How To Insulate An Attic Storage Space

[Jawgarage]

Hello all, need some help here as I am not sure what to use for insulation prior to finishing off this space for storage use only. Location is southern NJ. My goal is to both make it a "Clean Storage space" instead of the current attic space, and to try to reduce the heat and cold "Pocket" that is currently in this space that penetrates into the second floor bedroom through the common side wall. Let me explain as best I can:

1. The space is basically wedge shaped and located above my attached 2 car garage of the house.
2. Floor area is approx. 24'X16'
3. The tall side wall is 8'tall, the inner knee wall that separates it from the remainder of the attic area is 4' tall, there is one exterior wedge shaped side wall and one interior wedge shaped side wall that is shared with the second floor bedroom.
4. Access to this space is walk in through a closet door inside the closet of the bedroom
5. I have installed a thermostatically controlled attic fan in the wedge shaped exterior wall
6. There is an OSB floor down in this storage area already with insulation under the floor as well as insulation on the bottom of the entire attic space beyond the knee wall.
7. There is NO insulation on the two exterior walls nor on the roof of the attic space in this area
8. The shared interior wedge shaped wall is insulated with fiberglass batting that is kraft faced.
9. There is a full length soffit vent at the top of the 8' side exterior wall which is the highest point of this contemporary style house (think cathedral ceiling attic going from 1' low to 8' tall with this section for storage occupying the 4' to 8' tall section)
10. In the summer this space is massively hot (attic fan not hooked up yet) and freezing in the winter.

MY GOAL:

1. Lower the heat/cold swings in this attic storage space without creating some sort of moisture problem by using the wrong insulation behind the sheetrock on the walls and ceiling rafters
2. Close off the walls and ceiling rafters with 3/8 sheetrock to make the area a "Clean" storage area as opposed to raw attic storage
3. Insulate this area to reduce heat penetration into storage area
4. I will install several vent panels in the 4' knee wall when I sheetrock it to allow the power vent to keep air circulation in this space too.

Soooooooo.......what do I do for insulation in this space? simple unfaced fiberglass batts behind the sheetrock? roof rafters are 2x8 and walls are 2x4.....

Jeff

 

[DC73]

Having a bit of trouble visualizing your space. Maybe a sketch or some photos would help.

That said, and without knowing any more, you could use closed cell spray foam to accomplish your mission. Insulating under the roof deck any other way is tricky and often requires vent channels, soffit vents and ridge vents.

It might also help to have a well insulated door leading from the closet into the storage area.

DC

 

[Junkman]

I understand your description, since I have a similar build. The best thing to do is spray foam insulation on the underside of the roof deck and the end walls. I like the idea of the thermostatic fan, but it also needs to have a place for the air to enter.

 

[Jawgarage]

Thanks. I plan on adding seceral 24x24 inch vent grids along the knee wall and maybe a 12"x3" vent panel in each ceiling bay that would allow for external air to be pulled through the space and still provide cooling and ventilation to the unfinished attic space. Im really looking to simply make the large storage area cleaner. Eliminating heat would be great too but dont want to bring in a cendor to spray or anything. Im really mostly concerned about not trapping moisture behind the sheetrock and between the outside walls and roof sheathing. If I use fiberglass batts, would I use kraft faced or totally unfaced?

Jeff