Thanks zl700, I think it is probably convection current as it is very mild and mostly coming out the top slots rather than the sides. I didn't see any place in the heat exchanger area where there was any strong air coming out of cracks - it just seemed to be heat radiating from the flames visible at the burners. I also noticed while checking it out that my fan limit controls were set very high - about 115 deg for off and 140 for on. I suspect this was also further heating up the crawl space by keeping more residual heat in the exchanger between cycles. I adjusted them down to 85 for off and 110 for on to scavenge out more heat. I'll probably have it looked at next year after I see how the remodeled house performs over all four seasons. There's also an air conditioner unit above the furnace that hasn't been working or needed in at least 10 years, but with significant changes to the house (roof changed from light to black, stories changed from 1 to 2, more windows) I need to see if A/C is actually needed or not.

I would not install an 80% furnace in MA unless it was physically impossible to do otherwise, which doesn't sound like the case here. For zoning, I always recommend a 2 stage, variable speed furnace minimum. It's doubtful your existing panel and thermostats would be able to handle this properly. A modulating furnace would be even better for zoning and great for that area if you could swing the cost. In my opinion, the best zoning systems are the ones sold by the furnace manufacturers and designed to be used with that particular unit. Examples: Lennox Harmony, Carrier Infinity/Bryant Evolution, Trane Comfortlink/American Standard Acculink. Those also tend to be the most expensive. If you would like something less expensive, make sure to get a panel that handles staging properly, i.e. stages based on the number of zones calling, not a timer. Don't worry about brand. They are all comparable quality at each tier. Hire the contractor you like best, and just go with the brand he prefers. Zoning isn't easy to get right, so make sure he's experienced with it. Also be sure to hire someone who does a Manual J load calculation to figure out the right size for the replacement furnace. Many contractors go by their "years of experience" or "your house is XXXX square feet and therefore needs this size unit" or "your old one was size X so I'll replace it with one of the same size". None of those are valid sizing methods! This post was edited by hvtech42 on Fri, Nov 7, 14 at 15:28

"The closet the gas furnace is in, is not ventilated. The closet does not have a roof, but opens up into the attic. He does not think there is enough fresh air making it down to the furnace, and he does not think the fumes from the furnace are making it up into the attic." the closet is actually very well vented if it is open to the attic at the ceiling (roof?) of the closet. "He has instructed us to nail some gutter pipe (gutter pipe, because it is square, and will fit the limited space better than round pipe, but to mee gutter pipe seems awfully small diameter) into the closet to increase circulation. One peice going 12 inches into the attic, and another peice 12 inches off the floor. To me this seems awfully suspicious, I cant see how this will work, and I'm scared." I usually install a ceiling in gas furnace closets using ductboard (doesnt burn) from inside the attic. Usually a 5 or 6" vent pipe from inside attic..12" above insulation with a bug screen. the pipe goes thru ductboard ceiling to where the air intake of the gas furnace is located. I've started putting an inline manual damper..open when furnace is in use..closed for cooling season. "He also noticed that someone has stapled fibergalss insulation to the inside of the closet door, and we should remove that. That the entire door needs to be replaced with a very tight fitting door." Someone was trying to overcome the temp transfer from top of heating closet being open to attic. Bat insulation is not a good idea..but ductboard works well. and door should be weatherstripped. while the venting will supply the air needed for the furnace, it won't vent fumes. there shouldn't be any fumes if furnace is operating properly..there are vent pipes attached to the equipment that vent out of the roof. as for the smell...it could have been a sealant that he used or many things. I would call the original person who did the install and tell him your concerns. Granted there are better materials to use but it sounds like he/she was on the right track. better to close in ceiling and make it air tight and bring fresh air to the furnace than to leave the ceiling open to the attic. just my experience here in hot humid La. it may vary if your area is different. best of luck.

The vapor that comes from our propane fueled furnace is quite acidic which might be one reason that yours might damage the metal of the generator. Ours runs year-round since it is the hot water (runs both the hot water and the heat for the house). I am not sure if it's the heat or the acidity, but it does kill the grass by the vent pipe (~3' stretch) as well as having damaged the cementaceous siding that was nearby. If I were you, I would dig up a chunk from the side of the shrub to transplant as well as trying to start cuttings so that hopefully one or the other survives. Depending on your fuel and how the vapor dissipates, it may or may not kill the hydrangea, but I am fairly sure that it will damage it.