Pond Boss Forums GENERAL QUESTIONS Pond Boss Anyone have any experience with a trombe wall?

I'm probably going to build a pole building to raise fish indoors in a recirc system next year -- possibly as early as next spring. Anyway, I'd like to make it as efficient as possible and use passive heating in the winter as much as possible.

I'm intrigued by a south facing trombe wall for winter.

For those of you that don't know what a trombe wall is, it's typically a block wall painted black which is behind a wall of glass or glass windows. The space between the windows and the wall is only about 4 inches. Allegedly the wall heats up to 140 to 150 degrees in the winter in full sun. There are a set of vents on the top of the block wall and near the bottom of the block wall. The heated air from the sun and blocks rises naturally and exits into the main building through the two top vents. The cooler air near the floor of the building on the other side of the wally enters the glass side which creates a rising current on one side and falling current on the reverse side.



http://en.wikipedia.org/wiki/Trombe_wall

I will insulate the building as well as possible with sprayed on foam (hired), and foam block footings in the ground.

Thoughts?

Cecil are you talking a constructed, block wall, or a poured concrete wall? I wonder if the poured wall might provide a greater thermal mass, since blocks are hollow?

Cecil, these walls work really well in a mild climate with lots of sunshine. In this part of Va. it is mild in the winter but is usually cloudy much of the winter so they are not very practical here. It would not matter if it is a poured or block wall as the insulation will give you the heat. The sprayed on insulation is much more expensive then the regular type. Insulating the floor with foam insulation is a really cost effective method. If you plan on living in your house for a long time it could be a good investment. You can find out the number of sun hours from a weather source. Good luck.

Block wall.

I respectfully disagree. My log home which has a lot of glass facing south along with a cathedral ceiling will get into the 80's in late fall and early winter if we leave the blinds open. Of course it's less so in mid winter but every little bit helps.

This is a pole building though. Not my house.

Are you going to fill the blocks with concrete? I think a solid mass would tend to radiate a little residual heat even after the sun went down, better than a hollow wall would. Just a thought.

Cecil, does your home heat up like that on cloudy days? I have a greenhouse that will get over 100 degrees on a sunny day but is about the same temperature as the outside when Sol is missing. Tony a solid wall will generate more heat but is not so cost effective. Solar was really popular here in the eighties but nearly all of it has been taken out here.

I agree, put rebar inside the blocks and fill 'em with concrete. Foam under the floor, and make sure the foam on the inside of the building is protected from getting wet. Instead of 3 layers of glass, they are now making triple pane insulated windows.

Don't forget to insulate the roof, but leave an air gap between the roof and the insulation.

Nope just on sunny days but i wouldn't expect it to. It's all about using what's available to reduce energy costs.

Can you expand on foam under the floor? Never heard of putting foam directly under tbe floor. On the sides yes but under tbe floor no.

Yes, a lot of folks are insulating under the floor. I think it started when radiant floor heating is installed. Seems like more and more, it is being used. I don't have a drawing of it handy right now, but I believe they put down like 4"+ of insulation.

I like your idea. How about a possibility of a circulating fan for an extra assist. Have you seen the pop-can heaters? Seems like a very similar idea. I always wanted to experiment with it and see where it would lead.

Possibly a useful link for you:
http://www.naturalspacesdomes.com/bear_creek_dome/test_results.htm

Cecil, as you progress with your plan keep me informed on what kind of and how much glass you will need. I worked in the glass business for 36 yrs and still have a few contacts. Glass is cheaper to make from scratch (mostly sand) than it is to recycle so there are literally tons of glass tossed into the dumpster every yr. Also when you get started I'll be glad to give ya a hand.

Cecil, what part of my post do you disagree with? The floor is insulated with rigid Styrofoam. 2 inch thick is best. I really like a wall of windows but they will usually be a net loser where heat is involved. You have a short day and glass is not nearly as good at retaining heat as an insulated wall.
'

Thanks Bob. I may have to look you up.

Can the foam be put under gravel which is what i was going to do? Seems like it might not work as well as concrete.

Circulating fan is what some use. Definitely an option. I'll have to look up the "pop can heaters."

As far as radiant floor heat that is what the saltwater shrimp growers that i know use. They use radiant floor heat to heat their Intex pools they use to raise the shrimp. The pools make full contact with the floor. After they get all their pools heated the heated water keeps the well insulated building warm. Not perpetual of course but more efficient thsn putting heaters in the tanks.

Kenc,

I misread your post. I have tendency to read too fast. I thought you were pooh poohing the concept which you were not.

As far as widows being a net loser of heat aren't there high tech windows that are far ahead of others? Seems to me I've also heard of ways to insulate the windows at night? I do know I've seen economical shutters to cover the windows in the summer that are made for trombe walls. The overhang is supposed to block direct sun in the summer also.

I don't think gravel would work over the insulation, but I will defer that question to any builders out there that might be able to answer it. I just assumed you were going to have a poured floor, my bad.

I still might and would prefer that. Just thought I could put money somewhere else if concrete wasn't needed. I've seen some gravel bottomed greenhouses that seemed pretty decent.

Cecil, there are windows that are much better then others as far as heat loss is concerned but their cost is much,much more then windows that are readily available. You seem to be like me as you want to get the most bang for your buck. A window is always going to lose heat in any situation over a solid insulated wall. You can use the gravel over the foam insulation, the trick is to use rigid insulation. You should do a concrete buffer at the door ways and then pack your gravel. I would use crush and run and level it with a tampering machine you can rent. You may want to put 6 inches of stone instead of the regular 4. Good luck.

I'm confused here...I thought the whole purpose of this project was to allow the sunlight, via the glass, to heat up the concrete wall. Then, convection will cause the warm air that is trapped between the glass and the wall to rise, where it will exit through an opening into the "working space" of the building....as it does so, cooler air from the working space will enter from an opening at the bottom of the concrete wall, where it will be heated by the sun and begin to rise....completing the cycle?

If this is true, then the glass in question will not be in "contact" with the working area....there will be a nearly solid wall there, with openings at the top and bottom. How much heat loss through the glass can there be?

I'm thinking that there should be a shutter-type vent at the top and bottom of the wall, which could be closed once the sun went down and the concrete wall stopped radiating heat...then opened again once the sun had risen.

Matter of fact, I once had a cold-frame that used a mechanically actuated, thermostatically controlled, hinged lid....when temps inside the cold frame reached a pre-set number it would begin to open the lid so the plants wouldn't bake. And when it cooled off, it allowed the lid to close, trapping what heat remained, inside.

I'm thinking vents at the top and bottom of the concrete wall, with thermo actuators....no wiring needed, for hands-off, automatic operation...close the shutters after the wall cools down, and heat loss through the glass should be negligible?

Cecil,

Back in the mid-80s I built a very energy efficient home. I put a two story sunroom on the south side of the house. I used high quality casement windows on the second floor, and sliding glass doors on the first floor. It was separated from the main living space by double sliding glass doors. I calculated the roof overhang so that there was no direct sun coming in mid-day for most of May, June, and July. In December, the noon sunlight came well into the main part of the house.

I had 2"x6" pine boards milled with rounded edges, which we prefinished before putting them down over joists we prefinished. We left about 3/8" gaps between the floor deck boards for air flow. We also put a large whole-house fan in the second floor ceiling to suck cooler air from west side basement windows, and north-side first floor windows. That saved a lot on air conditioning.

The sunroom was built on top of 4-5 foot deep concrete walls over the footers. We filled the space to within about 4 inches below the top of the walls with gravel, topped with 4-inch foam insulating panels. That got covered with 10 inches of concrete. I had the finishers trowel grooves in to make the floor look like terrazzo tile. If the floor were to settle and crack, it was my hope it would be in these grooves. It never did crack.

Anyway, it provided a significant amount of heat in the winter, and with the big exhaust fan, it assisted with cooling in the summer when we weren't using the AC.

Good luck,
Ken

Cecil,
Several months ago an Architect gave a talk about a new building that used this system. It was a multi-million $$ building and a much more sophisticated system than you are looking at. But the pros and cons are generally the same. Going from memory here are some thing to consider.

Use dampers top and bottom. Their system automatic opened or closed the dampers when the temperature difference was +/- 5 degrees or hit the desired temp IIRC.

Provide outside vents on top and bottom so during the summer you can release the heat that will collect inside the cavity without sucking the cool air out of your space.

How are you going to clean inside? They used a 24” wide space with a door from the side. (I’d need 36”).

The one they presented was two stories, 80’+ long double glass wall that used the interior stone floor as the thermal mass. I have also heard of ones where solar hot water systems are in this space also. You can also have small windows in the block wall for better daylighting inside.

Looking forward seeing how this turns out.

Tony, I was talking to Cecil about windows in general. The wall is a different animal. The reason that filling the block is no big deal is that the empty air space is a better insulator then solid stone. I am still with chemo brain but if memory serves me correctly, a foot of wood is equal to one inch of insulation. I think it is 10 feet of stone to one inch of insulation. This is why you need to load up on insulation. Some people use the glass blocks to make the inside brighter but this hurts your heat generating ability. I have built several homes trying to help out on the heating but the most cost efficient way is to insulate, insulate and insulate.

No problem Ken, just wondering if I understood the concept correctly. If I do, (which is questionable at this point), whatever glass or windows are used won't even be seen from inside the structure, and will not directly contact the inside of the work area. That's why I can't understand why they would lose that much heat.

If there was no vents/shutters to stop circulation, I think it would lose heat in main building on non sunny days. Cold temps coming in thru the windows would sink and enter the main building thru the vents and reverse its purpose.