Home>Discussions>PLUMBING>Radiant floor can’t keep up?
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Stateslug
Radiant floor can’t keep up?

Had radiant floor in stalled on my first floor about two years ago and what I’m finding is it has a hard time keeping up on the coldest New England days. Current config is 3/8 Onix stapled up. Aprox 2” air gap with foil foam and fiberglass bat.
Tried maxing the mixing valve but still don’t get much over 65.

60’s 1 ½ story cape recently renovated, new windows, doors, fully insulated.

Thanks

johnjh2o
Re: Radiant floor can’t keep up?

Was there a heat-loss done before the system was installed? It sounds like you don't have enough radiation or the water heating source is not keeping up.

John

Stateslug
Re: Radiant floor can’t keep up?

Not sure on the heat-loss, system was installed as part of a full 1st floor renovation.
Boiler was sizes for an eventual addition and an indirect hot water tank.

johnjh2o
Re: Radiant floor can’t keep up?

Doing a heat loss is the first step in any heating system, with out that it's just a shot in the dark. I would check with the contractor that did the job. Depending on the area of New England your are in the system should be designed to heat your home to 70 when it is 0 outside with a 15 MPH wind.

John

ChrisM
R-Value

A regular heat loss won't help you out. You need to reverse engineer the system and start with a radiant heat loss and design. This will tell you whether you can or cannot heat the space radiantly based on the existing installation method.

In radiant there is more to the loss. You must use the subfloor and finished floors R-value to calculate the needed water temp to overcome the heat loss. Once this is done you then look at the existing system.

Is there enough tubing in the floor? How is it zoned? Are there floor sensors? Is solar or some other outside heat gain influencing setpoint? Is the floor off for a long time and we can't catch up due to response time (chasing the night).

I've fixed hundreds of systems done in the fashion you have and you must start as if the radiant isn't even in the home. Do the math, re-engineer, compare and solve.

jkirk
Re: Radiant floor can’t keep up?

im with chris on the question regarding the zones. did the installer correclty size each zone. if the zones are too large the system will be straining to keep the correct temperature as the water will not return to the boiler quick enough to maintain the correct temp

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