Insulation, Radiant and Vapor Barriers - Attic Insulation Questions

1. I live in Richmond, VA. and I'm finishing my attic.
What type (r factor) do I need to put at the roof line?

2. What r factor should I use for the exterior walls in my attic?

3. Do I need a special/different insulation near my chimney or duct work?

Thanks for your help!

#1 What do you have room for. Is this to the under side of the roof????Can you get air over it?

#2 R -13 paper to the room side


#3 No the fiberglass or cellulose will be ok

ED;)

#1 ) Answer to your question..
Yes, this is the underside of the roof.
The rafters are 2"x6". There will be air between most of the rafters as I am installing the styrofoam baffles so that channels of air will vent between the soffit and the ridge vent. The baffles take up about an inch or so.

Given this info, what do you think I should use for this insulation?

Thanks!
Joe

A 2"X 6" is only 5 1/2" take away the 1" for the foam you only have 4 1/2". So that lets you go with the R13 is all you can get in there now. If you add a 1"x or a 2"x on to each rafter you could use the R19 thats 6 " .I think thiswould be the way to go it would pay you back.

ED;)

Joe....I'm using r13 for my knee walls, R30 for the ceiling.I also have 2x6 rafters. I installed foam baffles and am going with r19 for my slope walls.

You dont get the full R of the insulation when you compress it .

ED ;)

hmmmmmmm.....interesting Ed......so 1" compression of the r19 would lose more heat than r13 which would actually have a gap between the foam baffle. Think I'd get more r value out of the r19 regardless of the 1" compression. ;)

On the slope rafters just add a 1"X or a 2"X you got it made.

ED;)

The density of the insulation is what determines the R-Value as much as the thickness. The air space is also considered to have an R-Value of 1. When you compress insulation heat can travel trough it faster by way of conduction you are paying for 19 but will end up with maybe 14. As Ed said fur it out you will be better off in the long run. ;)

I just spent 45 minutes writing this nicely but it was blown away by some silly timeout to make me scream with rage.

I want to stuff my rafter spaces with fibreglass as I apply hollow cladding/soffit boards. A DIY book says that I should install spacer battens so that the fibreglass doesn't touch the roofing felt under the tiles. I think that this may be sophisticated nonsense and do NOT want to do it. I cannot afford to buy fibreglass that fits the space (which would be needed for battens to work), I need to use up clumsy council fibreglass that obscured my joists (and is the wrong width for anything ever made) by stuffing it behind attached boards without spacers or nonsense.

I could leave out the fibreglass but I need to use it somehow without it annoying me by spoiling my rewiring - need lots more lights due to diabetes.

Is there any risk of a bad outcome if I do what I want to do?

Check with home depot and lowes. They have a foam rafter vent that you have to use in there so the insulation dont touch the under side of the roof.



ED ;)

What evil would befall me if the fibreglass touched the underside of the roof?

One cladding site suggests using cladding on its own. Would this be much less good than fibreglass stuffing? :confused:

Why would foam touching the felt be OK but not fibreglass?

I live in the Unhappy Queendom so know not these American stores.

What this is all about is in the winter condensation can form up there on the roof boards and drip back down into the insulation. Thats why here on other post we talk about the vents in the attic. like any nails that you see up there now do they have rust on them??

ED :confused: