Adding insulation to floor

[daleslad]

Just got a cabin in the Sierra's in CA at around 6300 ft and want to insulate the underside of it.
I've never tackled anything like this before so I would appreciate any help I can get.
I can't get up there just yet because of the snow so I don't have any exact measurements. I've added a photo of the underside of the floor which is about 12 - 15 feet off the ground so you can see what it is like.
Thanks

 

[inspectorD]

Insulate it with some fiberglass, Kraft faced paper insulation. This is the least expensive route.
Just make sure the paper goes toward the heated space in your climate. This means you should not see the paper when you insulate from underneath. The paper will be up against the bottom of the floor boards. Use wire insulation stantions to hold it in place if you need them.
Then put some plywood underneath, no plastic, just to keep out the critters.
If you are in a fire prone area, you may need to use a fire resistant material. I have used durarock in the past , but there may be similar materials in your area.
Good luck.

 

[daleslad]

Thanks Inspector, what rating should I put there or should I just put as much as the space will allow between the floor joists.
Also do I need to worry about ventilation when I box it in.

 

[inspectorD]

You will need to install whatever depth the joists are. The closer the better. If you install it compacted, it looses efficiency. So no jammin it up there.
No ventilation on floors or walls, just ceilings where all the heat goes. Those are the basic rules...but are subject to change depending on roof styles.

Sounds like your ready, post some finished pic's when you can....good luck.

 

[inspectorD]

That spray foam is triple the cost of fiberglass. On a cottage you probably don't need it. But it is better.

 

[daleslad]

Hey thanks Inspector and Roofing god, I think I can handle it now but I will probably stick to the least expensive insulation. It will be awhile before I can get up there to do anything but I will try to remember to post the finished product if I can.