[Greenbuilding] basement insulation

[Keith Winston]

First, I'd say making sure you've addressed exterior moisture issues, if 
they exist, is the most important step. Then, I'd agree that you want to 
hold interior humidity levels down for several reasons. A dehumidifier 
can be a reasonable way to do that. Finally, I'd go with higher 
permeability rather than lower, especially if you're using spray foam: 
the issue of providing an air barrier is addressed by the foam either 
way. If you hold your framing off the wall, you can spray behind/around 
it, thereby reducing bridging & leakage issues.

Good luck!

Keith


Paul Newby wrote:
> I'm attempting to come to an understanding of the
> best option to insulate the inside walls of a
> walk-out basement in a cold climate taking into
> account moisture control.  I presume you need to:
>
>    1) allow an evaporation path for moisture coming
> from the outside (through the walls and footings); and
>
>    2) prevent moisture from entering the wall from
> the inside.
>
> I don't see how you can (easily) accomplish both
> objectives at once.  An insulation contractor recommends a
> layer of spray foam applied directly to the inside
> concrete walls.  If the foam has a low vapour permeability,
> you accomplish 2) at the expense of 1).  If it has
> a high vapour permeability, you get 1) but not 2).
> I would think that the best solution would be to
> opt for high permeability and ensure a low humidity
> environment within the basement living space so that
> any moisture accumulation that may occur during
> the cold season evaporates out during the warm seasons...?
>
> Thanks in advance for any insights/suggestions.
>
> Paul N.
>
>
>
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-- 
Keith Winston
Earth Sun Energy Systems
3927 Madison St.
Hyattsville, MD 20781
301-980-6325
keith at earthsunenergy.com
www.EarthSunEnergy.com