Help understanding air-to-air heat exchanger options/issues

[Guest guest]

I have a house with no central heating system. We use a wood burning stove and

natural air

circulation and a backup propane free standing stove in case we go away.

I am addressing a moisture problem in a crawl space but am thinking ahead to

what will help

me live there again - as I am highly sensitized.

Would a heat exchanger bringing in fresh air be helpful, I am guessing it would

be. What

type of installation make sense in an older home with no central system? Are

there individual

units like these new split AC units? We do not presently have AC in the house.

I may also need positive pressure in the space in the event that parts of the

" crawl space " in

our home cannot be accessed - these are not wet areas but they do have silt that

maybe

housing spores from whenever...

I appreciate people sharing their expertise, Thanks! Jackie