Thoughts on radiant floor with hydronic air handler

B.J.

Hello, I'm building a new home and am considering on doing I plan to use radiant and forced air via hydronic air handler. I'm located in northern WI, the basement floor and garage floor are going to be radiant in floor while the upstairs will use the air handler. My thought was this would still give me air movement in the house. What do you think? What type of boiler is good and air handler? I don't know that much about this stuff

GMcD

Heat recovery ventilator

For the air handler, why not go with a Venmar or Lifebreath air to air heat recovery ventilator with a small re-heat coil or zone reheat coils on the supply air duct or ducts to each zone/room. Operate the HRV on a time of day timer with a humidistat/thermostat override, with the reheat coil(s) modulated from a room thermostat and you should be covered. Boiler should be a good quality condensing boiler to suit the radiant heat system. Just watch the reheat coil selections to get selections suitable for the lower heating water supply/return temperatures that the whole system will be operating at. The HRV will be able to supply "warmed air" which the hot water reheat coils will boost up to the supply air temps needed for the heat losses of the "air heated" spaces.

Dave Yates (PAH)

works great!

We've installed many systems like the one you're describing. We've also used hydro-air systems as the second-stage heating zone to allow for deep set back of thermostat temperatures. The hydro-air provides fast recovery with the radiant then carrying the continuing load.

The reset ratio between them is radically different, with the hydro air needing high temperature water to grant warmth to what's felt. Coil size can make a large difference in how that's managed.

In one system we installed last year, we installed a fully condensing modulating boiler (a Munchkin) and utilized a larger than normal coil to ensure the return water temperatures would be well within the condensing range. We're running three temperatures with an indirect, some Runtal radiant wall panels and the hydro air. They'd had an oil-fired beast that became bothersome following the basement's conversion to a movie theater. Same for the oil-fired water heater. With hydronics, we were able to locate the boiler on the opposite side of the home (required for utilizing direct venting) and piped the twin S&R lines in 1" PAP due to a very constricted ceiling space.

We just finished a retro-fit where a heat pump had kept the occupants in misery for too many years. The first floor now has radiant, while the second floor is warmed by the hydro coil maounted in the air handler. The owner closes off the dampers to the first floor registers during the winter. The new direct vent boiler has a flat plate heat exchanger for the domestic hot water production, which now by-passes the old electric water heater.

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B.J.

Thank you

Thanks for the thoughts

Roger Litman

Radiant heat with hydroair

I installed this type of system with radiant in the basement and the master bath- I used the domestic water tank as a buffer tank with a plate heat exchanger for the radiant heat- I used the boiler direct for the air handlers so that I wouldn't get cold air (95°) from the air handler-the system is kept at 50-55° and then heats up when we are using the house- I controlled the master bath with a floor sensing probe so that I will have a warm floor even in the summer when the AC is on. The system is relatively simple so that it can be worked on by an average tech. As I am using air handlers and a boiler, I do not have outdoor reset, which would be a problem with intermittent house use- I zoned the master bedroom separate from the rest of the house so that the entire output from the boiler would heat up the room quickly- for this reason the coil in the air handler is oversized so as to use the boilers capacity- The system is filled with non-toxic antifreeze so as to avoid problems with malfunctions, and the alarm system has a low temperature sensor.

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