I can give is homes are being developed in Austria that are air tight , super insulated and use photovaics for most of their power buying and selling on the grid. The stud walls are made with TJIs , cavities filled with mineral wool and have an annual operating cost of 200 dollars. This would be remarkable considering the substancially higher energy costs on the other side of the Atlantic.
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some of our power use is to fight summer temps of 90 degrees at 11 PM and 100% humidity.
Aparently the plastic channel is mold resistant and I would assume is installed with a slight slope to drain the condensation
Hi Gary, welcome to BT. If you click on your name you'll have an opportunity to fill in your personal profile, the most important part being your location. Where are you building?
I built an underground house in a humid climate that, to follow the full plan, would have included earth tubes to temper the air (and ground). To date I know of no one who's used earth tubes in a humid climate. The fear is molds. I think I know how to avoid the exposure, but I'm not gonna be the guinea pig. And it entails an additional active system to scrub the air. Active systems are something I avoid. Like you, passive makes more sense to me.
We use an air-to-air heat exchanger in our air system (our sole active system), but it's similar to the commercial ones on the market today, mounted inside the house. The one you're referring to has both incoming and outgoing air going through a buried exchanger? Doesn't sound like it'd be worth the effort unless the earth tubes were very long. Which makes the argument of why bother with an air-to-air exchanger. Or perhaps you're really thinking of air/earth heat exchange, rather than air-to-air.
http://www.axwoodfarm.com/PAHS/UmbrellaHouse.html is an excerpt from the book I followed and has a brief section on earth tubes and how they work.
PAHS Designer/Builder- Bury it!
Hi VaTom. The reason for burying the air tubes is to temper the air coming into the heat exchanger,an air to air being necessary in an air tight house.One can imagine if it is forty below outside the expelled air from the house and the limited efficiency of the exchanger would make it necessary to add a significant amount of heat to the house to offset the loses.The cost of burring the tubes would also be recuperated by eliminating the need for air conditioning as the air drawn in during the summer would cool the house.Condensation would be a result of the temperature differential which would occour even in low humidity.I live just north of a desert and our sesonal temperatures vary almost to extremes -40 c to +42 c thats -40 f to +106 f. Such factors plus an north american life style combined with transporting goods and services across the worlds second largest country that has the population of mexico city makes us the worlds largest energy consumers on a per capita bases. Kinda makes me feel obligated to do my part to help save tera firma and all we exist with.Also if I can't find the plastic channel i'm lookin for I may just use sewer pipe with a gradual slope for drainage,soften the bends,leave a permenent draw line in place and periodically pull a cloth covered, bleached spherical plug through to clean it. Thanks for the reply . Some day I'll learn how to space paragraphs on this new toy of mine
Hi Gary, thanks for filling in your profile. There's someone floating around here with a large amount of experience with air-to-air exchangers, goes by "experienced". I'm thinkin' BC, but I might be off a province.
Gotta disagree with you slightly.
A tight house, as we have (and you want to build), requires air changes. We do .5 ACH with unequal fans to slightly pressurize the house. I've been told here that we over-change, but I'm not backing that off. With our passive heating/cooling system the penalty isn't significant. Our air quality is excellent, often noticed by visitors. We also live in a moderate radon area, further reason to change the air.
As you know, the only thing the air-to-air exchanger does is warm up or cool down (depending on season) the incoming air. Which is the same thing earth tubes do. You don't need both. Furthermore, if you consider the heat storage of the dirt, you wouldn't want to (air) temper the air you send to it. Did you read that link? I thought it pretty clear. And done correctly, you won't have to power the fans that I use. All passive, even better.
A very short earth tube won't have any significant effect, leaving you with the air-to-air exchanger doing all the work. Takes a lot of dirt mass to do much tempering.
I'm well aware of the function, would prefer it code required. Exchangers, that is, not earth tubes. If I lived in your climate I'd have earth tubes and a passive system instead of what we have.
Paragraphs would make your posts much easier to read. If you come up with a link to the hardware you were asking about, I'd like to read about it. May be something that I've not envisioned. PAHS Designer/Builder- Bury it!
Cool I couldent figure out why you were in disagrement until I cheked out the sight thanks. My design would be in a more typical suburban development that would require more above ground exposure and less land not allowing for such an umbrella. The intention was to vent the exausted air directly outside. Hopefolly a green roof will be incororated.
Good you understood. Sounds to me you want a simple air-to-air exchanger. I built mine. Let me know if you'd like the Popular Science how-to article. Very closely resembles the Lossnay. My last house client found his exchanger on ebay for just over $100 US, good for his 26k cu ft.
Regarding green roofs... I live under one but have mixed feelings as to applicability. Seems to me they're excellent in some applications, like mine, but that they can be very expensive (and high maintenance) in others. I'm of the opinion that my roof was the cheapest, and functions the best, of all possible roofing systems- for my application. Your house may very well differ. Of course you can always design the house such that one is clearly appropriate.
What's your water source? Any need for rainwater catchment? Then a non-green roof would work better. Or, if you want to collect hot air under your roof for winter use of the heat. Lots of possibilities.
Good luck with your project. If all the pieces fit, result will harmonious.PAHS Designer/Builder- Bury it!
The popular science article would be greatly appreciated. As for the green roofs we had a forest fire come through here a few years ago and take out almost 300 houses. It missed me twice by 3k which is'nt much considering the winds were causing it to jump 2k. A sprinkler on a green roof could be a saving factor. It is also my desire to promote them in this area as I design and build. Unfortunatly most people are only interested in ausentatious energy consuming enginered drywall stucco boxes with resale value being paramount, but I'm stubborn and on a mission to change the world.
LOL We also live in the woods. Moved here from Colorado. I was set on a house that wouldn't burn. Most here thought me peculiar. I don't argue. Forest fires are unusual here, but not unknown. Makes little sense to me to build houses out of flamable bug food. I'm also disinterested in any exterior maintenance, ever.
I'm not trying to change the world, just wanted something better for us. And am now in converstion with 3 new clients here. Yikes! What was that about a better mousetrap? When I point out that it's common to spend 1 month's income on annual heating/cooling costs, while I don't, really gets ones attention.
Here you go. I used a sheet of corrugated aluminum roofing for my core. And our green roof, which has no need of a sprinkler system. Been sheltering us admirably for over a decade. PAHS Designer/Builder- Bury it!