Brown versus White Roof?

[Doug]

I believe when I was a youngster, my dad put a white shingled roof on our house and as I recall, we were the only one or two in a large subdivision with a white shingled roof. This was on Long Island, NY. I don't recall them ever talking about the electric bill but I was probably too young to care. My personal thought is that a white shingle roof is probably minimally beneficial because since I've lived in Texas and traveling around Houston and Austin, I don't recall seeing any white shingled roofs. I would think with the heat we get for many months a year, if it were really beneficial, they would have a lot more of them around here. So my conclusion is that my father (a builder then) and the homes I see now, do it for cosmetics more than anything else.

[krw]

That is completely false.

That is so wrong, it's not even funny.

If there were "NO ability to transfer heat IN ANY DIRECTION to or from the interior of your house", there would be no need for a furnace or AC, at all. The fact is that heat transfer is finite and proportional to the delta-T. Lower it and you *will* save money. The heat transfer is really delta-T/R, so there are two knobs to turn. True, R is usually the easier knob to turn but your statement, as made, is wrong.

There is warming of the attic space in the Winter. Attics *should be* designed to stay cold, but there is heating due to the sun. If there weren't, ice dams would be unheard of.

But physics is *so* much different in the Winter.

[Home Guy]

I didn't say that it was possible to have zero heat transfer.

So stop being disengenous.

You know dam well that a house can't "harvest" heat from the attic in the winter.

You know dam well that your goal should be to have as little ability as possible to transfer heat to or from the interior living space to the attic. And given that goal, that the very idea of having dark shingles for some kind of heat-benefit in the winter is crazy.

In the winter (as is the case in any season) -> an attic space can (or WILL) get warmer THAN OUTDOOR AMBIENT TEMPERATURE.

So what?

What good is it when it's 20 F outside and 30 F in my attic - when I want it to be 72 F inside my house?

What am I going to do - install a heat pump in my attic to extract the paltry amount of extra heat in the attic space?

You did not comment on that statement.

Why?

Because it was true / accurate?

[HeyBub]

If you live in an urban environment, the white shingles will turn brown given enough time. The particulate matter from auto exhausts - and other pollutants - will stain them, but not evenly.

[Tony Sivori]

Ok, I decided to check. I put a wired inside / outside thermometer up there this morning.

It is now 3PM local, 90 and sunny outside, the roof is in 30% shade from trees. The attic temperature is 121.

So I'd guess it could easily exceed 130 on the hottest days of summer, but exceeding 140 might never happen in my particular attic.

[Tony Sivori]

OC does make a hip and ridge cap, it is in one the brochures that I got with an estimate. In the photos, they don't look as thick as the ones from GAF.

[krw]

Read what you wrote.

Write what you mean. Or learn something. Either way...

Wrong. Heat transfer is delta-T/R. Lower delta-T means a lower heating bill.

"As little as possible" is *not* zero, as you said. For every 1F you can drop delta-T, you save something like 2-3% of the heating bill (assuming an average

30-50F temperature rise).

It changes delta-T, that's what.

Because you only raising the temperature 42F rather than 52F, a 23% savings on heat escaping through the ceiling (which you said was zero, above). Is 23% =

0?

I know it's almost impossible, but you might try thinking.

Because you're a liar? Any heat in the attic *will* help. For completely separate reasons, you want to minimize the heat in the attic, but it *does* matter, here.

No, because I already had.

[krw]

Not to mention that "bright red Georgia clay and how it stuck to the roof, after the Summer rain". ;-)

[HeyBub]

In my part of the country, we call a mixture of red clay and water "adobe."

[krw]

Nope, don't know that one. Maybe if you hum a coupla bars. ;-)

[Steve Barker]

IF (note the IF) the attic is insulated properly, the roof color will be of no consequence. You will also be able to see the fungus on the north side a lot more with the white than with the darker color. If your roof does not have a north side, then disregard.

[HeyBub]

I can believe that if you live in the Dakotas. My attic reached 150 before a massive effort to reduce the temp was undertaken. The effort consisted of four wind turbines, a ridge vent, and a SIGNIFICANT amount of fascia vents.

Now it seldom gets above 130.

[HeyBub]

I think the reason you don't see light-colored roofs in a Texas urban environment, or any urban environment for that matter, is they discolor from the gunk and particulate matter in the air. The roofs, moreover, don't discolor uniformly. They streak and in general look just horrid.

[Doug]

Yea but the colors on the roof now show the same thing so I don't think that's a white issue. I admit white might show a bit more contrast when discoloring.