Is there any way to inexpensively add outside air to a home. For instance can I just tie a 1" or 2" pvc pipe from outside to my return duct to add outside air. I am not sure if this is a crazy question or not but it would seem OK. I live in the Philadelphia area so it can get pretty cold - so if I did this would it cause the heater to have to work significantly harder?

I doubt an inch or 2 pipe would bring in that much air. A 4'' dryer vent might make more difference. And yes, bringing in cold outside air would increase your heating bills. How much would be hard to say.

What is the problem? A better filtration system or air purifier might be a better situation. Not only would the outside air cost more to heat, but it would also be drier, making the house feel even colder.

Thanks for your response!

No real problem but I just wanted to be sure that I have enough "new' air coming in. My house is about 1 year old and is pretty tight. Using gas fireplaces and heaters I thought adding some outside air would be a good thing.

I have tightened my older house up to where my wood burning fire place didn't draw right. I ran a 4'' duct out the back of the fire place. It has a cap outside, and a metal plate to regulate it on the inside.

With the new high efficiency furnaces, they're piped to bring in their own fresh air. The gas fireplaces don't use that much air for there to be a problem.
PECO would love your idea though!

An air to air exchanger would be a good investment. Depending on your climate there are two different types. It will bring in fresh air as needed, maintain humidity and some have HEPA filtration. Contact your local HVACr contractor.