toxicity, 'earthtube', other building materials ?

So most earth tubes I have seen have been PVC pipe. I know PVC pipe exposed to UV leaches toxins in water. I suspect it is more then likely bad to breath.  Any good alternative not so toxic piping that can be substituted for PVC in earth tube construction?

What is "earth tube construction"?

There are types of PVC that are UV resistant.  Further, the PVC that would be underground would be safe from any UV issues.

A trend lately has been to substitute polyethylene for PVC.  I think the pipes themselves are cheaper, installation is cheaper, and the plastic is less toxic.  It isn't as strong, tends to give a little bit over time, and the fittings are apparently more expensive.  Rather than a solvent weld, as is done on PVC and ABS pipe, the fittings make a simple mechanical connection.

I'm with Paul on wondering what an earth tube is.

Basically a tubing system for heating and cooling.

Here's some info I have on it:

Earthtubes (earthtubing) are, in a word, sustainable, non-electric, passive geothermal solar heating and solar cooling systems.   Earthtubing utilizes conventional, thin wall, plastic pipe to passive solar pre-heat your home's air intake.   Fresh air enters a system of these pipes which are laid around the interior of your home's foundation.   You can let the air draft naturally through your earthtubes for a truly sustainble, non-electric, passive geothermal system or add fans and filters to supplement the home's back-up heating and cooling system.   Be careful with Earthtube details, though ... while architects are warming-up to the idea, they are making very elementary mistakes, like using large concrete (cement) pipe that is impossible to clean.

The link is http://www.thenaturalhome.com/earthtube.htm

I'm sure google would provide even more info than I have.

I think he's talking about using buried tubes as a heat-exchanger.  Usually these are used to cool incoming air for passive refrigeration or air conditioning.

"PVC - The Poison Plastic

PVC (polyvinyl chloride) plastic, commonly referred to as vinyl, is one of the most hazardous consumer products ever created.  PVC is dangerous to human health and the environment throughout its entire life cycle, at the factory, in our homes, and in the trash.  Our bodies are contaminated with poisonous chemicals released during the PVC lifecycle, such as mercury, dioxins, and phthalates, which may pose irreversible life-long health threats.  When produced or burned, PVC plastic releases dioxins, a group of the most potent synthetic chemicals ever tested, which can cause cancer and harm the immune and reproductive systems.

New Car or Shower Curtain Smell?  The Smell of PVC

PVC is useless without the addition of a plethora of toxic additives, which can make the PVC product itself harmful to consumers.  These chemicals can evaporate or leach out of PVC, posing risks to children and consumers.  New car smell?  New shower curtain smell?  That’s the smell of poisonous chemicals off-gassing from the PVC.  One of the most common toxic additives is DEHP, a phthalate that is a suspected carcinogen and reproductive toxicant readily found in numerous PVC products.   Children can be exposed to phthalates by chewing on vinyl toys.  While it is still legal for US retailers to sell PVC children’s and baby toys containing dangerous phthalates, the European Parliament voted in July, 2005 to permanently ban the use of certain toxic phthalates in toys.   One EPA study found that vinyl shower curtains can cause elevated levels of dangerous air toxins, which can persist for more than a month."

I once read about somebody making large sewer pipes by making a long balloon-ish thing that would shape the inside of the pipe.  They would lay down the balloon-ish thing and grease it up a bit and then cover it with a mixture of 14 parts dirt to one part portland cement.  Then wet it a bit and then let it sit a couple of days.

Maybe not what you were hoping for - but it is an alternative.

Does anyone know of a list of building materials and their relative toxicity? 

travisr wrote:
Does anyone know of a list of building materials and their relative toxicity?

Toxicity is difficult to define in this context in a useful way.

Pharmacologists use LD50 (dose lethal to 50% of the population: Paul uses such a figure in passing without mentioning its name, as he discusses master gardener training and herbicide) as a measure of acute toxicity, but chronic toxicity has no similarly standard measure that I'm aware of (I've heard of dioxin equivalent, but that seems limited to organohalide compounds).  And even LD50 is just a shorthand, about as useful in understanding toxicity as IQ tests are for understanding intelligence.

The LD50 would be much higher (indicating greater safety) for PVC than for copper or even galvanized pipe.  But copper, zinc, and iron have much different effects over the long term than the additives in PVC, and of course the interaction of pipes with good drinking water (i.e., hard water) is entirely different in polymers versus metals: metals tend to interact very strongly at first, but build up layers of reaction products over time, slowing at an exponential rate, so that lead pipes that have been in use for 20 years might be safer than galvanized pipes in their first year.  Polymers barely interact at all, but additives or free monomers can drift through them and into the water at a fairly constant rate.

travisr wrote:PVC is useless without the addition of a plethora of toxic additives

That is good info, but it doesn't really apply here, as phthalates and similar are for softened PVC, which is the same underlying polymer but in a different universe of additives from what we're discussing.  Pure PVC with no additives is actually quite useful, but the quote is correct in that such a material is too brittle for curtains or clothing or chew toys.

The stuff in pipes is actually hardened instead of softened, using mineral fillers: phthalates would be counterproductive and unnecessarily expensive.  It's very much like the difference between brain-cured buckskin and traditional (hide glue-based) gesso: one common ingredient, but very different processes with very different goals.

One of the main issues with earthtubes is that when you use them for cooling in a humid climate they tend to have moisture condensing on the pipe walls and then mold growth. This in turn causes indoor air quality issues. I have been trying to think through ideas of incorporating these tubes in with a cellar so you have access to clean the tubes etc. but nothing concrete that will fix this issue. If you live in a dry climate then my guess is you might have some slight issues with condensation but it shouldn't be a real problem. I don't know because I live in Alabama where it is humid as can be and have never really lived in a place with low humidity.

Something that you can do to help with your electricity bills in the summer is to dig some basic tubes that will lower the temperature even 10 degrees and to connect this with the intake on your AC unit. The AC unit should filter out any sort of air quality issues from mold that might develop and the air being 10 degrees cooler will cut your electricity bill significantly. I haven't ever done this since I rent places and move but I would figure that this would work well. Just make sure your the area of your air intake is comparable to the air intake for the AC unit. Can anyone think of any issues concerning this?

One idea that occurs to me is to make sure the ends of the tubes slope up into the house.  At the bottom of the slope would be a drain or well that can accept condensation and sink the water into the ground.

I had thought of that but it would have to be a decently steep slope I would assume to overcome the ability of water to stick to a given surface. This would of course depend on the individual surfaces since water will probably be more likely to stick to certain types of plastic and not to certain types of glass etc.. Maybe you can treat the tubes with Rain-X and that water will just bead up and run off. Anyone know the equivalency of coefficient of friction for water on PVC pipe? There's got to be someone nerdy enough on these forums that knows this.

My best guess is that one will need to once a week have access to the tubes to pass a swab through there soaked in alcohol that will sterilize the surface and keep it free of mold. Any other ideas?

Kabir424 wrote:it would have to be a decently steep slope I would assume to overcome the ability of water to stick to a given surface.

One more reason to like polyethylene.  It's fairly hydrophobic, about like grease (no coincidence there, by the way), whereas PVC has some polar character to begin with, and PVC pipes (as I mentoned above) have a mineral filler that increases their affinity for water.

A polyethylene tube would not need such a steep slope as any other common building material would.

It might be worthwhile to have a condenser plate where these tubes enter the house, though, to prevent moisture from condensing on first wall it reaches.  The plate could be just a strip of aluminum flashing with a drain underneath it, but accessible enough that it can be cleaned off a few times during the warmer part of the year.

Joel Hollingsworth wrote:
Toxicity is difficult to define in this context in a useful way.

Pharmacologists use LD50 (dose lethal to 50% of the population: Paul uses such a figure in passing without mentioning its name, as he discusses master gardener training and herbicide) as a measure of acute toxicity, but chronic toxicity has no similarly standard measure that I'm aware of (I've heard of dioxin equivalent, but that seems limited to organohalide compounds).  And even LD50 is just a shorthand, about as useful in understanding toxicity as IQ tests are for understanding intelligence.

The LD50 would be much higher (indicating greater safety) for PVC than for copper or even galvanized pipe.  But copper, zinc, and iron have much different effects over the long term than the additives in PVC, and of course the interaction of pipes with good drinking water (i.e., hard water) is entirely different in polymers versus metals: metals tend to interact very strongly at first, but build up layers of reaction products over time, slowing at an exponential rate, so that lead pipes that have been in use for 20 years might be safer than galvanized pipes in their first year.  Polymers barely interact at all, but additives or free monomers can drift through them and into the water at a fairly constant rate.

That is good info, but it doesn't really apply here, as phthalates and similar are for softened PVC, which is the same underlying polymer but in a different universe of additives from what we're discussing.  Pure PVC with no additives is actually quite useful, but the quote is correct in that such a material is too brittle for curtains or clothing or chew toys.

The stuff in pipes is actually hardened instead of softened, using mineral fillers: phthalates would be counterproductive and unnecessarily expensive.  It's very much like the difference between brain-cured buckskin and traditional (hide glue-based) gesso: one common ingredient, but very different processes with very different goals.

I understand the problems with defining toxicity.  I mean water is toxic if you drink 10 gallons in 1 hour and your brain swells and you die.

Long term wise would you use PVC for ducking or water use?

My post earlier was a quote so I don't really understand this stuff like you do Joel and I appreciate and insight on likelihood of long term toxicity. 

Kabir424 wrote:
I had thought of that but it would have to be a decently steep slope I would assume to overcome the ability of water to stick to a given surface. This would of course depend on the individual surfaces since water will probably be more likely to stick to certain types of plastic and not to certain types of glass etc.. Maybe you can treat the tubes with Rain-X and that water will just bead up and run off. Anyone know the equivalency of coefficient of friction for water on PVC pipe? There's got to be someone nerdy enough on these forums that knows this.

My best guess is that one will need to once a week have access to the tubes to pass a swab through there soaked in alcohol that will sterilize the surface and keep it free of mold. Any other ideas?

I don't have any ideas but I am questioning how "bad" mold and bacterial exposure can be from condensation.  Developing countries have not or little reports of allergies but its a rampant problem in developed countries.  Many scientist think it has to do with developed countries sterile environments as compared to developing countries.


I personally fear relatively new chemical exposure because we do not understand the effects it has on us as humans. Our bodies know how to deal with mold and bacteria but I doubt evolution has provided any defenses against Formaldehyde or other volatile organic compounds that are leaching or off gassing from our building materials.

travisr wrote:
I don't have any ideas but I am questioning how "bad" mold and bacterial exposure can be from condensation.  Developing countries have not or little reports of allergies but its a rampant problem in developed countries.  Many scientist think it has to do with developed countries sterile environments as compared to developing countries.


I personally fear relatively new chemical exposure because we do not understand the effects it has on us as humans. Our bodies know how to deal with mold and bacteria but I doubt evolution has provided any defenses against Formaldehyde or other volatile organic compounds that are leaching or off gassing from our building materials.

If you are "questions how 'bad' mold and bacterial exposure can be from condensation" then you have never had to deal with indoor air quality issues as a result of this. Trust me when I say that for some people it can be a real problem. Within a week of moving into a house my father's family moved out because of this issue. He can have asthma attacks and my step-mother has some other health issues that were worsened by the mold issue. But, for some people it would only be a mild annoyance. Regardless, you would more than likely have a house that would constantly smell "moldy". You might not have any health problems but it would still be unpleasant to live in. You can learn a little bit about indoor air quality issues as a result of mold at the link below.

http://www.epa.gov/mold/moldresources.html

I have scoured the internet for information on earthtubes for several years.
I see a lot of fear about mold and I see mention that in Europe they use heat exchangers.
Does anyone have information on the european heat exchangers?
Thanks

for a good article on earth tubes check out: www.thenaturalhome.com  In a nutshell; he says that mold and mildew are a problem and must be built with a solution at hand...  That solution is in the design of being able to clean them regularly.  Think; cloth on a string, fish through pipes, pull string back through pipes.

David Wright covers the topic quite extensively in his book Natural Solar Architecture. He recommends using glazed clay pipe and a dry well to collect the condensate before the air enters the house.

I installed a closed loop Earth tube system in my house in Saskatchewan.  The major cost was the trench dig. I used PVC pipes with a 2% grade to a moisture collection point.  The pipes then slope up into the house.  I used a mechanical "fish" to install a rope to pull a rag through the pipes with bleach to take care of the mold problem.  The results in winter were awesome as the heating bill went down. But we developed a leak in the following summer and groundwater got in. I pump it out and it fills again. I feel totally lost about what to do next. If anyone has solutions I am open. I am considering trying to sneak a 3 inch pipe through the present 4 inch pipes but then that still leaves the contaminated outer pipe where mildew and contaminants can enter the house. 

We are putting earthtubes and this whole PVC vs Polyethylene debate  has been going on in my head for a bit.  I stubbed the walls out with PVC (per naturalhome.com) site.  Then had some pvc outsided and poly inside pipe i used as well.

However as time goes by I really don,t want the air exchange to be made with pvc.  My knowledge of the chemicals is not that good .  BUT , when i cut pvc with a skill saw the smell makes me want to puke.  When I cut black plastic tubing absolutely no smell.  Me thinks pvc is nasty stuff 

I think I will use black poly pipe instead.  The corrugated stuff has also been used in an earthtube install i have seen online.  They ran a circular saw down the bottom of the pipe.  This allows any condensation that does occur to drain into surrounding soils.  Obviously with a high water table this might not be the best way to go lol. 

I do not think that the corrugated black poly is as strong as the pvc (compressive strength) but it would certainly be easier to install vs the 10, sections the pvc pipe comes in and all the elbows that would be to be installed.  I would imagine that the flexible pipe would decrease the resistance that air would have coming in, being that there is no hard angles to slow draft.

The corrugated poly pipe also have double the surface area (roughly) of pvc allow more surface area to allow heat exchange.  This might allow a shorter distance the pipes would need to be run. 

hi - you all seem very conversant with plastic tubing and ducting -  i've been trying to determine the best (and cheapest) ducting to use to transfer fan-driven solar-heated air to an underground heat storage bin (gravel) - it will be a closed system so i'm not concerned with out-gassing - some of the ducting will be buried as deep as seven feet in heavy clay soil -
so, you can see my concerns are something that will not soften from heat possibly reaching 160 degrees and strong enough to maintain it's profile even with considerable burial pressure - i'd like to stay in the four to six inch diameter range -

any suggestions ?  or, anyone aware of a commercial supplier offering such product details in their info sheets ?

thanks !

Hm...cheap, soil-stable ducting with high compressive strength at 160F...

Maybe wine bottles? A large investment in time, so maybe not appropriate, but you can scribe them near the bottom and where they're narrow enough to socket into one another, then pour on a little boiled water (about the temp. you'd make green tea with) to finish the cutting process. They can be joined with lime mortar.

You might need a special jig to scribe them at an angle, if the runs are not all straight, or you could buy a few ceramic sewer fittings. There's the option of leaving more of the bottle neck to add some turbulence and enhance heat transfer, or to favor flow in one direction over the other.

Sometimes a restaurant will be a steady source of "magnum" bottles, which will give you more length per effort. Some municipalities collect bottles as though they would be recycled, but are too isolated to afford shipping, so talking to the right person might get you free delivery of a container of bottles.

Odd-sized bottles, filled with mud and sealed with mortar, might be cheaper than gravel and have a higher thermal mass...the space between them could be filled in with scraps and off-cuts, as well as gravel.

I built earth air pipes for our old farm house and they helped a lot, bringing in warmed fresh air. My purpose was for the winter air warming rather than the summer air cooling. The summer use is what causes the mold in the pipes. In the winter the incoming air is ultra-dry and too cold. Incoming outdoor air came up above freezing - impressive in our northern Vermont climate. For details see:

http://sugarmtnfarm.com/blog/2008/09/earth-air-tubes.html

That used four parallel 70' long 4" diameter PVC pipe on a slope. I have some concerns with the PVC but realize that cold air isn't going to pickup much toxins - temperature has a lot to do with volatility. However, for the new earth air pipes I'm planning I may build them out of granite - something I have lots of. I've been saving large flat skins for this purpose. Another way I might do it is concrete channels and another is simply caverns. It isn't this year's project so time to think...

Cheers

-Walter
Sugar Mountain Farm
Pastured Pigs, Sheep & Kids
in the mountains of Vermont

how about a post hole digger before the slab goes in? or concrete saw and post hole digger goin straight down(hopefully not hitting a spring lol ) should be able to go say ~ 8 - 10 foot depending on location and 4-8 holes . pour concrete around and maybe a couple cups in the slightly sanded cup or atleast make a plug or bond in a screw on cap
atleast something to think of

Either the PVC pipe or the corrugated pipe will not crush if buried a foot deep or so, unless you drive a full dumptruck over it repeatedly. This I can tell you from experience, as we've put in MANY PVC and corrugated drains on gutter systems and not had one fail yet, even after driving a 1 ton dodge truck loaded with 4 yards of fill dirt over it. As long as its deep enough, no damage will occur. All the broken or cracked pipes I've seen are due to being bent while refilling the ditch and not bedding the pipe.

I checked out the natural home website, but I see several problems with the earthtube system. A nylon rope to pull a rag through? That is a very short lived solution. The rope will break and then you'll be stuck with a rag in your tube. At least this is my luck. Second, the site compares them to HVAC ducts. There is no comparison since HVAC supplies dry air, hence no mold likelyhood. Whats the solution after you get mold? Just cap them and forget the tubes exist? It looks like several of the drawings used on the website show the tubes under a concrete floor - well what about an earthen floor or outside the foundation? After a good rain you have a moisture problem it seems. Would a mold problem in the pipes be an issue in a greenhouse with all the plants (air cleaning effects of plants)? THATS one question I'd love to see addressed.

a newbie to "permies" but not =green] to alternative energy, i was wondering if anyone has tried "ultraviolet" light in their earth tubes? by means of a cleanable plenum at entry point

A couple brainstorm additions:

I wonder if carnauba wax or beeswax could be applied to the interior surface of a smooth pipe to encourage the condensate to bead up and roll downhill to a collection point. Secondarily, maybe it would seal off any toxins in the pipe material. It seems that this "earthtube" concept might be a potential source of distilled water, in addition to conditioned air.

How about a "pig in a pipe"?
If I remember correctly I heard the term years ago in reference to cleaning oil pipelines. The idea was just a weighted ball that would be forced through a pipe.
Provided the curves and joints are made with this in mind it should be possible to roll a heavy ball through the pipes on a regular basis. If necessary you could clamp a cover on the interior opening of the pipe and use a compressor to provide added pressure. You could even use a SLA battery in a clear shell with UV lights if you wanted to better disinfect the pipe.

Maybe lube the ball with a mix of bleach and hand sanitizer?

I remember when I was in high school band, some of the brass players would blow a sponge ball soaked in alcohol through the tubes, so maybe a disinfectant soaked nerf ball?

What about ozone?

If you used the right material could the same tubes be used for air tubes and for the flue for a rocket stove?
Not at the same time, just switching back and forth; when it's cold run your rocket heater to heat the house AND the ground around or under the house, let the fuel burn out, switch the vents and blow enough air through the pipe to clear exhaust gases, then draw air through the tube as an air pipe?

https://permies.com/t/9598/wood-burning-stoves/RMH-Air-Conditioner-Trombe-Wall

https://permies.com/t/9580/rocket-stoves/Rocket-mass-heater-converts-cooler