Q.I've seen window glazing area recommendations for energy-efficient houses stated in two ways: as a percentage of conditioned square footage and as a percentage of exterior wall area. Which is most useful, and why?A.Contributing editor Paul Fisette responds: While there are many excellent sources that relate window area to square footage of living space, I'm not a fan of this approach. Conduction and air leakage are the main ways that heat escapes a building envelope, so any meaningful energy analysis should be directly related to these dynamics.Conduction is a function of the surface area of the wall, the thermal properties...