Author Topic: Paint my roof white? Concerns and questions  (Read 7191 times)

GregO

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Paint my roof white? Concerns and questions
« on: June 29, 2015, 01:39:16 PM »
I posted a while back about getting window films for our west-facing porch(http://forum.mrmoneymustache.com/ask-a-mustachian/window-film-to-reduce-solar-gain).  During the discussion, painting the roof white also came up.  Painting the roof white has always been something that intrigued me, but we've had other house projects that needed to get completed first and haven't had the time or money to tackle it.  The other projects are finally getting finished up, so my wife and I have been talking about painting the roof as our next project now.  I did a little research on it and have a couple of questions.  I thought this forum would probably have some good advice for it:

1. During my research, there were many people who said their roof substructure had rotted out because water wasn't able to escape once their roof was painted white.  Most of the people that posted this were from FL.  It is very humid there, which could be what makes the roof painting a prolem.  I live in CA, which is far from humid.  Does anyone on here have knowledge of this issue?  TomTX eluded to this issue (in the linked thread above) when he referenced the FL restrictions on painting the roof. I don't want to go screw up a perfectly good roof to save a few dollars during the summer.  Is this a realistic concern, something localized to humid climates, or a scare tactic by the roofing industry?  Has anyone else done more research on this than me or work in an industry that knows about this?

2. What products have you guys used / recommend for painting their roof?  I have a typical asphalt shingle roof.  There's a lot of expensive elastomeric paints out there that say they are designed for this application, but are very expensive.  The product home depot carries is $300 for 5 gallons.  I'm sure there's better and cheaper product than what HD carries, but any elastomeric paint is expensive.  Are they worth it or should I just go with an exterior white paint?

3.  Any other tips or suggestions on this issue?

Thanks for the help!

Tester

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Re: Paint my roof white? Concerns and questions
« Reply #1 on: June 29, 2015, 02:23:20 PM »
I admit I did not read all the terms of using this forum.
I hope external links are allowed.
http://www.builditsolar.com/Projects/Cooling/WhiteRoofExperiment/WhiteRoof.htm
That could help you with some data and a place to ask your questions directly to someone who already painted his roof in white.
I think that site should be a good read for any mustachian trying to decrease his heating/cooling/energy bills.
Not directly related to your question but a very interesting project on that site:
The Half Plan -- Cut Your Energy Use, Energy Cost, and CO2 Emissions in Half
http://www.builditsolar.com/References/Half/Half.htm

TrMama

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Re: Paint my roof white? Concerns and questions
« Reply #2 on: June 29, 2015, 02:52:48 PM »
I have absolutely no experience with roof painting, however I do live in the PNW. Excess humidity in the attic is caused by insufficient ventilation. You fix that problem by installing continuous soffits, ensuring the soffits don't get blocked with insulation and adding more roof vents. I'm pretty sure a roof that "ventilates" through the shingles will also leak when it rains and would've rotted regardless of the paint treatment.

So, I wouldn't worry about rotting the roof joists after painting, unless you also have insufficient ventilation in the attic. If you don't have great ventilation, then the roof is more likely to rot regardless of whether you paint or not. Clear as mud?

TheLazyMan

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Re: Paint my roof white? Concerns and questions
« Reply #3 on: June 29, 2015, 03:13:03 PM »
"Coating existing asphalt shingles to make them cool, however, is not normally recommended or approved by shingle manufacturers."

http://energy.gov/energysaver/articles/cool-roofs

EDIT: See also the section on moisture control.
« Last Edit: June 29, 2015, 03:14:44 PM by TheLazyMan »

Mother Fussbudget

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Re: Paint my roof white? Concerns and questions
« Reply #4 on: June 29, 2015, 04:04:20 PM »
Are you asking about something like "Snow Seal" or "Snow Roof" coating used on flat roofs, or RV?
That stuff seals for leaks, comes in either black or white, and I've heard of it being painted over shingles to seal for leaks  (and in my experience it didn't work well for that purpose). 

But to use it primarily for reflective use only... the type of paint would depend on the shingles being used.
Concrete paint for composition shingles, and any wood paint (latex house paint?) for wood shingles.  Any feedback on using Snow Seal / Snow Roof for this purpose?

GregO

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Re: Paint my roof white? Concerns and questions
« Reply #5 on: June 29, 2015, 04:25:03 PM »
http://www.builditsolar.com/Projects/Cooling/WhiteRoofExperiment/WhiteRoof.htm
That could help you with some data and a place to ask your questions directly to someone who already painted his roof in white.
That site was interesting.  He white washed the shingles, which is interesting.  That's one cheap way to do it, that's for sure.

GregO

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Re: Paint my roof white? Concerns and questions
« Reply #6 on: June 29, 2015, 04:28:47 PM »
So, I wouldn't worry about rotting the roof joists after painting, unless you also have insufficient ventilation in the attic. If you don't have great ventilation, then the roof is more likely to rot regardless of whether you paint or not. Clear as mud?
The concerns I've read aren't about moisture in the attic, they are about rotting the plywood under the shingles.  I guess it could eventually rot the joists too, but the roof would be leaking pretty bad before that happened.  I could be wrong, but I don't think attic ventilation will dry up the plywood if it has standing moisture between the shingles and the plywood.

GregO

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Re: Paint my roof white? Concerns and questions
« Reply #7 on: June 29, 2015, 04:35:37 PM »
"Coating existing asphalt shingles to make them cool, however, is not normally recommended or approved by shingle manufacturers."
Yes, I've seen that note.  But shingle manufacturers are directly losing money when people coat their roofs instead of replacing them.  This is why I was wondering if it's truly a concern on a scare tactic to retain business.

Are you asking about something like "Snow Seal" or "Snow Roof" coating used on flat roofs, or RV?
Here's a couple of links to the products I'd seen at Home Depot.  I'm sure there's many other products as well:
http://www.homedepot.com/p/Gardner-5-Gal-Eterna-Kote-S-100-Silicone-Roof-Coating-5570-1-30/205314046
http://www.homedepot.com/p/Gardner-5-Gal-Sta-Kool-780-Cool-Roof-Elastomeric-Coating-SK-7805/202057691
They are products marketed specifically to keep roofs cool.  They also market that they extend the life of the roof...

GregO

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Re: Paint my roof white? Concerns and questions
« Reply #8 on: June 30, 2015, 10:49:16 AM »
There really aren't any mustachians out there that have painted their roof white?  I thought this would be something right down the mustache alley...

SunshineAZ

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Re: Paint my roof white? Concerns and questions
« Reply #9 on: June 30, 2015, 11:43:04 AM »
When I was designing our house in Honduras and researching passive cooling techniques, I learned about the benefits of a white roof, and therefore our house there has a white metal roof.  We also kept all the mature trees around the house so we get the shade benefits as well.  (Not that I would have removed any trees that I didn't have to, but it was nice to know they had a practical benefit, in addition to being beautiful.)

RelaxedGal

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Re: Paint my roof white? Concerns and questions
« Reply #10 on: June 30, 2015, 12:03:37 PM »
I have no personal experience, as here in New England a dark roof makes more sense.  However the US government has Energy Star ratings for roof products: Energy Star Certified Roof Products.  They also have a roof savings calculator linked from that page.  Hopefully that will help your decision.

Telecaster

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Re: Paint my roof white? Concerns and questions
« Reply #11 on: June 30, 2015, 02:01:42 PM »
There really aren't any mustachians out there that have painted their roof white?  I thought this would be something right down the mustache alley...

I don't live in a cooling climate, so I haven't really looked into it, but  have studied energy efficiency/upgrades quite a bit and I can see a couple of potential problems right off the bat.  At least things worth looking into further.

For one, the roof is a brutal climate.   Paint just isn't going to last long up there.   That means frequent reapplications.   It is not good to walk on roofs.

Another thing I wonder about is if the roof would perform properly.   I can see how if the coating wasn't thorough and even the roof wouldn't shed water properly.   

And finally the cost.  Paint isn't cheap (especially not the $300/gallon stuff).   Do you really think this is the most cost effective way to reduce your energy bills?   I don't know, but I'm guessing it isn't.   




GregO

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Re: Paint my roof white? Concerns and questions
« Reply #12 on: June 30, 2015, 04:03:02 PM »
And finally the cost.  Paint isn't cheap (especially not the $300/gallon stuff).   Do you really think this is the most cost effective way to reduce your energy bills?   I don't know, but I'm guessing it isn't.
Well I wouldn't get the $300 stuff, but I was thinking about the $100 per 5 gallon stuff.  So yes, it'd be $500ish to paint it.  I haven't done any calculations on ROI.   Using the DOE calculator (http://web.ornl.gov/sci/roofs+walls/facts/CoolCalcEnergy.htm), it comes out to 10 cents per SF, so roughly $150 of savings.  I don't know how accurate the calculator is (or any other way to esitmate the savings), but 30% is a great ROI if I was actually able to approach that.

We are also going to build a sun shade over our southwest-facing porch.  What other options would be more effective?

Telecaster

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Re: Paint my roof white? Concerns and questions
« Reply #13 on: June 30, 2015, 08:25:23 PM »
30% ROI is pretty great.  I noticed the calculator is for flat roofs, so keep that in mind.  Maybe the best thing to do is just to try it, and see if it works. 

Typically the best bang for the buck is attic/wall insulation, followed by duct sealing.   For a cooling climate, a solar powered attic fan might make sense. 

Almost never makes sense to replace windows. 

GregO

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Re: Paint my roof white? Concerns and questions
« Reply #14 on: July 01, 2015, 12:38:25 PM »
30% ROI is pretty great.  I noticed the calculator is for flat roofs, so keep that in mind.  Maybe the best thing to do is just to try it, and see if it works. 

Typically the best bang for the buck is attic/wall insulation, followed by duct sealing.   For a cooling climate, a solar powered attic fan might make sense. 
I didn't notice the calculator was for flat roofs, but I don't really expect to save that much anyway.  I'd guess $100/year is more realistic.  I am much less concerned about the ROI (I'm confident it'll reduce my cooling load significantly and extend the life of my shingles), and much more concerned with rotting out my roof.  I was about to just throw caution in the wind and go do it, until I started reading about it.  Here is one of the main threads that I read on this subject:
http://www.finishing.com/116/34.shtml

I'm still leaning towards doing it, just trying to find a product that makes sense.

partgypsy

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Re: Paint my roof white? Concerns and questions
« Reply #15 on: July 01, 2015, 01:04:59 PM »
I'm in the southeast (humid area). I don't know anyone who has painted their roof, as others have said roof is a harsh climate for sun, rain, etc. It seems paint (especially white) paint would not wear well for this application, and maybe reduce lifespan of the shingles.
If you really want to do it, find a least a couple people who have done it in your climate (with same roofing materials), look at the results, ask questions. Otherwise you may be making a perfectly fine roof look like crap with no cost savings.
Once your roof does need to be replaced, there are plenty of light colored asphalt roof shingles you can use, and oftentimes they have a rebate associated with them.
« Last Edit: July 01, 2015, 01:14:27 PM by partgypsy »

partgypsy

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Re: Paint my roof white? Concerns and questions
« Reply #16 on: July 01, 2015, 01:28:46 PM »
Hmm, here is a post you might find interesting, recommending exterior latex paint.
http://www.painttalk.com/f2/painting-asphalt-roof-shingles-23433/index4/

GregO

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Re: Paint my roof white? Concerns and questions
« Reply #17 on: July 01, 2015, 02:22:07 PM »
Hmm, here is a post you might find interesting, recommending exterior latex paint.
http://www.painttalk.com/f2/painting-asphalt-roof-shingles-23433/index4/
Wow, that was a really good post.  Pretty convincing from a guy who has a lot of experience.  Thanks for sharing.

Bob W

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Re: Paint my roof white? Concerns and questions
« Reply #18 on: July 01, 2015, 03:14:43 PM »
Nope don't do it.  You can find reflective paint for the underside or reflective film.   Good ventilation should  be all you need though.  I suggest finding another projects.  Houses with white roofs will not sell.

GregO

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Re: Paint my roof white? Concerns and questions
« Reply #19 on: July 01, 2015, 05:33:00 PM »
Nope don't do it.  You can find reflective paint for the underside or reflective film.   Good ventilation should  be all you need though.  I suggest finding another projects.  Houses with white roofs will not sell.
If white paint extends the life of my shingles and reduces the heating load, then that is 2 really good reasons to do it.  It seems to me that painting the roof would be cheaper, easier, and more effective at reducing the heating load than adding ventilation to the attic or adding reflective film to the very tiny attic.

I'm not too concerned with resale concerns for a lot of reasons, but mainly because I would rent out the house before I ever sold it.  I also live in California, there are plenty of people who are very concerned about energy conservation (and electricity is expensive), and the roof of the house is not visible.  I don't think it'd be a major issue.  Are there other reasons that you don't think it should be done?

Bob W

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Re: Paint my roof white? Concerns and questions
« Reply #20 on: July 04, 2015, 09:09:07 AM »
One reason is the danger factor.  Being on a roof is right up with skydiving as far as danger.  Honestly,  I've never seen it done.   Why are shingles not sold.white?

Jack

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Re: Paint my roof white? Concerns and questions
« Reply #21 on: July 04, 2015, 09:44:45 AM »
One reason is the danger factor.  Being on a roof is right up with skydiving as far as danger.

Well, shit. I must be a closet extreme-sports junkie!

Why are shingles not sold.white?

White shingles do exist, but they don't sell well because they're ugly and therefore aren't worth keeping in stock at Home Depot. (Or at least, they would only look good on houses of particular style / color.)

Greg

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Re: Paint my roof white? Concerns and questions
« Reply #22 on: July 05, 2015, 08:28:09 AM »
Painting asphalt shingles is stupid.  Like painting your gravel driveway stupid.  Don't do it.  If you want a cooler, lighter colored roof, replace your roofing.

Roof paint is for flat torch-down or hot-mop tar roofing, nothing else. 

Gribble752

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Re: Paint my roof white? Concerns and questions
« Reply #23 on: June 28, 2016, 04:40:16 AM »
I agree. White roofs help in a lot of ways. Dark-colored roofs absorb more heat from sun rays hence it makes a lot of heat inside the rooms. This cause energy wastage and your air conditioners have to work more. One of my friend in India told me that the only color they use for roofs is white. From my personal experience, i would suggest white color for roofs. Even roofing companies like Royal York Roofing in Toronto recommends white color for roofs. But there are other factors you need to consider other than the color.
« Last Edit: June 28, 2016, 09:44:03 PM by Gribble752 »

Fishindude

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Re: Paint my roof white? Concerns and questions
« Reply #24 on: June 28, 2016, 05:28:20 AM »
Do not paint a shingle roof.   Further, I doubt the return in energy savings you get would be much.
Just wait until next re-roof and change to a lighter, more reflective color at that time, or consider a light colored metal roof.

Attic insulation and venting would be money much better spent to improve your cooling situation.

Jack

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Re: Paint my roof white? Concerns and questions
« Reply #25 on: June 28, 2016, 05:30:10 AM »
FYI, y'all have revived a thread that's been dead for a year.