We are considering radiant floor heat in our addition, and radiant baseboard heat in our new basement. I’m starting to understand our options, but I still need to hear it in very basic terms. Our original house is an 850 sf Brick Ranch, built in 1945, with an 850 sf basement where we spend a lot of time. Current heating system is a forced air furnace, installed 5 years ago. We're adding on 360 sf on the main level, as well as a 360 sf basement (we cut a hole into the wall of the existing basement). We need to figure out how to heat the new addition with radiant, and potentially leave open the possibility of converting the rest of the house to radiant when time and budget allow (ie, 5 years down the road).

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I’m open to suggestion as to which system would work best, but I would like to know, specifically:

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- How should we fuel our system? Should we install a tankless dedicated to radiant heat only? A tankless that fuels both DHW and Radiant? A gas boiler? (We got a quote from an installer who suggested a Laars Mini-Therm or Triangle Tube Prestiege). Any other recommended makes and models of tanks or boilers? Just wondering the pros/cons of using a tankless vs. a boiler...

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- We have a 1-year-old Whirlpool 50 gallon Energy Smart gas water heater. It’s not approved for radiant heat, nor is it as efficient as a tankless, but “smarter” than a regular 50 gallon. Should we just remove the Whirlpool and install one tankless to fuel both DHW and heating instead? Or keep the 50 gallon dedicated to DHW and install a tankless for radiant? Basically I’m wondering if our drinking water should be tied into our radiant heating, or if we should dedicate a separate tank for DHW?

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- From what I’ve researched so far it seems that a closed loop with a tankless might be a good option? Are open systems for the birds? And what’s this about a heat exchanger? Enlighten me, please!

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- Someday we might switch the entire house to radiant heat. With this scenario, is it possible to install a system small enough for 720 total sf, that can be expanded to 2400 sf later on?

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- Basement height is an issue: the concrete floor has already been poured and we’ve only got about 7’4” to work with – even less once the flooring and ceiling are complete. Therefore we’re leaning toward radiant baseboards. Unless, of course, someone can tell me how to put tile over the PEX and make it 1” or less.

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- I’ve seen conflicting opinions on PEX size. Is there a consensus here?

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Currently our house has 1 bathroom, but by the time we are done remodeling we will have 2.5 baths. There are 5 people in our family. There are 6 windows and French door in kitchen/dining room addition. Main level has hardwood floors.

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I’m new here to this forum so I’m not sure of the etiquette – whether or not it’s ok to recommend other websites to purchase from or to do business with. If so, I’m all ears. We're doing most of the work ourselves but my husband has the skills of a contractor. And we’re doing it on a shoestring! Thanks so much in advance!

Are you sure that you have to use radiant - there may be enough room in the joints for some creative designs. Or look at higher pressure systems that allow small ducts.

Sure, we're open to other possibilities. What do you mean by "Some creative designs?" And can you elaborate on "higher pressure systems"?

Sorry the formatting got all messed up in the original message. I guess that's what happens why you copy it in from MS Word!

unless you're going electric, generally I do not advocate for using tankless heaters for radiant applications. they are kind of a square peg for this sort of thing. If efficiency matters, you want a mod/con boiler like the prestige, if it doesn't because the heat load is very low, then a tank water heater is a better choice for economy than a tankless. never do an open system.

you can use the same heat source for both, but fluid streams must be separated. either using an indirect water heater (tank with a coil in it) or heat exchange.

There is lots of consensus in the industry: use the smallest you can, because it doesn't affect heat output much at all. you only need pipe large enough to push the flow you need. the only people who disagree are people who are trying to let your whole potable water flow go through your floor loops.... that's the only reason to use larger pipe, less pressure drop for 300 foot shower legs, in effect.