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jjackstone

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Reply with quote  #1 
I've seen a number of discussions talking about use of reflectors on the site. Just thought I'd toss in a couple of pictures of mine.
Out to Patio.jpg This first one is looking out the back door onto the patio. Every where you see aluminum there is concrete beneath it. There is about 150 sq ft of reflector material there which is just shy of five sq meters. Realistically only about half of the area is ever being shined on at any given time of the day.


Patio reflectors.jpgHere is the opposite view looking back into the house.

The back of the house is almost due south so most of the sun is hitting the patio right around noon. I got this idea from the house in Australia. I imagine most of you have seen it but if not I can look it up for you. So all these panels are made of is a very strong fiber infused aluminum foil adhered to quarter inch polystyrene foam that is normally used for flooring insulation. I think they call it fanfold insulation. It normally sells for around $30 for a fifty foot section but I found a ton of it going for $7 for fifty feet a couple years back. I bought the foil on line at $80 for a 4 ft x 250 ft roll. It is pretty tough as long as you don't use things that gouge like high heels. I have been walking on it for a couple years now. I do notice that the reflective material is actually wearing away in some spots as I can see the pink foam through it. If we did the math and "asss-umed" a kw/sq meter and also assumed about 80% reflectivity (manufacturer specs) and that about half the material gets sun for five hours a day, we might get 800 watts times 2.5 sq meters = 2 kw times five hours a day = 10 kwhrs per day of energy hitting the back door. I would guess though that our double paned doors would block at least 30% of this heat though so maybe 7 kwhrs inside per day on a good day. Not too bad for passive heat. And very,very bright!!! Oh, you can't see it (maybe a bit in the first picture) but I also have this material stapled to the underside of the patio roof so that when the light reflects up high it can then be reflected back down and into the house.

Enjoy,
JJ


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JJ

sundug

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Reply with quote  #2 
Thanks for the post, it's interesting. I searched sources for fiber infused aluminum foil, but it didn't turn up many sources, much less cost. Please post your source and cost. Thanks, Doug   http://www.presserv.com/products/coverings-and-mechanical-protection/glass-fiber-reinforced-aluminum-foil/
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jjackstone

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Reply with quote  #3 
Bought it from ebay. Below is a stock advertising blurb for it. It's called a reflective radiant barrier. It appears I misspoke about the fiber. They call it this...polyester scrim reinforcement. This one is rated at 95% reflectivity. I use it for a number of things including the obvious reflecting the sun into the house. Last summer I built a quick little three sided box with a ground reflector in addition and used it to heat a few gallons of water a day. Then I just put the hot water in a 5 gallon igloo water dispenser. It will stay above 100 degrees over night. That way there was no need to run cold water down the drain while I waited for hot water to reach the sink. Being retired gives me the time to turn the reflector every couple hours. I could build a larger version but from late spring to early autumn I only use less than $10/mo of natural gas. A couple of those months are around $6/mo.

Link: 
https://www.ebay.com/itm/1000-sqft-Diamond-Radiant-Barrier-Solar-Attic-Foil-Reflective-Insulation-4x250-/152465167625?hash=item237fa1d509

Quote:
For residential retrofit, particularly in the attic laying over existing insulation, and some OEM applications. Available in 500 and 1,000 sq. ft. rolls or custom lengths. Only available in perforated 4' widths. Super R Diamond?? brand radiant barrier was the first product developed by Innovative Insulation. Super R Diamond?? is two-sided reflective aluminized polyester film with reinforced scrim inside, designed to reflect radiant heat no matter what the season. Choose Super R Diamond?? to retrofit an existing structure. It can be stapled to the underside of the roof rafters in an attic Key Benefits Meets new ASTM E84 and E2599 fire code Clean, Lightweight, Easy To Install Saves Energy and Money For Residential Retrofit Product Specifications Meets ASTM C1313 Standard Specifications for Sheet Radiant Barriers for Building Construction Applications Product Description Two-sided reflecting metalized film with polyester scrim reinforcement Weight 16.35 lbs per 1000 sq ft roll Tensile/Tear Strength Length: 2.32 pounds force Width: 1.50 pounds force ASTM D2261-07a Pliability 70??F??5??F & 50??5% Relative Humidity - No Cracking or Delamination ASTM C1313-05 Adhesive Performance 180??F??5??F & 50% Relative Humidity - No Bleeding or Delamination ASTM C1313-05 Flame Spread & Smoke Class A/ Class 1 0 Flame Spread, 10 Smoke Development ASTM Method E84-10 Resistance to Fungi PASS - No Growth ASTM C1338-08 Permiability 9.6 Perms ASTM E96-05 Thermal Properties EMISSIVITY: 0.05 REFLECTIVITY: 95% ASTM C1371-04a



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JJ
sundug

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Reply with quote  #4 
Ok, that's different. I have had the radiant barrier tacked up underneath my attic rafters for years, it helps keep the attic cooler. 
What did you use for adhesive?

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jjackstone

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Reply with quote  #5 
Just used Scotch 77 sprayon adhesive. Best way to use it is to spray it on both surfaces very lightly. It doesn't like to stick as well  if it goes on "wet". And then the obvious, have both surfaces clean and dry. If you keep all your pieces to where they can't blow around then everything seems to stay together pretty well. However if you have a good amount of wind and flexing I would suggest adding aluminum furnace/duct tape down the edges so the wind can't get under the edge and slowly start peeling them apart.
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JJ
pianoman8020

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Reply with quote  #6 
I was recently invited to a sales meeting hawking a aluminum attic insulation cover for $3.64 /sq-ft installed. I find the following things that should give anyone pause about doing such a thing. The key word here is "reflective". Most attics are dark so there is no reflection going on here. If the surface should get dusty the effectiveness decreases by 30-40% the first year and 10% there after. Aluminum is a very good conductor otherwise.

They could also could provide an aluminum paint for interior surfaces for $1,500 / 5 gal.

Jim from IL
jjackstone

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Reply with quote  #7 
I'm pretty sure that when they talk about the reflectivity of aluminum used for insulative purposes they are talking about the reflectivity of heat as opposed to visible light. Once the heat goes through a roof if there is an aluminum barrier mounted to the underside of the roof is should reflect the heat back outward. Although I have always wondered how much hotter that would make the roof itself. Sounds like something to look into. How about it Sundug, any observations on this?
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JJ
stmbtwle

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Reply with quote  #8 
I wish they could build that reflective barrier into SHINGLES!

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Willie, Tampa Bay
jjackstone

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Reply with quote  #9 
Quote:
I wish they could build that reflective barrier into SHINGLES!
 
There are a number of them out there. None as effective as the aluminum foil but it is at least being addressed. Here's one.
https://www.certainteed.com/residential-roofing/solar-reflective-shingles/

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JJ
sundug

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Reply with quote  #10 
My first attic roof was white asphalt shingles, the attic would get unbearably hot in summer. I bought the radiant barrier online for considerably less than was quoted above, but it was years ago, and I don't recall the price, altho 50 cents a sq ft comes to mind. Tacked on the bottom of the roof rafters, and leaving a gap top and bottom, it did help keep the attic cooler. But the biggest difference in attic temps came after I covered the shingles with 40 year quality bright white steel roofing panels. On a hot sunny day, the metal read 50*F below the shingle temp. I have had soffit and ridge full length vents and gable end vents from the start. I used to have an AC powered attic roof fan , but found there was no need after I put the metal on. Now attic temps run very close to outdoor temps. I even tried painting a coating on the shingles, it didn't seem to make much difference. Even a bright white asphalt shingle absorbs a lot of heat compared to a same color steel roof. Doug


"As previously mentioned, various cool roofing materials are used for different roofing types.  Because of this large variability, the U.S. Environmental Protection Agency has a list of over 3,000 ENERGY STARĀ®-rated cool roofing materials, which should be chosen based upon building type, roof type, and location.

Asphalt Shingles are composed of asphalt mats made from organic felts or fiberglass.  Their Solar Reflectance Index (SRI) is relatively low, as white shingles are only about 30% reflective and other color tiles even less so.  They are widely used in the residential sector because they are low in cost and simple to install.
Metal roofs, one of the most popular roofing materials used today, can achieve a solar reflectance of over 70%, allowing buildings to remain much cooler and lowering their energy costs.  Metal is also extremely durable and weather-resistant, lightweight, and 100% recyclable at the end of its useful life.

https://www.go-gba.org/resources/green-building-methods/cool-roofs/

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