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Old 05-07-12, 10:47 AM   #31
lucerne96
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Several years ago, I was involved in a yearlong study of white roof coating. We used a product called Acrymax. We painted all the roofs in an entire city block in Philadelphia. Temperature sensors were installed in various places throughout the block; light poles, roofs, peoples houses, etc to generate data. The same was done in an adjacent city block, whose houses had traditional black tar roofs.

In general, it was found that the white roofs were 50-80 degrees cooler than typical asphalt roofs. The top floor of the homes about 5 to 15 degrees cooler (depending on insulation levels of the houses). This meant that a strategy of summer cooling whole house fans rather than A/C could be used. Average energy reductions were in excess of 30%.

Another interesting point I remember was the average street temp in the height of the summer was 5 degrees LESS that the adjacent (black roofed) street (urban heat island effect).

+++

A have just recoated my white roofs (over metal roof) with the initial coating lasting about 10 years. Recoating cost about 70 cents sq ft.

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Old 05-13-12, 10:44 AM   #32
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I was repainting my house bright white with sky blue trim (it was brown with a dark brown roof when I brought it) and thought why stop at the roof line, so I bought two 40lbs bags of hydrated lime (at $12 each, much cheaper than paint) and whitewashed my roof and it is now a bright white to match the walls. The advantage of whitewash is that it will gradually wear off, so by late winter the roof should be back to its original color and absorbing the winter's sun for warmth. It only took 2 hours to whitewash the roof with a paint roller, so the whitewashing process is quick and cheap enough to be an annual spring event. Also as it weathers, whitewash only releases calcium carbonate onto the surrounding landscape rather than whatever unknown chemicals are released from paint as it weathers. It should also help extend the roof life by greatly reducing the 24 hour temperature swing experienced by the shingles.

Effect: it hasn't been hot enough for A/C use since I whitewashed the roof, but on the previous day the attic vent fan (set to turn on at 120F) kicked on at 11am and shut off at 4pm, while on the two days following the whitewashing the fan never turned on. All 3 days were sunny with a high of 79F. On the original dark brown roof, I could feel the heat radiating (almost too hot to touch) off the shingles at noon, whereas the white roof just gets slightly warm to the touch.
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Last edited by basjoos; 05-13-12 at 10:48 AM..
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Old 05-13-12, 02:46 PM   #33
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I would do some research to check out what the potential interaction might be between whitewash and the material your roof is composed of. I know that a problem has recently been observed around the use of copper flashing & wood shake roofs; because of the wood preservative being used leeches out & reacts with the copper.

You might also consider if it matters that the whitewash will change the Ph of the ground surrounding your house, potentially having an effect on whatever is growing there.
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Old 05-13-12, 07:14 PM   #34
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Quote:
Originally Posted by lucerne96 View Post
I would do some research to check out what the potential interaction might be between whitewash and the material your roof is composed of. I know that a problem has recently been observed around the use of copper flashing & wood shake roofs; because of the wood preservative being used leeches out & reacts with the copper.

You might also consider if it matters that the whitewash will change the Ph of the ground surrounding your house, potentially having an effect on whatever is growing there.
Whitewash is just calcium carbonate (limestone) and has no detrimental effects on a composition shingle roof with no flashing. I live in an area with acidic soils and have to add lime to the garden soil from time to time to raise the pH. Any calcium carbonate leached from the whitewash on the roof would have the same effect as liming the soil.
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Old 05-13-12, 07:34 PM   #35
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According to this https://docs.google.com/viewer?a=v&q...tptvt4fFhUmBXA

an article from the 4th Int Symposium on Roof Technology; Re use of fly ash in shingle manufacture:

"A common specification among shingle manufacturers is a limit to the free lime content in filler. Roofing industry experience has shown that an excess amount of lime can react with certain asphalt constituents to greatly accelerate granule loss from the shingle, resulting in premature failure of the roof."

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Old 05-13-12, 10:31 PM   #36
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I'm using metal roofing supported by metal beams. I have vents in the ceiling located outside the house.

So I'm thinking that if I repaint the roof in white. it'll make a big difference in heat reduction is that right? or am I better off putting a layer of that foil wrapped foam sheets inside the ceiling (which may entail taking off the ceiling to put it in..fyi I have a low ceiling)


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Old 05-14-12, 09:01 AM   #37
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I would white coat the roof with Acrymax Acrymax Technologies, Inc. - Flexible Solutiong in High-Perfomance Coating Systems! AND insulate the the space under the roof. Remember, heat travels by radiation, conduction & convection; so the best game plan addresses all three. WRC only really addresses radiant heat gain.

Perhaps a access hatch could be made in a closet ceiling to gain access.

I have metal low slope roofs on my 1880's Second Empire style house & it has made a bid difference.

I power washed the roof; put down the base coat (with roller). You then roll out a layer of fiberglass mesh which becomes embedded in the wet undercoat. Then you roll on the final reflective coat. I first did white roof coating in about 1984 (when I learned about it from the National Park Service), and did a top layer recoating last year.

I also tried EP Henry's & Ames Labs similar product, which are less expensive. That is because they have more liquid and less pigment. The roof I did with EP Henry lasted only about 4 years, Ames about 7. I have gone back to the Acrymax.

To maximize its efficiency, you have to keep it clean, so consider giving it a wash before hot weather.

PS: I have NO affiliation with any material supplier or manufacturer whatsoever. I am only interested in results.

Last edited by lucerne96; 05-14-12 at 09:05 AM..
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Old 05-14-12, 09:53 AM   #38
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Quote:
Originally Posted by lucerne96 View Post
According to this https://docs.google.com/viewer?a=v&q...tptvt4fFhUmBXA

an article from the 4th Int Symposium on Roof Technology; Re use of fly ash in shingle manufacture:

"A common specification among shingle manufacturers is a limit to the free lime content in filler. Roofing industry experience has shown that an excess amount of lime can react with certain asphalt constituents to greatly accelerate granule loss from the shingle, resulting in premature failure of the roof."
The paragraph above refers to excess free lime in the finely pulverized mineral stabilizer filler used in the interior of the shingle during the manufacturing process. Filler is used inside the shingle to keep the asphalt from flowing when it gets hot on the roof. That article proposed using fly ash as replacement for the pulverized limestone traditionally used as filler. It isn't referring to the much larger sized grit imbedded on the surface of the shingle.

What I am doing involves just the upper exterior surface of the shingle. The granules on composition roofing are usually made of limestone (calcium carbonate), which is what hydrated lime turns into as it cures. I'm just adding a thin layer of unpigmented (white) limestone on top of the pigmented limestone grit that is already there. Calcium hydroxide has long been used as an additive to the asphalt used for paving roads to make pavement last longer.

Fly ash is a mix of silicon dioxide, aluminum oxide, and iron oxide, which chemically is very different from the calcium hydroxide in hydrated lime.
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Last edited by basjoos; 05-14-12 at 09:57 AM..
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Old 05-15-12, 09:23 PM   #39
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Quote:
Originally Posted by lucerne96 View Post
I would white coat the roof with Acrymax Acrymax Technologies, Inc. - Flexible Solutiong in High-Perfomance Coating Systems! AND insulate the the space under the roof. Remember, heat travels by radiation, conduction & convection; so the best game plan addresses all three. WRC only really addresses radiant heat gain.

Perhaps a access hatch could be made in a closet ceiling to gain access.

I have metal low slope roofs on my 1880's Second Empire style house & it has made a bid difference.

I power washed the roof; put down the base coat (with roller). You then roll out a layer of fiberglass mesh which becomes embedded in the wet undercoat. Then you roll on the final reflective coat. I first did white roof coating in about 1984 (when I learned about it from the National Park Service), and did a top layer recoating last year.

I also tried EP Henry's & Ames Labs similar product, which are less expensive. That is because they have more liquid and less pigment. The roof I did with EP Henry lasted only about 4 years, Ames about 7. I have gone back to the Acrymax.

To maximize its efficiency, you have to keep it clean, so consider giving it a wash before hot weather.

PS: I have NO affiliation with any material supplier or manufacturer whatsoever. I am only interested in results.
Thank you very much Sir! Will be looking for that. I just hope it'll handle up to extreme tropical weather. 7 months sun (100 degrees Fahrenheit at peak sun) and 5 months rain. I have several months to source it out since rainy season has begun already.

oh and I like that closet hatch idea, been contemplating If i had to make a hole in the bathroom or in the hallway..now that's definitely better and wont make the house look messy
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Old 05-15-12, 10:21 PM   #40
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Quote:
Originally Posted by Exalta-STA View Post
Thank you very much Sir! Will be looking for that. I just hope it'll handle up to extreme tropical weather. 7 months sun (100 degrees Fahrenheit at peak sun) and 5 months rain. I have several months to source it out since rainy season has begun already.

oh and I like that closet hatch idea, been contemplating If i had to make a hole in the bathroom or in the hallway..now that's definitely better and wont make the house look messy
When blowing insulation thru a ceiling hatch, I start at the farthest point I can get the hose and work back to the hatch. If you can't reach the entire crawlspace, consider cutting a 6" circular hole in the roof, blow in insulation then install a mushroom or turks head vent in the hole.

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