Thank you for the quick response. I read through the study rather quickly, and will give it more time this evening. I don't doubt that a condensing boiler can be used to save energy on existing systems designed for 180*F. water, although the savings will be somewhat reduced and the payback time will be greater. What I do have a problem with is supplying sufficient heat to keep the room comfortable.
From some parts of the study I found these statements. I may be taking them out of context, and will give them further thought when I have more time:
Conventional baseboard hydronic distribution
systems are most common and these are designed for water temperatures in the 180 F range, well above the saturation temperature. I agree.
The heating system as tested combines space heating and domestic hot water loads using an indirect, 40 gallon tank with an internal heat exchanger. Tests conducted during the summer months showed that the return water temperature from the domestic hot water tank heat exchanger is always below a temperature which will provide condensing operation of the boiler. I feel the use of the domestic water tank skews the test somewhat in favor of the condensing boiler.
The results included in Figure 26 and 27 show that the condensing boiler yields higher efficiency than the non-condensing boiler in actual use. However, the increase in efficiency achieved with the condening boiler during the heating season is smaller than might have been expected.It comes as no surprise that the condensing boiler has higer eff, but most of the savings in this study seem to be in low demand situations and operating this unit in the summer for domestic hot water is not a fair comparison in my opinion.
The primary conclusion of this work is that condensing boilers can achieve energy efficiency benefits, even when used in homes with common baseboard radiators by incorporating a reset control which modulates the water temperature supplied to the baseboards with outdoor temperature......This of course depends upon the oversizing of the baseboard convectors relative to the design load of the home and the excess air level on the burner.The report seems to indicate in several places that adding baseboard or convectors will be necessary to provide adequate heat. The study was to determine what percent of the year that savings can be obtained, not if an existing system will function without adding additional heating units.
One must keep in mind the number one primary purpose of a heating system. It is to keep the occupants comfortable. Energy savings can be a very important factor, but if you install a system that can not keep the owners comfortable, they may use any money they saved on utilites to hire a good attorney to come back and sue you.