# Attic insulation - 2 questions



## oh'mike (Sep 18, 2009)

I suggest installing the baffels even though the soffits are not vented at this time.

Some day yo may wish to add some vents.

As to the foam/plywood sandwich---I don't like it --but I see no harm if it's used only for light storage.

I doubt if there is any harm --any moisture under it will vent out the sides of the joists.


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## Windows on Wash (Aug 30, 2011)

Air Seal, Air Seal, and Air Seal.

Do that first before you add more insulation without fail. 

You can dense pack that area of storage for proper insulation and dense packing stops air movement as well. After that, you could ad a layer of rigid foam (do not tape of seal the seams) and then a layer of plywood over that (effectively creating a sip panel).

Use a minimum of 2" of Poly Iso. More is better in this case so if you can put down 2 layers at 2" that would equal about an R-25+ and combined with the lack of thermal bridging and what is under the floor...you should be good to go.

+1 on potentially adding baffles if you decide to vent the soffits. Once you air seal, your necessity for ventilation goes down even further and if your attic is moldy already, it will be that much dryer after you air seal the floor.


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## aejamison (Nov 3, 2008)

We had an energy audit w/ blower door so I am definitely up to speed on the air sealing - it will be messy but worth it in the portion of the attic not used for storage. I'm going to pull back the old insulation a section at a time, air seal, put the old stuff back down and blow in more cellulose.

As far as not taping the seams of the rigid foam - is that to allow any potential moisture migration up through, or is it just not necessary if dense packed below? Do you think I could cause potential problems with my initial idea using the rigid foam?


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## Windows on Wash (Aug 30, 2011)

ajamison said:


> We had an energy audit w/ blower door so I am definitely up to speed on the air sealing - it will be messy but worth it in the portion of the attic not used for storage. I'm going to pull back the old insulation a section at a time, air seal, put the old stuff back down and blow in more cellulose.
> 
> As far as not taping the seams of the rigid foam - is that to allow any potential moisture migration up through, or is it just not necessary if dense packed below? Do you think I could cause potential problems with my initial idea using the rigid foam?


Not sealing the seams in the foam board would just be to allow for any moisture movement if at all required. 

Also, it is not really required from the standpoint that they do not need to be air tight.

If you dense pack under the storage area, it is a not issue anyway.


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