Question: Steve asks: A lot of homes in my town outside Philadelphia are about 100 years old and made of stone or brick walls (no exterior wall insulation). They lose a lot of heat in the winter and it is usually not a good idea to add an interior insulation barrier.
Are there any economical options for adding exterior layer of insulation?
Steve, it will be very difficult for you to insulate the exterior walls if they are old construction, which is typical brick, concrete or cinder block with masonry, wire lathe and plaster. I would not even try to insulate these walls because it will never provide you with a ROI that you could justify.
A more efficient use of your time and money would be to perform an energy efficiency audit with a blower door test on the home and, assuming the house is inefficient, focus on stopping air infiltration leaks. You may find that the loss of heat through windows, under/around doors, in connected garages, through ceilings/outlets, etc… may be significant.
Also, if your attic is not insulated that should be an area to scrutinize for loss of heat. By investing in new energy efficient windows you may realize significant improvements in heat loss.
Focus on installing windows that have a higher R-Value, such as triple paned argon-filled windows with high-performance “Low-E” coatings while reducing the house’s air infiltration rate, you may notice a difference right away.