New Windows & HVAC Sytstems

[friesenk51]

I have posted before with questions about ductwork design however I realized that designing a "balanced system" is more than likely out of my "overly aggressive" do it myself realm. I contacted the installer of my current furnace (furnace was put in 9 months before I bought the house). He stated that he used a fancy program and he feels that the system size is correct. He stated that he calcualted the home with new windows and not the current windows.

My question is this, I have read in books (builder books at home depot and online) that "winterizing" your home is the best way to help reduce energy bills, wear & tear on the furnace. By winterizing I mean making sure that all cracks are filled, etc... and that windows are your "last resort". Is this proffessional right that all new windows (single pane with storm to double pane low e) is going to make that much of a difference? my house is 73 yrs old

[LazyPup]

Most of the books and articles that are describing"Winterizing" are addressing the immediate needs that can best be addressed by the homeowner or DIY'er such as applying attic insulation, caulking, applying weather stripping, door sweeps and such, therefore changing the windows and doors is the most aggressive, and definitely the most expensive part of a winerizing project.

However, when you do a heat loss study on a structure often "Infiltration" accounts for nearly 40% of the actual heat loss. Infiltration is the amount of heat loss as a result of air air passing through the finished wall or radiation from the glass surfaces. Given that infiltration is the amount of air passing through the wall, it is then apparent why caulking or weather stripping has such a high effect.

Replacing conventional single pane windows with double pane glass would then reduce the radiational loss by about 60% while triple pane glass would reduce it by 75 to 80%. In fact, in most instances replacing the old single pane windows with triple pane glass would yeild a better payback than adding insulation in the walls.