Re: [Phys-l] paint your roof?

["John Clement" <clement@hal-pc.org>]

> I'm more concerned about the heating portion of this--in our climate MUCH
> more energy goes into heating than cooling and if anything your
> 'subjective
> data' might support black for heating purposes.  (I spend about $100
> annually running the central air but can run a $200 natural gas bill
> during
> December and January.)  If white is only a small benefit--or of no
> benefit--for the heating season, it won't sell in my neck of the woods!
How about black with a radiant heat barrier?  Actually, just a radiant heat
reflector would give most of the benefit because it would prevent heat loss
during the long nights.  As I recall this is available in a lightweight film
designed to be installed in the attic.

The problem with any roof treatment is that it gathers thermal energy where
you don't need it, when you need it the least.  Then heat infiltration is
reduced by attic insulation.  A method of storing the energy and releasing
it later could be of enormous benefit, but that is currently fairly
expensive.  But there are other benefits to a white roof.  The high
temperatures probably cause the roof to age more quickly, so a cooler roof
may in the end cost less.  There might also be smaller temperature swings in
the attic which also would prevent deterioration.

Gee only $100 for the entire AC season!  In the South where many have
migrated, that would be cheap per month.  AC can easily exceed $200/month
for at least 6 months.  But they are now building some small inexpensive
homes in Houston which are supposed to have much lower utility bills.  I do
not have any details, but I remember reading about the project.  Most of the
existing small homes are old and tend to have minimal insulation.

Since it hardly ever freezes on the Gulf Coast, and basements become
swimming pools, the water pipes run through the attic.  But some builders
did not put insulation above the pipes so new homes have had pipes burst
during the rare freezing spells.  Old uninsulated homes with heat never had
this problem.

John M. Clement
Houston, TX