Does Heat Resistant Glass Stop the Suns Rays Coming in?

[Karanight]

I'm building a solar powered wood drying kiln and would appreciate some input from members.
I have a wood burner to heat the downstairs of my house and also my wife does a bit of woodturning, so I'm always looking for free wood for both.
Both requires the wood to be dry hence the kiln

I was going to single glaze but I think it might be a better option to double glazing as it lets heat from the sun in but doesn't let it out so quickly
I've been given a pile of toughened, heat resistant glass and I don't know if it'll let the suns rays will get through as good as normal glass.....does anyone know the answer or have any comments.

Untitled

• Karanight
• 19 Jun 2014
• 1

 

[endecotp]

I've been given a pile of toughened, heat resistant glass and I don't know if it'll let the suns rays will get through as good as normal glass

I think you should be fine with "toughened heat resistant" glass.

I would worry more if it were described as "anti-glare" or something.

Does it look fully transparent?

 

[Karanight]

The glass looks completely transparent. I was just a little concerned that it's heat resistant. The way I understand it, is the suns rays are different from heat, and the heat resistant element of the glass should keep the heat in, but, if I double glaze it, will the suns rays turn into heat between the two pieces of glass and then be stuck there.

 

[endecotp]

the heat resistant element of the glass should keep the heat in

No, the "heat resistant" element of the glass means that it can withstand a fire for longer before it breaks.

 

[doitall]

Modern glass/glazing keeps the heat in, therefor it also keeps the heat out

 

[Karanight]

Modern glass/glazing keeps the heat in, therefor it also keeps the heat out

You are correct that modern (double) glazing keeps the heat in, and therefor it also keeps the heat out, but (maybe I'm wrong) I think the suns rays can't be just heat! (there's radiation as well)
My conservatory is roasting in the summer (hotter than outside), we open the doors to let the heat out!! I put thermometers in the shade in the conservatory, and, in the shade outside and after just 10 minutes the heat in the conservatory is 50% higher than outside. I couldn't stand the heat in the conservatory) any longer so opened the doors to let the heat out.

 

[endecotp]

Modern glass/glazing keeps the heat in, therefor it also keeps the heat out

Not really, no. It is true that double glazing is symmetrical for heat conduction, but solar heat is radiated not conducted. The coatings on modern glass can reduce radiated heat loss, but they are asymmetric i.e. only one side is coated.

It sounds like the glass in this case is toughened but does not have a coating.

The thermal properties of the many south facing conservatories demonstrate what will happen.

 

[Karanight]

/quote]

It sounds like the glass in this case is toughened but does not have a coating.

There must be a way of finding out if it is coated but I don't know how, I don't think it is.
I got it from freecycle and the guy that gave it to me had light's fitted in his works, the lights ran very hot and the glass that went under the lights needed to be both toughened and heat resistant but, he didn't want the glass fitted. I understand that the toughened bit should be OK for the suns rays to go through but I don't know if the heat resistance will trap the heat between the pane's if I double glaze it

 

[big-all]

what are you trying to achieve ???

kilns are warm to hot constant temperature or controlled with slow change over several days
you would be better with air dried as a "box"would need ventilation to allow the moisture to escape

 

[Karanight]

what are you trying to achieve ???

Most of the wood I want to dry is for burning and if what I build doesn't suit wood for wood turning then I'll find another way to dry that

kilns are warm to hot constant temperature or controlled with slow change over several days

Normally this would be correct but for wood burning it doesn't matter if the wood is mistreated whilst drying, plus I intend to put "Heat bricks" from old storage heaters strategically placed to release heat after the sun goes home

a "box"would need ventilation to allow the moisture to escape

The box will have ventilation to allow the moisture to escape on the top and also ventilation to allow air into the box at the bottom at the front of the heat collector.
[/quote]

 

[big-all]

i think you are greatly over estimating the heat you will harvest
also timber does not like wildly varying temperatures along its length whilst drying this can cause twisting and warping

 

[Karanight]

I've looked at lots of designs for this and I've come up with my own design taking the best bits that suit me, my first enquiry to this forum is about the glass I've got.
From the amount I've read on the internet the drying time can be reduced from 3 years down to 5 months, as for the wood twisting and warping I don't think my wood-burning fire would mind lol
Here are some of the designs I've come across http://www.builditsolar.com/Projects/WoodDrying/wood_kiln.htm

 

[big-all]

a lot off bother for a wood burner

are we talking a little un or a big un???

 

[Karanight]

a lot off bother for a wood burner

One man's meat is another man's poison.
When I had the fire fitted it cost me in the region of £2500 and I know that it'll never pay for itself, but it's what I wanted, when you compare switching on the central heating to lighting the fire you could say that's a lot of bother but I enjoy it.
When I looked at the logistical problem of storing wood for burning and the drying times it became very obvious that I needed a drying solution. If I don't use a means of drying the wood I need a minimum of 100 square foot of floor space in the garden to have a regular supply of dried wood plus space to store freshly acquired wood waiting to be prepared to replace the wood used.
When I build the kiln (that's going to cost nothing to run and also cost almost nothing to build) I'll need less than half the space including the kiln. Add to this the pleasure of preparing to build and actually building the kiln it's not a lot of bother at all.

solar heat is radiated not conducted.

Back to the question of whether heat resistant glass would stop the suns rays getting through, discussing it here has made me think about it more and I think I know the answer, the suns radiated will go through both pieces of glass because they're rays.....not heat, Thanks endecotp

 

[JohnD]

they are infra-red rays, which are a form of heat energy.

most of the heat that double-glazing saves is not radiated (infra-red) but conduction of warm air touching the glass.

the objects inside your room will be far cooler than the surface of the sun, so they will emit very little heat as radiating infra-red.