Note: This topic was split off from an earlier discussion of a small earth bermed house going up in upstate NY:
http://countryplans.com/smf/index.php?topic=5690
Quote from: speedfunk on July 21, 2009, 01:38:10 PM
The earth tubes are really just to help moderate incoming temp and keep fresh air. So many people now believe that they have to make a house air tight which is unhealthy. In a conventional house where heat is store mostly in the air it's a bitch lol, you almost have to? The mass here should allow me to swap out air for a better indoor environment without losing my heat. There are 2 incoming 4" tubes and will be 2 tubes going out the back for exhaust with fans setup on them. A great resource for earthtubes is the http://www.thenaturalhome.com/earthtube.htm. He had some good tips on cleaning and maintenance. I'm not sure about a few of the details but overall it's a great site and where I first found out about drystacking as well.
We're planning on using a lot of the ideas from thenaturalhome.com (http://thenaturalhome.com), I just can't wrap my head around earthtubes in our area of Missouri. We talked about different ways of treating the air (to remove humidity) before it enters the house through the tubes including weep holes below grade. Just can't come up with one that's efficient or effective enough without raising maintenance tasks.
The best we came up with (and I believe it was John who suggested it) was to use the weep holes and then have a rag tied to a string both ways in the tubes to allow for cleaning in the future (like you run string in a dead electrical chase for future expansion).
The other contender was to have the intakes as high as possible in the air and running them into external shed and in there use a whole house dehumidifier and then let the air fall into the underground portion of the system and then into the house.
I guess I read the cleaning thing on thenaturalhome.com site... ??? Credit where credit is due... I know John and Glenn both had ideas. Guess I'll read my own post again.
Lister:
You pretty much described what we are going to do. The earth tubes with have an overall downward slope from the house. Both in the front and the back. The slope should be pretty substantial , maybe 20 degree's in the front and 15 in the back. We will do the weep holes and the string so we can pull the cloth through just like natural home which seems like a very good idea. We will also have fans setup to control the air. Natural convection is supposed to work but it's the one part of the house that I'm making "Active".
There is little to no info on earth tubes that I've found so if you see something send it my way!! I'm guessing on the amount of tubes also but I think it scales well lol. we will see.
One thing I didn't think made sense with natural homes way of running earthtubes is that they ran them right next to each other. The PAHS book I read on them did not recommend that. I've separated mine so we will see. BTW if you do want more info on earthtubes, this is by the far the best book I've found! I cannot plug this enough, just a very unbiased, logically way of looking at passive heat storage.
http://www.earthshelters.com/PAHS_Improving_ch_1_intro.html (http://www.earthshelters.com/PAHS_Improving_ch_1_intro.html)
I believe the earthtubes should start uphill and fall to the house with drains at the bottom by the house, as cool air is heavier than warm air so as the air cools it will fall pulling in more warm air from the top of the hill. As it cools it loses it's capacity to carry moisture so the water will run out at the low point at the house along with the cool air.
Whitlock mentioned a house north of here where the tubes were put in wrong, high at the house and ran down hill and they worked backward pulling warm air into the house as the heavy cooler air exited down hill.
Quote from: drainl on July 16, 2009, 10:30:30 AM
....... and get the pvc earthtubes intakes up to floor level THEN dirt backfill
Jeff
Hi Jeff, I googled for earthtubes and found your thread.
I read the entire thread but this is the first mention of earthtubes.
Will you please describe what you plan and the results you hope for?
I am working on a property in Arkansas near the Missouri border and hope to put the earthtubes in, in about two weeks.
My property is on a slope, and I had the bulldozer guy make me a flat spot.
My plan is a 40 by 40 foot pole barn with a concrete floor, using 4 earthtubes that are 15 inch diameter and about 100 feet long, buried about 6 feet deep, straight runs to daylight.
My son is an engineer so he and another engineer made up a spreadsheet for me and 15", 100" is what I plan, hoping for 2 tons of cooling per tube.
Quote from: glenn kangiser on July 31, 2009, 11:16:20 PM
I believe the earthtubes should start uphill and fall to the house with drains at the bottom by the house, as cool air is heavier than warm air so as the air cools it will fall pulling in more warm air from the top of the hill. As it cools it loses it's capacity to carry moisture so the water will run out at the low point at the house along with the cool air.
Whitlock mentioned a house north of here where the tubes were put in wrong, high at the house and ran down hill and they worked backward pulling warm air into the house as the heavy cooler air exited down hill.
If the tubes are run your way, how would the condensate drain out?
I have been searching the internet for three years hoping to learn about earthtubes and no one else suggests running them downhill to the house.
Most of the websites suggest combining earthtubes with solar chimneys, to create an upward draft.
My engineer suggests a high rate of flow that may not be possible by natural forces, so I am considering solar powered attic fans to assist.
Quote from: ListerD on July 30, 2009, 11:44:54 AM
We're planning on using a lot of the ideas from thenaturalhome.com (http://thenaturalhome.com), I just can't wrap my head around earthtubes in our area of Missouri. We talked about different ways of treating the air (to remove humidity) before it enters the house through the tubes including weep holes below grade.
Lister, my plan is to put an earthtube in each of my four corners of the building.
Each tube will go down about 5 feet and then run straight to the edge of my plateau which has a dropoff of about 7 feet.
That will give a nice slope to each pipe, allowing condensate to run out of the pipe.
Drawing hot air thru the cooler earth causes dehumidification.
Faster air flow causes more dehumidification.
Because I prefer to pay as I go and do all the work myself,
I will set the earthtubes, then erect the building.
By the time I get the walls closed in the experiment will be functioning.
I will be able to determine how much natural airflow I am getting with the solar chimney effect and can install one fan to find out how much difference it makes.
If I need more cooling or more dehumidification, I can add more fans.
thenaturalhome website assumes you are on a flat property and takes a rather negative approach to the success of earthtube climate control.
I may be over optimistic...we will see.
several people have suggested that I set up an experiment first to see how it works.
Yep, thats what I am doing. A full scale, full price experiment, but I see no way to experiment on a smaller scale.
(maybe we need to create an earthtube thread?)
The tubes running "downhill" makes good sense to me. Glenn points to the common sense part of cool air falling that I keep forgetting.
I still can't wrap my head around the weep holes in some ways. I know it's not enough moisture to worry about and I'm sure it would be readily absorbed, but introducing additional moisture under my slab somehow makes me nervous. ???
bgarret - where are you located?
speedfunk - I think the idea of placing them together was to get as much as possible absorption out of the ground. I figured a larger pipe made more sense since it provides more surface area.
Just fyi:
I read recently that Rob Roy, author of earth-sheltered houses, does not endorse earthtubes in his book because of Radon concerns.
OK, I'll bite - IF the tube is open outside *above* ground, *sealed* for the entire underground distance (except for possibly a few small weep holes) and then opens up in the home *above* ground, how does the radon get in? ???
Surely Radon can't pass through the tubing? ??? :o I know it comes in via unsealed/cracked foundations, bad sumps and etc... I thought it was too dense to pass through most materials.
Maybe I'm dense? ;D
If the house takes in ventilation from low points besides the tubes, or the flow is high enough from the tubes the ventilation should be high enough to have it eliminated. No?
Cool, thoughtful discussion on earth tubes going on.
bgarrett welcome!
wow ..that seems like a substantial project . Please keep us posted on how this turns out. Sometimes as a good friend says " ya can't be scared" go for it! We need people to try this stuff so we all can learn
I'd like elaborate on the goals of this setup for me. B/c I think each of us has a different climate and needs for earthtubes. First off I'm in cold upstate NY so to be honest cooling is not really that big of a deal. I know the system will cool a bitin summer but I'm really not designing for that goal in y mind. I'm also not expecting earthtubes to completely heat my house. The mass around my house will moderate (heat/cool) our house and provide the storage of heat for the earthtubes to use to warm incoming air and retrieve some of that outgoing heat. The intakes for me are just taking the chill out of the winter air in the most passive way I can, and keeping us happy and healthy, while also trying to recoup as much heat as possible on way out.
Condensation: something that is usually brought up, but for me personally winter air tends to be dry and warming it up will not add any moisture (I BELIEVE!). In the summer here in NY which can me humid The reason to pitch the tubes downward makes sense also. Why invite water (run off or condensation )to drain into your house. So this is why I"m doing that. This will also allow me to clean the tubes using alternative methods. I could run a hose temporarily to them when I want to clean them and follow that with the rag on a string and a good chemical free cleaning that will dilute and drain any bad stuff that MIGHT grow in the tubes.
Radon: Following listers logic on this one. I can't see how radon would get into the earthtubes except for VERY minor amounts that will be diluted by a massive amount (relative to the intake of drain holes that the radon could get into) of fresh air being brought in. I think the big thing here is that as long as you constantly have fresh air coming in you will have healthy home. locking it up tight allows small amounts of bad gases ( ;D ) to linger and pollute your indoor environment.
ListerD: Yeah a larger pipe does have more total surface area but smaller pipes have more contact area per volume unit of air. This make sense, I;d have to do the math? lol d* . The reason that the pipes being separated is good is b/c eventually if you have all the pipes in one area the ground around that area around group of pipes will equalize to the pipes temp and losing it's effectiveness. As in where the pipes are separated by farther distances that earth doesn't have as much stress put on it to heat or cool the air and can maintain it's temp better overr a longer period of time.
Great discussion all.
Lister, there will be no 'weepholes' in my earthtubes.
Therefore no radon entering.
The only thing entering my earthtubes is outside air.
Thank you for the welcome Jeff.
Let me say again, all I have is ideas.
There are no facts yet.
I will document and share my results.
My tubes are going downhill so the condensation will drain out the open intake.
Earthtubes are used in conjunction with a solar chimney so air is drawn in and continuously moves upward til it leaves at the top of the building.
The earthtubes are located at each corner of the building and are far apart.
Placing several tubes in one excavation will defeat the purpose of using the earths normal temperature to temper the air in the tubes.
I have been searching the internet for 3 years for earthtube information and what I find suggests tubes from 6 to 18 inches, about 100 feet long.
Using a 4 inch tube would be like sucking thru a very small straw.
You want easy flow of air but not tubes so big that the air passes thru without being affected by the earths temperature.
I have a flow chart make up by real engineers and will be happy to share it, if I can.
It allow the user to plug in any size pipe and see the results.
My goal is to get as close as I can to room temperature equalling the earths temperature.
This is not achieveable, of course but will decrease my need for additional heat and cooling.
Quote from: bgarrett on August 04, 2009, 05:23:09 PM
My tubes are going downhill so the condensation will drain out the open intake.
I'm not sure about this as I can see that as temps fall in the house at night, the cycle is reversed and it allows the cool air to fall out of the home and then drawing air in from the top, reversing the chimney effect. Rather than maintaining the temps via the mass releasing heat into the home.
Guys? Sanity check?
Quote
Earthtubes are used in conjunction with a solar chimney so air is drawn in and continuously moves upward til it leaves at the top of the building.
See above.
Quote
I have been searching the internet for 3 years for earthtube information and what I find suggests tubes from 6 to 18 inches, about 100 feet long.
Using a 4 inch tube would be like sucking thru a very small straw.
You want easy flow of air but not tubes so big that the air passes thru without being affected by the earths temperature.
Makes sense to me.
Quote
I have a flow chart make up by real engineers and will be happy to share it, if I can.
It allow the user to plug in any size pipe and see the results.
Oh PLEASE DO share it! [cool]
bgarrett: yeah please share the flow chart, that would be very helpful!! It sounds like you given this a lot of time. ;D
I'm kind of stuck with 4"s though lol. I'm ok with that though, it's what I decided on. My thought is our house is not all that big and wouldn't need that much air exchange. I never sat down and figured out "real" values though. So it is what it is.
Its a Microsoft Works spreadsheet.
How can I transfer it to this forum?
Quote from: bgarrett on August 01, 2009, 08:20:51 PM
Quote from: glenn kangiser on July 31, 2009, 11:16:20 PM
I believe the earthtubes should start uphill and fall to the house with drains at the bottom by the house, as cool air is heavier than warm air so as the air cools it will fall pulling in more warm air from the top of the hill. As it cools it loses it's capacity to carry moisture so the water will run out at the low point at the house along with the cool air.
Whitlock mentioned a house north of here where the tubes were put in wrong, high at the house and ran down hill and they worked backward pulling warm air into the house as the heavy cooler air exited down hill.
If the tubes are run your way, how would the condensate drain out?
I have been searching the internet for three years hoping to learn about earthtubes and no one else suggests running them downhill to the house.
Most of the websites suggest combining earthtubes with solar chimneys, to create an upward draft.
My engineer suggests a high rate of flow that may not be possible by natural forces, so I am considering solar powered attic fans to assist.
You would have to make a way to drain it at the bottom but that is the natural way cooling air will want to flow - downhill.
Cooling air gets heavier so wants to fall - you are right - moisture will be dropped as the air becomes heavier and it will flow downhill toward the house. A cooling tower could be incorporated as in the middle east to enhance the flow. Solar chimneys could help to draw the cool air across the house.
This is information I studied in flight school on avoiding CAT (clear air turbulence).
Making the cool air go uphill would have to be power assisted.
There is a house near here where the tubes go downhill and warm air is sucked into the house as the cooled air exits downhill. It will not naturally work that way - it will need power assist.
this forum will not accept the spreadsheet
it says "The upload folder is full"
If you want to email it to me I can share it from my webserver.
http://cid-3ceb429f78459841.skydrive.live.com/self.aspx/Public/heat%20exchanger.xls (http://cid-3ceb429f78459841.skydrive.live.com/self.aspx/Public/heat%20exchanger.xls)
Here's the EarthTube spreadsheet that was mentioned earlier.
Not sure I'm following it, so if you can explain it that would help some. d*
Rick, I clicked on your link but do not see it
Is it working?
I sent two of the spreadsheet, one with 16 degrees outside air and one with 95 degree air.
This is a working spreadsheet and you can substitute any ground temp and outside air and pipe size.
Column A (misspelled the word 'iteration') which means repetition or sequence
this column numbers the 100 feet of the pipe with
Column B showing each foot of the pipe
Column C is the same as B but in meters (dont ask me why the engineers did that)
Column D is the diameter of the pipe and you can plug in any size you want and get results
I put in 15" because the plumber has it available
4" would be too restrictive and 36" would be too expensive
Column E is 15" in meters
Column F and G are way beyond my comprehension, I guess you'll have to google
Column H is another where you can substitute your ground temperature or any other
Column I is where you plug in the outside air temperature
I have lived in hot humid Louisiana all my life, so I put 95 degrees here, looking for the amount of cooling I could hope for
I also plugged in 16 degrees because I wanted to know the temperature of the outlet on a cold day
Columns J thru N are Engineers stuff--I dunno
Column O to T are airflow which will have to have mechanical assist to be reached
Column U and V--ask an engineer
and Finally Column X shows the temperature of the air each foot of the 100 foot pipe and at the outlet
I hope this helps you understand what the spreadsheet shows and my limited understanding of it
Quote from: bgarrett on August 06, 2009, 11:03:32 AM
Rick, I clicked on your link but do not see it
Is it working?
Yes, click the big spreadsheet icon.
This should also work as a direct download:
http://yqtynw.blu.livefilestore.com/y1pRoCtS55V4HIrkYrgwbei1exC4eUthRgwMEF6x4SVl9VM31XU7mPmNbK-o5BWEKGynkgifz8ltbwxWkyNDp_jMA/heat%20exchanger.xls?download (http://yqtynw.blu.livefilestore.com/y1pRoCtS55V4HIrkYrgwbei1exC4eUthRgwMEF6x4SVl9VM31XU7mPmNbK-o5BWEKGynkgifz8ltbwxWkyNDp_jMA/heat%20exchanger.xls?download)
Thank you for posting it, Rick.
I hope everyone can see it.
I look forward to comments.
I am trusting the engineers, but not sure if what they are telling me will work. :)
I plan to start digging and burying the pipe in just a few days so y'all Speak Up!
Some websites say that earthtubes were a fad in the 70s and 80s but nowhere do I find any other information telling whether they succeeded or failed.
Has anyone seen any results?
If mine doesnt work I will say so and of course if it does work I will tell that too.
July 30 - August 3
It feels like we didn’t get much done in July for various reasons, but I feel a little better when I look through our photos from the month. Jeff finished up July getting the inside of the house parged so we could bring it up to floor level with dirt. There’s been a lot of rain this summer, so timing has been tough. My main job is still stacking blocks, which were getting hard to lift onto the wall, so I’m happy the ground is higher now.
Here’s our supervisor checking out our work from our lovely front stairs.
(http://oursideofthemountain.com/familyblog/wp-content/uploads/2009/08/img_0282.JPG)
We got the two sonotubes filled with concrete for the posts.
(http://oursideofthemountain.com/familyblog/wp-content/uploads/2009/08/img_0312.JPG)
Photos of the two earth tubes (which I know nothing about so I won't add to that conversation!)
(http://oursideofthemountain.com/familyblog/wp-content/uploads/2009/08/img_0310.JPG)
(http://oursideofthemountain.com/familyblog/wp-content/uploads/2009/08/img_0311.JPG)
All ready to go! Jeff had to move a bunch of materials inside and outside the house to make room for Vinny and the excavator.
(http://oursideofthemountain.com/familyblog/wp-content/uploads/2009/08/img_0314.JPG)
First he filled in the ditch for the electrical lines.
(http://oursideofthemountain.com/familyblog/wp-content/uploads/2009/08/img_0316.JPG)
Then the inside of the house got filled. I had fears of one of my walls getting knocked down, but I had nothing to worry about!
(http://oursideofthemountain.com/familyblog/wp-content/uploads/2009/08/img_0319.JPG)
(http://oursideofthemountain.com/familyblog/wp-content/uploads/2009/08/img_0320.JPG)
And then on to the biggest project - Jeff decided it’d be best to put in the two posts (aka trees) while we had the machinery. They were successful as you can see. We’ll debark the trees and poly them eventually. Until we get the roof on we’ll need the extra bracing. It’ll be interesting to see what our inspector thinks of the trees. They look impressive when you drive up to the house. They’re 2-3 feet taller than they need to be, so we’ll trim them when we get to the roof. You can also see we left area open in the bathroom for a crawlspace.
(http://oursideofthemountain.com/familyblog/wp-content/uploads/2009/08/img_0322b.JPG)
Total bill for the day was $708. Now we need to place an order tomorrow for more block (6 pallets were thinking) and a pallet of SBC. That and installing windows will keep us busy for awhile. We really want to get the roof on before the first snowfall. Last year we got 8″ mid October. Fingers crossed!
Looking Good!
I apologize for kinda hijacking your thread
So are your walls the only mass?
I'm assuming you'll do another poor for the floor, what thickness?
It's always fun to see progress! Thanks for sharing your journey [cool]
That is cool. Thanks for the pix.
John does not have room to load files to the forum so they have to be loaded elsewhere and linked to. Scribd is one place for some kinds of files.
Quote from: bgarrett on August 06, 2009, 11:23:42 AM
Some websites say that earthtubes were a fad in the 70s and 80s but nowhere do I find any other information telling whether they succeeded or failed.
Has anyone seen any results?
If mine doesnt work I will say so and of course if it does work I will tell that too.
...
It sure is quiet here
It seems most final results are lacking. We look forward to hearing of yours.
Jonesy in Australia was going to report but got busy and we never heard if he finished.
The report I did hear of was from a friend of Whitlock's who put them dowhill and as I suspected they work in reverse drawing warm air into the house and expelling the cooled air downhill. A fan in this situation would have to overcome the heavier cooled air to reverse it's natural flow and push it backward into the house.
This would not then use the natural heaviness of the cooled air to power the system.
Let me do a bit of thinking here on earth tubes, insulation and seasonal heat storage.
When thinking about earth tubes you have to start with the soil temperature (and moisture content, but let's just deal w/ temp for now).
Down 2'-3' in the soil the temperature tends to stabilize at the annual average temp plus a degree or two from warming from the core of the earth.
In my Pacific NW cool climate the earth temperature is 50º to 53º. This is most easily determined by measuring the water temp of a fresh draw from a deep well. In strong four season climates with high summer temps that seasonal average may be 60º or higher. What is your soil temperature Glenn?
Dry soil is a very poor conductor of heat so don't expect much heat transfer from slightly warmed air running through a plastic tube and conducting into soil. You could set up a simple experiment with a couple of thermometers and compare soil temps a foot away from the earth tube to an undisturbed area of soil at the same depth. You could then put insulation on top of the soil over the tube and see how much that raises the temp.
In cold climates earth tubes can be used for cooling purposes in the summer as it will cool outside air. Some folks have also used these tubes for preconditioning incoming air to a furnace or heat pump reasoning that if the outside air is -10º and we can warm it up a few degrees this is heat we don't have to purchase.
To attain the goal of seasonal heat storage so that you can have a yearly flywheel of thermal energy you can make deposit to in the summer and withdrawls in winter you will need:
• A container that will hold the BTU value of your winter heat load.
• The container will need to be highly insulated since insulation r-value is a measure of resistance to heat flow over time and we are counting on holding the heat for 6 months or more.
• In order that we do not need to build an enormous, highly insulated container we will want to store these BTUs in something with high heat content such as water. (Soil is not good for this as it is tiny bits of rock separated by air.)
About the time you get to this point in the calculation you start thinking about ground source heat pumps and realize that it can do the job for less money and it provides both heating and cooling while taking advantage of the soil temperatures.
I have just uploaded Bruce's spreadsheet. Click on the file name and "save link as" to your own computer or open with Excel.
http://www.countryplans.com/Downloads/heat_exchanger.xls
Bruce replies to my post above about seasonal storage
"Soil temperature here is about 58 degrees.
I will have some water going into the sand around the earthtubes, think soaker hose. Seasonal heat storage is not my goal nor any part of my plan.
Since I own a backhoe and will ignore the cost of diesel to operate it, the cost of earthtubes is the cost of the pipe, the sand to fill around it and fans to get the airflow required.
I see this as the cheapest possible way to have a constant flow of 58 degree air thru my building. At 58 degrees, I will not need Air Conditioning and will need to add only about 10-14 degrees of heat in the winter."
Please put a minimum of two digital temp probes in with at least one the tubes. One probe reading the air temp at the inlet side of the tube and one at the outlet or exhaust side. Then you can track these two numbers with the interior temp and this will let you do simple experiments like turning fans off and on for two days when the outside temps are similar. Did it change the house temp? Did I use more or less heat?
Your theoretical maximum heat transfer between the soil and air would be attained if you were always able to get air into the house at the same temperature as the deep soil temp. Then you would get the benefit you mention above. Since the conduction between the air and the deep soil is a long way from perfect, your actual temperature rise or fall in the tube will be something different - how different depends on lots of things we don't need to get into and it doesn't matter anyway. Your probes will tell you all you need to know.
I am sure your tubes will be a help for summer cooling. I wouldn't expect the air coming in to be 58º, but even if it's 78º that will be useful for cooling. This is the benefit I get from my earth coupled crawlspace air loop.
I am not convinced you will have any benefit in the winter time. I will venture a guess that if you do the experiment I suggest above that you will find you will use less purchased BTUs to get the interior temperature to your comfort point when the earthtubes have the fans turned off and are capped closed.
Thank you John!
I like the statement below your posts.....None of us are as smart as all of us.
If I am way off base, someone speak up and save me a lot of money and work!
I do plan to keep a record of outside air temperature, earthtube outlet temperature and room temperature thru the summer and winter in order to see what is accomplished.
(You dont know what you have unless you take inventory)
As you mention, I dont expect to get exactly 58 degrees as the earthtube outlet temperature, but anything cooler than outside air should be a benefit.
You mention winter benefits from the earthtubes....in my naivety I imagine that 16 degree air drawn thru the earths temperature of 58 degrees will warm the air coming out of the earthtubes...Are you saying, maybe not?
I suspect that if the outside air is 16º you may well get air that is still close to freezing at the interior of the tube. Unless you immediately feed this into a heater and raise it to perhaps 10º above room temp you will feel a cold draft. That's why I suggest you design the tubes with tight fitting caps.
In the winter you don't want a lot of outside air to heat up - doing so is expensive. The normal stack effect of a well sealed house provides plenty of air change and drying when you have such a high temperature differential between inside and outside.
With super-insulation cold climate techniques you try to cut down the air change rate with tight construction and then install a simple heat exchanger to supply fresh air that is heated with the stale air headed out. These have a much higher heat transfer rate than would an earth tube and even they need heaters to warm the air when the outside is 16º.
Quote
To attain the goal of seasonal heat storage so that you can have a yearly flywheel of thermal energy you can make deposit to in the summer and withdrawls in winter you will need:
• A container that will hold the BTU value of your winter heat load.
• The container will need to be highly insulated since insulation r-value is a measure of resistance to heat flow over time and we are counting on holding the heat for 6 months or more.
• In order that we do not need to build an enormous, highly insulated container we will want to store these BTUs in something with high heat content such as water. (Soil is not good for this as it is tiny bits of rock separated by air.)
About the time you get to this point in the calculation you start thinking about ground source heat pumps and realize that it can do the job for less money and it provides both heating and cooling while taking advantage of the soil temperatures.
Check. we have a container that will hold the heat designed.
Check. We will have 2 layers of r10 techfoil and a vapor barrier (6 mil plastic), which will also act as shingles under the ground to keep water from changing thermal properties. The house will have 4" of rid polystrene on outside of brick wall. the roof will have 4 inches of polyurethane rigid foam board.
I bet a ground source heat pump will be more expensive overall. There is the advantage of using the earth's conductivity rather then water for transfer of heat. It's still mass just less dense. It requires no electric,this for me personally is big. I want a very passive simple home. There is also no equipment to service or maintain. I'm not sure the exact cost differences though, varies by sitituation i'd imagine. The main costs of using earth as storage and conduction is the large area that needs to be excavated and the insulation blanket. Maybe some one can share what a whole house geothermal ground source heat pump costs to install and keep running! if I remember right somewhere between 10-20 Grand for initial install and 1/3 the cost of heating from then on. I know of a few people around here who love their geothermal heat pump setup. The idea of a utility bill scares me and is going against my goal of VERY affordable living ;D.
bgarrett: I'd love to see pics and some posts on your setup while your installing . Please consider starting a thread. Maybe between all of us we can start to make earthtube science more open for all to examine and customise! I believe there is a lot of promise and look forward to any real world info. I've been debating with my self over the intakes and whether two 4 inch pipes will be enough. However with fans I can increase the draw and suck MORE air if needed. I know what info i need to figure out, just have not done it lol. To be honest I'm not at that stage of the building.
1. Whole house volume of air.
2. how much air a 4" tube x 125' (approx) with a variable speed fan can exchange ( x'2 x for my situation)
3. how much air exchange is needed for "healthy" air :-\ Maybe someone can shine the light on this one. I'm going to talk to a guy I work with who runs a k-12 school. The state mandates a certain air exchange rate and that would be good info to know when designing a system.
The trick though is how quickly air will take to (in my case pre-heating) warm up. This can be changed if using fans by regulating air draw. The only real numbers that matter in the end are what john and bgarrett mentioned. The inlet and and the where the tube enter home. If for some reason the air doesn't have enough time to get to whatever temp you want adding more pipe would help. I would think that in the beginning of the earthtube where your temp differentials are highest the most work will take place. As the air travels farther along and gets close to it's in house destination and the temp starts creeping toward ground temp the less the difference the less quickly the air will be affected. So there is probably a point of diminishing returns based on how long the pipe is. So getting the same exact temp as ground would seem difficult, however getting temps very close should be obtainable.
John, measuring the soil that does not get sun, I get 70 degrees.
Interesting that the area in the sun is at 89 degrees at 8:35 AM/
I to fully plan to incorporate earth tubes in my house. But I also do not plan them for a heating/cooling source.
During the summer I will have a very open house concept lots of windows and doors open allowing fresh clean lively air to flow through.
In the winter when things are closed up (Western canada) I will have a fire place, gas water heater, gas dryer, gas stove. these things need an air supply. also in a tight house the Range fan, and bathroom fan also need an air supply. This is where my Earth tubes will come in, these appliances drawing air will pull fresh air through the earth tubes.
I will have a slap floor and the tubes will run below the floor and insulation before entering the house. The tubes will flow up hill to the house with no weeping holes in the pipe. At the entrance to the tubes will be a vertical pipe with a rain cap coming out of the ground. air will be drawn into this vertical pipe into a Dry well. then enter the earth tube, all condensation from the tube will flow back down hill to the dry well. This air as said before will be mechanically pulled by appliances in the house. As the air travels the earth tube and warms up it will become lighter and a natural air flow will want to occur. Remember the out side is cold and heavy, the air inside the house is warm and light. The ceiling is well above ground level so the air will naturally want to escape the house at a high point and enter at a low point. This is basic physics. The problem people are having is only looking at the Earth tubes, the house is part of the system too. And the Ceiling will be well above the ground level in all seasons.
I'm not looking to heat air with the earth to heat the house, I'm looking to reduce a cold draft.
Sounds like a smart way of looking at thing mcbane! 8) . You will have to update us with info when you eventually get to installing. You mention also that the house is part of this equation , insightful! I'm thinking of a wood stove heating up the air , then exhausting through the upper earthtube and CREATING that pull of air. No doubt will be interesting to play with.
John, interesting discussion on earth tubes and seasonal heat storage. There is a thread in General about Noble Homes. Here is a link to a part of the Noble web site that talks about heat storage.
http://noble-home.net/design.html
If I read it correctly, they are offering to help a home owner with material costs for a heat storage system.
Hope this is on topic.
Very helpful! It's nice to know others want to advance building earth stored heated homes. I'm still " digging" d* through their site thanks!
http://countryplans.com/smf/index.php?topic=4752.80 (http://countryplans.com/smf/index.php?topic=4752.80) Additional thoughts this morning on humidity control for the earthtubes for our home in Missouri.
http://mb-soft.com/solar/saving.html
above is a link that some may find interesting.
Im installing three hundred feet of four inch tubing that is house to house. and five hundred feet of four inch tubing that is fresh air to house. there will be 8 - 100 ft runs. Im now thinking ill run my last three fresh air tubes up hill away from the house. that makes sense to me. My house is a little over 1600 sq feet and will have a vented stack in the roof to let hot air out and hopefully pull air threw my tubes to cool my house. [cool]
the link above explains its not so much the size of the tubes it's the number. hope this helps
I love the topic
llamaman great to hear it. I like your idea of 100' run and more of them.
I just upgraded my house to 6 total earthtubes 3 intake 3 exaust. I also think I'll run it about 100' also.
Here is a link I wanted to share from sugar mountain farm. He ran earthtubes 70' and describes his experience.
http://sugarmtnfarm.com/blog/2008/09/earth-air-tubes.html (http://sugarmtnfarm.com/blog/2008/09/earth-air-tubes.html)
I think we have to most comprehensive list of earth tube related material on the web lol. woohoo.
Someone else may have addressed this, but I was contemplating the feasability of venting the earthtubes into an atatched garage or outbuilding and installing a heat pump in it to let it do its job. Not sure if this would be good for the heat pump or the garage though? My first thought is that it is generally too cold in Iowa for a heat pump to work effeciently but using the earth tubes as a source of much warmer or cooler air than outside temperatures in the winter and summer seems to be a plausable soloution but not sure if it is a viable answer. What problems would a person run in to in such an install?
Likely the experimentation may be the bigger problem. Some of the expensive systems use extensive trenching and buried pipes - tubes etc. I only vaguely know of them - have seen a few but never followed up on them.
Sorry about the confusion but I'm talking about a typical heat pump and not a geothermal heat pump. I would be making my own heat tube system that would be vented into the garage or out building where I would install the outdoor portion of a typical heat pump.
One of these days I'll place some drawing up of the system I'm planing, but until then I have a few questions.
first off, if your tubes are on a slight slop descending from the house, do you feel you need drain holes in the tube, or just let the condensation flow down the 100ft to the end and trickle out?
Also I have been thinking of placing an 80mm computer case fan at one end of the tube to try and make sure that the air always flows one direction, this is not to "force" air into the house, but to resist backward flow down vent pipes in hot water heaters and such. Any ideas?
AS I said before it will be the appliances in the house drawing the air in my earth tubes, (ei bathroom fan, dryer, gas hot water heater, fireplace ect) I'm just thinking of ways to make sure the air current is always in the right direction, I have thought of using the dryer type vent doors on the inside of the house, that would only allow air movement one way, but not sure how they would work with natural draw, compared to the forced air they are designed for.
I came across this system today. While I don't know much about earth tubes I thought of this thread. While it might not be useful info, it also might be useful... :-\ Just thought I would share.
http://na.rehau.com/construction/renewable.energy/ground-air.heat.exchange/system.overview.shtml
thanks homeschool for sharing that link!
Eco:
I'd really like to see your idea . I've even given my system a bit more thought and might post a picture as well. Your question about the weep holes is a good one. I've noticed that with the pipe I'm using, that if you didn't drill a hole in the low spot there would be no way that it would COMPLETELY drain. There wouldn't be much water in it, but there would be some. Another idea would be to not glue the tubes together that way it would eventually works it way out the cracks of the pipe.
The fan sounds like a good backup plan. trying to make it naturally draw air through the house and if that doesn't work turn the computer fan on. So if I understand you idea right. You want to use the heat that your appliances generate to create a draft out your upper earthtubes thus drawing air up ito your house from the lower earthtubes?
I gave a good amount of thought to the earlier posts about the need to have the pipes at different heights. The tubes that are in the back of house (bermed side) would be higher then the front side (solar collector side). The more I think about it the more it makes sense. The trick is that an insualted 20' skirting has to drain the water in the immediate area of the house so it's pitched down (even in the back bermed part of the house). So my thought is that it can go down for a bit then after the insulated skirting ends go up and out of the ground. Angle toward wind and done.
I've also given a bit of thought to angling the upper pipes toward the prevailing wind. So instead of relying solely on temp differentials to create the movement use the wind? Wind would blow in upper pipes pushing air down into the house. Coldest air would selttle in bottom tubes and exit. On the way out some heat would be recovered. Pic would explain better... lol.
Great thread.
I'm wondering why nobody directly mentioned the classic Hait camel's nose auto-reversing heat-exchanging convective system? He suggests laying both pipes side by side in the same trench once they leave the house.They rely on the difference in temperature between floor level (where the "lower tube" enters the house) and ceiling level (where the "upper tube" comes in), and between the house and the storage zone around it. He says the difference between outside temperature and inside temperature has nothing to do with it. I quote Hait's book:
If we can make the tube "breathe," then the air will take turns going one way and then the other. In this way the wave-front can be kept from reaching the interior and bringing the outdoor weather directly inside. Thus the earth tube becomes a counterflow heat exchanger just like a camel's nose! However, we do not want to use this as an excuse for shortening the pipes since the breaths are not all the same length. Air may still flow in a single direction for quite a while before it reverses, although it will probably balance-out over the entire year.
Later he adds:
The greater the temperature difference between the home and the earthen heat storage (thus the greater the need for heat or ventilation,) the faster the air flows. If anything tries to suddenly raise or lower the temperature the earth tubes will work harder to try to even it out again.
The over all effect is to moderate out the temperature differences which try to occur, just as with conduction.
If I understand this correctly, this means that in spring and autumn, when outside temperatures are agreeable, the airflow will be minimal. Will it be sufficient to ventilate the house (say at night when outside doors and windows must be closed)? A tight house needs permanent ventilation. It may be that an electric fan should be installed in the system and used if there is no air movement. Hait himself suggests that having fans available may be "prudent".
Hait says that earth tubes should always have a slope to them because they must function as heat traps. His tubes, both "upper" and "lower" always seem to slope downwards, away from the house.
Hait's idea is very attractive because it is entirely automatic in summer and winter - no need for thermostats and fans most and maybe even all of the time.
Bruce
I am more than a year since the last posting... But we all start some time. I am looking to break ground for my home next spring and have done a lot of research on this topic (including burring hundreds of dollars of sensors in the earth).
Radon was brought up. In the "old days", people used that kind of 4" flexible drain pipe that was easy to lay but had holes all over it. The ridges and frequent curves slowed down airflow and all the holes gave a lot of surface area for radon to get in... I actually know of an Earth sheltered home in my area (Michigan), built in the 1970's, that found they may as well have been smoking 2 packs a day for the past 30 years. Pretty bad situation. They said they were sad they had to seal the system because it had worked so well for humidity and temperature moderation, but obviously they couldn't let that continue.
A more modern design using sealed (or mostly sealed) PVC pipe with a larger diameter and as few turns as possible would work much better and shouldn't have any problems with Radon that it didn't cure by bringing in a lot more fresh air.
As for the humidity problems...
It is cold where I live, at least in winter. But in summer it can be hot and muggy. If I make my tube go deep as soon as possible (slightly upward but deep into the side of a hill), then the summer temp drops quickly (as my expensive research grade probes will tell you). If the temp outside is 95 degrees and 100% humid, and then is cooled down to something like 60 degrees by the earth tube (the earth temp is 51 degrees), then that would drop its humidity to 100% for that temp (fully saturated at 60 degrees). Then the air enters my 70 degree home and as it warms up, the relative humidity would immediately drop to 70%... Not ideal, and some dehumidification will still be needed, but better than 100% humidity from outside air. If my tubes are a bit longer, and I could some how get the air temp down to closer to my 51 degree ground temp, that air would warm up to 70 degrees with a RH of 50%, with is considered ideal.
As for the camel nose... I don't believe that the exchange is direct enough... I think I am better off keeping the tubes as far apart as possible and letting the earth moderate. I have read John Haits book (I actually own a copy), I am just not convinced. I am sure I will read it one more time before I build.
Anyway, like several others on this thread, I plan to take good data from my full sized experiment and will try to let the world know how it all worked out... Even if it is embarrassing. :-[
Oh yea, one more quick thought. Some people on here were concerned about the cool air falling and escaping out the lower air tubes when you would prefer to keep it in the house... Someone even suggested running a small computer fan just to keep that from happening...
The passive way to sort that out is a light, but stiff, flap over the lower air tube entrance. When air is coming up the airtube, the flap should be light enough to easily flutter out of the way... But when the air tries to reverse (seasonally or daily), the flap needs to be stiff enough to close the tube... Typically, the flap is hung so that in zero air flow, gravity would bring the flap down and close the pipe (the pipe opening should be parallel to the ground).
A friend of mine did this for the air intake into his wood shop and it works perfectly. He just taped a piece of thin transparent plastic over the opening and let gravity and back pressure take care of the rest. It is important that the "closed" air tube have a nice flat pipe end to rest against and that the angle is right so that gravity puts the flap in the closed position if no air is coming up in the right direction... Otherwise "slow" air may leak down without moving the flap into the closed position.
Barn fans do something similar with thin metal louvers that open when the cooling fan is on and close (too keep the heat in) when it is off.
I'm glad to see this thread resurrected, and anxious to hear how things are working for those that are farther along in there build. :)
I must say my knowledge of earth tubes has come mostly from this thread and the links provided here. Thanks folks!
I have been giving the earth tube idea a fair amount of thought and I have a few ideas I would like to bounce off you guys.
My build will be in the Ozarks so I have more cooling days to deal with than heating days. I think the point made about being sure to include the house it self as part of the system is a big one and it seems to me that thinking of the house as a heat separator only makes sense. If the house is closed up with no fans or HVAC systems moving the air around the heat will naturally separate. The lowest floor being cooler and high spots holding the warm air. It seems to me that 1 set of exhaust vents up near the ceiling for moving heat out in the summer, and another set near the floor for moving heat in for the winter would be the best solution. It was mentioned that a small fan or flaps could be used to prevent unwanted back flow. Here is my twist, why not add a simple solar heat collector to replace the fan. https://sites.google.com/site/glenssolarheater/ This is just an example, I think a big insulated box of rocks to make a heat sink would work better for our use and we probably don't need a fan. If you had your summer air drawn in to the house through earth tubes and vented high on the north side of the house then the exhaust tube exiting the house on the south side connected to the bottom intake of the solar collector. Its seems to me the collector would stay much hotter than the indoor air and keep everything moving. During the winter months have the incoming earth tube air connected to the collector to pre heat it further before entering the house low on the south side.
Clear as mud right! d*
What do you think? ???
Hello, I'm newcomer, and don't speak english very well, so forgive me please.
I realised this is an old thread, but most interesting, so I'd like to share one idea.
As we are trying to get a flyweel from winter through summer, why not to split it in two?
if for instance we divide the heat storage zone by isolating the north side of the ground from the south one, and arrange the earth tubes to operate independently.
the idea would be to have a set of permanent earthtubes collecting heat, and other set collecting cold.
another adjustable set would connect the house to the storage zones.
in a cold climate you can place the hot storage zone under the house, in a hot climate should be better the cold one.
that way you could possibly get more heat and more cold than with only one common storage zone.
the cold one always shaded, the hot one in the sun,
if you think about it, it has many possibilities (place of tubes openings, dedicated solar collectors, etcétera)
just an idea, waiting for your thoughs and knowledge.
cheers
Manu