All wet...yeah, that's funny!

I don't have a problem with your on-paper reality. I'm sure that what happens in the field is exactly what happens on paper. Right? (sorry for the cynicism) What I do have a problem with is all the talk about how it was in the 70's and 80's with electric radiant with no experience installing low voltage, all while neglecting the issues that hydronics have always had (evidenced here and on the RPA site). How could all these problems exist if they're based on "physics" and are designed by engineers? They couldn't be wrong. It must be someone else's physics.


Badger:
Yes, I design, sell and install low voltage radiant systems. I believe your sign on is "BadgerBoiler". You sell what... sneakers?

Dana, I didn't realize that baseboard radiators would be more efficient that wall units. That's what GC wanted to use in the first place. I'll definitely look into this. Thanks!

Complexity leads to design, maintenance & reliability issues, but the physics remains- BTUs & KWH are completely fungible- both are simple units of energy.  I used a nearly-worst case efficiency example in my very-real-world specific case to make the point- even a worst-cast hydronic system will have half the operational cost. Most do better- MUCH better.  And even poorly designed or neglected systems that someday need thousand-dollar repairs will have saved many thousands in operational costs in the meantime.   Add a 75% or even 100% multiplier to the operational costs for maintenance & repair and any reasonably-designed hydronic system still wins the 10-year economic argument.

The fact is, the vast majority of hydronic heating systems are somewhat reasonably designed and run for decades with minimal maintenance, and there are armies of trained techs to fix 'em should they break down.  When you have orders of magnitude more installed systems, even if the failure rate was much LOWER, the number of web-forum questions would be much higher. And until you can show 20 year data on the reliability of the low-voltage systems and compare repair costs you can't really back the argument that you're trying to make. (I'm sure they NEVER need to be repaired, sensors never go bad, the solid state contols are EMP hardened & yet the parts will be readily availbable at the local hardware store after the warranty is up etc. etc.  ;-)  The check's in the mail too, I s'pose!   http://heatizon.com/files/trouble_shooting_procedures-slc500.pdf )  The only decades-old electric radiant systems I'm familiar with have run about a 35-50% failure rate and are difficult or impossible to repair, but i'm sure the new stuff is better (or at least HOPE it is, eh?)  But it's no more efficient- can't be. It's that danged physics problem again...

BTW: While I'm working as an engineer, my degrees are in math & physics (not in "physics" in quotes.)  Having designed all sorts of power electronic & controls I'm sure I'm competent to debug failed Z-mesh controls to the component level.  But since, I can do the math, I do.  I'd only install hydronic additions an existing hydronic heating system, and reap both the raw economic efficiency of the hydronic system for the addition, but also the efficiency improvement to the system as a whole that accrues with a higher duty-cycle.  The only time I'd consider such a system would be for a tiny heat load in a zone that for some reason made for an extremely difficult hydronic install. Not likely the case here. 

But it was the case in my biz-partner's isolated 2nd story bathroom floor in an 1830s vintage 3.5 story house, where for structural reasons the heating plumbing couldn't share the same chase as the rest and would have had to pass through difficult to access unconditioned space wall cavities with probe-detectable blockages. Fishing wire through those cavities was possible, PEX & insulation, not.  The heat load was miniscule- an 80 square foot room with three walls + floor & ceiling common to conditioned space, one tiny window on a ~65-75 square foot insulated (4.0" of rock wool) exterior wall.   The rest of the place is heated with 1920s vintage high-mass hydronic radiators utilizing a micro-cogenerator & a mod-con as the heat source (he's making far more electricity with his hydronic cogenerator system than the electric radiant floor uses anyway!  See: http://www.freewatt.com/ ).  Were that YOUR electricity was as "green" as his. 

But I'm sure retrofitting Z-mesh everywhere would have been cheaper up front than the cogen & mod-con was to install when it came time to dispatch the hydronic boiler that had served the place reliably for 70+ years.  Maybe he shoulda done that! (NOT!!)  Based on data accrued since the current system's installation, with the ancient beast of a boiler the system was running somewhere around 60-65% efficiency, and still would have KILLED electric radiant in a $-per-heating-season contest.  Simple payback on just the fuel costs (with no credit for electricity generated) looks like it will come in at under 5 years- call it 7 if you assume the sucker is gonna break down and need fixing to the tune of $1000 every couple or three years. (It's well into it's 2nd heating system without issues, but who knows, eh?)

Just for yuks I tried to come up with the rough market share between hydronic & radiant, and I googled up this from 2006:

http://www.radiantandhydronics.com/CDA/Archives/BNP_GUID_9-5-2006_A_10000000000000128431


"Tubing shipments have stayed relatively even, hovering near 330 million lineal feet for the past three years. Tubing shipments had enjoyed an average annual growth of 19 percent for each of the past 10 years prior to 2005. That year, the survey showed a jump in tubing shipments of 37 percent.

On the electric side, shipments amounted to 6.19 million square feet, down just under 2 percent from 2005"

Hmmm... assuming their survey numbers are at least close, at roughly 1 square foot of floor per foot of tubing, that makes the electric-radiant portion somewhat less than 2% of the market. (~6.2milliion square feet out of ~336.2 million square feet.)

I'm gonna hazard that it's not 'cuz the buying public likes to waste money on extra building & repair costs for otherwise equivalent systems.

Like the hydronic world, the electric radiant biz has been on a learning curve- I sure HOPE the current stuff is more reliable than what was sold 2-3 decades ago. The hydronics have gotten both more efficient & more reliable (complaint rates from failed DIY and other systems on websites notwithstanding.) The economics haven't changed much though- if anything it's been tipping slightly more in favor of fossil-fueled heating boilers than 30 years ago (despite last summer's oil price spike.) Electric radiant is only ~100% efficient- it would have to be 250-300% efficient (heat pumps, anyone?) to compete on operating cost with natural gas in most markets.

You just can't sell it on an efficiency argument and win. If you could, there'd be subsidies for it from all the green-state programs, the same way you can get rebates for installing mid-efficiency or condensing boilers, or higher performance heat-pumps. (I guess regulators can do the math too, eh?) Where utilities give a rate break to electric radiant floor customers, it's usually a (state regulated) rate that applies to all electric-heating customers, not specifically for electric radiant.

Bottom line, while flexible, easy to install, and gets high marks for creature comfort, electric radiant floors are not now (nor likely to be in the future) a "green technology".

It's not entirely clear how radiant hydronic floors qualify as particularly green either. Sure, it's easier to tweak the best efficiency out of your boilers with low-temp solutions like radiant floors, but the measurable fuel-economy benefits are usually in low double-digits, and efficiency robbing design/implementation screwups are common (especially but not exclusively in the DIY crowd.) But even poorly designed hydronic heating systems usually have a lower carbon-footprint than the best electric resistance heating. (It has to be REALLY bad to trip over that low hurdle.) In retrofits & staple ups, radiant floors are more about the creature comfort than dramatic efficiency gains. Only when you go to low temperature slabs does the efficiency gain stand out in a significant way.

Dana, staple ups and retrofits can often be designed to run at temperatures as low as many slabs. Be careful with generalizations ;)

Hey Rob; nobody's perfect but Dana is getting pretty close...hehehee

I love this guy!

In a rough and fraternal, plumber, kind of way of course. hehee

I am a boiler nut, but look to solar and water to water heat pumps for many future designs. If we just had sunny days in Minnesota!

OK it is sunny today but a typical 4°F.

:-) :-) :-) :-) :-) :-) :-)

Yeah I know, I know, but there's that huge gray void between what "...often can be designed", and "...happens most often in the real world", eh?  ;-)   For every generalization there are scores of counterexamples.

I can't say as that suspended slab running off the Polaris on that other thread is buying any efficiency over what 160F baseboard or staple-up would have provided either.  Implementation can count as much or more than design, even when the design was a work of perfection.  (I suspect neither was the case in that other system. :-(  )

Generalizations can be true, even when not factual in a precise fits-all-cases sort of way. Take the generalization that "electric-radiant zones aren't nearly as green as natural gas fired hydronic radiant" f'rinstance...  

...a hard argument to make with any conviction for the electric-radiant zone at my biz-partner's cogenerator-heated mostly-hydronic house (though true in general.)

So, I'll continue to be the babbling amateur techno-nerd making the generalizations, and you & Morgan can keep on correcting me when I'm chewing on my feet. :-)

Next new subject heading:

Engineers and the plumbers who love them....in a rough and fraternal sort of way, of course! :)) I'm sorry, that's just too funny Badger.

(isn't that still illegal in MN?)

Glad you have a sense of humor warms. Your not such a bad guy when you're not exaggerating the truth.

Fact is, I think Zmesh is great when it is properly applied. Sometimes you're just too scrappy for your own good (reminds me of me).

Your biased opinions aside, we're probably more alike than we'd both choose to admit.

Horrible situation. I was excavating my bathroom floor and broke one of the plastic tubes that are part of the floor heating system. Does anyone know how I can mend it? It started leaking and I turned off the water main, but there are a couple of holes in it. Is there a repair kit for the tubing, could it be mended with copper fittings? Any help would be greatly appreciated! Zara