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Question DetailsAsked on 7/30/2013

What are the risks or dangers associated with hydronic heating for the house?

I heard about mold being a problem. Others have said that if the system is running constantly, there is no danger.

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Voted Best Answer

Hydronic heating systems use hot water to heat - running in pipe (typically around the outer edge of the subfloor), with long, low-profile radiators along the walls to provide the heat. The only time mold is a problem is if the piping develops a leak.

Hot air, or forced air, heating systems use metal or plastic ductwork to distribute the heat to different rooms, where the warm air enters the room through (typically) floor gratings or vents. Mold in the ducts is relatively common in moist climates, especially if you do not have air conditioning and humidity control as part of your HVAC system.

Hydronic systems tend to provide more even room temperature as the systems cools slowly after the thermostat turns off circulation and the heat is radiant (heats entire room by radiation), but because they do not actively circulate the air you can get less even temperature across the room (particularly at top versus bottom of room), and more difference between rooms with radiators and areas like kitchens and halls that typically do not have them. Hydronic systems, because the pipe runs through the subfloor between radiatiors, also heats the floor, so the floor tends to be much warmer than with forced air systems.

Because the radiators are typically located under windows (the cold spots) they generally reduce window condensation and icing more than forced air.

If you have a multi-story house, if you do not have doors blocking off the levels from each other, hydronic systems tend to heat the upper floors more than the lower ones, because the heat on the lower levels rises to the upper levels quickly - hot air rises. Forced air systems put heated air into each level and circulate it there and then pull it back to the furnace on the same floor as it comes in, so temperatures in cold periods tend to be more even on all levels. This can be partly compensated for by setting the downstairs a bit warmer setting, so effectively most of your heat comes from that zone for the entire house, including leakage.

Because hydronic heating requires piping all the way around the perimeter of the walls, it generally costs more and is more destructive of wall finishes as a retrofit then forced air installation.

Hydronic systems, because they are filled with water, do have two flaws -

1) in extended winter power outages, unless you have an independent power source or have a system that self-generates the gas controller power, they will not heat so can freeze, with risk of bursting the pipes and causing leaks. There are hydronic systems that do not need an external power source to fire, though you will not have pump circulation other than by convection, so while that would normally be enough to prevent pipe freezing it will not heat the house. It is possible to run an antifreeze in the hydronic system, but if you do ever get a leak it is much more messy than water to clean up. Forced air, of course, does not work either without electricity for the fan, but will not be hurt by freezing.

2) Also, if you use a fireplace for an extended period of time in very cold weather and the thermostat is affected by the thermostat, it can sense the fireplace created temperature and decide no heating system heat is needed, so the water does not flow in the pipes and can, over the course of several hours in sub-zero temperatures, freeze in the pipes.

Here are some more article links on the two alternatives - google this phrase -

hydronic versus forced air heating

Personally, having had both systems in several houses, I prefer the hydronic for the more even radiant heating and lack of that cold draft across the back or feet when the forced air system first kicks on, but as a house gets older you begin to worry about water leaks in old pipes, so forced air starts looking better and better, even though my currently 31 year old copper piped hydronic system has never had a leak other than very minor ones right at the furnace dielectric couplings and valves, where it caused no damage.

At this point, if I were building a new house, I honestly don't know which way I would go fopr a cold climate. Certainly, in an area where it is hot enough to need air conditioning then forced air is the way to go, because both systems can use the same ducts, whereas with hydronic you have two totally separate distribution systems, which will cost a lot more.

Answered 4 years ago by LCD

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