Expert: Ted Barnhill (Principal, Design45 LLC) - 2/8/2009

Question
hi i am having replacement windows in a porch which have no insulation in the cavity at moment which is the best insulation material to use that which is not over expensive
thanks sheila

Answer
Sheila,

Alas, "the best" and "expensive" often go together!  You haven't told me where you are located, but assuming it is a fairly cold climate, the best insulation to use in your situation is probably closed-cell spray foam.  I say this because your porch walls are probably 2x4s, and only closed cell foam will provide good insulation (R20+) in that depth.  You need all the insulation you can get, because you will lose a lot of heat through your many windows (even new windows).  Is it expensive?  For a small room such as yours with lots of windows, foam may cost $500 or so, which is much more than fiberglass would cost.  However, the increased comfort and lower energy costs may make this worthwhile.

Another option is to use ridid foam board cut to fit between the studs.  You can then seal them tight with DIY spray foam.  This isn't as airtight a solution, but is much less expensive for a small space such as yours (especially if you can do the labor yourself).  Enjoy your enclosed porch. -Ted