Comments on: Build a Solar Attic

By: John Canivan

John Canivan — Tue, 28 Feb 2012 02:48:17 +0000

Looks like this could work if you pump the hot air that collects in your attic into your house on a sunny cold day.
Seems like you’d lose a lot of heat through the glazing, but you have the right idea…
Good luck
John

By: Rob

Rob — Wed, 22 Feb 2012 03:57:15 +0000

Hi George,
Good luck with your project. I’ve experimented with a few simple collector designs but haven’t installed anything permanent under the roof yet. Other projects have taken priority. The polycarbonate seems just fine after 3 years. I hope you are right about the >20 year life span.

By: Rob

Rob — Wed, 22 Feb 2012 03:51:33 +0000

Hi Wayne, I believe the roof pitch is 5/12. It certainly isn’t ideal for capturing winter sun, but you work with what you have.

By: George Adams

George Adams — Sun, 19 Feb 2012 22:47:52 +0000

Rob,
Go for it! And thanks for insrumenting and measuring performance of your handy work. My own plans for a similar integrated roof collector are still just plans but I will have a purpose-built 2:1pitch due south facing and with 4 foot rafter spacings.
I have some 20year old installations of that polycarbonate roof and nothing but praise for the material.

-George

By: Wayne Willim

Wayne Willim — Mon, 06 Feb 2012 04:06:12 +0000

Hello,
Great concept, I was wondering what pitch of roof you have.
Wayne

By: EK

EK — Mon, 23 Jan 2012 21:42:02 +0000

Great idea. I plan on doing something similar on my garage renovation this summer. It might help to have an additional layer of glazing, say a thin sheet of plastic sealed to the backside of the rafters. It would have to be baffled or have flow channels, but I imagine you could achieve additional heat gain from this insulated layer, as well as stop night-time convective losses back out of the glazing. As opposed to using corrugated polycarbonate, I want to use 4mm twinwall in two layers (4″ apart).

By: Tom

Tom — Thu, 29 Dec 2011 00:06:00 +0000

I have a 4×8 pop can solar collector outside my garage that has a blower with a attic fan sensor to turn on and off the fan. I also put a bathroom exaust fan in my garage attic to blow the warm air down into the garage when it also warms an attic fan sensor. Both sensors are adjustable to what temp. they kick on and off. When it is about 30 f outside and it is sunny the garage warms up to about 50 f, With the wall insulation the garage is about 40 f in the morning. The garage has an eight a foot ceiling that is covered with osb and insulated, it is also 22′x40′. In southern Wisconsin.

By: Lois

Lois — Sun, 07 Aug 2011 17:17:59 +0000

I’m a single female. I’m very interested in using the collected heat in the attic. As I live in Arizona, and attic heat is vastly available. Could some one get me a plan to bring it from the attic into the house. Would an exhaust fan work,installed to flow from the attic to the inside,in possible 3 palces in the home? I have a 1450 Sq foot home. Also interested in using the attic heat for heating hot water.

This has me thinking. I loved reading of the possibilities, and even tho I probably could not do it myself, I possible could pay someone to construct what I need. Thanks much,

By: Jonathan

Jonathan — Tue, 01 Mar 2011 10:30:23 +0000

A client has just given me a kitchen extension brief which includes an active (fans) solar roof and Trombe wall combined (the Trombe wall is higher). You illustrate how simple stuff can be. Always a good idea to cautious with roofs and heat. Stuff can get very very dry with obvious risk especially with curved surfaces and water pools as lenses (seen it). If anyone is interested in non invasive methods I have Hundreds of high contribution ideas that pay back quickly.

By: French Women :

French Women : — Tue, 26 Oct 2010 11:24:21 +0000

ceiling fans are great for cooling a warm room with large area. i prefer them over multiple desk fans~;*

By: Rob

Rob — Sun, 20 Jun 2010 04:51:34 +0000

Hi Tommie,
The solar attic is doing great. A few drips around some screw heads at first (maybe 1 out of every 20), but they were relatively easy to fix (just removed the screw, deburred the hole with some sandpaper and replaced the screw). In the past 2 years, the polycarbonate panels have stood up to 50 km/h winds, 2ft of snow, and temperatures ranging from -20 to +55 degrees C (inside the attic) without any problems. No mold or mildew either. They are as clear as when first installed without any maintenance.

I’m still experimenting with solar collectors in the upper attic. Actually I’ve decided the attic IS a solar collector and what I really need is just a heat exchanger to move the heat down to the main floor where I’m installing radiant floor heating. In the lower attic I’ve installed a “grow op”: nine 8ft long rows of tomatoes and peppers. They sure love the heat. I can plant them in my solar attic almost two months earlier than I can outside and I don’t have any problems with weeds or pests. I collect rainwater off the same roof to water the plants.

By: Tommie

Tommie — Thu, 17 Jun 2010 18:33:18 +0000

Would love an update on your attic solar collector. Needing to reroof a 1930s home with half of the house roof with southern exposure.

By: Allan

Allan — Sun, 09 May 2010 10:16:26 +0000

I painted my roof black, covered it with toughened glass from the recycle shop, then fan the hot air from under the iron down in to the house. I have seen 84 deg Celsius coming in. It heats air to 30 -35 deg in the rain. Hot air flows through a car air conditioner condenser to pre-heat water. (this water then travels through a parabolic trough reflector to heat it to 80 deg C) It is all automatic with thermostats. A small motor and gearbox close the vent when the fan is not running.

This thing collects some serious heat in our cold southern climate. We heat the house to 30 deg C nearly every day. The house stays warm all night with heat stored in furniture, walls, books, everything in the house is warm. The fan blows 800 cubic feet of hot air into the house every hour.

The house is always 20 deg C in the mornings, even though outside temps drop below 5 deg C. I have sealed all the air leaks and double glazed the all windows.

I have about 30 square meters of collection area.

A better looking but more expensive alternative would be to use your “Suntuf” (we have “Laserlite” here in Australia) spaced 5 mm or so above an iron roof with a rubber washer.

I have two hot water cylinders inside which “leak” their heat into the house.

My goal is to eliminate the use of firewood.

This has been a very worthwhile project.

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.