I’m doing an addition on a house with vinyl siding. We are putting in new Anderson windows in the existing house. Stripping the existing vinyl and wood shingle underneath down to the plywood. 40 year old house has 1-1/2″ wall insulation. The new windows are taller so I am going to upgrade the insulation in the cripple pockets under the windows. To increase the r value of the walls we want to put 3/4″ rigid foam. My questions are: Does anyone have other suggestions for increasing the r value. Short of major destruction/reconstruction. And when installing rigid foam is it wiser to run the foam up to the windows and install the J-channel over it or to use a deeper j-channel and nail it to the plywood directly.
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Since you're stripping the siding, this might be a good time to blow in cellulose.
Al Mollitor, Sharon MA
I would run the insulation right up to the new windows and j channel on top ,you might also think about adding housewrap too.I did the prevouis described on house I owned and it made a large difference in the heat bill
How about nailing 1"X4" pine onto the plywood (around the window openings). Then running the foam up to the pine. You could then nail the window flange to the pine assuming you could get extension jams which should be available with new Anderson's... Do your new Anderson's have the "j" channel build into the window? If so, I do not think you would need to add "j". Just some thoughts, I am really no window expert.
i'd install the windows.. run some 3/4 shim stock around them... flash with Grace membrane... then butt your 3/4 insulation to the shim stock... next nail on a 5/4 casing and a false sill.. and butt your j-mold to the casing and sill.. your sill can have a rabbet to receive the j-mold..
if you run your insulation right to the vinyl jamb of the Andersen window.. , then apply your j-mold you are going to lose all of your reveal and the j-mold will be proud of the jambMike Smith Rhode Island : Design / Build / Repair / Restore