Retaining Walls

[StoneHeartFarm]

GlueGuy,

Hadn't thought of gasoline. (Of course, I've never tried to store gasoline in a foam container.) /w3tcompact/icons/wink.gif Actually, that's a pretty clever way to make a casting. Hmmm, I gonna have to kick that one a around for awhile. Every now and then I have a need of some small piece of technology like that. Making shapes is probably the single most important skill a human can have, technology wise. If you think about it, everything man builds requires making shapes. If you can't make shapes, you can't build, only repair.

Anyway, the open grid idea for the retaining wall sounds interesting? The same type of thing can be accomplished with precast blocks (I've seen them made from chimney blocks) cemented together, but I don't think you would get quite the same strength out of them that you would get from a poured grid.


SHF

 

[StoneHeartFarm]

Matthew,

What are you going to use to blow the air down into the tubes? I think there are standard blowers available for 6" tubing. Will you be using any solar? A DC blower could probably run off a small solar panel. The advantage is that the blower will only run when there is sun. But, since that's also when your greatest heat gain can be expected, it seems the two would go hand in hand.

Also, have you considered how you will prevent the heat which has been transferred down the tube from simply coming straight back up the tube (chimney effect/thermosiphon) when the temperature falls?


SHF

 

[mlmartin]

I expect that I'll be using two squirrel cage blowers, one at each end of the building. I have 20 amps at 220V available at the building site, so I'll be using that for powering the blowers. I'm going to use two thermostats to control the blowers. One near the ridge to turn them on when there is enough heat to be worthwhile and another either in the rock bed or at bench level to prevent heat collection when it's not required.

Since the risers will be connected to manifolds at the bottom of the storage, there will be little thermosiphoning. The chimney effect should be minimal as long as the greenhouse vents are closed. If it becomes a problem, I'll install counter weighted dampers that will be opened by the air pressure from the blowers.

Matthew

 

[StoneHeartFarm]

Matthew,

Sounds good. Keep us posted. I'd be interested in seeing the rough sketches when you get to it, and of course pictures of the construction! /w3tcompact/icons/wink.gif

SHF

 

[mlmartin]

Thanks for the questions. They forced me to think through some things that I had been putting off. Right now it looks like the greenhouse is going to be a Spring 2002 project.

Matthew

 

[GBear]

Sitting here at my desk, I can see out the window and part of a 400 foot retaining wall made from Allan Block, AB3’s and AB12’s. 65 tons of block and 125 tons of rock. I built it without help and did a lot of it by hand, with a mattock, wheelbarrow, hammer, and chisel. The Kubota and a diamond blade in the Skilsaw helped too.

One of Glueguy’s links was Allan Block, which is what I used. Each block weighs 80#. It is flexible construction and no concrete or steel are required, perfect for the owner/builder. Water drains through the block, but in some parts I ran perforated drain pipe in the gravel behind the wall to daylight.

I actually put the last cap in place last week. I started last September, but I chugged along at a pretty consistent 20 or so hours per week on this huge project. It is some classy looking stuff. It is as artsy as it is functional and I got pretty creative with the several sets of steps, curves, tiers, planters, and turnouts built into it. I knew nothing about masonry or retaining walls when I started. Look at that site; it’s where all my ideas started. You can download all kinds of instruction manuals in PDF format and pictures at both the AB and Keystone sites.

Nothing against boulders, but the block option has a totally different look, can be integrated into the landscaping, and can do a lot more than just hold back the dirt.

 

[GlueGuy]

The poured grid would be the strongest, but without holes to let out the water, it would tend to "tip". If you ever go that way, I would like to see what the plans look like.

We have a couple places where we want to put retaining walls. A couple of them are relatively short, but one is going to be a big job. The big one will probably end up being the alan block; not decided yet on the two short walls...

The GlueGuy

 

[MarkV]

Mlmartin,
Your greenhouse project made me think of a passive solar heat/cooling system I have always wanted to try. I see that you have a backhoe and the system I was thinking of uses a "U" shaped ditch, below frost line, with standard culvert pipe laid in. The idea is to end up with an intake and outlet of the culvert loop into the building. The intake has a small blower to move air through the culvert and the air is conditioned by the constant ground temps. If I remember right the gound temps below frost line mantains at 68 year round. May not be practical for your site, but I bet your thermal engineer friend would have a handle on sizes of pipe and amount of run required. Plus it could be fun to dig that trench./w3tcompact/icons/smile.gif

Another passive solar system using culvert pipe I saw involved capping the ends of several pipes, filling them with water, painting them black and standing them where they would get sun. This provides a large mass, in a relatively small space. Guess the down side would be that it would work just as well in the summer when you didn't want the heat gain./w3tcompact/icons/frown.gif

MarkV

 

[StoneHeartFarm]

<font color=blue> if you ever go that way, I would like to see the plans </font color=blue>

GlueGuy,

Actually, I was kinda hoping you'd have some ideas /w3tcompact/icons/crazy.gif

SHD

 

[StoneHeartFarm]

MarkV,

Ground temp will depend on the location and the time of year. The ground temp is like a fly wheel, warmer in the fall (after summer sunshine) and cooler in the spring (after winter). I thought about the tube heating plan, but, this far north the ground temps don't rise enough to get an acceptable gain. So, the system would need some kind of air to air heat exchanger that would trap the warm air inside the house. Otherwise, heat from the house would be warming the ground since heat likes to move from warm to cold.

What the tubes are good for is cooling. The ground temperature is almost always lower than the air temperature, except for a short period in the spring and another in late fall. Here, we call them "cool tubes" and I have 2 built into my new home. They are made from 6" S&D PVC and tie into the crawl space approximately 11' below grade. From there, they rise diagonally along the main floor rear wall and surface at each rear corner of the house. When finished, they will have "candy cane" tops with screens and screw on caps. The idea is to cool the air in the tubes where it is in ground contact. Cool air falls and that will create a negative pressure at the top, which will draw warm outside air into the tube, to be cooled by the earth contact. If it works, it should "power vent" my crawl space, if it doesn't...well, I needed a couple of extra vents to meet code anyway and there was basically no other place to put them. /w3tcompact/icons/crazy.gif

Somewhere around here I've got a book that charts the annual temperature change and gives the high/low point by month. If you're interested, I can try to dig it out and post the cycle for you.

SHF

 

[DocHeb]

Take a look at this site for a solution to water retention behind walls:

http://www.americanwick.com/vdapps.html

 

[mlmartin]

MarkV,

Here in central Massachusetts the temperature below the frost line is never that warm. I've given thought to using a similar scheme for air conditioning. Ideally, having a house with a long upward slope by the house. Bury multiple clay/concrete culverts the whole length of the slope. Add input vents with screens at the uphill end. Put a dry well at the downhill end and then take the air into the house and distribute as required. You would end up with a supply of cool, (and more importantly) dry air. The longer the run, the dryer the air.

As far as additional heat storage is concerned, I've gotten myself convinced that I will have pleny with 3 1/2 cubic feet of rock per square foot of greenhouse. If I do anything, it will probably be to insulate the north wall.

Matthew

 

[StoneHeartFarm]

Matthew,

I understand the dry well, I basically did the same thing with my cool tubes, making a gravel filled sump at the bottom. Is there a reason you would use clay/concrete culverts as opposed to large diameter PVC?

SHF

 

[mlmartin]

Clay or cement culvert sections will transfer heat more quickly. The inside surfaces are also rougher than PVC giving more surface area for condensation. We're talking the about getting the last few percentage points of performance. I wouldn't rip out PVC to replace it with cement/w3tcompact/icons/smile.gif

Matthew

 

[StoneHeartFarm]

Matthew,

Okay, that explains the dry well, since the joints in the clay pipe would tend to admit moisture during a heavy rain and a drywell would probably have the capacity to remove it. /w3tcompact/icons/smile.gif

Sounds interesting. What are you going to use for the riser? (The stand pipe that exits the ground at the end.) With an up hill slope, you will get natural gravity feed of cool air during warm weather. Unforntuately, during cold weather you would have the opposite effect as the warm indoor air flows outward. What is your plan for closing the loop in the winter?

SHF

 

[mlmartin]

I'd put in a drywell with PVC as well, since relative humidity around here can be 90+% fairly often in the summer. You have to have a place for the condensate to go. Of course if you have an uphill grade to your house you can dispense with the dry well, but at the added expense of using a blower to pull the air up into the house.

I'm not actually going to implement this scheme, since the grades here don't lend themselves to it. I'd use a UV stabilized ABS risers with a couple of 90 degree elbows to point the inlet towards the ground. Removable end caps should take care of closing the inlets in cold weather.

There is another variant on this scheme that uses underground heat storage and heat pumps. The idea is to bury pipes well under the frost line to carry water for the heat pump. In the summer, you use the ground temperature water to cool the condenser side of the heat pump and put the heated water back into the ground. In the winter time you do the reverse. The heat pump extracts the heat from the water and puts the chilled water back into the ground.

If you have enough area you can really save on heating and cooling costs. I'm not sure that it would be economical to do unless you were raising and existing grade by 8 feet or more for some other reason. A few thousand feet of 1 inch black poly pipe is cheap enough, but digging down that far isn't.

Matthew

 

[StoneHeartFarm]

Sound's right. Now all we have to do is talk somebody into trying it. /w3tcompact/icons/smile.gif

SHF