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Old 08-10-14, 06:42 PM   #11
ICanHas
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Quote:
Originally Posted by AC_Hacker View Post
Sounds like an interesting and easily-staged experiment.

I'd like to see your results!

BTW, I have IR measured the night sky before and it goes surprisingly lower than 18-20F.

-AC
I tried it during the day, and night and that's what I got. Maybe I gotta try even clearer night.

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Old 08-11-14, 10:03 AM   #12
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I did an IR measure of the sky @ 6am and it read about 30F... we're in a bit of a heat wave.

-AC
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Old 08-15-14, 11:08 AM   #13
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I made a prototype sample of the mylar in a multi-layered configuration:


Here is a prototype sample I made. It consists of 10 layers of mylar space blanket material separated by 11 layers of bridal veil (yes, really). I'm fortunate to have a seamstress who lives on my block, who had enough bridal veil material scraps to do this prototype.

Cutting the 10 very thin layers of Mylar into 10" squares and also 11 layers of light, filmy bridal material was not easy, fortunately, I have a rotary cutter. Interlayering the pieces in an orderly fashion was taxing, to say the least. At one point, I sneezed, and the layers all went flying, and I had to start all over again.

Right now the assembly is just stapled at the corners, until I sew up the edges.


Here's a detail of a corner... it's pretty ragged, but the layers are visible.

The bridal veil layers are to prevent the mylar from touching, so that conduction from mylar-to-mylar us at the very minimum. In fact, on the Wikipedia entry for Multi Layer Insulation, they even refer to it as 'bridal veil', but in their photo, it is something more robust.

I haven't done any testing other than making this sample, and handling it. It does have a very curious handling quality, partly because of the mass of muted crinkling sounds, but also because of the unique, delicate tactile sense involved. Very curious. Also it does have a subtle, barely noticeable warmth because it reflects the heat of one's hand. It does seem just a bit like it could have been left behind by an alien spacecraft.

My son, who likes to sew, dropped by yesterday and without me even saying anything, he spotted the glittering prototype sample, and picked it up and was handling and marveling at it, and of course he wanted to know what his father was up to now.

I reminded him that a few Xmases ago he gave me a coupon for "One Hand Made Vest".

He is enthusiastically, "all in".

Best,

-AC_Hacker
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Old 08-23-14, 04:05 PM   #14
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[IMG][/IMG]I've been trying a multi layer radiant attic myself. No veil, just large breezy air gaps. Spray on radiant on the decking, kitchen foil on 2x4 rafters, radiant [IMG][IMG][/IMG][/IMG]double bubble across the collar ties and now the attic floor with r-6 foil faced fiberglass duct wrap. A roll is 4'x75' and if I remember costs me around $120. Temperature on the top of the attic floor foil has been no more than 2 degrees over outdoor high temp, 104f on a 102f day. On the few recent days we've had below 100 I've had a few max temps below outdoor max. Temp measured below the foil and r-6 has been about 4 degrees below outdoor ambient, 96 on a 100 degree day. All of this is on top of a R-38 attic. The additional benefit of the floor barrier is it covers the R-8 Flex and reduces heat gain into the ductwork.
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Old 08-23-14, 05:54 PM   #15
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Good going!

An attic is the best place to apply the multi-layer reflective approach.

Don't know if you saw the chart below, it pretty much tells the radiant heat reflecting story.


-AC
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Old 08-25-14, 09:54 PM   #16
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Quote:
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Good going!

An attic is the best place to apply the multi-layer reflective approach.

Don't know if you saw the chart below, it pretty much tells the radiant heat reflecting story.


-AC
The radiant heat transfer is dependent on the temperature difference and I think emissivity, reflectance and transparency. If you could somehow use radiant barrier on the roof, I speculate it woulId be an order of magnitude more effective. Maybe I'll test this out in my with the shield inside vs outside the windshield. I wonder why roof materials are usually black.
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Old 08-26-14, 01:32 PM   #17
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PLEASE NOTE: This post is not a response to the above post. I have no interest in feeding the troll.

* * *

I have moved this post over from the 3/4" insulation post, as I though it would be a better fit here, where multi-Layer Insulation is the topic under discussion.

* * *

Quote:
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...All I'm saying is that while the concept of using multiple layers of radiant barrier may be good in principle in a vacuum it won't work as you are advertising. But hey, if bringing physics to the table is being smug on this forum then I plead guilty. However, if you really believe that the stuff sold in the UK has over an over 20 R value per inch then I have this bridge I'm selling that you'll find is a real bargain...
Exeric,

I'm surprised that you criticized my post on technical merits (which you have no way of assessing), when the most vulnerable part of the product is cost. I think you must have been sleeping-while-posting.

I mean $1.75 per square foot would clearly choke a horse, and you missed that one completely. Especially if you consider that the $1.75 would only buy you R15.3 stuff. To get the R28, you'd need to go two layers of the 19 layer insulation, or $3.50 per square foot.

So obviously, you could now choke two horses.

But the potential applications are tremendous, especially in traditionally poorly insulated areas like exterior doors, where the R-value is usually R-2 or R-3.

In Oregon, they are begging people who are building 'advanced technology' houses to use minimum R-5 doors.

A typical door is about 20 sq. ft., so at the worst, 20 sq. ft. x 3.5 $/sq.ft. would cost $70, which is an absolute pittance for this kind of dramatic performance improvement.

I really do think that by assuming that our current practices are the best practices, we are missing some amazing opportunities.

* * *

Curiously, you can not buy this stuff in the USA. I have looked everywhere, and even at a one-horse-choking $1.75 per sq. ft. you can not buy this stuff. The web site even states that they do not export this material to the USA. I can't even find it on ebay.

Hey Canada!!! Can you get this stuff???

-AC
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Old 08-26-14, 02:10 PM   #18
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AC, actually I hope you're right about the stuff. And I did miss the extreme cost of it. But I'm not sure they aren't using the extreme price to lure in people with the reverse psychology of "it must be special to cost that much." Time will sort this out if it's the real deal. But part of my harsh reaction came from your implication, whether I misinterpreted it or not, that I was not a supporter of radiant barriers. That is clearly not the case. But I do believe in targeted application of it and the use of clear principles of cost vs benefit analysis in its use. Insulation is still required in houses over and above use of radiant barriers.
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Old 08-26-14, 02:22 PM   #19
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... But part of my harsh reaction came from your implication, whether I misinterpreted it or not, that I was not a supporter of radiant barriers...
I think that radiant barriers are great, if you think they are great, then we both think they are great.

My point is that it looks to me that multi layer insulation with multiple reflective layers might be a game changer, and I am extremely interested in its potential.

If I could get some, I would buy it and test it and publish my results.

Dead end there.

So, I'm going to try to make some. I have a fair amount of aluminized mylar (space blankets), but the thinsulate I ordered was too expensive and too thick. So I am searching for a good separator material so I can do some testing.

I don't thing that the bridal veil material is what I want, and the thinsulate brand stuff is not right either, but it is microfiber (good) and thicker than what I wanted (bad).

Still looking...

-AC
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Old 08-27-14, 03:04 PM   #20
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Multi foil insulation is available and used in the UK, however there still seems to be some debate as to how effective it is.
Last time I looked some building control authorities accept it and some don't.

The thermal performance quoted is only possible in the correct construction which is usually a 1" batton either side of it to create an air gap. This makes the minimum thickness of the insulation construction 2"+.

The biggest issue is that the material between the foil is a like synthetic wool, if you try to put a screw through it it wraps around it and usually sheers before fully tightening. Also impossible to drill as it wraps around the drill bit.

Whilst I could use it in my loft(attic) conversion I,m currently doing I decided to stick with polyurethane foam with foil on both sides. Using 4 layers of various thicknesses adding up to 150mm (6") which means 8 layers of foil so u guess it is multi foil in a way.

AC will be interested in your results as to how you get on with dig multi foil.

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