[Greenbuilding] hot water versus forced air--and window AC versus central

[Ben Pratt]

I would like to know which uses less energy to heat a home-all else 
being equal: forced air or cast iron radiators.
    I have radiators now, and like the even heat, but feel wasteful in 
that It is usually impractical to turn down the heat at night or when 
leaving the house for work.  I could get a deal on a forced air 
system (from a friend that pulled a newer one out of his house), but 
do not have a clear understanding of whether my gas bill would go up 
or down.
    I was also wondering whether having window AC units, and only 
using them in only certain parts of the house, makes sense versus 
getting a central air system.
     Certainly, the forced air and central AC is more convenient, and 
takes up less space, but which is more efficient? In surfing the web, 
it is hard to find a unbiased opinion.
-Ben

-- 
B  e  n  j  a  m  i  n   P  r  a  t  t
Professor
Department of Art and Design
University of Wisconsin-Stout
Menomonie, WI 54751