Basement insulation - 2" rigid foam

diggerd · 10-05-2012, 01:24 PM

Hi,
I'm in the process of building a workshop in my basement. I"m using 2" Rigid foam boards, glued and taped to the exterior walls. I was going to use spray foam to seal the top and bottom of the boards. The plan is to than put up 2x4 walls in front of the foam, and than drywall. The entire basement wall is below grade. House was built in 1955.

A few questions.
Is it necessary to fill the cavity with fiberglass insulation ?

I was also going to fit foam along rim joists and wanted to know if those areas should also be covered with drywall.

Also, do I need to put in fire blocking, and if so, where and how ?

Thanks

could post pictures if needed

Windows on Wash · 10-05-2012, 02:23 PM

1. It is best to fill the cavity.
2. They should be covered with some sort of thermal barrier whether it is drywall or insulation.
3. Depends on the structure. County codes vary. Most fire blocking is drywall and pretty straightforward.

Pictures will help.

diggerd · 10-05-2012, 05:17 PM

I meant do I have to fill the 2x4 wall with fiberglass insulation ? Isn't the 2" foam enough ?

Added some pictures.

Windows on Wash · 10-05-2012, 06:36 PM

Fiberglass is cheap and will improve the overall wall performance.

**Gary in WA** · 10-09-2012, 01:05 AM

Quote:

Originally Posted by diggerd

Hi,
I'm in the process of building a workshop in my basement. I"m using 2" Rigid foam boards, glued and taped to the exterior walls. I was going to use spray foam to seal the top and bottom of the boards. The plan is to than put up 2x4 walls in front of the foam, and than drywall. The entire basement wall is below grade. House was built in 1955.

A few questions.
Is it necessary to fill the cavity with fiberglass insulation ?----- you could get convective loops in the empty cavities moving heat around; http://joneakes.com/jons-fixit-database/743

I was also going to fit foam along rim joists and wanted to know if those areas should also be covered with drywall. ---- not required by most building codes in that location; http://publicecodes.cyberregs.com/ic...016_par015.htm

Also, do I need to put in fire blocking, and if so, where and how ?----- yes, between the house mudsill and the new wall to prevent fire from reaching joist cavities. Every 10' horizontally, #21, 22: How to fireblock framing

Thanks

could post pictures if needed

Added my answers in quote box, Gary
P.S. You really need egress opening for the basement, those windows are too high, too small...

diggerd · 10-09-2012, 08:24 AM

Thanks for info and links. About the windows, we had a bulkhead put in after we bought the house. When we replaced the front door, I had that door installed at the bottom of the bulkhead steps.