Silver foil does work

methods, materials, sources & prices, construction for separate Topics on:
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Re: Silver foil does work

Postby sirineou » Thu Dec 25, 2014 9:11 pm

Ians wrote:It is an interesting discussion as to the best method, under tile / sheet, on top of the ceiling or both. My home has both, under the tiles and on top of the ceiling, but I'm still not sure or convinced that on top of the ceiling is a good method.
I have been monitoring the roof space temp. over the past few months and comparing it to the inside and outside temp. - todate I feel that the under tile arrangement is doing a great job, on a typical hot day temp. have been - outside 34/5, inside 29/30 and roof space 31/32, I'm not that happy with the drop in o/night inside temp. some mornings it is above the roof space and outside temp., I am at this stage putting this down to the ceiling insulation retarding the inside temp. or maybe latent heat in the internal brick work holding up the temp., more investigation later when the real testing starts during the hot session -- I will monitor it more closely and log the temp. and rise over the day and as best I can o/night.

More later for more discussion.


One must remember that insulation not only helps keep things cool but also helps keep thing warm.

What insulation does, IMO ,is insulate , in the instance of temperature insulation , it prevents thermal exchange from one area to an other. In the instance of insulation on the ceiling it prevents thermal exchange from the living space to the attic space and visa versa.
in the daytime when and if it is really hot in the attic, it would prevent the heat from the attic permeating in to the living areas,
at night, depending on the construction method,
(one might have a metal roof that cools fast, might have brick external wall that retain heat, or might have heat producing items in the living areas such as people, electronic devises, refrigerator,cooking ets)
then the temperature in the living areas could be higher than the attic areas since heat rises and the insulation in the ceiling prevents it's radiation in to the attic space , then the temperature in the living area could be higher than the attic.
So one might need to weight the advantages of a cooler house in the daytime versus a warmer house at night
and if ones construction method is such where the temperature in the attic during the daytime is almost the same as the temperature in the living space, one could safely conclude that the ceiling insulation was unnecessary, but I guess one would not know that until one installs ceiling insulation. :D
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Re: Silver foil does work

Postby olavhome » Thu Dec 25, 2014 9:54 pm

Speaking for myself, I plan to have Q-con all walls and a roof overhang about 1.20. Also only 1 storey house.
So taken this into consideration isulation beetween living room and attic should be the best option (if not "overdo" :-) and make also under roof tiles).
If had 2 storey house and (or) use ordinary bricks, isolation directly under roof tiles would be an ok option.
Or do I misunderstand :?:
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Re: Silver foil does work

Postby roy.sokolowski » Tue Jul 25, 2017 8:45 am

I realize this is an inactive post but I would like to post my experience with radiant barrier premounted on 5/8 inch thick OSB (omni-directional strand board) in Hawaii. The foil layer is placed down towards the attic. We used an asphalt shingle roof with a ridge vent and a solar powered attic fan. The system worked fantastic and there was zero "insulation" involved (unless you count the 5/8 inch strand board as insulation), we also had no air-conditioning, just ceiling fans. We also vented the attic access panel to allow it to pull (relatively) cool air from the house into the attic. Insulation will slow the heat transfer but it does not stop it and is really better suited in my opinion to non-tropical areas (such as Northern North America or Northern Europe).
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Re: Silver foil does work

Postby Roger Ramjet » Tue Jul 25, 2017 10:52 am

roy.sokolowski wrote: Insulation will slow the heat transfer but it does not stop it and is really better suited in my opinion to non-tropical areas (such as Northern North America or Northern Europe).

And you'll have trouble finding those materials here, let alone having them installed correctly.
The technical colleges here are also cutting back on "farang" employees with that sort of knowledge, which is a shame as some of those students came out with up to date knowledge and experience and now they will emerge with just, how to lay a red brick, if they are lucky. The building trade is sorely lacking in technical colleges and most students go for the electrical and motor side of things. I live just 1 kilometre from such a technical college and was contemplating using them to build my house, but after going there and speaking with the one "farang" arjarn I employed a builder.
The whole education system is to blame from day one, even though the Education Department has the biggest slice of the budget and the only decent students they turn out are from "demonstration schools and special schools" attached to universities, those students will be sent overseas on scholarships and then are expected to come back and teach for 5 years and also pay the scholarship money back to their "sponsors". Most of them come from rich families anyway. The whole system is a crying shame.
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Re: Silver foil does work

Postby BKKBILL » Tue Jul 25, 2017 3:14 pm

I had foil backed gypsum installed on the ceilings of my house, also foil under the cement roof tiles, double qcon walls. My roofs are vented with a stepped design like this, no other insulation was used.

Screen Shot 2017-07-25 at 2.12.03 PM.png

soffits are of a slotted style for good air movement. Spent about three years designing this place trying to make it energy efficient. To that end also had a high pressure solar water heater installed

All materials used were sourced locally. Now I have not done any tests as to efficiency of the foil or roof venting, but having been here for over six years, we have been comfortable except for about two weeks in April. We are in Mae Taeng, Chiang Mai so don't have high humidity to deal with. If I were ever to get air conditioning it would be one for Heating, cooling and air purify (for the smoky season) in one unit since it does get cold up here in January. Something like this. https://www.daikin.co.uk/en_gb/product- ... emura.html
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Re: Silver foil does work

Postby Andyfteeze » Tue Jul 25, 2017 4:26 pm

Insulation works everywhere. Its not limited to northern semi european altitudes. The application may be different.
Science lesson number 1. Insulation does not insulate. It slows the transfer of energy.
Sure you can go with no knowledge and just build. You can also assume that you cant effect the outcome. Thats YOUR LOSS.
Here in thailand, unless your in the mountain ranges, you are trying to keep the heat out the most economical way. Airconditioning solves most problems. Now if you are conscientious and mind the pennies, you will try to maximize the efficiency of the build so it needs to be on minimally.
Designing an energy efficient house isnt rocket science or brain surgery. The basics are all common sense. Unfortunately, common sense is in short supply, lol.
Stopping heat getting in makes sense. Most people can understand walls and ceiling insulation, but equally critical criterea are the floor and thermal banks .
why do farang build thai style houses that are handicapped from the start? See red bricks, tile roofs and slab above ground. Why do thai build old style timber homes with a massive heat source as their roofing material- tiles? Once you see the inadequacies of these styles of building, you will wonder why .
Basic floor physics. The ground is at about 18-20 degrees c at about 1 foot depth. Use this to your advantage, sit the slab on the ground, not in the air. Air is a good insulator in small pockets ie foam beeds, but is a heat conductor in large areas. The ground is a great heat sink. Your slab is now trying to conduct heat from the top surface to the ground. If your slab is 1m above ground, it is trying to reach ambient temperature. This is 32-36degrees C in thailand. So which makes more sense? the slab trying to stay at 20 degrees or the slab trying to reach 36 degrees? I designed my grnd slab to be 200mm thick rather than the 150mm thai style. It works brilliantly.
Heatbanks. No matter how well you insulate the walls or ceiling, there will be a certain amount of air leakage. The idea of a heat bank is to absorb this leakage in energy . In temperate climes, you use this in winter to keep warm at night. The heat bank is positioned to absorb energy during the day to release at night. Here, its purpose is the opposite. So you want it to absorb very little during the day and so it stays cool at night. Put the two together and you have the basis of good design principles.

foil in the roof to me is just another aspect of keeping the insides cool. its not the only way, its not the most effective way, but if you have nothing else, it will make a difference. We are assuming here , for the sake of the argument, you can do better. You can now buy roll out foil covered fiberglass insulation. Ceiling ventilation can make a big difference too. Without adequate ventilation, a roof cavity can get to over 60degrees C. This is mighty hard to hold back. If the ambient temperature in your roof cavity is 34 degrees, your insulation will be far far more effective at keeping heat out.
I propose a relatively simple solution. Put foil directly under the roof tiles. This will slow down drastically the heat transfer from the tiles to inside the ceiling. Have vents in the ceiling cavity to equalise the temperature to ambient outside temperature. Then place proper insulation over the ceiling. I cant see any other method of using roof tiles ( or tin roof ) and insulation that will work as well. (ceramic tiles technology from the space shuttle havent trickled down yet)

"is really better suited in my opinion to non-tropical areas " is such a defeatist and brain dead statement.

So roy.sokolowski, it only takes a little bit of gray matter to insist on better house design from the start. If you intend on building from people whos only knowledge is " monkee see and monkee do", good luck. Thai builders are great imitators but lack understanding why things are done a certain way . They cant adapt. Even Engineers have a tenuos grasp of basic physics, like water doesnt flow up hill to go down a drain. Seen it with my own eyes, lol.
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Re: Silver foil does work

Postby Sheryl » Fri Nov 10, 2017 1:41 pm

Hi I am about to install a RB. 2 questions for you:

1 - any thoughts re pros and cons of 2 sided vs one sided?

2 - I understand it conducts electricity and that electrocultions have occurred during installation, any tips for safety measures for the workers? They will be affixing to metal rafters so have to use power tools and sparks may fly onto the RB.

Thanks!
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Re: Silver foil does work

Postby Sometimewoodworker » Fri Nov 10, 2017 4:01 pm

Sheryl wrote:Hi I am about to install a RB. 2 questions for you:

1 - any thoughts re pros and cons of 2 sided vs one sided?

2 - I understand it conducts electricity and that electrocultions have occurred during installation, any tips for safety measures for the workers? They will be affixing to metal rafters so have to use power tools and sparks may fly onto the RB.

Thanks!


1) Double sided is about double the price but since you get 70 metres in a roll it still isn't very expensive and then you won't need to persuade them that it must go shiny side down.

2) I've never heard of any danger of electrocution. If you get sparks in the foil they will go through.

The usual method is to drape the foil over the purlins and hold it down with the same fixings as the roof metal.

As I was not fitting roof metal at the same time I had to fit it to the bottom of the rafters.
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Re: Silver foil does work

Postby Ians » Fri Nov 10, 2017 8:02 pm

There were 4 workers electrocuted in Australia a number of years back from poor foil installation techniques.
Google "faulty insulation deaths Australia"
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Re: Silver foil does work

Postby Sheryl » Sat Nov 11, 2017 1:17 pm

I am also having to install behind rafters. Mine are steel/metal though and all the videos I see show affixing to wood rfaters.

Are your rafters steel?

And do I take it then that 2 sided is actually better than 1 sided?

Thanks!
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Re: Silver foil does work

Postby Ians » Sat Nov 11, 2017 2:42 pm

2 sided maybe marginally better in the short term until such time the upper surface gets "dusted". The reason why it is usually only 1 sided.
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Re: Silver foil does work

Postby Sometimewoodworker » Sat Nov 11, 2017 5:32 pm

Ians wrote:2 sided maybe marginally better in the short term until such time the upper surface gets "dusted". The reason why it is usually only 1 sided.

FWIW
When I bought my test roll there were 4 types available, 3 of them were double sided.
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Re: Silver foil does work

Postby Sometimewoodworker » Sat Nov 11, 2017 5:58 pm

Ians wrote:There were 4 workers electrocuted in Australia a number of years back from poor foil installation techniques.
Google "faulty insulation deaths Australia"

3 not 4

The deaths had little to do with the insulation, they were to do with the lack of care when installing it. At least 1 and probably 3 of the people who died did so because they shot staples into live electrical cables. Cure either don't put cables just under the roof or turn off the power first also be sure not to fire nails or staples into electrical cable.
One of the deaths was due to heat exhaustion on the first day of work.

So all in all it was virtually nothing to do with the fact that they were installing foil and everything to do with bad installation practice and lack of training.
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Re: Silver foil does work

Postby Roger Ramjet » Sat Nov 11, 2017 11:23 pm

The question was does aluminum foil conduct electricity and the answer is yes it does.
There is a simple test, take a battery and roll the aluminum into thin lengths, place a light at the end of each roll of aluminum and you'll be able to light the light. This is caused by electrons being able to pass freely through the material.
Just think of the two types of recommended wire for wiring a house, copper and aluminum and aluminum foil happens to be made of aluminum.
All it takes is one mistake, which is why live wires are encased in plastic (yellow PVC) and have a plastic coating.
As Thai electricians are not properly trained all it would take is one mistake and you'll have someone electrocuted.
Just make sure the electrical cables are encased in PVC conduit and at no point do the bare wires run over the aluminum foil otherwise you'll have a fire and also an electrocution.
If you put "is aluminum foil a conductor of electricity" into Google or any other search engine, you'll find hundreds of references.
Aluminum also is a conductor of static electricity, just brush your hair then pass the brush over the aluminum foil and it will lift it.
All electrical cables used underground must be firstly encased in plastic, then in PVC tubing to stop static from building up.
I think we have started another wizard's school called Hogwash that has no relation to Hogwarts.
Does it act as a barrier to heat, yes, but it also allows the flow of an electrical current.
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