On Sun, 25 Dec 2011 13:33:18 -0800 (PST), bob haller
wrote:

On Dec 25, 3:51*pm, leza wang wrote:
On Dec 25, 2:31*pm, bob haller wrote:

If its a double pane window replace the sealed unit. Its no expensive
in pittsburgh area you make appointment, take window and sash assembly
in AM and pick up in late afternoon.

much cheaper than a new window.

attempts to fix the seal are a grand waste of time

thanks for your reply, much appreciate it. what is seal?

the seal is the seal between the 2 panes of glass.. its generally a
rubber like gasket material that usually keeps the outside air from
entering between the 2 panes of glass.

the seal doesnt last forever when air enters as barometric pressure
changes moisture enters too, and you get condensation on the inside of
the glass unit.

a local window repairman can come out disassemble the sash and measure
the sealed glass unit, then return with a new sealed unit.

on older windows the big hassle is getting the frame apart that
surrounds the sealed unit.

thats best left to experts to prevent frame breakage

Is the glass a single pane or a double pane of glass? If it is
single, use glazing putty around the edge of the glass. This will
prevent air infiltration from the outside.

Also check the outside trim and caulk around the trim. That window
has window weights, so air can leak around the pulley at the top.

Use an incense (smoke) stick to find the draft from inside.

The window may not be well insulated and air will enter there as well.

A trick to seal the pulley can be found in this short video -- using
foam pad.

http://www.thisoldhouse.com/toh/video/0,,20051453,00.html