Solar Gain - Curtain Wall

[zeus]

Hi All

I'm sitting here with the sun streaming in through the window, the warmth making me feel quite sl.... sleepy  ..... which reminded me of an idea I started to play with a number of years back, but like everything else, did nothing with ... (yet) !!

I've got a S/W (230 degree) facing two storey unshaded wall which receives a decent amount of sunlight which I looked at trapping with a glass curtain wall (about 15'x15'), with the intent of pumping the heat into the actual house with a ducted fan system controlled by a differential thermostat ... has anyone seen or got experience of this kind of setup ?.

Cheers .... 
(There you go .... my first question  )

[JohnS]

Try searching for Trombe wall

or look here http://en.wikipedia.org/wiki/Trombe_wall

[zeus]

Try searching for Trombe wall

or look here http://en.wikipedia.org/wiki/Trombe_wall

Hi JohnS

Thanks .... I remember reading up on Trombe walls when I was considering this in the past, just looking for input from anyone with actual experience of a UK installation, possibly with metrics if available .....

Cheers ... 

[djh]

There's been some discussion of this but I don't remember whether it was here or on the green building forum. I think billi is in favour so perhaps he'll comment in a while ...

There are also some ideas on the builditsolar site.

[EccentricAnomaly]

This blog entry and the earlier ones linked might be of interest:

http://practicallyoffthegrid.com/2010/03/solar-air-heater-tools-and-expenses/

I haven't followed the links from this entry yet:

http://practicallyoffthegrid.com/2010/04/solar-air-heating-experiments/

I'd also second djh's suggestion of Build-It-Solar.

Personally, I'm not convinced by Trombe walls (solar collectors with thermal mass built in).  I suspect it's better to squirrel away the heat inside the house where you can hang on to it rather than try to store it in the collector where it'll leak out again before you get round to using it.  They had a Trombe wall on the Brighton Earthship but got rid of it because it didn't work.

[Baz]

I don't think Zeus was intending a Trombe wall, just a collector. It would need an inulating layer on the outside of the wall to ensure quick warm up. I have been considering this for my SE wall but with added complexity of an isolated air path viz: glass, unvented airgap, blackened foil, air path, insulation, wall.

[EccentricAnomaly]

Also worth mentioning Navitron's SFG20 as a possibility.

[dhaslam]

There are two problems with the idea.   The first is that if you have a south facing wall you will want to have windows in it.   The second problem is that  if there  is sun, south facing windows and insulation you won't need the extra heat.    However the idea of using a south facing  heat collector as a source of stored heat is  useful.

[zeus]

Hi All

Thanks for the info ..... the build-it-solar site has a number of updates since I last looked.

Baz correctly picked up that the idea would be to just use the area enclosed by the curtain wall to collect the heat and use a differential thermostat linked to an extractor to transfer heat into the house as and when heat becomes available, allowing the structural mass inside the existing insulating 'shell' to act as a thermal store. I too envisage using painted thin metal sheeting as an absorbing surface allowing both a higher temperature panel/air heat transfer and a faster warming cycle, although for a while I did consider a rigid ducting collector solution, however, I hadn't considered insulating the solid wall behind the collecting surface  ..... the curtain wall would probably have to include a set of conservatory blinds to as well as some ventilation to prevent summer meltdown.

The Curtain wall would probably be built from standard PVCu profiles (dark grey) and double glazed (apparently double glazed panels are actually cheaper than slightly thicker single glazing) as 'she who must be obeyed' insists that if it is built it 'must be asthetically pleasing' ..... whatever that means    

Cheers ....    

##Edit .... thanks dhaslam ... adjacent walls have windows, this is an existing 'blank' wall ....      

[welshboy]

I seem to remember reading about an idea of dark greenhouse shading behind the glass .The air has to pass through it picking up heat because of the small holes and  entering  the house via top vents with bottom vents having a thin anti reverse flow flap to stop the nighttime cooling of the house.

[EccentricAnomaly]

There are two problems with the idea.   The first is that if you have a south facing wall you will want to have windows in it.   The second problem is that  if there  is sun, south facing windows and insulation you won't need the extra heat.    However the idea of using a south facing  heat collector as a source of stored heat is  useful.

It's a bad idea to have more windows than you need to let in sufficient light, allow you to admire the view and allow you to escape/be rescued if there's a fire because the extra will cause heat loss during the heating season and possibly excess heat gain for a couple of weeks a year (in the British Isles).  On the other hand, there are often bright or sunny days during the heating season when gain from the rest of the sunny side of the building would be welcome. 

In summary, once the windows have enough area for their basic purposes additional heat gain is better done indirectly for better control of losses and excess input.