Comments on: Build a Solar Attic

By: Oli

Oli — Wed, 23 Sep 2009 09:12:28 +0000

Hi Nigel
Love the set up with the vacuum cleaner.
Where is this roof that gives 30-40 degree heat and can you give an idea of the size of it. Just working on a project in the UK and this sort of simple solution would be great although the heat available would be far less.
Really interesting about the solar hot water too.
Inspirational stuff – thanks guys
Oli

By: Rob

Rob — Tue, 14 Jul 2009 00:10:24 +0000

Hi Gary.
Your site, http://www.builditsolar.com is great too. I’ve been a follower since I first read your solar barn article in Home Power Magazine several years ago.

I did some experiments with the solar attic as an air heating collector. I did the simplest possible experiment and installed a blower in the access hatchway, just blowing air down to the floor below. It worked well at overheating the top floor of my house… as expected. This was an open system, drawing outside air into the attic, heating it and blowing it down into the top floor… not very efficient, but probably better than using the same power directly for space heating. Unfortunately there isn’t a convenient place to run a proper duct to move the hot air all the way down to the first floor.

When experimenting with water heating solar collectors in the attic, I saw apparent efficiencies on the order of 150 to 200% (ie the amount of heat absorbed by the collector was 1.5 to 2 times the amount of solar energy that actually hit the panel). In other words, the collector was functioning more like a heat exchanger than a solar collector. That being the case, I might experiment with some simpler designs, focusing only on moving heat from the attic rather than absorbing sunlight (the solar attic already does a pretty good job of that).

By: Gary Reysa

Gary Reysa — Sat, 11 Jul 2009 23:15:46 +0000

Hi Rob,
Really enjoy your site — some very creative ideas.

This is just a thought, but I wonder if it would be a good idea to first experiment with your Solar Attic as an air heating collector?
The advantage would be that it could be very simple — little more that some enclosure and a couple ducts and a blower. Of course, it does not give you any storage capability, but for a lot of homes, the house thermal mass is enough to provide storage for a fairly good sized collector.
I guess this is a bit selfish on my part, but I would really like to see how it performs as an air collector, and how happy you are with the distribution of heat and whether is has any tendency to overheat the house or not.
Just a thought.

Gary from BuildItSolar

By: Nigel

Nigel — Thu, 11 Jun 2009 12:45:50 +0000

…and of course the ‘nice’ thing would be a solar panel to run the blower eh. One sep at a time!

And be careful with that wiring!
N

By: Nigel

Nigel — Thu, 11 Jun 2009 12:43:04 +0000

Hi Rob!
I had a corrugated iron roof that I had let a few polycarb sheets into also. The iron was a great heat-trap too, as I deliberately painted the sun-ward side matt black and the cold side clean white.

I then put some flat sheets of slightly opaque fiberglass in the ceilings of hallways, the shower, and over the kitchen. This increased the light within the house greatly. To maintain some ceiling insulation over the fiberglass sheets you could fit a layer of clear flat 2mm polycarb on top of the ceiling joists.

I then hung an old flow-thru Electrolux vacuum cleaner hug in the apex of the roof. I fitted a ceiling fan thermostat (which turns on when it gets hot) to a couple of plugs in the roof space, then mounted a switch on the wall in the hall so I could turn it on and off to over-ride the thermostat. I then ran the hose from the cleaner (from the ‘blow’ side) down into the coldest room in the house. It worked perfectly pulling a steady flow of 30 to 40 degree Celsius air into the house. It cost very little to run, and the power used simply ended up as heat added to the air flow. Went for ever and made a real difference. I turned it on when I saw roof space temperatures get more than 10 degrees above the in-house temperature at some stage of the day, and it was on virtually all year working all by itself.

You obviously have some ‘instrumentation’ – I used those little electronic greenhouse thermometers which have an inside sensor and an outside sensor on a lead. One on the inlet and one on the outlet in the room. Worked a treat, and very cheap heat.

Good luck!

Nigel

By: Brian

Brian — Wed, 06 Aug 2008 04:59:43 +0000

Nice setup, would be hard to do that here in Alberta, Canada. Check this out. http://www.dlsc.ca
Neat way to collect and store the summer heat.

Good Luck
Brian

By: Rob Steves

Rob Steves — Mon, 14 Jul 2008 18:11:38 +0000

Hi Dan,
The great thing about the roof is I can experiment with lots of solar collection methods underneath without committing to anything up front. So my plans may change, but my current one is to install solar water heating panels (either commercial or home made) under the transparent roofing. The water will be circulated by pump to an insulated storage tank inside the house. From there it can be circulated through radiant heating tubes under the main floor (accessible quite easily by crawlspace in my home). Cold nights should not draw significantly more heat from the house than before since the attic space was already outside the building envelope and it was already vented. In the summer, if I have too much heat (likely), I will do one of: a. vent it through additional windows I’ve installed in the eves for this purpose, b. install silvered mylar under the roof to reflect the light, or c. use the additional heat to heat a hot tub.

By: Dan

Dan — Fri, 11 Jul 2008 22:11:07 +0000

Hi Rob,
I like the idea of your heat trap.
Is yor plan to vent the captured heat to the home using fans?
Are the cold nights going to draw heat from inside the home?
What is your plan for the summer?
Keep up the good thoughts all these ideas are an inspiration and an on going process.

Cheers
Dan