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skyking 11-07-13 09:56 AM

using suntuf as the only roofing on a large shop?
Hello all!
I am contemplating a large shop build for equipment and woodworking.
We have used standing seam hidden screw metal roofing on all the other structures and really love the security.
I had not given heating much thought, I figured it would be only heated when in use, and have a dehumidifier running for tools and such.
Now I see all these hot air solar systems with suntuf and I am a little excited :D
So, do I build fully independent collectors and install them over my roofing, or take a big leap and go with the suntuf roofing/collector integrated system?
1) I do get some wind. I am down in the trees so that helps some...
2) when it is not launching limbs at my roof!
3) the metal is said to last 50 years or more. With cleaning and painting I think it has no measurable service life. The same cannot be said for acrylic.

The pros are obvious, cost and simplicity.

My design already has the roof facing the proper way, but the south wall below it must be mostly doors. No big solar love to be had there.
I have an asymmetrical design with a 3' high wall between the roof pitches, so I can have south facing clerestory windows all the way across.
Nothing like natural light to work by.
That wall will be very easy to plumb all the air tubing through, and there is a generous eave projecting from the back roof to help with keeping weather off my windows and the plumbing.
So what say you folks?
Obviously I would still use metal on the north facing roof.

Daox 11-08-13 03:45 PM

Its a very interesting idea. If you go with the integrated design, which I like the idea of, you will have to think about summer (when you don't want heat) and how to deal with that.

skyking 11-08-13 03:51 PM

I'd still have copious insulation below the roof sheeting, and just turn out the hot air. I could also devise a reflective blind that would cover the black surface under the suntuf. that could get complicated.

Daox 11-08-13 03:56 PM

Haha, yeah that sounds cool but complicated. If you had an 'attic' area in the garage, you could vent it during the summer, and close up the vents when you wanted heat. Then just stick a fan up in the attic to blow hot air down like a few of us have been doing.

Exeric 11-08-13 05:41 PM

I think you have the right idea. No need for Suntuff. Many of us would kill for a standing seam metal roof. Those are the ideal solar collecters because they get HOT. All you have to do is paint them black on both the top and the bottom. Painting the top might be optional but you definitely should paint the bottom black. Black is the perfect energy reradiator and any energy radiation that is absorbed will then be reradiated downward.I would expect Suntuff would age, get brittle, and crack after not too long anyway.

Like Daox said, just put in a movable damper going to the roof vents. If I had it to do over again I wouldn't have put an electric damper in that position, because you will probably only move its position twice a year. Its function is too important in my opinion to be left to a motor that could fail. Just make sure you have access to the manual damper without tearing things apart too much. Then add insulation of your choice and stir.

AC_Hacker 11-08-13 05:47 PM


Originally Posted by skyking (Post 32887)
...Now I see all these hot air solar systems with suntuf and I am a little excited ...

I had a friend who had a house & garage. The garage had a questionable roof. So he tore off the old roof and nailed a bunch of corrugated fiberglass on the roof because it was so cheap.

Now, I'm not saying that this is a great idea for a serious roof, but it was quite amazing how much warmth the garage had in the winter, even on an overcast day. He ended up using the garage a a place to produce edible seed sprouts on a medium size scale... it was enough to support his family in a modest fashion.

I'm not championing corrugated fiberglass roofing or even edible seed sprouts, but the heat gain was well worth taking note of.

Something like THIS STUFF might be superb.


skyking 11-08-13 07:21 PM

I will elaborate on what I had in mind.
Imagine a 6/12 roof with OSB sheeting, with a black vapor barrier.
Then put on stringers to nail the suntuf on, forming a 4" air gap. Imagine a wall at the top edge of that roof to take the hot air into the building, with controls. Either turn the air in or turn it outside when things get too hot.
I would insulate under the OSB to minimize heat loss overnight and heat coming in when you don't want it.
funny how you think things through as you type :D
I can use traditional underlayment over the OSB sheeting, and seal it up good. Maybe even black roll roofing. It is cheap, absorbs heat like crazy, and will last indefinitely under the suntuf.
Punch a couple of curbed holes through near the bottom to admit the cool air. Curbed and sealed up nice so condensation from the bottom of the suntuf is properly channeled.

Now if the suntuf gets damaged, at least my structure is waterproof below till I replace the damaged panel. I can build drains into that system for both condensation and any damaged or deteriorated roof leakage.
Replace the suntuf periodically. I think it would pay off even if it had to be done every 10 years or so.

skyking 11-10-13 01:51 PM

Lots of things to ponder here.
Condensation + mold spores = very bad warm air.
I worry about how to keep the surfaces in my collector from growing anything bad.
Possibly a paint or coating?
automated damper system to cool the collector to ambient temperature at sundown, thus avoiding the temperature differential needed to form condensation?

Just tossing this out to see what others have experienced/dealt with.

AC_Hacker 11-11-13 08:00 AM


Originally Posted by skyking (Post 33072)
...Condensation + mold spores = very bad warm air...

If the sun shines on your roof on a semi-regular basis, it will dry out and heat up everything to the point that mold will die.

So, you might be over-thinking this thing.


skyking 11-11-13 10:27 AM

you're from Portland, so you know what happens around here. We get serious bad spells with no sun.
I have kicked it around all morning. I think the thing to do is build wall air collectors where I can, and put HDPE tubing under the standing seam metal for a liquid based collector. I was going with a dark green roof so that will deliver some heat OK.

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