I made my first passive heating panel last week. Spent a lot of time on the Desoto site (lots of good info there). It is small (about 3.5 sq ft) but fit in an existing "hole" in my wall. I've got it in my pump room which is attached to the garage/basement. Our pressure tank from the well is in there and it freezes once or twice a year when we get the -20 F stretch (I'm in southern WI). Anyway I'm hoping that it pumps out just enough to keep the room from freezing. This was a couple night project to see what it can actually do. Unfortunately it's been cloudy and crappy out since I put it in, hopefully this weekend will be sunny so I can see if it actually pumps out any heat.
My collector is the "type 3" variety, basically it has a S channel to help prevent drafts and provide a little extra insulation. Glazing is .08 acrylic, inside of the panel is 1/2" plywood painted w/ hi temp BBQ paint. Also I included two layers of black metal window screening. The screening is pretty much in the center of the channel, not flat against the "black wall". I offset it with a couple of wood spacers.
My main questions are (being a newb): What strategies do folks employ to capture UV wavelength light? The spectrum has a lot more area under the curve than the visible light. It's been awhile since I've been in my physics classes but I would think the flat black paint mostly absorbs visible light.
Does the thickness of the wood in the panel really have any affect? I was thinking that if I have fixed width to work with, it my be better to use 1/4" plywood to maximize the width of the air channels than 1/2" which has more rigidity and a higher R value (well, that may be negligible)
Has anyone tried using insulated glass panels (bascially what they use in window and doors)? I would think if non LoE glazing was used, you would retain pretty much the same transparency as a single glazing but gain a lot in insulation value (basically what a normal window would be).
Anyone this has turned into quite the novel so I'll cut it off here. I'm sure I'll have more questions for ya'll.
pjo wrote: > I made my first passive heating panel last week. Spent a lot of time on the > Desoto site (lots of good info there). It is small (about 3.5 sq ft) but > fit in an existing "hole" in my wall. I've got it in my pump room which is > attached to the garage/basement. Our pressure tank from the well is in > there and it freezes once or twice a year when we get the -20 F stretch (I'm > in southern WI). Anyway I'm hoping that it pumps out just enough to keep > the room from freezing. This was a couple night project to see what it can > actually do. Unfortunately it's been cloudy and crappy out since I put it > in, hopefully this weekend will be sunny so I can see if it actually pumps > out any heat.
First of all, thanks for the kind words!
It's tiny, but will put out /some/ heat. A thermometer should give you some strong clues as to how well it'll do the job. It should be putting out measurable heat even in full overcast.
> My collector is the "type 3" variety, basically it has a S channel to help > prevent drafts and provide a little extra insulation. Glazing is .08 > acrylic, inside of the panel is 1/2" plywood painted w/ hi temp BBQ paint. > Also I included two layers of black metal window screening. The screening > is pretty much in the center of the channel, not flat against the "black > wall". I offset it with a couple of wood spacers.
> My main questions are (being a newb): > What strategies do folks employ to capture UV wavelength light? The > spectrum has a lot more area under the curve than the visible light. It's > been awhile since I've been in my physics classes but I would think the flat > black paint mostly absorbs visible light.
See http://www.iedu.com/DeSoto/Astro/Absorber.html for a rough look at solar output (atmospheric filtering carves notches into this) and note that UV is a relatively small component compared to visible and lower frequencies.
This is a Good Thing - it lets us use UV blockers to protect UV-vulnerable glazings without major losses.
> Does the thickness of the wood in the panel really have any affect? I was > thinking that if I have fixed width to work with, it my be better to use > 1/4" plywood to maximize the width of the air channels than 1/2" which has > more rigidity and a higher R value (well, that may be negligible)
The thickness of the wood in the plenum dividers isn't particularly important. The depth(s) of the plenum(s) is considerably more important.
> Has anyone tried using insulated glass panels (bascially what they use in > window and doors)? I would think if non LoE glazing was used, you would > retain pretty much the same transparency as a single glazing but gain a lot > in insulation value (basically what a normal window would be).
In terms of "bang for the buck", you're better off spending for 6mm twinwall polycarbonate - and it's a lot less prone to hail/kid damage.
> Anyone this has turned into quite the novel so I'll cut it off here. I'm > sure I'll have more questions for ya'll.
> pjo wrote: >> I made my first passive heating panel last week. Spent a lot of time on >> the Desoto site (lots of good info there). It is small (about 3.5 sq ft) >> but fit in an existing "hole" in my wall. I've got it in my pump room >> which is attached to the garage/basement. Our pressure tank from the >> well is in there and it freezes once or twice a year when we get the -20 >> F stretch (I'm in southern WI). Anyway I'm hoping that it pumps out just >> enough to keep the room from freezing. This was a couple night project >> to see what it can actually do. Unfortunately it's been cloudy and >> crappy out since I put it in, hopefully this weekend will be sunny so I >> can see if it actually pumps out any heat.
> First of all, thanks for the kind words!
> It's tiny, but will put out /some/ heat. A thermometer should give you > some strong clues as to how well it'll do the job. It should be putting > out measurable heat even in full overcast.
>> My collector is the "type 3" variety, basically it has a S channel to >> help prevent drafts and provide a little extra insulation. Glazing is >> .08 acrylic, inside of the panel is 1/2" plywood painted w/ hi temp BBQ >> paint. Also I included two layers of black metal window screening. The >> screening is pretty much in the center of the channel, not flat against >> the "black wall". I offset it with a couple of wood spacers.
>> My main questions are (being a newb): >> What strategies do folks employ to capture UV wavelength light? The >> spectrum has a lot more area under the curve than the visible light. >> It's been awhile since I've been in my physics classes but I would think >> the flat black paint mostly absorbs visible light.
> See http://www.iedu.com/DeSoto/Astro/Absorber.html for a rough look at > solar output (atmospheric filtering carves notches into this) and note > that UV is a relatively small component compared to visible and lower > frequencies.
> This is a Good Thing - it lets us use UV blockers to protect UV-vulnerable > glazings without major losses.
>> Does the thickness of the wood in the panel really have any affect? I >> was thinking that if I have fixed width to work with, it my be better to >> use 1/4" plywood to maximize the width of the air channels than 1/2" >> which has more rigidity and a higher R value (well, that may be >> negligible)
> The thickness of the wood in the plenum dividers isn't particularly > important. The depth(s) of the plenum(s) is considerably more important.
>> Has anyone tried using insulated glass panels (bascially what they use in >> window and doors)? I would think if non LoE glazing was used, you would >> retain pretty much the same transparency as a single glazing but gain a >> lot in insulation value (basically what a normal window would be).
> In terms of "bang for the buck", you're better off spending for 6mm > twinwall polycarbonate - and it's a lot less prone to hail/kid damage.
>> Anyone this has turned into quite the novel so I'll cut it off here. I'm >> sure I'll have more questions for ya'll.
pjo wrote: > Is yellowing a concern w/ polycarbonate? Also what about > expansion/contraction vs glass?
Yellowing hasn't been a problem with any of the stuff I've used. I still have a scrap from my first twinwall project (almost thirty years ago!) and it shows no signs of yellowing. All of the stuff I've bought has been UV-protected on one side, and I've been careful to keep that side out.
I've only built one panel with glass - interestingly, it was a 3'x4' panel installed in an uninsulated 16'x16' milkhouse on my Minnesota farmstead - to keep my well head pressure tank and water line from freezing. That glass was secured with points and putty just like a window, and expansion wasn't a problem.
Expansion/contraction hasn't been a problem with the polycarbonate in temperatures ranging from -30F to +180F.
>... Expansion/contraction hasn't been a problem with the polycarbonate in >temperatures ranging from -30F to +180F.
My 4'x16'x10 mil double-glazed HP92W Lexan panels have a 3.75x10^-5F/F thermal expansion coefficient, so they become 16(1+3.75x10^-5(100)) = 16.06' long (0.72" longer) as the temperature rises from 0 to 100 F, which could let them flop and fatigue in the wind and bulge about sqrt(96.36^2-96^2) = 8.3" in the middle, were they not slightly inflated to 0.1" H20.
>> ... Expansion/contraction hasn't been a problem with the polycarbonate in >> temperatures ranging from -30F to +180F.
> My 4'x16'x10 mil double-glazed HP92W Lexan panels have a 3.75x10^-5F/F > thermal expansion coefficient, so they become 16(1+3.75x10^-5(100)) = 16.06' > long (0.72" longer) as the temperature rises from 0 to 100 F, which could > let them flop and fatigue in the wind and bulge about sqrt(96.36^2-96^2) > = 8.3" in the middle, were they not slightly inflated to 0.1" H20.
Hmm - good to know. I use the polycarbonate with the channels running vertically (typically 6' height) and provide vertical supports every 2'.
When I tried a 4' span between vertical supports I saw some bowing - but nowhere near the 8+" you describe with your Lexan. The two foot horizontal span I've been using has worked quite well.
On Tue, 18 Nov 2008 04:28:12 GMT, "pjo" <p...@microsoft.com> wrote: >I made my first passive heating panel last week. Spent a lot of time on the >Desoto site (lots of good info there). It is small (about 3.5 sq ft) but >fit in an existing "hole" in my wall. I've got it in my pump room which is >attached to the garage/basement. Our pressure tank from the well is in >there and it freezes once or twice a year when we get the -20 F stretch (I'm >in southern WI). Anyway I'm hoping that it pumps out just enough to keep >the room from freezing. This was a couple night project to see what it can >actually do. Unfortunately it's been cloudy and crappy out since I put it >in, hopefully this weekend will be sunny so I can see if it actually pumps >out any heat.
>My collector is the "type 3" variety, basically it has a S channel to help >prevent drafts and provide a little extra insulation. Glazing is .08 >acrylic, inside of the panel is 1/2" plywood painted w/ hi temp BBQ paint. >Also I included two layers of black metal window screening. The screening >is pretty much in the center of the channel, not flat against the "black >wall". I offset it with a couple of wood spacers.
>My main questions are (being a newb): > What strategies do folks employ to capture UV wavelength light? The >spectrum has a lot more area under the curve than the visible light. It's >been awhile since I've been in my physics classes but I would think the flat >black paint mostly absorbs visible light.
>Does the thickness of the wood in the panel really have any affect? I was >thinking that if I have fixed width to work with, it my be better to use >1/4" plywood to maximize the width of the air channels than 1/2" which has >more rigidity and a higher R value (well, that may be negligible)
>Has anyone tried using insulated glass panels (bascially what they use in >window and doors)? I would think if non LoE glazing was used, you would >retain pretty much the same transparency as a single glazing but gain a lot >in insulation value (basically what a normal window would be).
>Anyone this has turned into quite the novel so I'll cut it off here. I'm >sure I'll have more questions for ya'll.
>Thanks in advance, >Pete
hi, what is this Desoto site you're talking about?? thanks, graham
