[Strawbale] window construction

[Derek Roff]

> My first question is about thermal bridges. All the drawings I've
> seen use a timber mount/buck/rough frame to connect the window to
> the wall. Doesn't this cause a thermal bridge?

While a wooden frame does constitute a thermal bridge of a sort, it's 
important to look at the magnitude.  The window itself is a 
significant thermal bridge, and it has a large surface area.  The 
wooden frame around a window is slightly more conductive per unit 
area than a quality double-glazed window, but it has a tiny 
cross-sectional area.  Therefore, almost all of the heat loss 
relating to this kind of window installation will be through the 
glass itself.

It is perhaps ironic that the wooden window buck, which we perceive 
as a thermal bridge, is more resistant to heat flow than the rigid 
plastic "thermal break" element incorporated into some commercial 
window frames.  I favor careful design and detailing, but I try to 
minimize the amount of energy I put into looking for improvements to 
the right of the decimal point. My problem is, I find those tiny 
improvements fascinating.

derelict

Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek at unm.edu