Retaining Walls

[StoneHeartFarm]

Tubes through should work for you. Would be a bit of a problem here since any moisture in the tube would freeze in the winter. It's probably better to leave the moisture behind the wall than in the wall. But, you don't get that cold, so drain tubes should work. The problem would be having enough of them to allow the water to run off. I would also think you would need a run of drain tile to feed your tubes, so the water would basically get into the tile and then run into the tubes and through the walls.

Just to throw out yet another idea and I have no idea if its good, bad or would even work-- have you seen the new styrofoam blocks they are using to build basements? Basically a big styrofoam block with channels in it. You wire the blocks together run some rebar and fill with concrete.

If you used a product like that and then removed the foam, you would have a grid-type wall with vertical and horizontal bars that would leave good drainage. How do you get rid of the foam? I bet that firebug RPM could help ya. /w3tcompact/icons/laugh.gif

SHF

 

[GlueGuy]

I think the drain tiles behind the wall are still a good idea. In fact, I'd think they were required. If you look at the web site I listed earlier, they give installation information elsewhere on their site showing just that. I'd also throw in a geo textile to keep silt out of the tiles.

My understanding of the foam conrete forms is that the foam stays in there for insulation purposes. I think I saw them used on the Bob Villa web site somewhere.

The GlueGuy

 

[GlueGuy]

SHF,

Dug around on the net a little bit and found these links:

Foam panel foundation forms

Smartblocks

American Foam Products

General Information

The GlueGuy

 

[StoneHeartFarm]

You're right. Normally the foam stays. What I'm suggesting is the basic grid shape, and the foam was the easiest way I could think of to make it. Think of a retaining wall that looks like a big window screen, with holes say 6"x6". (Hence the blocks and then remove the foam). Plenty of space for planting something. Strawberries, flowers, etc. Excellent drainage. It WOULD need landscape cloth (the good quality stuff) to keep the soil from washing out during rain storms. But it should eliminate drainage problems and most probably frost heaving. Only problem would is I don't know how strong such a net would be. Probably strong enough though if they are building house foundations that way.

SHF

 

[mlmartin]

Thanks for posting those links.

Sometime in the future (when I get most of my _other_ projects done) I'll be building a greenhouse. I'm would like to store excess heat without taking up floorspace. I'm thinking of using the foam forms to build an insulated concrete foundation. I'd put perforated pipe on the bottom with some risers and cover the pipes with 1 1/2 inch stone. The risers would go to the roof peak at either end where thermostatically controlled blowers would move the hot air under and through the stone.

I'd set the blower thermostat a few degrees cooler than the thermostat controlling the power vents. I would think that a system like that could reduce the cost of heating dramatically.

Matthew

 

[StoneHeartFarm]

Matthew,

My upper body gets a good work out. Its the lower body that gets torn to pieces. This has blown my knees right out. I don't know how the old timers did it. Must have limped alot /w3tcompact/icons/laugh.gif.

I think I know what you want to do with your greenhouse. The gravel in the floor would basically act as thermal mass, getting warmed up during the day and slowly releasing the heat at night. Basically, you want to grab the hot air from near the roof and push it down into the gravel. This warms the gravel, which warms the greenhouse when the sun goes down. Is that about right?

I saw plans once for a greenhouse that was built out of old 2 liter pop bottles, filled with salt water and cemented together to form the exterior walls. The idea being that the sun would warm the wall during the day and it would radiate out at night.

I think your idea would work. I'm concerned about being able to blow the hot air down, though. If you can situate the greenhouse on a south facing slope, you might be able to scrap together a solar water heater, and use that to transfer heat from the outside into the gravel.

The foam box idea is solid. I've got 3" on the outside of my foundation. Use either pink or blue foam, but not Tuff-R or a similar product. Pink and blue foam hate water and will not absorb if. Tuff-R (according to what I've found on the net), actually LIKES water and that's why those products have foil and plastic vapor barriers on them. One warning about foam on foundations, though, cover it on the outside, even below grade. Two reasons, 1. mice love to tunnel down and nest in it. (I've heard of a fix for that), 2. Grass and weeds send out underground runners that will bore right through the stuff. Any little openings lets water get through and that makes a channel for your heat to follow on the way out.

I've come, through all of this, to view heat a lot like water. It will move from a place of high pressure (hot) to a place of low pressure (cold). Water flows downhill, heat flows uphill. Water will leak through any little crack and so will heat.

Let me know how this works out for you. There may be a greenhouse in my future too.

SHF

 

[mlmartin]

I don't think my wife would like a soda bottle greenhouse. I don't think I'd like the looks of it, either.

You understood what I'm trying to do with the greenhouse and stone thermal mass. Getting the warm air under the stone is the important part. I can start storing heat in October and have the whole mass warm by December, when we typically start getting freezing daytime temperatures. If I have to run electric heat in January and February, I will. I'm not trying to maintain 68 degrees, since most of my tropicals will survive 45. It shouldn't be too expensive.

Thanks for the pointers on foam. I'm inclined to use the foam concrete forms and then following the manufacturers guidelines on interior and exterior protection. From what I've read, I should be able to get close to R-20 through the foundation walls. I'll probably pour a concrete floor at the bottom of the foundation. It will be easier to insulate a level slab than compacted fill.

Having a five sided concrete box will also help keep water out of the stone. I'm going to put a sump pump in, just in case. I'll end up with about 3 cubic feet of storage for every square foot of greenhouse.

Matthew

 

[StoneHeartFarm]

Matthew,

I had some problems with the pop bottle job, too. You really can't see the bottles, because they're covered over with cement. But, just knowing 1/2 of my wall is hollow plastic filled with cement eating salt water was enough to turn me off.

The foam blocks would be the easiest method to build with. They make a much neater poured wall that what you or I could probably get by building forms. The only advantage a straight poured wall would have is that all of the cement could be used as additional thermal mass. With the foam blocks, you pretty much lose the cement as mass.

Will the back wall (North facing) be cement or frame? If you use cement you can paint it black and use that as additional mass. Basically, I'm thinking the more mass you have that can store heat, the longer it will radiate when no heat is being gained.

The slab is a two edged sword. It will keep water out, but also keep it in. The sump pump is a good addition. What sized pipe are you planning to run through the gravel bed?

SHF

 

[mlmartin]

Easy is good. In the time it takes to make a set of concrete forms, grease them up, use them, tear them down and _then_ attach foam to the concrete you could have erected the whole greenhouse/w3tcompact/icons/smile.gif As far as losing the concrete as part of the thermal mass, I'm planning on a 12' X 18' greenhouse. The percentage decrease in thermal mass (under 10%) is probably a fair trade for the extra R-10 on the insulation.

I'm planning to use R-3 twin-wall polycarbonate for all of the skin, even the north side. It will be in a protected area (in front of the new barn) with full southern exposure all winter long. It's really and ideal location, with water and power. The only problem is that I have to tear down the old horse shed that is currently on the site.

I haven't done all of the calculations, yet. I suspect that I will be using two six inch risers and a six inch manifold on each end. I'll use four inch perforated pipe as runners spaced as closely as possible. The runners will be interleaved to cover as much area as I can.

The guy in the next cube is a thermal engineer. He'll be helping me to size the pipes and blowers.

I'm planning to use aluminium flashing as a UV/root protector for the exposed foam. It should start behind the twin-wall, cover the foam and extend 10 inches into the soil. That should take care of any grass roots.

Matthew

 

[GlueGuy]

Well, you can use gasoline... /w3tcompact/icons/crazy.gif

When I wanted to make a "thing" (like an intake plenum, or other odd shape), I would carve out some styrofoam in the shape that I wanted, then cover it with fiberglass/epoxy (NOT polyester resin!!). I would remove the foam by pouring in gasoline; which melts the foam.

It was then easy to clean up the part with a little sandpaper/dremel whatever.

Not sure that would be practical on a retaining wall...

The GlueGuy