I need your help. I have purchased a home that has a new Hi-Effency forced air furnace. The house has a 2 1/2 ft crawl space - no basement. The heating and return ducts are below under the floor boards of the house in the crawl space. The crawl space is insulated as are the ducts.

My question is; When the furnace comes on, the return cold air ducts are BLOWING NOT SUCKING COLD air into the house. Is this normal and if not how can I fix this.. I have checked the duct work and there does not appear to be any leaks... The cold air gets somewhat less cold as the house begins to heat up BUT the RETURN ducts still blows and not suck...

I have tried to partially cover the return air vents - not sure if this is a good idea -

The furnace is inverted so that the hot air blows from the bottom and the intake (cold air) from the top. I have thought of detaching the cold air duct return from beneath the house to adapting a new duct return where the filter is at the top of the furnace inside the house. Do you think this will improve the situation?

Any help and advice is welcome and appreciated.

Dee Dee