Radiant heat efficiency

Mark Custis

I hear a 30% savings in delivery of BTUH.

George_45

radiant heat efficiency.

I keep hearing from more and more people that it costs more money to run a radiant system than a conventional heating system. I keep heaeing stories about jobs that other contractors have done where the peoples heating bills have went way up after they switched to radiant. I always thought it was more efficient because it has such a low water temp. If this is truse then why does outdoor reset save money. I don't do a ton of radiant but the systems I have done have never increased the customers fuel bills. If they have then they are not telling me.

George_45

i have never heard of anyones fuel bills going up either at least not on my jobs. Maybe they are doing something wrong

Mark Eatherton

It can go up...

Think about it, existing home has one thermostat, and comfort is only to be found if the occupants hover near the thermostat, which is typically located in the core of the dwelling.

Fast forward to retrofit. Numerous thermostats located throughout the home, and comfort from wall to wall. Heck yeah, your fuel bill went up, so did your comfort levels...

If you'd had as many forced error zones as you had hydronic RFH zones, you would probably have realized a 20 to 30% reduction in fuel consumption because you have eliminated mechanically induced exfiltration due to improper duct design/installation.. When your hydronic heating system leaks, you know it, and you fix it immediately.

Just my $0.02 worth.

ME

Paul Pollets

Sytem design and proper installation...

are the keys to efficient radiant systems. Installing a staple-up without plates, for example, will never deliver fuel efficiency because of the very nature of the design. Using methods that employ maximimum thermal output with a modulating boiler and proper controls will deliver comfort and low fuel costs. Some installers are not using the design software to the benefit of the customer. I see many projects that use tubing on 12" centers when 6" centers were required...the water temperatures must now be increased to satisfy load. I also see oversized pumps or more pumps than the system really needs. In all of our conversions, where forced air was replaced by either radiant and/or wall panel radiators, there has been a 30-50% reduction in fuel costs, compared to the former forced air system. If the customers' fuel costs increase, it is because the new system was designed or installed improperly.

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George_45

thank you for your reply. Thats what I was thinking. It's probably onix tubing with no plates.

Brad White_191

Plates

make all the difference as you may be finding out. If you have a choice, the extruded aluminum ones, the kind that get screwed to the underside of the sub-floor, are best of course. If existing staple up, thin "omega" plates might be what you are left with, short of a re-tube.. Assuming access of course. Perhaps there is a third option, I do not know.

Constantin

So much can change...

... take this old house. Conversion from forced air (ex-gravity system) to RFH (Quiktrak). Estimated fuel usage reduction: 4x b/c estimated heat loss is 4x less.

RFH has something to do with the fuel reduction (our boiler is running at 89.4% efficiency because of the low water temperatures) but the real trick was tightening up the envelope, insulating, etc. I.e. fixing things outside of the heating system that make a great difference.

Many forced air systems unfortunately run outside conditioned spaces. This should be avoided at all costs, IMO. RFH and hydronic systems benefit from being able to supply a lot of heating via relatively small pipes, allowing retrofits inside the conditioned space. Why heat the great outdoors if you don't have to?

Lastly, how many roofs have you seen where certain sections always melt first, regardless of sunshine and weather, on account of some genius deciding that running a AC duct under the eaves (and eliminating the roof insulation in the process) was a great idea. Nevermind the plethora of oversized heating systems in evidence every time you take a drive on an early design-day morning: absence of smoke from chimneys, vents. etc. is a prime indicator of that problem.