U factor measures the conductivity of materials.

I know of no window manufacturer that makes 'southern' versus 'northern' windows.

The same materials are used in all manufacturer's windows to my knowledge.

I read your other post about Simonton windows and all I can say is that you have had a poor installation job.

I have used Simonton windows almost exlusively for 15 years in both new construction and remodeling applications and have never experienced the problems you described except when the windows were improperly installed.

Thank You for your reply.
I will work on the installers. I had my builder here all day friday working on them
What series of windows do you install?
Builders or Construction.
The construction series are well built blocks in sides and blocks in bottom to stop air infiltration.
Compared to the certainteed vinyl windsow in our old house and the construction series by Sinonton the builder series seems to be lacking in construction quality, thats where the air infiltration is coming from.
thanks Clax

I have used both but have never experienced the symptoms you describe with the Builder series.

In fact, proper installation which includes placing insulation between the window and the framework, sealing and caulking should eliminate all drafts.