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Have I stumbled onto a promising glazing idea?

 
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I was able to salvage a pretty good number of large tempered glass windows.  I've been toying with different ideas for them.  The main problem with glass is the high heat loss.  The "sweet spot" for greenhouse glazing seems to be about 70% transmissivity.  More light transfer, as with glass, and you get very heavy losses of heat.  Less light, and plants suffer.  I thought of taking two sheets of the tempered glass and making a large "double pane window".  It would just have an air gap, anything more than that is beyond my knowledge and/or capability.  But then I remembered reading about using bubble wrap on windows for added insulation.  I first read about it on builditsolar.com.  I tried it and it definitely cut down on the cold I could feel coming in the windows.  So, here is my thought:  What if I used bubble wrap between the two panes of tempered glass?  I should still have good light transmission, but I higher R-value, maybe as high as using twinwall polycarbonate panels.  My tempered glass panels are large, mostly about 4'x8'.  Am I crazy?  Will this work?  Did I just discover the holy grail of cheap greenhouse glazing?  Thoughts?
 
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I love tempered glass, and if you figure out how to make this work, I want to know :D

I think adding bubble wrap between the layers would trap moisture, I know the bubble wrap I have on some cold windows harvests water. I think it would have to have a good air gap, and be arranged so the water flows out to a good place. Not sure how much a good air gap would affect the insulative layers.

Watching this thread, I want to know too! Good idea!!  
 
Trace Oswald
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Pearl Sutton wrote:I love tempered glass, and if you figure out how to make this work, I want to know :D

I think adding bubble wrap between the layers would trap moisture, I know the bubble wrap I have on some cold windows harvests water. I think it would have to have a good air gap, and be arranged so the water flows out to a good place. Not sure how much a good air gap would affect the insulative layers.

Watching this thread, I want to know too! Good idea!!  



Pearl, I thought about this a little, but haven't pursued it much.  I was thinking of putting some of those little moisture-absorbing packs in between the windows and then sealing the edges of the double pane with caulk and/or duct tape, but I'm not sure if water would condense between the windows and overwhelm the packets.  I could just dump of bunch of the crystals in, but no way I want to tear the window apart and replace them.  I may just build one of these into a frame and not install it in any type of structure yet so I can see how bad the moisture issue would be.

If this works, I may use it to build a kind of hoophouse tunnel-like structure for my chicken to exit their coop into in the winter.  I have a hoop house for that now, but it gets extremely warm on sunny days, and then the temperature plummets as soon as the sun goes down.  I ended up using the hoop house for the chicken with the end entirely open so they still have a somewhat warm place to go outside and don't have to walk in the snow, but without the temperature swings from 90+F to -20F at night.  If I can use these windows, I would make a more permanent structure with insulated walls/ceiling and a lot of stone for thermal mass to dampen the large temperature swings.
 
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I've played with silica and window condensation...  I'd say that if you can seal the panes together very well with the bubble wrap in there and some dry silica, it should stay free of internal condensation until your seals leak and let in humid air.  So potentially a fairly long time.

I'd assemble them in the coldest/driest conditions you have so the humidity is minimal in the trapped air.  If you had a way to remove, dry and reinstall the silica that would be a nice back-up plan.  There's no way to tell if the air inside the bubbles will condense but there's nothing you can do about that anyway.

I'm also guessing you want the bubble wrap to not be squished flat by the glass.  The R value comes from the number of surfaces between the air pockets.  So if the bubble wrap is just barely touching the glass you would have more surfaces for the heat to get through.  If you can get bubble wrap that doesn't have a flat side, I think that would be very helpful.

If this doesn't make any sense, I can make a crude drawing...
 
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Question: at 4x8 and tempered were they store windows or sliding glass doors? Both of those are more insulative than you'd guess. You might test them on the hoop house, see what they do.

And I'd guess crystals and dry packs won't work, having seen someone try them for a damaged double pane window (with a bunch of clear tape.) They didn't have a chance, they are made for residual humidity, not continually added.

Edit: Mike Haasl was typing when I was, I'd agree that if it could be sealed REALLY well it may work, it's not easy to seal REALLY well, think about canning a jar to get all the air out.  Testing it is probably your best bet. And tell us   :D
 
Trace Oswald
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Mike Haasl wrote: I've played with silica and window condensation...  I'd say that if you can seal the panes together very well with the bubble wrap in there and some dry silica, it should stay free of internal condensation until your seals leak and let in humid air.  So potentially a fairly long time.

I'd assemble them in the coldest/driest conditions you have so the humidity is minimal in the trapped air.  If you had a way to remove, dry and reinstall the silica that would be a nice back-up plan.  There's no way to tell if the air inside the bubbles will condense but there's nothing you can do about that anyway.

I'm also guessing you want the bubble wrap to not be squished flat by the glass.  The R value comes from the number of surfaces between the air pockets.  So if the bubble wrap is just barely touching the glass you would have more surfaces for the heat to get through.  If you can get bubble wrap that doesn't have a flat side, I think that would be very helpful.

If this doesn't make any sense, I can make a crude drawing...



You're exactly right about the bubble wrap.  My idea is to space the two panes of glass just like I was going to do, except with the bubble wrap between.  I don't know if I've ever seen bubble wrap without a flat side, but that's a good point.

Pearl Sutton wrote: Question: at 4x8 and tempered were they store windows or sliding glass doors? Both of those are more insulative than you'd guess. You might test them on the hoop house, see what they do.

And I'd guess crystals and dry packs won't work, having seen someone try them for a damaged double pane window (with a bunch of clear tape.) They didn't have a chance, they are made for residual humidity, not continually added.



The windows have never been used for anything.  I got them from a glass company.  They can't cut tempered and apparently it isn't cost effective for them to do anything with them, so they give them away.  I could have gotten truckloads of them, in any thickness up to about an inch, in pretty much any dimension.

It may be that I can't do anything about the moisture.  I'll have to test a little.
 
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Trace, how are you planning to attach all this together? The professionals seal everything to keep moisture out, and some add a desiccant to help further, so that you don't end up with moisture trapped (we've got that problem and it looks like the window's dirty, but there's no way in to clean it.) The bubble wrap might help this issue because it's not clear anyway. However, UV is still going to come through the glass, so I'm wondering if the bubble wrap will eventually turn to powder as so many plastics do? How soon that will happen is the big question, but it would make me want to plan the assembly in such a way as to make it easy to remove one of the pieces of glass, clean everything out, replace the wrap, and reassemble.

It's certainly an intriguing idea. The R-value is based on the movement of air. I've heard that the aluminized double layer bubble wrap has an R-value of about 3 and a bunch of that is due to the reflected value of the aluminum. I'm really not sure that the bubble wrap will add much more than the air gap on it's own.

If your goal is warmth at night, my thinking is to find a way to make a non-moisture absorbing curtain that's easy to raise and lower on the inside, for when I manage to get something built. The issue with that is managing that on the roof sections. My mother had a sliding door on a piece of curved furniture which was fabric on one side, and wood on the outside. If the fabric was thick and insulating, and the wood supportive and controlled the movement, there might be a way to do it. It's definitely worth thinking about as the big problem I find with greenhouses is the "too hot/too cold" cycle!

I like your idea of rocks for thermal mass on the inside. Are you planning to have the north was solid or glass? North walls tend to loose heat while not providing any useful light despite all the "all-glass" greenhouses we see in pretty pictures.
 
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Sounds like the price is right! Only concern I would have is the UV stability of the bubble wrap. I'm willing to bet it would break down over one season from the sun exposure (and likely wouldn't like the temp swings) but if you made it easy enough to replace then you might be onto something. Something cheaper than the $120 a 4x8 sheet for triple wall polycarbonate I paid.
 
Trace Oswald
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Jay Angler wrote:Trace, how are you planning to attach all this together? The professionals seal everything to keep moisture out, and some add a desiccant to help further, so that you don't end up with moisture trapped (we've got that problem and it looks like the window's dirty, but there's no way in to clean it.) The bubble wrap might help this issue because it's not clear anyway. However, UV is still going to come through the glass, so I'm wondering if the bubble wrap will eventually turn to powder as so many plastics do? How soon that will happen is the big question, but it would make me want to plan the assembly in such a way as to make it easy to remove one of the pieces of glass, clean everything out, replace the wrap, and reassemble.

It's certainly an intriguing idea. The R-value is based on the movement of air. I've heard that the aluminized double layer bubble wrap has an R-value of about 3 and a bunch of that is due to the reflected value of the aluminum. I'm really not sure that the bubble wrap will add much more than the air gap on it's own.

If your goal is warmth at night, my thinking is to find a way to make a non-moisture absorbing curtain that's easy to raise and lower on the inside, for when I manage to get something built. The issue with that is managing that on the roof sections. My mother had a sliding door on a piece of curved furniture which was fabric on one side, and wood on the outside. If the fabric was thick and insulating, and the wood supportive and controlled the movement, there might be a way to do it. It's definitely worth thinking about as the big problem I find with greenhouses is the "too hot/too cold" cycle!

I like your idea of rocks for thermal mass on the inside. Are you planning to have the north was solid or glass? North walls tend to loose heat while not providing any useful light despite all the "all-glass" greenhouses we see in pretty pictures.



Jay, I would just build a simple wooden frame from dimensional lumber, run some caulk and lay the whole thing in.  My thought was that the only thing "sealing" it would be the caulk.  I'm not sure if I really care about moisture getting in too much.  If the moisture is contained between the windows and the caulk keeps it from contacting the wood, it may not even matter.

I don't really need it to stay warm at night.  The original idea was just to somehow replace the hoop house attached to the chicken coop.  Currently, it's made from cattle panels with 4 mil plastic stretched over it.  On a bright sunny winter day, it will easily hit 90 F if I have it closed up, but the temperature drops to outside temps almost immediately when the sun isn't hitting it.  I would like something better, but if I add too much time and expense, I may as well build a complete greenhouse and let them live in that for the winter.

I do have plans for a greenhouse.  That will have glazing only on the south side.  In our climate, I'm convinced that glazing anywhere other than the south side is a net loss.  It will be heavily insulated on all other sides.
 
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Are your chickens out in this hoop house at night?  If it cools off at night is it an issue?
 
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Matt Todd wrote:Sounds like the price is right! Only concern I would have is the UV stability of the bubble wrap. I'm willing to bet it would break down over one season from the sun exposure (and likely wouldn't like the temp swings) but if you made it easy enough to replace then you might be onto something. Something cheaper than the $120 a 4x8 sheet for triple wall polycarbonate I paid.



You may be right about it breaking down quickly.  I hadn't considered that.  I may end up better off just using the panes with an air gab as I originally planned.

I know what you mean about the polycarbonate.  I bought 20 sheets of twin wall a couple years ago.  It was on sale, but I still wouldn't call it cheap.
 
Trace Oswald
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Mike Haasl wrote:Are your chickens out in this hoop house at night?  If it cools off at night is it an issue?



No Mike, they go into the coop at night, and then I lock them in, mostly for predator-safety.  It doesn't matter if it cools at night realistically, but if it stayed somewhat warmer than the outside, it would be a benefit to them.  I have two concerns about it.  One is simply that that coop isn't really any warmer than outside with the size and the number of chickens I have, so it's extremely cold sometimes, so if the hoophouse stayed warmer, I think it would transfer at least some heat into the coop.  My other concern is that the really large temperature swings probably aren't great for them.  It gives them a chance to warm up during the day, but they still might see a swing of more than 100 degrees on a given day.
 
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Have you considered compost in their run to generate some heat?  My leaf and coffee ground system cooks all winter to give them warm toes when they're outside in the winter.  And a couple cubic yards of compost in the spring.  It doesn't heat the coop but some day I may figure out a way to make that happen...
 
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Trace Oswald wrote:


The windows have never been used for anything.  I got them from a glass company.  They can't cut tempered and apparently it isn't cost effective for them to do anything with them, so they give them away.  I could have gotten truckloads of them, in any thickness up to about an inch, in pretty much any dimension.




Can I ask where this company is located?
 
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Mike Haasl wrote:Have you considered compost in their run to generate some heat?  My leaf and coffee ground system cooks all winter to give them warm toes when they're outside in the winter.  And a couple cubic yards of compost in the spring.  It doesn't heat the coop but some day I may figure out a way to make that happen...



I haven't tried it.  I'm surprised it keeps cooking over the winter.  All my compost piles freeze hard as a rock.  How deep did you go?  I'd certainly be willing to give it a shot.
 
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Ellendra Nauriel wrote:

Trace Oswald wrote:


The windows have never been used for anything.  I got them from a glass company.  They can't cut tempered and apparently it isn't cost effective for them to do anything with them, so they give them away.  I could have gotten truckloads of them, in any thickness up to about an inch, in pretty much any dimension.




Can I ask where this company is located?



The company I got it from was in another state, but I think all large glass companies do the same.  You can't go to the actual glass factory, it has to be the stores that sell to consumers/contractors.  When a customer backs out on an order, especially a custom order, or when they get returns, the glass is basically worthless to the store.  This is all according to one guy that owned one glass place, but he told me "they all do it".  He had racks and racks of glass.  He had to pay to dispose of it, so he was happy for me to take it.  He was stuck storing it or paying to get rid of it.  I brought back a U-haul with 15 or 20 sheets of glass in it.
 
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This is great topic, I love alternative glazing ideas.
Simply making a double paned window would be pretty useful and strait forward.
I think the bubblewrap creates more points of conductivity but also reduces convection.
I think simply sticking the bubble wrap to the inside of only one of the two window panes that made up our double paned window would be sufficient to avoid thermal bridging.
If its was used as it is in houses, it could be replaced with reflective insulation in the summer.
I think a lot of the UV damage will be mitigated by the window itself, but I'm not sure.
What else could we do?
The caulk itself would keep the windows apart once it set, so a pattern of caulk lines that created air pockets might work.
Slices of clear hose could be spacers until the calk set.
I can see PET bottles smashed flat and capped sandwiched between to sheets of tempered  glass.
EPE Foam is something I've considered as a green house glazing.
It also comes as a mesh that is used on fancy fruit.
With low thermal conductivity and a pattern that would create air pockets, it could be useful.

My chickens were very happy living in the green house I had built for them.
It was a caged and covered run , and they roosted in one corner.
Deep litter meant it never smelled, even at the height of summer.
A thin concrete slab kept out diggers, 1/2" mesh kept out climbers and chain link kept out everything else.
I don't have weasels or immature chickens that rats could get to, so it was enough.
If I had had those problems I would have used 1/4" mesh.
I added leaves or wood chips and fed them right on the floor of the coop.
It was perfect, but the MAN from the Department of Making you Sad came and said it was too close to the property line.
It took like 4 visits to for them to come at me with something that would stick, but they finally did.
Now they have a tiny coop and most of the back yard but they spend most of their time, rain snow or shine, on the 4x 20' compost pile.



I think your birds could really benefit from having a coop inside the hoop house.
Shade cloth or vines would be needed during the summer, but with that, it will be nicer than outdoors, year round.
A hoop house that gets 90 degrees during the day might benefit from air to earth or air to water heat exchangers.
If the compost pile is in the hoop house it will be a thermal mass and it could also be built around a barrel of water that receives air to water heat.
Any compost pile you want to stay a pile will need protection from them.
Mesh sides and a lid of tempered glass might work.
Glass sides and a mesh lid might work better, feed them on top of the pile and they will add some liquid energy to the pile.
4x8 is a nice size to work with.
You could pile compost against the sides of the hoop house, inside and out, and hold it in place with the glass panels and some t stakes.
the outside piles would get a glass lid and some winter hardy greens.
Come summer, open and spread out the piles, so they chooks can feast on any remaining seeds and bugs.

Check out Dirtpatch Heaven on YT for some great hotbed/ raised bed/ low tunnel in a hoophouse winter growing videos, and thanks for a topic that let my mind run wild!
 
Trace Oswald
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Lots of great ideas in that post William. One thing you mentioned, I'm already working on. It's temporary for this year, but I'm building a light framed structure of 2x2 lumber and putting plastic over it around their current coop. I've never done it before, and actually just got the idea last week. The plan is to extend it past the coop in both directions. It will go 6 feet or so over the end opposite the hoop house end  where the people door is to create an airlock of sorts. I'm not sure how far I'll extend it over the current hoop house on the other end. All the way would be best I think, creating another hoop house over the current one, but I probably wont get that far.
 
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Trace Oswald wrote:

Mike Haasl wrote:Have you considered compost in their run to generate some heat?  My leaf and coffee ground system cooks all winter to give them warm toes when they're outside in the winter.  And a couple cubic yards of compost in the spring.  It doesn't heat the coop but some day I may figure out a way to make that happen...



I haven't tried it.  I'm surprised it keeps cooking over the winter.  All my compost piles freeze hard as a rock.  How deep did you go?  I'd certainly be willing to give it a shot.


I subdivide my run into a bin side and a walking side.  The bin is 3-4' (front to back) as you go across the width of the 16' hoop house.  In the fall I fill it as high as possible with leaves.  I get coffee grounds from a coffee shop and pitch fork a hole in the pile and dump them in and mix them around a bit.  I aim for a 50/50 blend of coffee and leaves in that spot.  Since they're outside at the coffee shop, in the dead of winter I let the grounds heat up in the house for a few days before putting them in the chicken run.  Somehow those spots of coffee grounds start to heat up and once they're going, the whole bin has a heat source.  Each weekly coffee ground dump is a foot or two to the right of the last one until I've worked my way all the way across the bin.  I'm currently 90% of the way across the run.  Once I get to the end, I start over at the other side.  

When I'm ambitious, I go out there every day and dig a hole in the pile in one spot.  I dig down to incorporate as many loose leaves as possible into the compost.  I dig in a new place each time.  After going across the pile a couple times, I've usually gotten all the leaves mixed in.  

By late fall the huge pile in the pic below is level to the boards on the front that hold it in.  So the fluffiness reduces fast due to bird action and gravity.  Once the composting kicks in and the pile shrinks further, I start to fork it from one end onto the rest of the pile.  By spring it's about 3' high and 6-8 feet long.
20211017_153258_resized.jpg
compost-bin-hoophouse-chicken-shed
 
Trace Oswald
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That's impressive Mike. I love the idea of a knee wall too.
 
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