Roof color opinions: dark vs. light

Leprechaun
Leprechaun Registered Users Posts: 6 ✭
in General Solar Power Topics #1
I am replacing my roof before installing a 10kw system. The wife would like dark shingles to go along with new house color of a darker brown". We live in Florida and have cars with black interiors. I know that black absorbs energy and inside of a car it makes it feel hotter than a light interior. My question is what impact does it have with roofs. I thought I would ask the solar community if they have an opinion about dark vs. light shingles and the impact on realizing energy savings.

BTW, we will be installing shingles from Owens Corning. The shingles being considered (dark to light) are Onyx Black, Estate Gray, Quarry Gray.

Thoughts or opinions?

Onyx Black
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Estate Gray
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Quarry Gray
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  • Leprechaun
    Leprechaun Registered Users Posts: 6 ✭
    #2
    Re: Roof color opinions: dark vs. light

    The front of my house faces south so some of the panels need to face south. I am not sure how many yet but more than a few. We think a dark roof will make the panels less obvious from the street.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
    Re: Roof color opinions: dark vs. light

    Go with the dark.
    Yes, it absorbs visible light and turns it into heat. Light colours will reflect light and be a bit cooler. But you know what? Not enough to fret over. I've done a lot of roofs (and am doing one even as we speak!) and there is no discernible performance difference between colours. The main factor is how well the air circulates under the roof to keep it from getting too hot. Since you have to replace the roof anyway, now is the time to get the ventilation checked. Eave vents to ridge vent works best.

    BTW, I've had black and white roof on the cabin under the solar panels. I've noticed no difference between the two either for roof heating up or panel production. The temps range from -40 to +40 here so the roof (faces WSW) gets quite a workout.

    It's going to be green this time. :D
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
    Re: Roof color opinions: dark vs. light

    coot has been in the cold too long. nearly every home down there is white for a reason, it's too hot down there. also note that the roofing shingles that are considered for rebate are only in a reflective white color at least here in pa. not sure if that applies federal or not, but regardless if getting a rebate go with the lightest shingles you can as it will also add years to their condition too. none of your selections are light enough, imho.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: Roof color opinions: dark vs. light

    Bah! You Americans and your tax rebates on everything! You ought to try living in the land of 50% ! :p
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: Roof color opinions: dark vs. light

    look at it this way coot, when it's coldest up there at night the shingles with their dark colors will radiate the heat from out of the house as good absorbers of heat are also good radiators of heat too. it would stay too warm in florida with their ambient temps to radiate the heat out at night very well any time of the year and you don't want the roof area to make things worse by adding heat to the dwelling during the daytime. there's a reason why even here in pa that they only approve of the lightest color in the shingles for rebate and it isn't just to be a stinker on regulating.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: Roof color opinions: dark vs. light

    Niel, I just have to ask:

    Since roofing comes in a wide variety of colours, where is the cut-off in reflectivity to qualify for this rebate? 18% gray? 50%? Do they actually have ratings on roofing for that down there?
    I sure wouldn't want to have to factor that into a quote. Not that there's any chance whatsoever of my ever doing another commercial install, as you know.

    You have to admit our system is much easier to understand: hand over half your money and shut up about it. :p
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #8
    Re: Roof color opinions: dark vs. light

    From everything I've read about roof color - yes, lighter is a little better, but there isn't enough difference to matter much.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #9
    Re: Roof color opinions: dark vs. light

    i only know what a roof installer told me when giving me an estimate and i can't say to what degree of anything it is, but it was the whitest shingles he has access to and only the one qualified according to him. the rebates are irrelevant as what i said of heat absorption and emission are true. it will make a much bigger difference on a roof than you think in florida. maybe not as much in coot's area and we're in between, but would still benefit by it moreso than not.
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #10
    Re: Roof color opinions: dark vs. light

    When I got my new roof earlier this year, the only one that was Energy Star rated and thus able to get a rebate was the white one from Owens Corning.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #11
    Re: Roof color opinions: dark vs. light
    Windsun wrote: »
    When I got my new roof earlier this year, the only one that was Energy Star rated and thus able to get a rebate was the white one from Owens Corning.

    The question is: would any white roof qualify, or is this shingle particularly certified for heat reduction?
    I can think of ways of making standard asphalt roofing so that it would be much better at reflecting heat. It would cost more too. Of course. What doesn't? :roll:
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #12
    Re: Roof color opinions: dark vs. light

    The Energy Star rated shingles are listed here http://roofing.owenscorning.com/professional/energy-star-products/

    For most lines, the Shasta White is the only color that qualifies.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #13
    Re: Roof color opinions: dark vs. light

    Thank you for that, Windsun.

    Interesting, but a bit short on any data that shows this roofing works as claimed. Lots of muddling with qualifiers too. "Instant savings of up to 20%* off on your heating and cooling energy bills." Let's remember that "up to" starts at zero. :roll:

    The principal is sound, but it presupposes that reflecting some of the sunlight striking the roof will have a significant effect on the interior temperature of the building. In most cases, since buildings are built very poorly, this will be so. If you've got R42 in the attic and good venting under the roof this product would not be worth and extra five cents were in not for the tax credit. I just hope no one buys this stuff thinking they will automatically drop the A/C costs by 20% as a result. The tax credit is the main incentive, and that looks like the government throwing away money to me as there is no guarantee that any energy will be saved on a particular installation but the credit is across-the-board regardless.

    If I were still going to be doing this stuff I'd investigate further. Even so it wouldn't be much benefit up here, even in the desert.

    Only my opinion and certainly no one has to listen to me. :D
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #14
    Re: Roof color opinions: dark vs. light

    "Only my opinion and certainly no one has to listen to me. :D"

    what? did you say something?:p

    that shasta was the one he mentioned now that it was said. now i can't say if there wasn't any pushing of one company over another or not or why that shingle qualifies over another so there still may be something to what you said (that i didn't hear:p).

    sorry marc as i couldn't resist pulling your leg on this.:D
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #15
    Re: Roof color opinions: dark vs. light

    Last time I shingled my house I used light silver/gray. Not so much because I expected the inside of the house to be cooler ( R-80 in the ceilings), but so as to hopefully not cook, dry out and crack as quickly as black ones. Seems shingles are getting to be poorer quality every year, and the so-called 25 yer warranty is a joke. It's "pro-rated" and many people do well to get 10 years out of them before they need replacing again :grr
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #16
    Re: Roof color opinions: dark vs. light

    That's okay, Niel; I'm used to people not listening to me. Married, you know. :p

    I'd just like to see some test data. Nothing complex, just a couple of identical uninsulated sheds side-by-side one with black roofing and one with white, good under roof ventilation. Measure the interior temp at the center of each. Should be lower in the white roof shed. Then start adding insulation between the 'attic space' and the 'living space' and see if the white roof retains its advantage.

    As I said before, I've been in ventilated attic space of the same building mid-summer with both black and white roof above and 30+C outside: no bloody difference at all. So if this roofing is really doing a good reflection job I'd like to know about it.

    Only out of curiosity. I am not doing any more roofs, ever. This one should be good for 30 years, so the next person who has to replace it will be my now-4-year-old grandson. :D
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #17
    Re: Roof color opinions: dark vs. light
    waynefromnscanada wrote: »
    Last time I shingled my house I used light silver/gray. Not so much because I expected the inside of the house to be cooler ( R-80 in the ceilings), but so as hopefully not cook, dry out and crack the shingles as quickly as black ones would.


    Here's some 'weird' for you, Wayne; in my experience the colour that lasted longest was red! :confused: No idea why. Different granules? Better resistance to UV? :confused:
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #18
    Re: Roof color opinions: dark vs. light

    Good point "Coot". Could be the lighter ones let more UV through? But that raises the question: Why red better than black. Some things I think we're just not meant to know. Hahahaha
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #19
    Re: Roof color opinions: dark vs. light

    The "stone/gravel" is what provides the UV barrier for shingles (and hot tar type roofs--which are close to going away in our area--Don't last as well and the risk of injury from hot tar).

    Note that Red is typically the worse for UV and Blue is the best (red absorbs UV, blue tends to reflect UV--paints get their observed colors from the light energy the absorb--what is left/reflected is the color we see).

    Yea--Apparently asphalt shingles are having a hard time lasting past 20 years (my 25 year shingles are falling apart at about 30 years). I don't really like the look of architectural steel roofs (and used to have problems with small animals living under the steel; my roofer now installs screening/blocking to prevent house guests)--But going to try one now. They are supposed to be cooler because of the extra air gap--Plus this time there will be ridge venting too. See what happens in October when they are to be installed.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #20
    Re: Roof color opinions: dark vs. light

    Yes BB re the newer steel roofs, that's what many people fed up with asphalt are going with here now and so far they seem to be working out well. Got mine re done with asphalt a few years back and have been kicking my butt ever since. Of course no one mentioned the asphalt problems until after I had it done, then everywhere I turned there were horror stories followed by "Didn't you know?" :grr
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #21
    Re: Roof color opinions: dark vs. light

    In "innovative" CA, some regions require "Cool Roofs" for Conditioned Spaces, at least. Forget the details, possibly it is being phased-in ... forget. These apply to the more airid regions:

    http://www.consumerenergycenter.org/coolroof/

    Considered it for some new construction here, but opted for (dark) Forest Green. FWIW, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #22
    Re: Roof color opinions: dark vs. light

    It was sort of funny... We went in for asphalt shingle on a little 3 bedroom 1 bath rancher (who it going to put big bucks into a roof on one of those?).

    After we had all the basic costs worked out, I asked my wife if she wanted to talk about steel roof (roofer did not even bring it up). She did, and we ended up going with the steel instead (maybe 30-40% more). More and more homes in our area are installing the steel roofs (in California, we have a love/hate relationship with wood shake/shingles and wild fires--There are still a few people that want to install fire treated wood shingles on their roofs--And the treatment is suppose to negatively affect the life of the wood). The roofer pretty much said that asphalt shingles are on borrowed time past 20 years (home my other roof with 45 year shingles+solar panels lasts longer than that:cry:).

    Still don't really like the non-random look of a steel roof--But even my "cheap" 25 year roof (put on by the previous owner) had the top few courses of shingle blown off at ~year 10 (we don't get that much wind usually). My repair did last (I used dab of asphalt shingle glue under each tab). And now some other tabs are just starting to break loose now ~30 years in.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #23
    Re: Roof color opinions: dark vs. light

    If you go with steel make sure you have the best installer in the world. I've yet to see one not leak in the first year. :cry:
    My former neighbour in Langley put one on his brand-new million dollar house; leaked in the first rain that hit it. Got it fixed. Leaked in the next rain that hit it. Got it fixed.
    (lather, rinse, repeat)

    Asphalt doesn't last as long as they claim, especially in rough climates. But it doesn't leak before it fails. :roll: Just don't believe the warranty/50 year hype.
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  • rollandelliott
    rollandelliott Solar Expert Posts: 834 ✭✭
    #24
    Re: Roof color opinions: dark vs. light

    I did not read every response but fsec.ucf.edu did a study in florida regarding roof color and the heat reduction were 19%
    http://www.fsec.ucf.edu/en/research/buildings/zero_energy/lakeland/roof.htm

    http://www.fsec.ucf.edu/en/publications/html/FSEC-CR-1220-00/index.htm

    concludes energy savings are real around 3 to 5%
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #25
    Re: Roof color opinions: dark vs. light
    rollandelliott wrote: »
    I did not read every response but fsec.ucf.edu did a study in florida regarding roof color and the heat reduction were 19%
    http://www.fsec.ucf.edu/en/research/buildings/zero_energy/lakeland/roof.htm

    http://www.fsec.ucf.edu/en/publications/html/FSEC-CR-1220-00/index.htm

    concludes energy savings are real around 3 to 5%

    thanks for that info and confirmation of what i was saying.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #26
    Re: Roof color opinions: dark vs. light

    Yes, Rolland; thanks for that info and confirmation of what I was saying. :D

    5% energy savings is in the realm of statistical error and certainly not worthy of any tax dollars.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #27
    Re: Roof color opinions: dark vs. light

    coot,
    it does not change the fact that a light colored object will reflect light and heat away more than a dark colored object. and during the night the dark colored objects will emit more heat than a light colored object. i do understand your argument on how government selects some things over others though.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #28
    Re: Roof color opinions: dark vs. light
    niel wrote: »
    coot,
    it does not change the fact that a light colored object will reflect light and heat away more than a dark colored object. and during the night the dark colored objects will emit more heat than a light colored object. i do understand your argument on how government selects some things over others though.

    Niel;
    I've never argued that light doesn't reflect light and therefor its absorption and conversion to heat energy. My point has always been that it isn't significant enough to justify this rebate (hence my early earnest question as to what degree of reflectivity they allowed for the credit).

    All energy tax credits should be qualified on the basis of them actually doing something that is worth the monetary exchange. We had BC Hydro doing energy audit/retrofits here by 'certified' (means "paid a fee") contractors. No proof they saved any energy. I know because I had to undo a lot of their work on our house and re-do it right. Merely blowing insulation in to the attic doesn't mean your cooling/heating bill will go down.

    But governments base their actions on what is politically popular or lobbyist-paid, not anything to do with facts. Facts get in the way of good policy.

    The only reason our government doesn't do something similar is because they don't believe in letting us have any of our money back. :p
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  • rollandelliott
    rollandelliott Solar Expert Posts: 834 ✭✭
    #29
    Re: Roof color opinions: dark vs. light

    the 3 to 5% savings are for black vs white shingles

    for other root types like white metal the savings are dramatically higher. from the abstract of the article. the whole article is a good read. I dont' think it is really economical to replace your roof solely on these energy savings, BUT if you are going to replace it anyways I'd invest in the ones that reduce the peak demand by over 28 to 35%.

    "Measurements showed that the three white reflective roofs would reduce cooling energy consumption by 18-26% and peak demand by 28-35%. The terra cotta tile roofs and white shingles would produce cooling savings of 3-9% and 3-5%, respectively, while the sealed attic construction with an insulated roof deck would produce reductions of 6-11%."
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #30
    Re: Roof color opinions: dark vs. light
    techntrek wrote: »
    From everything I've read about roof color - yes, lighter is a little better, but there isn't enough difference to matter much.
    rollandelliott wrote: »
    concludes energy savings are real around 3 to 5%

    Thank you for confirming what I said. :cool:
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #31
    Re: Roof color opinions: dark vs. light
    techntrek wrote: »
    Thank you for confirming what I said. :cool:

    did we just go full circle?:confused:
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