Window Requirements
DP >= 35
Design Pressure of windows (and exterior doors) in our area of 140 mph wind requireements
DP >= 31 if mean roof height <15
DP >= 35 if 15 < mean < 25
Our roof mean height is approximately 15 feet. "More or less" will be a function of the final grade.
To avoid possible problems, make sure DP >= 35
SHGC <= .3
Solar Heat Gain Coefficient must be below this limit so windows don't let too much heat.
This is a problem for people who want solar gain in the winter.
Exception: A maximum of 2 windows having SHGC no greater than .70 shall be allowed. These windows should have no more than a total of 24 sq ft of glazing.
U-Factor <= .35
This measures how well the window insulates. Any energy start window should meet this.
Leave stickers on all windows to demstrate they meet these NC requirements.
Each pane must be less than 9 square feet
or else it is considered hazardous and has to be tempered.
A 72 x 42 window has 6 x 3.5 = 21 sq ft. Dividing by 2 for the two slider halfs yields 10.5 sq ft.
I think the window panes of a 72 x 42 slider are < 9 sq ft, but check with Pella before ordering.
Pella Series 250 Windows
That is what we have in our Northwood House
Sliders up to 72 x 44 have DP +35 therefore the maximum slider height we use will be 42" (3.5').
Double hung windows are more wind resistant than sliders, so DP will not be a concern form them.