Solar curtain.

In the latest effort to make bring the shop closer to self heating have added a solar curtain that rolls down over the inside of the south facing  shop doors and inflates double wall green house plastic to be the window to stop air interchange.  Open the sliding big doors to reveal a 20 foot wide by 15 foot high window.  The curtain rolls down from the top.  Both layers of greenhouse plastic wrap one way around the 5" pipe at the bottom and the lift ropes wrap the other way around the same pipe.  The pipe is a 23 foot length of aluminum sprinkler main line.

Setting the roller ropes up was a real pain.  And  I think I should have gone really clear plastic rather than the light diffusing as it does not put the heat in/on the floor as good.  Makes for great lighting though!!  Other mistake in thinking was how much floor space this would take.  But it rolls up behind the beam at the top as expected and the roller holds I rigid at the bottom as expected.   Originally thought I could  do it for a hair over $200 but came out a bit under $400.  Will still easily pay for itself in a year if it will knock 1/4 to 1/2 off heating bill.  Will only work on sunny, relatively calm days.  I know from previous years smaller scale playing that I can get  solar gain enough to at least break even down to about 20 below.(maybe even a bit colder once the inflation fan is in to hold the 2 layers apart. )  

The curtain runs down the inside of the door frame and rolls down from the top. It is only exposed when the big doors are open and it is rolled down. At night I close the doors over it so it is not leaking heat at night.(actually have to roll it up 5 feet just long enough to latch the doors but I can full close the doors over it before I do so heat lost doing this is minimal) Normal rules of thumb for passive solar say that the south facing window area should equal 20% to 30% of the floor space square footage. The curtain is just 13% so by itself so it can't win. The rest of the usable glazing takes that number to nearly 18%. So likely still not enough. Especially since I can't use this on windy days where a real glass window would be fine reduces my sun days. But I get the gain over the glass window in that the window is covered by the insulated door at night when normal windows are losing heat. I also get the gain in that the curtain can be down at night better sealing the front doors that have always leaked some which should also helps noticeably at night with the inflation fan running

As for life expectancy the green house plastic is rated for 5 years of sun exposure. Since this will be hidden from the sun most of its life either behind the doors or rolled clear up so it is behind the main beam for the door that won't matter. I can see already from the tiny bits of damage done already that likely it will be only good for 2 or 3 years because of physical damage.

To get clearance for some steel on the header beam I had to space the round wood closet rod 1 1/4" x 8' pieces that the plastic wrap clamps over out 2 inches. Because I am hanging over 100 pounds 15 feet over head the spacers are heavily glued and screw to the header beam.   At just over 4 feet from the floor that spacer moved out to 4" to clear the door latches.  The clamp is 1 1/4 black poly pipe with about a one inch strip cut out out of it, to form a long C shape of  snapped over the greenhouse plastic and over the closet rod.  Had to add some screw on clamp blocks to keep the pipe clamped tight enough at the top.  The original plan was to do the side clamps in 2 steps.   Most of the time leave the top 7 feet of the plastic clamped on the sides because most of what I need in and out is short enough to fit in 8 feet height.  Then remove the lower 8 feet daily so I can roll the pipe up high enough to reach the latches.  The problem is the bottom coming on and off all the time needs a gentler clamp that is ideally faster too.  The plastic is taking steady tiny damage.  So right I am fudging using a 1"X2" with a piece of foam pool noodle around it tucked back into the fold in the plastic and trapped behind the pipe and the closet rod at the bottom and held by a piece of twine about 6 feet up that is there to limit inflation size.

The plastic is 40 x 25 folded double down to 20 x 25 with the fold at the top.  The sides were folded in on both sides to bring it to roughly 20 x 21 and then the bottom end was taped to the pipe and rolled on.  Rolled clear down to floor level the plastic makes 2 plus wraps around the pipe that stay on.  The pipe turns over just over 10 times to get it rolled to the top so it hides behind the header beam.  The ropes run on the ends of the pipe beyond the plastic.  Lost 2 days running up and down a ladder adjusting pulley spacing's to get them tracking okay so don't expect this one to be easy.

Problems still to solve.

1.  Am I better off with light diffusing plastic or clear plastic?
2.  Anchoring the sides without damaging the plastic.(ideally in a really quick form.)
3.  Should have painted the roller pipe black where it wasn't taped because the amount of heat coming out the ends of it is amazing as it is.
4.  The ropes are slowly letting the plastic unroll from the roller at the bottom.  Need to anchor the rope to the pipe so it doesn't slowly slip around it.
5.  Would ideally like to automate raising and lowering it.  Right now it is heavy to pull on the ropes to roll it up and down.  Not a task for someone small.  Counter weight, capstan powered by a car electric window motor is the current best idea for this.  If I do it right I think I can have it work under both manual and electric.

Great idea.
I'm thinking of doing something like this on my bread truck this winter.

I think I saw something in Homepower magazine where they put 4 wood frames outside the door.
Covered them in plastic and had them hinged like bifold doors so they could be opened.
Garage door could be opened from the inside and the plastic sealed outside the door.



Something they had to remove and store in the summertime.

Nice project.

The way this is usually done is placing a translucid lace curtain behind the glass window. The curtain acts as an insulator against the cold air that comes from the cold glass, while at the same time stores heat from the sun rays.
For maximum heat gain, you need two glass windows, mounted in a non conducive frame (plastic, timber). You keep both windows closed for heating. In summer, you keep only one window closed for cooling. Or both opened when the weather is fine.

But it won't cost you under 400 bucks.

1. Clear plastic should allow more radiation, but it could be ugly.
2. Can't you just anchor the bar?
4. Can't you stick it with glue?
5. Use blinds polleys. You will need double length rope, but will need half the strength.

As far as anchoring to the sides just for the day, I have been doing stuff with magnets (set every 12 inches for my purposes) and matching washers they click to. Kind of a poor man's configurable magnet strip :D

Easy technique, mine are working for me, although I'm not doing the same thing. I'm doing curtains and styrofoam shutters that need to go up easy.

Pearl Sutton wrote:As far as anchoring to the sides just for the day, I have been doing stuff with magnets (set every 12 inches for my purposes) and matching washers they click to. Kind of a poor man's configurable magnet strip :D

Easy technique, mine are working for me, although I'm not doing the same thing. I'm doing curtains and styrofoam shutters that need to go up easy.

I had actually looked at magnets.   But because of the size of the curtain the magnets need to be really strong to hold in our breezes.  Figured I was looking at $60 to $100 in magnets.  Looking for a cheaper answer for now.  Think of it this way 15'x20' is 43,000 square inches.  Just 1 psi is 21 tons pushing on the curtain.  So even 1/4 psi is 5 tons which would make it hard to anchor.  While only part of that ends up on the sides it is still a significant pull.  I may come back to magnets but I would like to find a cheaper easy answer.