Cool Roof

[Noah930]

I live in sunny SoCal, where it was 100+ degrees today. Going to re-roof the house, and have been introduced to cool roof shingles by the builder (currently we have asphalt shingles). In this time of global warming, this sounds like a good idea.

In short, are these worthwhile? Do they work/make a measurable difference? Does the thermal reflectivity property last, or does it wear off over time? Almost everything I've read has been written by someone trying to sell the stuff.

We'll probably be in this house for the next 10 years, I'd guess.

[nota]

yes the roof heat can and will drive up the el bill

we painted our roof white [it was gray] with special roof paint
and dropped the bill about 20% in the summer
problem is trees/leaves and their effects that darken over time
requires a pressure wash and repaint every few years

no idea about fancy shingles but 3M or BASF should be ok quality

currently pricing metal roofing for hurricanes it will be white

[jhynesrockmtn]

Solar options? I see that Tesla has started selling their roof. I assume it is very expensive. Wonder how it will actually pen out over time.

[sammyg2]

If your roof temperature makes any difference at all, you do not have adequate attic ventilation or insulation.

Put your money where it matters. Not backaswards.

[Jim Richards]

^^^ it does make sense to ventilate your attic as a first step. It's cheaper and it might make enough of a difference that you won't see the need to do anything else.

[vash]

i have a white roof...the difference is amazing.

i think a white roof on any type of attic would help. venting the attic is much cheaper, but if you need a new roof, take the two prong attack.

[GH85Carrera]

Roof ventilation will help a lot. It keeps moisture from building up and lets the heat out.

Good insulation is just as important.

We have a conventional brick facade house and asphalt shingles and we went to the ridge vents. They look like part of the normal roof, but they let a lot of air out. We also have vents in the soffits. We went with impact resistant shingles since a hail storm wiped out out old roof. It is astonishing how much a new roof can cost. It was nearly as much as I paid for my 911. The old roof was 25 years old so it had already lasted longer than many in the area.

[kach22i]

Is this the product you are talking about?

Timberline® Cool Series® Energy-Saving Shingles
https://www.gaf.com/Roofing/Residential/Products/Shingles/Timberline/Cool_Series/Features

Thanks to the reflective nature of the Cool Series® Shingles, part of the heat radiating from the sun gets reflected, reducing the heat in the attic and heat going into the house. It may translate into substantial savings in air conditioning bills.

Cool roofs may save residents an avg. 7-15% of total cooling costs, depending on geography, structure, and climate. In warmer climates, cooling-cost savings may be greater year round.*

Many ways to lower solar heat transference rate to attic or ceiling spaces. Trick is doing it cheaply enough to recover the investment.

This looks like a simple fix compared to others I could tell you about.

Simply put, our Cool Series® Shingles use specially designed roofing granules that have greater reflectance than traditional shingles. This results in less transfer of heat to the space below—to keep you cooler in the summer.

Go for it.

https://www.gaf.com/Roofing/Residential/Products

Install Any GAF Lifetime Shingle & At Least 3 Qualifying GAF Accessories & You'll Automatically Get: A Lifetime ltd. warranty on your shingles and all qualifying GAF accessories!* PLUS Non-prorated coverage for the first 10 years! * To get even stronger coverage, choose a System Plus or Golden Pledge® Ltd. Warranty from a GAF factory-certified contractor!

[Evans, Marv]

As I've described before, I have a semi flat roof of flash down, bituminous (black) membrane. My scenario doesn't necessarily apply to your application but illustrates the difference in surface temps. After about two years, I applied a glacial white elastomeric coating. It wasn't as simple as just painting it on. It needed two coats of asphalt emulsion followed by two coats of the elastomeric coating. I used an infrared, hand held thermometer to measure the temperature before I applied it & afterwards. At ten to twelve AM, the temperature on a clear, sunny day was around 170 degrees. After the coating, it was between 100 & 110 degrees. So applying a coating like that reduced the surface temperature significantly. I also have good venting and ceiling insulation. Here the ratio of ventilation to floor space is code.

[1990C4S]

Originally Posted by jhynesrockmtn

Solar options? I see that Tesla has started selling their roof. I assume it is very expensive. Wonder how it will actually pen out over time.

Tesla do not have a manufacturing facility yet. These are a ways off....

[Noah930]

Originally Posted by kach22i

Is this the product you are talking about?

Timberline® Cool Series® Energy-Saving Shingles
https://www.gaf.com/Roofing/Residential/Products/Shingles/Timberline/Cool_Series/Features



Many ways to lower solar heat transference rate to attic or ceiling spaces. Trick is doing it cheaply enough to recover the investment.

This looks like a simple fix compared to others I could tell you about.



Go for it.

https://www.gaf.com/Roofing/Residential/Products

That's exactly it. Or, at least one of the lines our builder introduced to us. The other is by Owens COrning, but same idea. Apparently, here in LA we have no choice--ithe building code mandates we install a cool roof. We'll install attic insulation, as well, and we're also re-engineering the flat portion of our roof (which is mostly pitched, with the exception of our family room), to include insulation also.

I was just wondering if what I've read is all marketing hype, or if it really makes a difference in this hot, dry climate.

[RKDinOKC]

1.) The roof is not on a house to thermally insulate the house.
2.) The roof is there to keep the precipitation out of the house.
3.) The insulation on the houses ceiling in the attic is what insulates the living area of the house.
4.) The roof is ventilated mainly to let moisture in the attic dry out, but also lets excess heat out.
5.) Insulated roofing tiles only keeps the sun from heating the attic more than ambient temps outside (see #4).
6.) Heating an attic in the winter when snow is on the roof is bad. It causes the melt runoff covered by the snow to pool at the soffits, leak, and rot them. Hence the ventilation.

[cstreit]

Originally Posted by nota

yes the roof heat can and will drive up the el bill

we painted our roof white [it was gray] with special roof paint
and dropped the bill about 20% in the summer
problem is trees/leaves and their effects that darken over time
requires a pressure wash and repaint every few years

no idea about fancy shingles but 3M or BASF should be ok quality

currently pricing metal roofing for hurricanes it will be white

20%?! Wow. Whats the payback timeline on the treatment? Seems like it wouldn't be that long...

[kach22i]

Originally Posted by Noah930

We'll install attic insulation, as well, and we're also re-engineering the flat portion of our roof (which is mostly pitched, with the exception of our family room), to include insulation also.

Sounds like you have a good opportunity to get things done right, or conversely really get things screwed up. This is a serious business, and some of the problem is burying money into things no one sees yet there are tangible benefits to operational costs and long term benefits.

No pressure, but the attention to proper ventilation and flashings are going to help any system. Pretty smart of GAF to bundle package their products like that warranty wise, because the devil in is the details.

A decade or two ago some of the trade magazines were advocating a air cavity roof, meaning you have a regular roof minus the shingles, then lay vertical furring strips down, a layer of OSB on that, roof felt and shingle over the top. What you end up with is air layer that is vented top and bottom getting moisture from the due point out of the inside of the house and inside of the material themselves. In addition both sides of the shingles are now evenly cold or warm, making them last much longer.

SIP construction with Roxul on interior service cavity wall | GreenBuildingAdvisor.com


Also see this large image:
http://bkaviking.blob.core.windows.net/media/1172/roof-to-wall-venting-detail-ct10.png




You can imagine that this air cavity would do a good job of preventing heat from the shingles transferring through to the rest of the house.

From what I can tell looking on-line they now add reflective membranes into the mix to radiate energy (infrared) back out. And they seem to be more for cathedral ceilings where they can do the most good.

Lots of ways to spend money, lots of ways to overkill.

I say using a shingle with reflective properties is a no-brainer to start with. Don't skimp on ridge vents and valley flashings.

The flat roof can be problematic. Unless you are using only rigid insulation on the top, the batt insulation or blow-in insulation in between the ceiling joists really could benefit from being ventilated as well. This gets skipped sometimes and moisture can build up in the insulation causing sagging, dripping, mold, and in cold climates freezing. Below is the type of vent/flashing made to address such conditions.

Flat Roof: Flat Roof Upstand Ventilation


https://www.diynot.com/diy/media/untitled.15937/


Alternate-1:
Smart Flat Roofs: The Craft of Parapet Detailing | BUILD Blog


Alternate-2:
http://eureka4you.com/home/VentFlat.htm

Since most flat or compact roofs usually have ineffective ventilation , this condensation could get trapped within the insulation.

Since you are not doing this work yourself, just get a roofer than knows his business.

If you have existing flat roof drainage issues, perhaps look into adding tapered rigid insulation to increase the pitch.

Yes, they make white and reflective flat roof membrane roofing that helps lower cooling costs, look into it. Sounds like most of the people posting used the "come back and fix" type treatments and materials on flat roofs. There are retrofit and new or re-roofing materials as well to meet your criteria.

[Borders Reivers]

Three years ago we replaced the asphalt shingle roof on our house with Brava Tile shingles and at the same time re-decked with solar barrier decking. Cut our summer electric bill in half. Winter bill cut by 1/3. Ours was the second house in Dallas to use Brava Tile. People visit our house to see the roof. Two weeks ago a couple from Cedar Rapids Iowa flew to Dallas to see our roof.

Brava Tile looks like ceramic Spanish tile but weighs less than standard asphalt shingles so you don't have to strengthen a roof to use them. Brava Tile also has roof tiles that look like slate and ones that look like cedar shakes.

https://www.bravarooftile.com/

(Our house was designed/built by a couple from Los Angeles and it doesn't look like a typical Dallas house.)


Winter shot to show insulating properties of Brava Tile roof

[nota]

Originally Posted by cstreit

20%?! Wow. Whats the payback timeline on the treatment? Seems like it wouldn't be that long...

paint was about 65 a 5 gal bucket 10 years ago
took about 5 buckets to do 1200 sf as it is very thick
we did the painting so under 400 total cost
bills were about 350 before dropped to high 2xx peak summer
a/c is a mid 90's and low er rated maybe 10

problem is the huge royal poinciana tree that flowers
and attracts ants that bring aphids that make honeydew
that creates black mold on the roof requiring pressure washing
after a few years the mold stains the paint to a gray and we repaint
but as the thick paint base is still ok just stained
repainting uses far less thinner normal paint 2 buckets to do the whole roof
and the paint is far cheaper

if you do not have a tree+ant+aphids=staining
it should last longer and require less pressure-washing or repainting

[nota]

I would NOT use OSB on any house ever anywhere
not even a dog house
esp on a roof
as once a leak starts that crap crumbles
and hurricanes love to turn OSB to debris

[kach22i]

Originally Posted by nota

I would NOT use OSB on any house ever anywhere
not even a dog house
esp on a roof
as once a leak starts that crap crumbles
and hurricanes love to turn OSB to debris

Sure 7/16" OSB with those little metal clips suck, and real plywood is much better. Just try getting a owner willing to pay more for something they cannot see.

I just call out "roof sheathing" and let the builder settle with the owner as I have near zero influence on such matters.

Where this matters most is extreem cold or hot and humid climates, the local guys know what to use.

I once helped a buddy repair a bay window where there was not continuous house wrap. The OSB wall sheathing fell apart like "nota" describes. I'm not a fan to say the least, very unforgiving of less than perfect work.

From what I understand Europeans laugh at our temporary stick built houses, if you want to get serious, concrete is the way to go. That's what the rest of the world uses.

[eastbay]

You live in Cal, tile or slate, asphalt is for roads

[Noah930]

Originally Posted by nota

paint was about 65 a 5 gal bucket 10 years ago
took about 5 buckets to do 1200 sf as it is very thick
we did the painting so under 400 total cost
bills were about 350 before dropped to high 2xx peak summer
a/c is a mid 90's and low er rated maybe 10

Do you recall the name/manufacturer of the product? Was it a Home Depot purchase, online, or from a specialty supplier?