There are a number of choices to insulate inside the cavities
between the old window frame and the rough framing. 
Spray PU Foam is the easiest because it doesn’t require full
removal of the trim if the nozzle can be inserted into the gap. 
Be sure to use a PU Foam that has been tested in accordance
with AAMA 812 for low pressure development, to avoid impart-
ing pressure to  window frame that may void window warranty.
Foam insulation board and fiberglass batts are not effective air
seal material between the window and rough opening. Foam
boards need to be cut precisely and do not create a seal without
caulking. Fiberglass insulation is also not effective as it does not
create a seal and may absorb and retain moisture creating an
environment for mold and mildew. Compressed foam tape con-
forms to the contours between the RO and the new window and
are typically installed more commercial applications.”
Finally, Air Seal along interior using a quality low odor,
paintable latex sealant to eliminate air infiltration and sound
intrusion.
Window Fitters Guide to Window Installation 
14                ©2022 AWDI, LLC Do not reproduce without permission
Make a Small
Access Hole
Remove Trim and Wallboard
Piece to Gain Access
Insulate the Cavities
Thermal Images of fully
insulated and air-sealed
gaps, using any of a variety
of material choices, 
demonstrate that the total
opening will block air 
infiltration and heat loss 
as well as the new window.
SAMPLE MANUAL

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