I have a 1969 Cape Cod 2,300 square feet, brick and vinyl sided home with cathedral ceilings that I want to update insulation in. I have the original R-7 fiberglass in the walls and R-12 in the ceiling. The roof has soffit and gable vents. There is only a 4 inch access in the ceiling from the attic.
Filling this with insulation would block the venting from the soffit to the gable vents. I had some companies offer to blow cellulose in the space and make it a warm roof. Other companies said not to block airflow because it would cause problems with the roof. The house is 50 feet across the back. There is a lake view so the first story has three large sliding doors and a wide chimney. There is less than 6 linear feet of wall to insulate.
All the bedrooms are upstairs and on the back wall and again have very little wall due to the chimney, French doors and large windows. I got a quote for about $2000 for retro foam in the side walls and front of the house. They said it would make a big difference stopping airflow in the walls because the side of the house took a lot of wind from the lake.
Another company would not give me an estimate because they said due to the large amount of windows and doors and because the ceiling was under insulated, retro foaming the walls would not make a noticeable difference. I have replaced all the doors and windows in the house and installed a high efficiency furnace. I live in Michigan with cold winters and warm summers.
Is it worth insulating whatever I can?
The ceiling is built to the trusses. I went up into the peak and realized that there are cross braces so there is no way to insulate the ceiling over the bedrooms without removing the roof or tearing out the plaster ceiling. So the question is: will I notice a difference in comfort putting retro foam in the walls if the roof is only about R-12. I realize that it will take many years of energy savings to make up the $2000.