PSP underground building

[Christopher(Guest)]

I am hoping to build an underground house using the methods of Mike Oehler, but I have one concern (beside code evasion - topic for another day). Moisture in underground homes seems to be a problem. I am worried that water in the summer air will condense on my walls, ceilings and worse on the carpeting of the house, because there will be no insulation between the wall and the dirt. Dow blue board insulation is outrageously priced, so I am trying to come up with a cheap alternative. I was thinking of duct taping 2 liter plastic bottles side by side and laying them one row at a time in between two sheets of plastic as I install the wall boards and tamp in the dirt (shoring-plastic-bottles-plastic-dirt). Does anyone think this will give me enough insulation to stop the condensation and keep my walls at close to the same temperature of the air in the house? Anyone try something similar or have other ideas? Also could I bury this under my floor? Any ideas would be much appreciated.

[glenn kangiser]

I don't think it will work, Christopher, - You won't get enough compaction outside of the bottles and leakage of water will probably be worse.  Condensation has not been a problem.  The boards with the outer vapor barrier seem to prevent condensation just fine. A warm fire in the winter keeps the place plenty dry.  Deviating from Mikes plans can be more of a problem as he has things pretty well worked out for reasons and if you deviate from them you are really experimenting on your own.  Plastic doesn't like to be pushed around with tamped dirt so if not tight against something solid it will probably tear - Mike goes into pretty good detail on how to do this properly.  I sometimes use 30# felt (tarpaper) to protect the plastic from rocks when backfilling.

The earth is what tempers your inside air.  It keeps you cooler in the summer and warmer in the winter.  You don't want to insulate yourself from the earth in most cases -exceptions being very cold areas.  French drains can take away excess moisture if that is a problem.

I don't know what area you are planning on doing this in but each area has it's own considerations.  The uphill patio is important as well as drainage.  Mike now recommends a EPDM liner over the roof for better longevity and durability.  It is expensive though.

The carpet if put over dirt is protected by a 6 mil vapor barrier under it.

[Christopher]

Thank you Glen for responding. As I said my concern was moisture in the (humid) summer air coming into contact with walls whose temperature is below the dew point and therefore condensation occurs. Rob Roy said he had some condensation in his homes near the footings which were not insulated. He built with concrete and concrete is a much better conductor than wood, but I was concerned. (I am convinced Mike's methods will keep water from getting in.) I guess we will have to see about the condensation problem. I suppose you live in one of those beautiful areas of CA where you have never had Hazy, Hot *and* Humid. My friend was from Simi Valley, and he never experienced humidity before coming to visit me in the summer. You said you put 30 # felt between the earth and the plastic to protect the plastic, did you attach the felt to the plastic or just pull it up and attach at the top and infill.

I was planning on using the EPDM layer on the roof and put 2 in. of sand on that and then put plastic on top of that. I figure most of the moisture will be blocked by the plastic (Rob Roy does this for his earth roofs).

I am going to be building in a more northern climate (southern NH), and I was hoping to cut down on the amount of earth on the roof by using some type of insulation. I would like to do ten foot spans. Rob Roy uses these numbers to determine typical load: saturated earth: 10 pounds per square foot per in.; Crushed stone 10 pounds per square foot per in; heavy timber framework 15 pounds per square foot. On top of this I will have to add the snow load for my region. I am hoping to use the logsol timber jig to cut all my own planks (I have almost 100 acres of trees).

I read Mike's book (borrowed from local library) awhile ago, and did some drawing and loved his method, but kind of abandoned the idea from fear of big brother, but I am now at the point of thinking it best just to post my land and wait for the town to come armed with a search warrant. I will be buying the book and the videos in the next month or so. I hope to start building this summer.

[lodestar]

You might like to check out the passive annual heat storage ideas...at Rocky Mountain Research.  I umbrella'd much of my underground house...and it is built totally of wood...cedar posts, norway girders and rafters, 2x6 T&G pine sheathing on walls and roof.

http://www.earthshelters.com/Ch_1.html

[glenn kangiser]

The plastic you don't want to attach at the top -  leave extra up there and try to keep it pulled up as you go - do alternate sides partially to keep side loading even.  The felt I just put loose in over the plastic then backfilled behind it to hold it in place.  

Use 1 1/2" boards on side walls with 8' spans -3/4" will work on 4'  spans - add exra post or supports as needed or the sidewalls will bow in when you backfill.  A smaller post will work for interstitial supports.

[glenn kangiser]

I was hoping you would post on this Bruce.  I know you know about this stuff in the colder areas.

[Ailsa C. Ek]

I read Mike's book (borrowed from local library) awhile ago, and did some drawing and loved his method, but kind of abandoned the idea from fear of big brother, but I am now at the point of thinking it best just to post my land and wait for the town to come armed with a search warrant. I will be buying the book and the videos in the next month or so. I hope to start building this summer.

Ah, I am enlightened now.  We are looking at buying in northern MA/southern NH and had pretty much given up on building due to sheer expense.  I'd love to have a go at one of Mike's houses, but am loathe at this point in my life to move far enough north that I'd feel safe trying it.  I hadn't considered the "Oh, the heck with it, do it anyway" approach.

Good luck with it, I hope it works out.  (Where in southern NH, btw?  We're looking at Salem, Pelham, Windham, Nashua and Hudson, and had been looking at Plaistow, but the taxes are too high.)

[Christopher]

Bruce thank you for responding. After looking at the link you provided, I believe that everything would work exactly as the site maintains. (I will be reading the book soon) Unfortunately, I am trying to balance efficiency and comfort (two areas that Passive Annual seem to excel) with construction cost. Maybe I should not even use the word balance. I want to build the least expensive home I can, and have it be relatively efficient and comfortable. If I can maintain a constant temperature in the home with a masonry stove, and keep the condensation to a minimum on a humid day in the summer, I will be happy. My interest in alternative building techniques is driven by cost. I am not interested in spending a little more or less than a conventionally built home, in order to get more efficiency and comfort. I am interested in not having a mortgage, and not having to make a ton of money. Therefore, the attraction to the PSP technique.

That said I would be interested in using these ideas for all the earth sheltered walls, if I could find something to insulate with that was not $29 for 32 sq ft at R-10 (the cost of Dow Blue board 2 in. at Lowes). Do you know of anyone who ever did this using something else for the insulation. I mentioned empty 2 lit. bottles in my original post. Since they would be away from the wall and not cause leaks could they work, or would the weight of the earth crush them and kill any insulative qualities? Maybe I should have named the topic alternative insulation that can get wet and be cheap?

[Christopher]

Alisa,

I have some land about 20 miles south of Keene NH. The property taxes are outrageous, but I do not think they can take your land for non-payment. They can only put a lean on the property. The person who owns land next to me, inherited his land and house from his father, who owed property taxes, so he is unable to sell the land without paying the back taxes at the time of sale. However, he was able to inherit the property.

As for just building and letting the town come after me, I really think it is the only way to deal with the local planning board. I used to think I should just be nice and try to get along. This might work for some people that are trying to build and are willing to get a mortgage, but I just do not think it will work for what I am trying to do. I want a safe, somewhat efficient, inexpensive shelter/home, that I will not have to spend the rest of my life paying for. This type of home is not what the code is written for.

[glenn kangiser]

Christopher, in cordwood construction they use a mix of sawdust and lime for insulation- lime repels the bugs and vermin - It would require that you make another wall inside your PSP wall - PSP to stop moisture- maybe another layer of plastic inside then fill from the top - keep the insulation on the inside to keep it dry.  Just an idea -  Maybe plastic or burlap coffee bags of the same on the ceiling - they used it in a circa 1920 restaurant  cold storage room.

It may sound crazy - what's new??

[lodestar]

Christopher...I built my 700 square foot home for 3500 bucks back in 1984.  You can check the link under my profile for some pics.

Insulation is trapped air.  How you trap that air is up to you.  Making an umbrella with 60 mil rubber can be very effective...what you place between the rubber and the building could be clean, dry sand...it could be dry cellulose in one of it's many forms (if you use straw, or some such stuff, I'd be certain to mix diatamaceous earth in amongst it.)  You could gather styrofoam packing material...or bubble wrap...Mass should be part of the concept.  Insulate above the mass.

Regardless of what material you use, I'd seriously consider using the umbrella method.  Make certain that you have a dry heat storage medium next to the building...The tubes are the least important part of the whole plan, to me.  I don't have them.  I do have 4 inch plastic pipe that snakes through the uninsulated earth, 6 feet+ below grade, which brings air low into my pantry.  I have a 4 inch vent pipe that exits my pantry high.  It keeps the place cool in summer or winter.  I have a 6 inch plastic pipe which feeds outside air to the draft of my massive woodstove to avoid using the air inside my house to combust the fire...it also pressurises the house.

We use very little firewood.  Solar siting is important.  I don't have the south of my house buried...but 3 feet of the southern wall is below grade to balance forces.

Good luck to you.

Don't let anyone tell you that you can't do anything.

[John Raabe]

Most interesting Lodestar. A well thought out project and inspiration to all...




Am I correct that this is your place?

[lodestar]

Thanks John...that's an old photo!

Now we use the roof to grow our squash crop...




This is what it looks like after a snow storm!

[glenn kangiser]

Nice squash, Bruce.  Do you use compost  or anything on it?

[lodestar]

Each spring I break open some more strawbales on the roof, make mounds from the compost pile...about 6 to 8...and plant a squash plant in each.  The leaves shade the roof during the summer, keeping the house cool.  After harvest, I break open some more strawbales and shake them around on the roof to tuck is in before snow flies.

[lodestar]

My thinking is that wet organic material pretty much weighs what water would...62.4 pounds per cubic foot, which is less than half of what earth soils could weigh.

[Christopher]

Bruce,

I love all your buildings (at least the ones I found on the web). Your homestead is real inspiration to me. I do have a few questions if you would not mind answering them.

I was wondering if you could give me an idea of what the layers of your roof are? Did you use plastic, then dirt, then insulation, then plastic, then more dirt?

Did you go the full 20 ft out and insulate/water proof the ground?

What R value did your insulation have?

What did you use for water proofing?

I am sorry to ask so many questions. I have the book on passive solar coming, but I was curious about these specifics.

BTW your squash garden is brilliant.

[lodestar]

My posts are white cedar from near here, the girts and rafters are norway from our land.  Then I sheathed the whole building with tongue and grooved 2x6 pine.  Walls and roof.  Then I coated the building with coal tar...not asphalt...but coal.  I did the same to the bottom of the cedar posts before emplacing them.  Then I used 90 pound roofing felt on walls and roof...then one inch of Extruded polystyrene on the walls and two inch on the roof...then several layers of 10 mil black poly on the walls and 60 mil rubber on the roof.  A number of years ago I dug out the east side of the house and built the pantry...at that time I umbrella'd the east and west sides of the house out about 10 feet with 60 mil rubber.  We hope to dig up the west side of the house and add a laundry/bathroom and will bury it again, letting the umbrella go out another 10 feet from that.  I have 10 mil poly that goes out and away from the back of the house about 2 feet below grade...and also in the front.  I didn't read about the PAHS until after I built my house, but think the umbrella idea is fabulous and over time I'm incorporating a bit of it into my design.  Starting from scratch I'd follow the ideas much more closely.

Whatever you do...if you heat with wood, bring in outside air to pressurise your house and to provide combustion oxygen for the fire.

I wrote back and forth to Mike Oehler as I was designing and building my house.  I used some of his concepts and consider him a friend.  He's an odd bird...but I've been called that very often, too.

Amended to add that I have as much as three feet of organics on my roof...they keep breaking down, and I keep adding more.  Most of my mass is in my house.

This is from last year..


And the first snowfall this winter:

[Sassy]

Beautiful!