Does so-called thermal-glass really make much difference to heat loss?
Answer Steve, Sorry for not getting back to you sooner, but it seems that the AllExperts server was down over the weekend when I first attempted to answer your question. The answer to the latter part of your question is that thermal-glass has more insulating value than a simple wood sash with a single strand glazed light. The answer to the first part of your question, however is a little less clear cut. A typical wood frame stud wall with fiberglass batt insulation filling the voids between the studs has an R value of about 13. A typical Andersen window or door has an R value of about 2. So as you can see, the wall minus the openings is about 6 to 7 times more resistive to the transfer of heat compared to a glazed window or door unit. You must however consider a few things before concluding that it will be a mistake to put in all the glazing which you are considering: Do a calculation to determine what the total area of exterior wall is for your house including the new walls of the ext
