My house is a similar size in Syracuse, so we have more heating days than you. But, I would also be concerned about putting an HVAC unit in the attic. That will be outside the insulated envelope of your home, subjecting the unit to the cold and heat that's outside. The unit might be ok with that, but pulling air out of the house into the uninsulated/unconditioned attic, then heating/cooling it, and pushing it back into the conditioned portion of the house is going to tend to give you conditioned air that is closer to the outside temp than what you are looking for. Plus leaks in the ducts will send your expensive conditioned air into the attic. At least leaky ducts in the basement leak the conditioned the air in the house. I agree with the poster who suggests that you do as much insulation as you reasonable can. Not just for the money savings but also for the comfort of your home. We have spray foam in our 2x6 walls and it's great. I can sit by the window in a T-shirt with the cold wind whipping and be comfortable. The other thing I did that I am happy with is during construction I would come into the house on the weekend and spayfoam (the cans you buy at home depot) all the holes and seams that the contractors did a poor job filling - and there were a lot of them. I probably used dozens of cans. And that was on top of what the builder did. Good luck!

Thanks for the post! I walked through the house with the HVAC guys this morning to figure out alternatives. Unfortunately, there aren't many... I looked for alternative routes for the duct work but it really only works by going across the basement ceiling - up behind the fridge - through an already small closet, up the attic and then popping in from the ceiling. Asked about setting up a small furnace up in the attic to feed the second floor bedrooms independently of the basement and first floor but that would cost at least as much (and likely more) than the duct work. With the temperatures that we are comfortable with at night (60's), I'm hoping the baseboard electric does the trick. We recently insulated the attic and, even with the vents closed in the rooms, there is adequate heat up there now. I'm now thinking that when the furnace gives out, I may look into converting the house to hot water heating instead which should solve all these problems. Thanks again, E

You don't mention where the furnace and duct is located but being in a cold basement or especially an attic where cold air naturally falls, you could have some migration. In addition you may have a fresh air make up duct that is letting even colder outdoor air into the return duct from the outside. This you should check, some are wide open to the outdoor intake duct and can have a manual damper while some have a motorized damper that should be controlled with blower operation. Make sure the return duct doesn't have any leaks and check connections and cabinet for leaks and cracks for air to infiltrate. Most furnaces have lousy gaskets on the blower doors and do not seal well. You might try taping the seams with a good aluminum duct tape. The problem with covering the return is having the furnace turn on without removing the cover could result in unit control and/or blower damage, including overheating and fire.

Thank you rweigand - I will check and also try to get some photos of the setup. The filter was replaced just a few days ago. Do you reckon having humidity meters on each floor is a good idea? PS: We're in Massachusetts. The weather has been all over the place in recent days. Its rainy and 11C today and tomorrow, and then dry and 21C on Thursday! Hows that for xmas eve? Never thought I'd see that kind of temperature for xmas! mike_home - There is no doubt we have air leakage issues. We have drafty windows (and it is a very old house anyway) that will be replaced in the 2nd week of January and then insulation will be blown in to the external walls on 19-20th of January by a MassSave contractor. Should we wait it out to see what changes the windows and insulation will bring before blaming the HVAC system for all our humidity woes?