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I am considering including a hydronic (Pex tubing) radiant heat system in my new house (still in the planning phase). I have done some reading/resaerch...here was a straight-forward, mercifully direct and short, non-“buy me!” write-up: https://www.everything-about-concrete.com/concrete-floor-heating.html

My main take-a-ways/questions:

-- Is a radiant floor heating system and a traditional HVAC/furnace system necessarily duplicative or overkill? Or can be considered supplemental to each other.

-- “Properly locating the manifold”…I am not sure of the implications of “properly locating.” Can't just be anywhere convenient in the garage, for instance, as long as a hot water line is available?

-- Shocked (as usual) about the cost per sq foot estimates…it is just Pex, zip ties, some basic labor additional for each square foot; the basic planning/layout and manifold/control unit are up-front single costs amortized (or whatever word) over the whole covered area. Am I missing something?

-- I gotta wonder what the “catastrophe” rate is, either at install time (e.g. after the slab is poured) or during the life of the home (e.g. a severe crack in foundation splits Pex; inferior Pex used and it starts to leak)?

-- “Radiant floor heating usually lasts around 20-35 years”…huh? Important to know if this means the manifold/controller (easily replaced) or the Pex system itself?

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Lots to answer here. I would have posted this as a comment, but I have too much to say.

I have an 8 zone hydronic (in floor concrete) heating system...probably "over-zoned", but that's a different issue.

When you say "the manifold" that implies only one zone. I have 8 manifolds.

PEX is awesome and will last a lot longer than 35 years.

There are a lot of considerations when designing an infloor system. IE: what is your heat source? Electric boiler, Propane boiler, Natural gas boiler? Air to water heat pump? Geothermal heat pump? I love my in-floor heating, esp, during the winter, but bear in mind it's SLOW SLOW SLOW to heat up a space. You can't do typical night-time setbacks on your T-stat by more than a couple of degrees. Also, of course, in-floor heating doesn't give you A/C. My house is set up with an air handler and ducting for A/C as well as aux heat for when the in - floor heating system can't get up to set point. That's done via a fan coil from the boiler to the air handler and is controlled by the T-stat as Aux-Heat.

As I've said here before, and hate to say it bc this is a DIY site, but you should at least consult a pro in this field to give you a design, with tubing layout, temp loss calculations...you don't want to screw this up...it's hard to fix later.

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  • I appreciate the thoughts and benefit from your experience. I will absolutely consult with a professional (via my GC/builder), but forewarned is forearmed, as they say...or some sort of corollary for this instance :--)
    – mblatz01
    May 9 '21 at 17:35
  • I still just can't see how the marginal cost per square foot works, though. Arggh!
    – mblatz01
    May 9 '21 at 17:36

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