If you've got the money to install an entirely new system like that, go for it. I am strongly biased in favor of hot water heat. It's cleaner (no dust), it's not nearly as drafty, can be quieter and is more efficient and consistent (because it radiates heat to the room contents rather than heating the air, which is an insulator). A boiler would give you back some more space because it's smaller than a furnace. (Some of the smallest hang on the wall and are about the size of big microwaves.)

Sounds like it would be one bear of a project. And copper isn't cheap, which is what the pipes would be made of. If your basement makes the perimeter walls entirely accessible, then it may not be too bad. This would be an opportunity to zone off as many rooms as possible to disperse the heat how you want it.

One question, though... Why would you heat the attic? Unless that's living space, it should remain vented to the outdoors.

Hi Braytonak. Thanks for the reply.

Regarding the attic, I meant to say that it would be easy to heat it with radiant if I ever decided to finish it off. Just run a supply and return pipe. There's room for 2 full bedrooms and a bath up there. But if I just replaced this furnace with a new one, I'd need to use a different means to heat the attic later on, or else do some major demolition/construction to the main floor, on order to heat the attic.

As for the cost, by my initial figuring, installing a boiler, perimeter piping, and radiant baseboard or radiators is not that much more expensive than installing a new gas furnace and all new ducts. That hasn't kept people (including the hvac guys) from scoffing though. They seem to think the only people who should be using hot water are those with no other choice.

I realize subfloor tubing would allow lower water temps and more efficiency, and might be the cadillac in comfort, but it would add remarkably to the install cost and install work. So I'll stick with a perimeter system.

Thanks.

Good choice. I did just that last summer for my 1 level condo and put in 3 zones. Got rid of all the problems associated with hot air ( the worst form of heating) including dust wild variations in perceived heating and inefficiency for zoning.
My oil bills dropped by 35% and the comfort level went up by 100%.
Go for it!

joeplumb--did you put in radiators, or baseboard, or subfloor, or a combination? I'm curious how close radiant baseboards and radiators come to the comfort of subfloor, if anyone has an opinion.

I thought the old style (large) radiators were meant for higher temperature water. Baseboards are relatively small and are designed to run at 180°F. I've allowed my system to run as low as 130° using the outdoor reset module. Subfloor heat would be nice, but it also has some minor downsides. (Any low-temp heat is going to take a while to change the ambient temperature when the thermostat is adjusted. Installing it could be a pain. It may, depending on installation, end up heating your basement a bit, too.

I saw an episode of Holmes on Homes where they were doing repair on a house that had subfloor heat installed from the basement side. It was tacked to the subfloor between the joists and then covered with foil-faced bubble wrap sheets.

There are both baseboard radiators and freestanding radiators meant to work at 180 degrees and below. They vary though in terms of how much heat is truly radiant, and how much is convection.

I considered the staple-up installations you refer to, but they are more costly and can be plagued by problems like expansion noise, Mainly, I couldn't find any concensus among the installers about how it should be done. So I decided to go with the sure thing.

In Florida my experience may not be applicable but I found a gas fired baseboard unit very expensive to run. Replaced it with a heat pump and with other energy saving strategies eventually got my energy bill down to about $100 a month for a 1500 sq. ft house. It's hard to properly insulate the wall behind the baseboard unit...the temperature differential makes for a lot of loss there with perimeter baseboards.

gary--that's an interesting point. The walls here originally had no insulation in them, but I had them filled with blown-in cellulose, so the R-value in theory should be around 13-14. But I can see how the high differential in temperature would lead to heat loss through the outer wall nonetheless. I''ll look into whether supplemental insulation could be used behind the baseboards.

It gets too cold here for a heat pump to be the sole source of heating, so I will likely stick with the gas boiler.

Dave11,
I used baseboard for economy and aesthetic reasons, but functionally radiators are far superior in that their added heat capacity ( more metal) slows the decrease of room temperatures.
And, by the way, unless you are sitting very near the emitter ( high view factor), there is very little radiative warming effect on the human body; both baseboard and radiator emitters radiate about 1/2 of their convective energy to the local air and the radiant remainder to its environment-- walls , furniture, etc. If you are within a small distance of the emitter, you will increase your
"view factor" and capture a good part of the total radiant energy. If you are not, then there is virtually no direct radiant warming to you.
Finally, the best heating solution is the floor radiant where your view factor is the highest and you derive the most comfort. However cost may be a factor in your case, but I really dont see a case for expansion noise you are worried about, not at 110 degrees at the floor.

Hi Joeplumb. I agree with you that subfloor is the most comfortable, but after doing a lot of research, I found so many conflicting opinions about the best method, that I decided to drop the idea. Whether or not to use transfer plates, what sort of plates to use, the amount and type of insulation to place beneath the joist space, and on and on. Everyone feels strongly that their way is best, yet the next person says just the opposite, and feels just as adamant. And when I asked for results of reliable studies to support what I was being told, no one could provide it.

PEX expands quite a bit from heating, and I've talked with several people who had trouble with noise, even at temps used for subfloor. This was generally blamed on the install method, though every method seems to have had this as a problem at one time or another.

Keep in mind that the copper pipes in a traditional installation could do the same thing. I've heard pipes in some homes that would drive you insane, then others that are silent. A good installation would properly use hangers and ensure that the pipes weren't touching surrounding materials.

Before you spend more time I hope you have a grasp of the money you are talking about to put in a new hot water system. You say you think the price would be about the same as replacing the furnace and the ductwork in the basement. Has any contractor agreed with this? I would guess you will be closer to double the price.
I'll agree that a HW system is superior and has advantages that you talked about.
I'm assuming that you have no need for AC?

If you're going to be in the home long-term, I think it's a smart move, especially if you don't like the quality of the heat you're getting from your current system.

If you're handy, you can certainly install the system yourself and leave the final hook up to an HVAC person.

It just takes some planning on your part to make sure that you have enough heat going into the room.

One thing I would suggest is dividing your home into zones, with each zone with its own thermostat.

That way you can save even more by ramping back on the sections of the house you're not in.

There's a new generation of wireless thermostats that are getting good reviews, as well.

I'm not sure, but it's possible that you could have one central thermostat sender unit with multiple controls to work the zone valves.

I was planning on doing the majority of the work myself, mainly because I couldn't find an installer locally who I thought would do a proper job. I was planning to buy the boiler locally, from an installer, so he'd be willing to deal with the installation.

Thanks everyone for all the input.

There is an abundance of reliable information comparing different heating and cooling systems based on numerous measurable metrics (comfort, efficiency, noise, exergy, response times) Âa few suggested readings with links:

From the International Energy Association, Table One (pg 25), Fig 25 and 26 (pg 35 & 36), Table 6 and from "Heating and Cooling with Focus on Increased Energy Efficiency and Improved Comfort Guidebook to IEA ECBCS Annex 37, Low Exergy Systems for Heating and Cooling of Buildings, Summary Report

http://www.lowex.net/english/inside/frames/text/material_in.html
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ASHRAE Research Project 1036, Develop Simplified Methodology to Determine Heat Transfer Design Impacts Associated with Common Installation Alternatives for Radiant Conduit, FINAL REPORT

http://www.ngml.ksu.edu/research/project_archive/project_archive_publications/ashrae/1036_final_report.pdf
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Development and Demonstration of a Performance Test Protocol for Radiant Floor Heating Systems, Amit Khanna, Thesis submitted to the Faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of Master of Science In Architecture Dr. James Jones, Chairman, Prof. Robert Schubert Dr. Mike Ellis, 2006

http://www.chple.arch.vt.edu/CHPLE%20Research%20files/Khanna,%20Amit.pdf
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Radiant Floor Heating In Theory and Practice, Bjarne W. Olesen, Fellow ASHRAE, ASHRAE Journal, July 2002

http://www.flextherm.com/doc/b%E9n%E9fices/Radiant_Floor_Heating_in_Theory_and_Practice.pdf
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Ontario Association of Architects Conference Slides on Radiant Cooling and Heating

http://blogs.healthyheating.com/2008/05/ontario-associa.html
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As far as expansion noise:

For those who insist on using pex to pipe up high temp radiators or baseboard and then complain about noise...

http://www.healthyheating.com/photogallery/Pipe_Expansion_Graph_small.jpg

See also Page 14: http://www.toolbase.org/pdf/fieldevaluations/HFHSchenectadyFinalReport.pdf

Ticked Off, How to Reduce Noise from Heat Transfer Plates, John Siegenthaler

http://www.hpac.sartech.ca/digimag/display.asp?a=481

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There is academic research and practical field knowledge for just about any topic related to HVAC - most of it available free of charge to the public.

Use from it what makes sense to you - and if so motivated - dig deeper into that which is more challenging.