header sizing

[dug]

For 20 by 30 1 & 1/2 story-

I have a 6 ft. opening for window on non- gable wall, there is no loft above this area. Plans call for three 2 by 10's if supporting loft above or two 2 by 8's on upper floor of this wall. Is this the chart I should use (Two 2 by 8's)?

Thanks

[MountainDon]

So in other words, this is a side wall and there is only the main floor and a ceiling and a roof? 20 ft wide building, no upstairs floor.

My IRC2006 which is what most of NM uses, calls for

2-2x8 good to 6'10" header for 30 # snow load. One jack stud at each side.

But for 50 # snow load 2-2x8 header is rated to 5'11" header span and require two jack studs per end.
Two n2x10 and two jack studs per header end would do 50# up to 7'3".
That would also cover 70# snow up to 6'6"

[dug]

So in other words, this is a side wall and there is only the main floor and a ceiling and a roof? 20 ft wide building, no upstairs floor.

Yep. that's it. Thanks Don!