DIY Earth Tubes?
 

I'm starting a project that involves digging out a root cellar here:
ecorenovator.org/forum/renovations-new-construction/2278-backyard-earthship-root-cellar-bottle-wall-sunroom-top.html ( sorry this board won't let me post links yet.:mad: )

and I had envisioned an "earth tube" system to circulate air to both rooms at least in the summer, preferably all year.

We do have some temperature extremes out here in the desert, so it seems like a no-brainer to try and get some stability from the earth, not to mention passive airflow or even if we have to power and pressurize it, it would be inexpensive.

My questions are:

1. Corrugated pipe is obviously a bad idea, yet all of the contractors are using that stuff and huge rolls of it. This is a small, one room, space that the tubes will underrun. So, can't I just use ABS? It's smooth-er than that corrugated stuff.

2. What size of pipe and how long should it be for a small application like this? Anyone know of an online calculator or something for this?

3. Can anyone please point me in the right direction for finding info on how to build a "drain" for the earth tube project? Contractors seem to talk about a drain like it's something more than a hole in the ground filled with gravel. If not, what exactly is it? If yes, what are the average dimensions of the thing?

Thanks!

This is a newbie mistake. Take it from a programmer that fixes sites like this for a living. Worried about a little spam and you're upsetting possible good members. Doh.

PM me if you guys would like some pointers on how to make this a better forum. Normally, I wouldn't offer to help for free. But, this is a good cause.

And, one more. Silly, huh?

Finally, my original post, which I had the sense to copy into a text editor since I'm aware how funky this software has been configured.

Here's an idea using 4" PVC or ABS. The air goes in the upper tubes and gets blown out the top, the treated air comes in the lower openings in each room. I think maybe a small fan might be necessary to keep the air moving the right direction, plus maybe I'd need some sort of one way valves at all the openings?

It would be sweet to make it totally passive, but I also don't want mold. Oh yeah, and the snaking tubing would of course be slanted about 2 degrees or a 1/4" per foot towards some kind of drain area. I still need help with that part.

http://i1078.photobucket.com/albums/...earthtubes.jpg

Remember those "Got milk" commercials?

Got Radon?

is radon a valid concern in NM? I've never heard of anyone even bothering to consider it up here. I got the feeling it's pretty location dependant.

Re: Radon. This is definitely a concern, depending on where in New Mexico you live and your local geology.

From Wikipedia - 'Radon is produced by the radioactive decay of radium-226, which is found in uranium ores; phosphate rock; shales; igneous and metamorphic rocks such as granite, gneiss, and schist; and, to a lesser degree, in common rocks such as limestone.'

If you are building on/in/near any of the above types of rocks, or if you can find old uranium mines on the USGS quad maps of your area (there are some not very far from my house) - I would suggest getting a radon test.

Re: Mold. This should probably be less of a concern unless you live in a river valley or a particularly wet part of New Mexico. Given the usual humidity levels here (single digits right now) mold shouldn't be too big of a problem.

FWIW,
Tim (living in Northern New Mexico)

If you insulate the cellar walls and above grade walls of the structure (or use an self-insulating material) but leave the cellar floor in direct contact with the subsoil - would you even need the earth tube? The temperature of the earth 8 feet below grade should be quite consistent and suitable for a root cellar.

With the rest of the structure well insulated (or with enough thermal mass e.g. adobe, rammed earth, etc.) the structure should be comfortable year-round. Insulate the floor and you can have a cool root cellar and the above ground sun room (with good shading) could be comfortable for people too.

It's worth your time to talk with a local architect/builder, especially someone who has built structures similar to what you are considering. There is a definite learning curve to designing a building with good passive temperature regulation.

FWIW,
Tim

Thanks Tim, But if I felt like paying some overpriced yahoo I wouldn't be here asking questions. I'm usually handy enough to not need someone to do it for me.

Isn't it crazy that the first thing people try to do is discourage you from doing anything? Radon? Don't you think I would have thought of that before even considering this? Thanks for your concern, but no there's no radon here.

I like the idea of not even needing the earthtubes but that again is just trying to discourage what might be a good idea.

The idea is to have air constantly circulating in both rooms. Earth tubes seem like a great way to do that and possibly even passively, though I might pressurize the tubes slightly to increase airflow, like in the hot summer months, to help cool the sunroom at least, even if the root cellar doesn't need it.

I hope that settles all this discouragement nonsense now and I can start getting some real input.

Thanks again Tim for the thing about the mold. I didn't think it should be a big concern here in the desert either. I wonder if you have any actual experts here yet though? They do seem to live in this general area and Taos.

Although, so far what I can find online is just rich old hippies trying to make more money off all this so I'm not holding my breath.

Yay, I can post pics now. I also got the hidden geometry turned off in sketchup.

http://ecorenovator.org/forum/member...rthtubes-2.jpg


http://ecorenovator.org/forum/member...rthtubes-1.jpg

Please ignore the green colored ground. If it's ever green it'll be artificial grass. :D

I haven't used sketchup in months and I can't remember how to change that! Anybody know where the setting for the background images is?

Here's a better view:
http://ecorenovator.org/forum/member...rthtubes-3.jpg

I even added an inline fan, colored weird but easier to see in the model. I think it could run at a very low speed. I didn't have time to add arrows to the screenshot but obviously hot air would get sucked into the upper vents, travel through the earth tubes and exit the lower vents into both rooms.

It seems like each "hole" could lead to an actual adjustable vent like is common in forced air headed homes.

I just have no way to tell what size tubes to actually use; 4", 6" or maybe even 8". But, it's such a small space.

Aw, man I just realized I'd also need some sort of one way valve for at least one of the openings.

I believe that you will need more area for your collector..

Quote.. Home Air Conditioning

"However, if your air conditioning needs are for more than a few hours at a time, this approach will soon lose its effect. Gradually, the soil underneath the basement floor will warm up. Since it is a finite volume of soil (basically the size of the house), once it has all warmed up, the cooling effect would be greatly reduced, until an extended period of non-use occurred so the soil could again cool back down. Anyone who has tried to cool their house in this way has noticed the reduction in cooling effect over time."

Thanks, that was part of my original question(s). Does anyone know the formula or where I can find an online calculator for that?

...for finding the necessary surface area? That would help me figure out what size tubes to use.

The site I linked to is a long read but if you read it fully, it will answer a lot of your questions.

No, I read it. I saw it. It didn't register right away. You're talking about the area of ground not being able to handle cooling the two rooms.

It's a good point. This little bit of ground might not have enough cool to bother with running tubes through it.

ok. You do know engineers are usually pussies right? I wish I could just get a decent equation for this shiznit.

you guys are pretty useless so far beyond the odd discouragement. wtf? are you all just here to sell sh1t?

Arg, sry just damn wtf? Are all you guys dumb or what? You either know something or you don't. I've never seen a forum with such sleight of hand.

Is everyone dumb or greedy or what? Too realistic? What is this huge block in creativity in energy and homes? Is there some sort of resistence and not awere of ? The builders? Why would they care?

Quote(s)..
"This drawing suggests a very compact arrangement. For example, if a 50 by 50 foot area of yard was involved (about 1/16 acre), nine parallel tubes (six feet apart, or 48 feet across all of them), and each 50 feet in functioning length as shown, a total of around 450 feet of functional tube length would dissipate house heat into the soil. You would probably need around double that amount of the sewer pipe, since they are "bundled" together on their way to and from the building, as the small cross sectional drawing shows. Our drawing does not show the three (or more) identical tubes above the top of the drawing This arrangement would represent a way of installing around 500 lineal feet of heat exchange surfaces in that fairly compact area (counting the bundles). Such a configuration makes sure that one or another of the tubes is within three feet of well over a million pounds of cool soil. (Simple engineering calculations show that that much soil represents over 10,000,000 Btus of cooling available!)"

"In case you're still skeptical, the "heat exchanger" arrangement we are describing has a coefficient U that is around 8 Btu/hr/square foot/°F difference. If you look at ONE of our nine tubes, its circumference is around one foot and it is 50 feet long, so its area is around 50 square feet. If the house air begins at 90°F and the deep soil temperature is 53°F, there is 37°F difference. Multiplying these (8 * 50 * 37) gives an effective rating of 14,800 Btu/hr. That's ONE of our tubes, and there are nine of them! This suggests that the total system is capable of about 135,000 Btu/hr cooling, around four times as much as the normal house requires! Well, it could (almost) actually do that for a few minutes, but there are a number of factors that would get it down below 100,000 Btu/hr of cooling in under an hour and within a few hours to the 36,000 Btu/hr that we designed our "standard configuration" for."

"There have been (many) other people who have said they intended to only install four tubes (mostly to save on the cost of digging the trenches) and they figured that was an "improvement". Note again that such an installation would likely only provide around 300 cfm of cooled air to the house. That is certainly enough to nicely cool two or three rooms, but not really enough airflow to give the comfort level that we spoiled Americans expect for a whole house!"

"There are many variables involved, but many installations should be able to use 4" plastic (thinwall) ABS or PVC drain/sewer pipe (called DWV), available at any local 'home' store."

http://mb-soft.com/solar/kelvin.gif

It should be noted, the described system and calculations are based on a heat exchanger that is separate from the conditioned space. The drawing on that site is in plan view. Each tube in the heat exchanger is surrounded by 6 feet of earth for the heat to exchange with. DirtFlinger's design doesn't appear to conform.

Okay, I get it. It's not the surface area of the tubes you're talking about it's the area of ground maybe not being large enough to cool the tubes and the air in the tubes.

I think somebody mentioned it would be buried under about a foot of dirt, with between 1 1/2 - 2' of dirt between each 4" tube.

I really doubt at that depth that that area wouldn't be enough to cool a snaking tube. After all, if it had any airflow that wasn't passive, it would be sleight. I could probably just use a computer fan instead of the inline fan.

Honestly, I expected more from this forum. You guys are starting to seem a bit boring.. at least compared to the only other forum I use... for diy working on old jeeps.

Anyone know what's up with the stuffy tude?

Allow me to provide a short timeline of events. You came here with some interesting ideas and started a few discussions. Then, you insulted everyone on the forum by saying what we're doing is useless (even though it seems you yourself are here to do the same thing), and we're "all stupid f'ing cows". Now, you're wondering why you aren't finding this forum all that helpful.

Nice logical progression. Apparently, OffGridKindaGuy still had to find the equation for you, even though it was in the link he posted.

Enough what? Thermal connection to magic energy connectors?

You will get no cooling from this arrangement*. You are merely increasing your total thermal mass, and changing the proportion of above grade conduction and below grade 'losses'. I started my system like this on Saturday. You don't need burried tubes, you just need to move air from the basement to the top floor.

*
Hour 1 - 1 ton.
Hour 12 - 0.5 ton
Day 6 - Same temperature as living space with 1' larger depth variable in ground surface area.