best tromb wall color

i can't use black or grey (i married...).
best to paint it dark blue or dark red or dark green?

I don't think there is anything better than black, but I think that besides that it really doesn't matter so long as it's as dark as possible.  If you were planning to use the light inside to grow plants at all (which is unlikely since a trombe wall is set up to collect too extreme heat for most plants), I would say dark red, since red reflects out in a spectrum of light that plants most appreciate.

We've got one trombe wall house and a couple of other rooms with half-trombe-walls, at our school They do work well to keep a space warm!

You only have to see the dark colour from outside. Of course you don't paint the interior wall dark. I might agree with your spouse that a big black wall facing out can make a house look ugly. But it really does make the room warm!

One mistake I saw with early trombe walls in my region was some of them had only small windows into the room. That made the room very dark and depressing. At our school we make sure to keep nice big windows in the trombe wall, so the room is bright enough.

Also I don't like the traditional trombe walls, that are sealed, and you have to operate vent holes in the top and bottom every day. Instead, at our school we keep the trombe wall about 6 nches (15 cm) away fromt he glass, and we don't seal it. That way we can reach inside to pull a curtain or clean the glass. I like that much better. Then we don't have to operate vent holes, which people always forget. For the coldest part of winter we can operate a curtain between the glass and the wall.

Our region has extremely cold winters but sunny, and various forms of passive solar heating work very very well to keep the houses warm.

At our school we make sure to keep nice big windows in the trombe wall, so the room is bright enough.  

Also I don't like the traditional trombe walls, that are sealed, and you have to operate vent holes in the top and bottom every day. Instead, at our school we keep the trombe wall about 6 nches (15 cm) away fromt he glass, and we don't seal it. That way we can reach inside to pull a curtain or clean the glass. I like that much better. Then we don't have to operate vent holes, which people always forget. For the coldest part of winter we can operate a curtain between the glass and the wall.  

Rebecca.  I like what you are saying here, a lot.  I'm having difficulty visualizing it exactly though your photos are great.  I do understand that you have windows in your wall to let light into your room, and that your Trombe Wall is 6 inches from the exterior glass.  Do you have glass on the light giving windows (and if so they must be operable?)?  It seems, from the photos and from you writing the part about not sealing your Trombe Wall, as having these windows permanently un-glazed?  You say you can clean the inside of the Trombe Wall glass in that 6 inch gap, so you must be able to reach far enough to do so from these windows.  What % of the wall is light giving windows?

Hi Folks,

yesterday I watched a longer Youtube video about earthen plasters. The guy managed to darken his clay plaster by mixing in finely ground coals left over from his wood stove. Looked good, dark but not pitch black.
This could also be applied to tromb wall plaster.

Ralf

Explaining some of the photos above:
In the big hall with four tall arched windows, the inner windows have been unglazed since that whole south wall was rebuilt 3 years ago. Just recently we installed window frames, and will get some glass or polycarbonate in soon, so that we can close the inner windows at night. But the whole building has stayed pretty warm in winter, because of its huge mass, and because the two rows of rooms next to that big hall have normal walls and seasonal attached greenhouses, rather than trombe walls. We've been using curtains for winter nights. But it will be warmer in mid-winter nights and early mornings after we get the inner windows glazed, I'm sure.

The small house above with the somewhat conventional trombe wall (except it's not sealed) does have inner windows with glass. This is going to be its second winter; last winter it did get a little cold in mid-winter, but it may have still been damp from construction, and there were 14 teenaged boys living in it who just WOULD NOT close the door. Now we've got the volunteers in there, including a Canadian, so I feel confident the door will be kept closed more of the time

Below are pictures of another half-trombe or phony-trombe wall room. This one has almost 50% of the south wall as window for light, and no inner glazing, only curtains in winter. We had double-glass as the outer layer, though, but since it was homemade and the room is attached to the kitchen, it got condensation and dust inside the double glazing.

Ralf Siepmann wrote:Hi Folks,

yesterday I watched a longer Youtube video about earthen plasters. The guy managed to darken his clay plaster by mixing in finely ground coals left over from his wood stove. Looked good, dark but not pitch black.
This could also be applied to tromb wall plaster.

Ralf

coal is insulation.

The color you see is the color that is not being absorbed.  For example we see plants as green so grow lights are designed to emit red to infrared and blue to ultraviolet. If you se pictures of them with only that light the plants look black.

The light spectrum that will heat the wall the most is from yellow down. Therefore a blue wall would be best and it will give the impression from outside that it is reflecting the sky. Reds and browns would be good for the inside of the wall. White on the inside is perfect because it increases the reflection of ambient light which has been limited by the tromb wall.