Silver foil does work

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Re: Silver foil does work

Postby Sometimewoodworker » Sat Sep 13, 2014 10:04 am

fredlk wrote:
Sometimewoodworker wrote:The foil I use works ......

Are you sure? :lol:

My thermometer is :lol: and my head, which used to get heat from a 62 degree C surface, is :D :D

So I think so
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Re: Silver foil does work

Postby Roger Ramjet » Sat Sep 13, 2014 11:55 am

Sometimewoodworker wrote:Sure that is RR confusing things

Are you now saying that heat is not energy?
fredlk wrote:The article you link to is also not comprehensive and gives an incorrect reason "minimize dust accumulation" for the orientation of foil.

I had no idea you were better qualified than a US government scientist/physicist but please do keep posting about placing the wrong side up or down whichever way you look at it. By the way it's not physics 101 it's only SGCE or when I went to school Matriculation and I do recall doing radiant barriers in the 3rd form.
Sometimewoodworker wrote:You are fixated on a misunderstanding. And wriggling around to try to prove your misunderstanding is correct.

I'm not trying to prove anything except you have the radiant barrier (foil) facing the wrong way. If you like I can post about twenty university peer reviewed papers about the side it should face, along with the rest of the SGCE physics that are all involved at some point or another, but it would be pointless because you will still insist you have it (the foil) facing the right way. Point out one scientific paper that says you should have the shiny side towards the floor? It's like saying a thermal/space blanket (the military call it a Casualty blanket) should be wrapped around a patient with the shiny side facing outwards and the camouflaged side facing the patient.
I can't believe this!
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Re: Silver foil does work

Postby thailazer » Sat Sep 13, 2014 3:29 pm

Wow, a lot of interest in this thread! For conduction, you really need to know how to do thermal resistance calculations. For radiation, it is a different and more complex set of equations. The basic premise with the foil backed insulation is to cause a high thermal resistance for conduction with the air-cell foam, and to provide a reflector for radiation with the foil backing. It's not rocket science, but it is science.
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Re: Silver foil does work

Postby Sometimewoodworker » Sat Sep 13, 2014 7:58 pm

Roger Ramjet wrote:
Sometimewoodworker wrote:Sure that is RR confusing things

Are you now saying that heat is not energy?
fredlk wrote:The article you link to is also not comprehensive and gives an incorrect reason "minimize dust accumulation" for the orientation of foil.

I had no idea you were better qualified than a US government scientist/physicist but please do keep posting about placing the wrong side up or down whichever way you look at it. By the way it's not physics 101 it's only SGCE or when I went to school Matriculation and I do recall doing radiant barriers in the 3rd form.
Sometimewoodworker wrote:You are fixated on a misunderstanding. And wriggling around to try to prove your misunderstanding is correct.

I'm not trying to prove anything except you have the radiant barrier (foil) facing the wrong way. If you like I can post about twenty university peer reviewed papers about the side it should face, along with the rest of the SGCE physics that are all involved at some point or another, but it would be pointless because you will still insist you have it (the foil) facing the right way. Point out one scientific paper that says you should have the shiny side towards the floor? It's like saying a thermal/space blanket (the military call it a Casualty blanket) should be wrapped around a patient with the shiny side facing outwards and the camouflaged side facing the patient.
I can't believe this!


:roll: :roll: :roll: From the Austrian government site "Face reflective surfaces downwards or keep them vertical. The anti-glare surface of single sided foil sarking should always face upwards or outwards." http://www.yourhome.gov.au/passive-design/insulation QED :roll: :roll: :roll: :roll: Is that good enough or are they wrong too??? :lol: :lol: :lol:

Shiny sides of radiant barriers must always have an air gap or they don't work, so of course a space blanket, if it has only 1 shiny face, must have that face out.

You are still confusing (from your own URL) "Radiant barriers consist of a highly reflective material, usually aluminum foil, which is applied to one or both sides of a number of substrate materials such as kraft paper, plastic films, cardboard, oriented strand board," which work by being poor radiators with reflective insulation systems. which work by reflecting heat and must also have an air gap. They are often combined which could explain your confusion.

Please post a couple of your relevant papers that contradict the Australian government :roll: . Please note they must have single sided foil without any other insulation and relate to roof radiant barrier insulation. As you have 20 to choose from there must be at least one that supports you and opposes both me and the Australian government.
Last edited by Sometimewoodworker on Sat Sep 13, 2014 8:02 pm, edited 1 time in total.
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Re: Silver foil does work

Postby Sometimewoodworker » Sat Sep 13, 2014 8:00 pm

fredlk wrote:
Sometimewoodworker wrote:The foil I use works ......

Are you sure? :lol:

Still having fun watching :)
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Re: Silver foil does work

Postby fredlk » Sat Sep 13, 2014 8:13 pm

Sometimewoodworker wrote:Still having fun watching :)

Fun isn't what I'd call it. Exasperation comes to mind and any number of synonyms.
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Re: Silver foil does work

Postby Sometimewoodworker » Sat Sep 13, 2014 8:24 pm

thailazer wrote:Wow, a lot of interest in this thread! For conduction, you really need to know how to do thermal resistance calculations. For radiation, it is a different and more complex set of equations. The basic premise with the foil backed insulation is to cause a high thermal resistance for conduction with the air-cell foam, and to provide a reflector for radiation with the foil backing. It's not rocket science, but it is science.


If you look at all normal Thai installed barriers which are glued to the roofing material the foil face is there for its poor radiation not its good reflection.
http://meekings.selfip.com/nui/Groups-of-photos/Non_Sa-At/Pages/Grandmums_House.html#222
image.jpg
Colorbond with factory insulation
image.jpg (51.04 KiB) Viewed 433 times

image.jpg
Cheep roofing
image.jpg (54.55 KiB) Viewed 433 times
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Re: Silver foil does work

Postby Andyfteeze » Sat Sep 13, 2014 8:55 pm

I give up, its no use me trying to reason, so ENJOY hahahahaha.
Glad it works for you.
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Re: Silver foil does work

Postby Andyfteeze » Sat Sep 13, 2014 9:53 pm

Hahaha, i am back.
Just found this on a science site.
" Most common insulation materials work by slowing conductive heat flow and -- to a lesser extent -- convective heat flow. Radiant barriers and reflective insulation systems work by reducing radiant heat gain. To be effective, the reflective surface must face an air space. Dust accumulation on the reflective surface will reduce its reflective capability. The radiant barrier should be installed in a manner to minimize dust accumulation on the reflective surface."

Shinny surface " reduces the radiant heat GAIN". In other words, the heat coming of the roof itself is trapped between the roof and the foil. The foil is reflecting manfully but the 60c is overwhelming the reflective ability of the foil and so the foil heats.
Insulators work by " slowing conductive heat flow". The foil is allowing some heat through. ( 2mm sheets would heat to 60c and radiate manfully ).Foil is hot to touch, but because of its low mass, its radiating a small amount of heat BECAUSE its low mass absorbs relatively small amounts of heat. Most of the heat stays upstairs, small amount gets through.
Room is same temp as ambient temp.

Dust is a problem because it absorbs heat. The heat source, hot dust particles, is in direct contact with the foil and so passes the heat efficiently. Also the dust particles reduce the amount of surface area reflecting the heat.
But again, 60c is enough to heat the foil anyway, so the diminished ability is relatively small, the foil would heat up irrespective of dust or no dust. But the dust could pose a fire risk.


Is this any clearer?

Also. Paper has a low thermal conductivity factor. 0.05
Aluminium. 205
Iron. 80
Brick. 1.5
If aluminium is such a GREAT conductor of heat, why would you use it for insulation? The first thing is to think, oh, its reflecting the heat. So why is the foil hot to touch? Shouldnt it be cool, its reflecting the heat?
I am trying to make it easy for you to understand the dynamics at play here.

Paper alone, without treatment, is not used to insulate because ITS COMBUSTIBLE. 60c would be a
Fine call, lol

I am only persistent because understanding the basics helps us make better decisions.
In your case, i probably would have done the same with the foils orientation as it would make minimal difference compared to the other forces at work.
As i said at the start, right conclusion just funny logic.
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Re: Silver foil does work

Postby Mike Judd » Sun Sep 14, 2014 5:00 am

One thing that I have noticed is that all the Sarking or Foil is placed on the roof rafters first in the U.K. and Oz ,then the battens fixed on top of it. In Thailand they put it over the battens, the difference being a slight air space with the former,which I would think better, how much difference in practice would be for you guys with a scientific bent to say. Insulating ceilings in Thailand is not something I would be doing though as keeping the heat in is not something usually wanted in hot climates. Solely through practical experience I have found that it's best to have foil under the tiles to reflect the sun's heat through the day, but because it also stops any heat rising from below through the day, it needs to be well ventilated. If Air-con is used then the more insulation is used throughout is going to save money in the long run, walls, ceilings and even double glazing going to the extreme. 8) 8)
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Re: Silver foil does work

Postby Roger Ramjet » Sun Sep 14, 2014 6:09 am

Sometimewoodworker wrote:From the Austrian government site "Face reflective surfaces downwards or keep them vertical. The anti-glare surface of single sided foil sarking should always face upwards or outwards." http://www.yourhome.gov.au/passive-design/insulation QED Is that good enough or are they wrong too???

I take it you've never been to Australia and also you didn't read the article in its entirety, just selective parts. Australia is a land of extremes, in summer you need to keep the hot air out and in winter the freezing temperatures out and the hot air in. You read the part about keeping warm air in in winter and didn't bother reading any further.
Sometimewoodworker wrote:Shiny sides of radiant barriers must always have an air gap or they don't work, so of course a space blanket, if it has only 1 shiny face, must have that face out.

Well done, you've just put the space program back 40 years and killed a lot of soldiers and astronauts. The human body is not totally flat, it also gives off radiated heat, the heat from the person is trapped inside the space blanket, does the heating.
http://www.radiantbarrier.com/physics-of-foil.htm
http://www.moneysavinghome.com/radiantb ... mation.htm
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Re: Silver foil does work

Postby splitlid » Sun Sep 14, 2014 7:19 am

Great thread. :-(
Regarding the few pics posted above concerning the thai metal sheeting with attached insulation.
That stuff is shiny on both sides.
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Re: Silver foil does work

Postby Sometimewoodworker » Sun Sep 14, 2014 7:22 am

Roger Ramjet wrote:
Sometimewoodworker wrote:From the Austrian government site "Face reflective surfaces downwards or keep them vertical. The anti-glare surface of single sided foil sarking should always face upwards or outwards." http://www.yourhome.gov.au/passive-design/insulation QED Is that good enough or are they wrong too???

I take it you've never been to Australia and also you didn't read the article in its entirety, just selective parts. Australia is a land of extremes, in summer you need to keep the hot air out and in winter the freezing temperatures out and the hot air in. You read the part about keeping warm air in in winter and didn't bother reading any further.
Sometimewoodworker wrote:Shiny sides of radiant barriers must always have an air gap or they don't work, so of course a space blanket, if it has only 1 shiny face, must have that face out.

Well done, you've just put the space program back 40 years and killed a lot of soldiers and astronauts. The human body is not totally flat, it also gives off radiated heat, the heat from the person is trapped inside the space blanket, does the heating.
http://www.radiantbarrier.com/physics-of-foil.htm
http://www.moneysavinghome.com/radiantb ... mation.htm

Thank you for a reference that makes my point for me. It looks as if it is you that can't read
from your own reference material

The amount of radiation emitted is a function of the EMISSIVITY factor of the source’s surface. EMISSIVITY is the rate at which radiation (EMISSION) is given off. Absorption of radiation by an object is proportional to the absorptivity factor of its surface which is reciprocal of its emissivity.
Although two objects may be identical, if the surface of one were covered with a material of 90% emissivity, and the surface of the other with a material of 5% emissivity, the result would be a drastic difference in the rate of radiation flow from these two objects. This is demonstrated by comparison of four identical, equally heated iron radiators covered with different materials. Paint one with aluminum paint and another with ordinary enamel. Cover the third with asbestos and the fourth with aluminum foil. Although all have the same temperature, the one covered with aluminum foil would radiate the least (lowest [5%] emissivity). The radiators covered with ordinary paint or asbestos would radiate most because they have the highest emissivity (even higher thn the original iron). Painting over the aluminum paint or foil with ordinary paint changes the surface to 90% emissivity.


As where is the one of the twenty university peer reviewed papers about the side it should face
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Re: Silver foil does work

Postby Sometimewoodworker » Sun Sep 14, 2014 7:31 am

splitlid wrote:Great thread. :-(
Regarding the few pics posted above concerning the thai metal sheeting with attached insulation.
That stuff is shiny on both sides.

It may well be. However one side is in direct contact with the insulation so has no significant effect. If the insulation is poor it will transmit the heat by conduction to the foil however in the reference that RR has so kindly produced it will then radiate only 5% of that heat thus it is a radiant barrier

image.jpg
RR linked document
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Re: Silver foil does work

Postby Roger Ramjet » Sun Sep 14, 2014 7:34 am

Sometimewoodworker wrote:Thank you for a reference that makes my point for me. It looks as if it is you that can't read
from your own reference material

The amount of radiation emitted is a function of the EMISSIVITY factor of the source’s surface. EMISSIVITY is the rate at which radiation (EMISSION) is given off. Absorption of radiation by an object is proportional to the absorptivity factor of its surface which is reciprocal of its emissivity.
Although two objects may be identical, if the surface of one were covered with a material of 90% emissivity, and the surface of the other with a material of 5% emissivity, the result would be a drastic difference in the rate of radiation flow from these two objects. This is demonstrated by comparison of four identical, equally heated iron radiators covered with different materials. Paint one with aluminum paint and another with ordinary enamel. Cover the third with asbestos and the fourth with aluminum foil. Although all have the same temperature, the one covered with aluminum foil would radiate the least (lowest [5%] emissivity). The radiators covered with ordinary paint or asbestos would radiate most because they have the highest emissivity (even higher thn the original iron). Painting over the aluminum paint or foil with ordinary paint changes the surface to 90% emissivity.

Which means you have your foil facing the wrong way.
I notice you never correct yourself when you make mistakes. Tell me about what space blankets do again. The Telaban and IS love them, it hides their heat signature from the FLiR in choppers. I wish you'd instruct them to turn the shiny side out..... just like your kitchen.... no that's wrong the heat is from the floor there.
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