Tennessee? What do you mean, the window manufacturer's recommendations are for a house in Tennessee!!! The Europeans are ahead
of us (again) here - they buy their windows by selecting a frame, then they select the glazing to go in the frame.
Remember
that replacing windows is REALLY expensive and the efficiency return-on-investment may be doodley-nothing. Address your air
leaks first. Old wood windows can often be repaired, by contractors who specialize in this work, with added storms (exterior
or interior) for the same price as installing new windows. If you add storms or do air sealing, make sure you do not have
moisture building up between the windows and the storms. Windows are made with ways to drain, and if you plug those drainage
routes Bad Things Will Happen. The wood frames can rot, the sills can rot, you can get freeze-thaw problems.
Volume 1 has a page on windows. This is one place where the
recommendations have CHANGED. The ultra-platinum-LEED-Net Zero builders now say to use the minimum windows, because even with
the highest R-value windows you get R 7 or so, which is lots less than the R-value of the rest of the wall, and it makes a
thermal leak. WELL. I LIKE windows. So do my plants and my cat. But windows also fade upholstery and carpets. So, put windows
where you need them, and get ones with a low SHGC - solar heat gain coefficient. Install them properly. Put insulated curtains
or cellular blinds above them, and when fully open the coverings should not block the glazing. The back of your sofa, and
your shrubbery, should not block half your window, either.
When you look at windows, you should consider repairing them rather than replacing them. Be aware of lead paint (painted pre
1970?). Unstick windows that are painted shut. Remove the window sashes. Remove old glazing and re-glaze as needed. Strip
paint from the sash frames. Weatherstrip the jambs and sashes. Then, add Low-E airtight storms that come out in the summertime,
and insulated drapes or cellular blinds.
