[Greenbuilding] ERV strategy

[John O'Brien]

On Sun, Oct 24, 2010 at 9:59 PM, elitalking <elitalking at rockbridge.net> wrote:
> I am getting ready to install my first ERV as my house step by step gets
> tighter.  It is next on my list of steps before I seal the deal (my occupied
> house).  I have been reviewing last month’s thread regarding ERV’s.
>
>
>
> I am still a little confused regarding the dehumidification affect of
> ERV’s.
>
>
>

You seem to be making the issue more complex than it needs to be I
think. Assume both inside and outside temperatures are the same. You
have nicely dehumidified all your nice inside air to lets say a bone
chilling dry 20%, while outside it's raging ontario swamp heat wave at
100%.

With an HRV you're exchanging 20C air with 20C air... Check. HRV is
done. You've just replaced X amount of dry air with X amount of 100%
humidity air.

With your ERV, you've exchanged 20C air with 20C air again, but you've
also transferred your 20% in_humid with your 100% out_humid, which I
will assume will give you a new entering humidity of something in the
middle.. Let's say 60%. You now have 40% less humidity to remove.

Numbers don't make sense, but the concept is correct if not very
simplistic. I think what Steve was talking about was with regards to
exhausting 100% humid bathroom/shower air, with the ERV you're
actually recyling some of that moisture back into the house. I imagine
the next SUPER_RV will have humidity sensors to disable exchange
depending on interior and exterior flow conditions.

j