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smhaff · Mar 19, 2006, 12:05 PM

I am replacing my old existing AC/heating unit and my contractor recommended not putting in a fresh air return in the system. My impression is that one is needed. Our house was built in '64 and is not air tight. I want to insure we do not have a sick house syndrome. Any educated information would be appreciated.
Thanks.

ridgid002 · Mar 19, 2006, 12:24 PM

When u say fresh air return system are u talking about an outside fresh air source or an inside return air system to your furnace... please let me know and ill be able to answer further thanks

smhaff · Mar 19, 2006, 04:22 PM

I am referring to an outside air source that allows for outside air to get introduced into the system.

Thanks

labman · Mar 19, 2006, 04:31 PM

Do you mean pulling in additional air from outside? If so, I doubt that it would be necessary. How was the old system working? Were you having respiratory problems, allergies, odor, etc. problems? If not, I see no need to increase you electric bill by cooling and drying more outside air. Modern construction is much tighter than is the 60's. You should have plenty of fresh air infiltrating. The original materials should be done outgasing.

I see mold as the most likely case of any problems. Getting rid of the old ''A'' coil might be a big step forward in controlling it. Another good step would be cleaning the existing duct work.

ridgid002 · Mar 19, 2006, 08:59 PM

Definitely not there is no reason... aside from any medical... to bring in outside air into your system a house built in the 60's is certainly not air tight and would only cost u money... A on the installation and B on your fuel bills as long as the system has adequate air flow... ie the correct cfms of supply and return for each room I can see no reason other than u would personally want it... to bring fresh air in from the outside

dherman1 · Mar 20, 2006, 06:04 AM

The only reason that you may need to have a cold air return installed is that it may be required by your cities code. Give them a call and see what they have to say.

If you do opt for one, make sure that the HVAC installer doesn't actually plumb it into the cold air return. (This will suck in the outside air every time the system runs, whether in A/C or Heating mode). Instead, have them run it along side the furnace and then into a five gallon bucket.

The static air pressure will keep the air from just dumping and making the floor cold. With it put into a bucket, intake air would only be introduced when there is negative pressure in the house. (Like when a bathroom or kitchen fan is run or the clothes dryer).

Another item to consider is an air to air exchanger. This type needs to be plumbed into the ductwork as it diverts some of the returning air (or from the kitchen/bath fans) and then sends it through a "black box" to allow it to give up it's heat energy to the incoming air which is then fed into the cold air return.

If you have windows that fog up on the inside, this is the type of system you need.

Good Luck, Dan