Re: [Phys-l] paint your roof?

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

> Heating is at 20% and the white roofs would increase (to some extent)
> heating demand.  

White roofs would probably actually decrease heating demand.  The most
demand for heating is at night in northerly climates.  A white roof reduces
radiative losses during the long winter nights.  So the balance between
daytime loss in radiative heating and the nighttime gain in radiative loss
would probably favor the long nights.  Actually most of the heat loss in
northern climates is probably through the windows and doors, so it would be
a small effect at best.

Actually if you can reduce heat loss enough in a northerly climate, the heat
gain due to appliances, lighting, and human habitation can keep the house
warm.  There is a school in Canada where they use the body heat from the
children to keep it warm.  Rather than venting the heat during lunch they
pump it to the classrooms to maintain the temperature.

John M. Clement
Houston, TX