I would advise thoroughly investigating a new boiler system and keeping the radiators as a lot can be done with modern hydronic systems. They are very efficient, up to about 96%; they can be wall mounted and are very compact taking up no floor space at all. They can also incorporate an instantaneous domestic hot water capability so you would not require a reservoir tank or separate device. Also they are quiet and induce no drafts. High efficiency condensing gas boilers can be side vented meaning that the present condition of the chimney may not be a factor at all. Having NG means that you can have a gas stove, dryer, fireplace and outdoor BBQ. A gas stove and fireplace would mean that you would have access to heat and cooking during a power failure. Keep in mind that a hydronic system, particularly one with cast iron radiators, is fully compatible with a geothermal heat pump that can provide heating, domestic hot water and central cooling without ever having to install duct work. Keeping the hydronic system will also maintain the original look and feel of the home as well as its heritage value as time goes by. Any renovation or new addition could also include radiant in-floor heating with the hydronic boiler system. This is particularly nice in kitchens and bathrooms. These are highly prized features when it's time to sell. Even with, or dare I say especially with the 'old' cast iron radiators, a modern hydronic system in the 21st century is NOT your parent's heating system at all! SR

Thanks to everyone for your replies and advice! ryanhughes -- No, I did not share sizing info among contractors; they all came to 3.5 tons on their own. I did, however, mention to Company 3 that I already had an estimate for a 90K BTU furnace, so Company 3 guy said, "well, I was going to suggest 80K, but in that case, let's go with 100K." Also, I did let all estimators know that I'm planning to add on 150-200 sf in the next year or two, so they should take that into consideration. baldloonie -- Nope, not much insulation. some was blown into the attic floor in the 70's, so it's (somewhat) compacted now. Otherwise, nothing at the roof, in the crawlspace orin the walls. And yes, lots of windows -- at least those have been upgraded to double-pane. It's been stinkin' hot this year with several weeks of 90+ temps so far... and we're probably in for a few more (it's a dry heat, though ;-)). Winter nights can get into the 30's during cold years. A few more questions... 1. Company 3 also sells York, and I'm looking into the LX series A/C for space reasons (smaller footprint). In terms of sound levels (dB's) nd reliability, what's your take on Carrier Comfort/Performance vs. Trane XR13/XL14i vs. York LX series? 2. Would I be better off with a completely matched system (e.g., Trane furnace/Trane A/C), or can I mix and match furnace and A/C (e.g., Trane furnace, York A/C)? 3. A couple of the estimates I received included the option to add on a higher-end air filter -- Carrier Infinity (Company 1) or AprilAire 2400 (Company 3). Is it worthwhile to do this? 4. I have allergies and pets. Is there a noticeable difference in adding an air cleaning system? I guess the real question here is "are they worth the money?" 5. Company 3's estimate is about $2K higher than the other two. I assume this is due to the higher price of Trane components, the additional fabrication for the sound-attentuation work, and their fabrication of an "accessible" filter box. Thoughts?

I was able to get info on the existing furnace from the data plate. It's a Carrier Model 58ss140-BC, Series 110, 167,000 BTU. The data plate said the blower is "157", whatever that means. The motor spec was 1/2 hp. Mfg date 1982. That's all I found on the furnace. I found next to nothing on the a/c. The data plates outside are gone. I could see where it was but there was just rivets. A single, long rectangular unit outside. Like I said, vintage 1974, from the builder. According to my mother, the quoting contractors guessed that the system was 4 or 5 tons. I don't know anything about who said what. Turns out the Lennox/Costco guy was the only one to quote an upgraded unit. He also quoted: Option #3B. $9,185. Platinum Package. A/C XC17-048 and 2 stage gas furnace SL280UH135 with variable speed and I-Comfort Communicating Controller. I'm having a hard time getting her to look at the Am Std quote because they didn't quote her an upgraded unit option and their basic units were only about $1,000 cheaper than the upgraded Lennox units. ($9,145 vs $7,945). About the house, I tried to describe it above. Built 1974. 3200 sq ft. and two stories. Attached garage. Full sun exposure--the property is not shaded. Brick exterior with not a whole heck of a lot of insulation. (I remember my parents being mad that the builder gipped them on the insulation.) High quality house though, expensive neighborhood. Stick framed over a full basement. Attic with pitched shingle roof. Colonial. Original single pane wood windows with storms windows, maybe a tad drafty. After being widowed with 4 kids in 1978, she never had the money to remodel anything and everything is pretty much 1974. Anything else you want to know about the house, please ask. This is all I could think of.

garyg, It is an either or situation XL14i with variable speed air handler, aluminum evaporator coil and Trane touch screen thermistat. Include 10 years parts and labor. No need to replace the lines because they are large enough. Heat Pump $ $9105 includes 2 -5K heat strips. or hybrid below 2 XL14i condensor with 2 Stage variable speed furnace $8208. XR13 with variable speed air handler, aluminum evaporator coil and Trane touch screen thermistat. Include 10 years parts and labor. No need to replace the lines because they are large enough. Heat Pump $ 7150 includes 2 5K heat strips. or XR13 condesory with 2 Stage variable speed furnace $6985. Gas rates are somewhat confusing for two reasong 1. They under reported July and caught in August. 2. we have distrubtion rate, gas supply rate,weather normalization adj rate, base rate adj and EE cost rate. All of which is different.