You have a few words wrong.

Make up air is a term used with large exhaust hoods like those
found in restaurants. They have one blower bringing in the amount
of air that the exhaust hood is removing.

Your HVAC requires two things: both combustion air and fresh air.

Code requires a percentage of fresh air in the return/supply
system of the furnace to provide a healthy mix for humans.
Continually recycling the same air with no fresh will lead to high
CO2 numbers. Not a huge deal at home compared to a school or
other high usage setting, but now very much required by code.

Combustion air provides the air that the flame needs to burn
efficiently. This must be supplied by open access to outdoor air,
not robbing air from the room. A furnace on an outside wall is
usually satisfied with an open louver system with one high and one
low. There are other arrangements when the furnace is not at an
outside wall that involve ducting. I am not familiar with a fan
driven combustion air situation, though they may well exist.

--
______________________________
Keep the whole world singing . . . .
DanG (remove the sevens)




"JohnnyC" wrote in message
...
I've got to have an HVAC guy add make-up combustion air to my
fha furnace. This is a requirement from the local building
inspector.

I had a guy come buy and recommened a 'fan in a can'. Couple of
questions...what are these -and- how much do they cost to
install?

I can't seem to find something titled 'fan in a can' with
google.
thanks.