A lot of people who put in radiant are either doing it in a new home or doing a complete reno so the opportunity is there to properly design the system for the home, and not piecemeal. Just because there are no individual t-stats, it does not mean there is no control. I can change the slope (curve and offset) anytime I want to fine tune the system (and appease she who is always cold). Also, the loops are balanced for the building and can be tweaked a bit if need be. It is definitely not all or nothing.

Yes: you are trading design and involvement complexity for material.

for most contractors a site visit is about as expensive as a thermostat. sooo.....

Rob is right. Keep'in it real.

We advocate ODR and would like to run some building in that fashion, especially rental properties, but the best we can hope for is taking out ridiculous setback thermostats (usually set to Permanent Hold), and programming the boiler to setback water temperature while all are sleeping and/or working.

TRV's go on many an old radiator and nearly all of the homes--new and old--with panel radiators.

Wow,not what I would have guessed,especially with such a comfortable source of heat such as radiant.

It seems more like a study in human nature.So people would actually like to have a Tstat in every room,I guess? And the setback Tstat,a waste of time for most people?

most people don't want nor would benefit from a thermostat in every room. but also, in my experience with my clients, most people don't want to only adjust the whole building only as a single zone, nor do they want to have to do fiddling with flow rates or other indirect measures, evaluate, and continue twiddling until they hit some balance point they like. Even fewer want to pay a contractor to do that for them. thermostats or other temperature control devices make for a very easy interface.

there are cases where room by room control IS desired.

setback thermostats are not a waste of time in all cases, but on simple outdoor reset hydronic systems they have limited utility. recovery is so slow you can't get a significant set back temperature. but efficiency is higher the rest of the time because of the outdoor reset, so it's probably not worth abandoning for setback. Best, of course, is a system smart enough to allow setback, elevate water temps for recovery, and go back to reset during cruise mode. but that requires "complex" controls. We still use them on most projects to great effect despite the 'complexity'. then the client can have everything.

I will say if mike's primary business is solar, I have noticed that radiant clientele and solar clientele have some overlap, but solar people include "deep greens" who are very happy to wear sweaters to reduce energy usage and "independance" minded people who will do the same to reduce cost in many cases as well. mike's clients may well live in homes better suited for single or no zone control, and they may say they are very happy with the level of comfort they have. This doesn't mean he's wrong or I'm right... we are just working with different people. My biggest beef with his methodology is what happens when they sell the house? the NEXT owners have no idea what the esoteric choices made on this system were or why and they likely don't care. I had one client who did a system like Mike did, and he liked it just fine, but he had to retrofit thermostats to sell the home later on.

Posted By NRT.Rob on 26 Feb 2013 10:27 AM
most people don't want nor would benefit from a thermostat in every room. but also, in my experience with my clients, most people don't want to only adjust the whole building only as a single zone, nor do they want to have to do fiddling with flow rates or other indirect measures, evaluate, and continue twiddling until they hit some balance point they like. Even fewer want to pay a contractor to do that for them. thermostats or other temperature control devices make for a very easy interface.

there are cases where room by room control IS desired.

setback thermostats are not a waste of time in all cases, but on simple outdoor reset hydronic systems they have limited utility. recovery is so slow you can't get a significant set back temperature. but efficiency is higher the rest of the time because of the outdoor reset, so it's probably not worth abandoning for setback. Best, of course, is a system smart enough to allow setback, elevate water temps for recovery, and go back to reset during cruise mode. but that requires "complex" controls. We still use them on most projects to great effect despite the 'complexity'. then the client can have everything.

I will say if mike's primary business is solar, I have noticed that radiant clientele and solar clientele have some overlap, but solar people include "deep greens" who are very happy to wear sweaters to reduce energy usage and "independance" minded people who will do the same to reduce cost in many cases as well. mike's clients may well live in homes better suited for single or no zone control, and they may say they are very happy with the level of comfort they have. This doesn't mean he's wrong or I'm right... we are just working with different people. My biggest beef with his methodology is what happens when they sell the house? the NEXT owners have no idea what the esoteric choices made on this system were or why and they likely don't care. I had one client who did a system like Mike did, and he liked it just fine, but he had to retrofit thermostats to sell the home later on.

I would love my primary business to be solar but, in Canada, there is little solar thermal going on (there used to be when a different party was in power), unlike the USA where you have some nice tax credits. I've been a boiler and floor heating guy since the late 80s and solar when it is feasible and desired, and a carpenter before that. With a wife like mine, there is no way I could be a "deep green" when it comes to the indoor temp.

I can see some of the issues Rob mentions happening. Many of my clients these days are people who are looking for close to net zero energy consumption but most of those people are rural and have enough land to situate the house for the best solar gain etc. They also probably live in the house for decades.

But, I live in a densely populated part of the city so a lot of the houses are 100 year old brick beasts that will never see the net zero dream come true. The average size of houses I work on is 2000ft2 and aside from a few 35,000ft2 behemoths with commercial boiler rooms over the years, this is my market. Hence my comment about one zone per floor which is often quite appropriate. I take heat from over heated areas and deliver it to the basement at times but a home owner cannot typically understand the details behind some of the things we do, so they leave it up to us.

Most people are used to one t-stat in a house anyway so it is tough to get rid of it and I am not always successful in doing so. Multiple t-stats make sense in some situations but not that many IMHO. That said...every house I do has a laminated piping and control diagram so anyone coming after me can understand what I did.

Not many issues with it so far.....

Posted By MikeSolar on 24 Feb 2013 01:36 PM
It is interesting in that we (north american heating designers) tend to plan so that the home owner has a great degree of control over the heating system. But as Rob and I have both noted, there are drawbacks, complexity/cost being the biggest one. We (my company) are going even more down the opposite path which is having the system run only on outdoor sensor and a control that takes care of floor heat/HRV/DHW and cooling all in one. No indoor t-stats. It is a different philosophy. Some people like it and some can't handle not having control. It started from our commercial work where one person would turn a t-stat up and another down and nothing worked right.

BTW, floor heat is very resilient and you can have equal comfort with temps up or down a couple of deg. I have never seen a system where HE and SHE both like the same temp as much as radiant.

This is very well stated and consistent with our design approach as well. Multi zones where appropriate...YES. Multi T-stats...NO. Zero T-stats and just simple comfort number entry for each zone...BEST. T-stats are more for controlling heating systems that can quickly change air temp...which is not a hydronic radiant heating system. If you have indoor, outdoor, and slab temps, and a comfort setting for each zone, the controller can do a better job at actually maintaining this comfort level than a human can by changing T-stat settings.

We are the type that benefits from multi T-stats. We set up our home to have three guest rooms. Each has a T-stat. We insulated all the walls so each space is to it's own. When it's cold out, I have seen a 12 deg difference. This means I'm not heating those rooms so much It does take some time for the room to get up to temp when a guest come to visit. We just turn the T-stat up the day before they arrive. We also have a south facing wall of glass. The room can be 5-6 deg above the N rooms when cold and sunny out side. We are glad it has it's own T-stat or it might over heat. NRT Rob did our design and we purchased all the parts and material from them. Though complex, we installed it ourselves. (Thanks to the good DWGs) We have been very satisfied with their work. We have 9 T-stats and all but one turned out to be good planning. The last one is in my office just off the sun room. The sun room heats so well, I have never turned on the T-stat. I guess, I like control Patrick T

This is a great thread, thanks guys.

I built a 2,000 ft2 house, very well insulated R35 walls & R60 ceilings + very good windows. Zone 5

I wired in 3 thermostats, 1: greatroom/kitchen on 1st floor, 2: master bedroom on 1st floor, 3: upstairs 2 bedrooms & bath.

!st HTP modcon boiler krapped out at 10 yrs. I replaced it 18 months ago with a TT Solo60 & repiped near boiler to use constant circulation & only control off of the great room thermostat.
I have flow control valves on each loop of pex.

As I like the GR about 8* warmer than the master BR, I reduced flow to master.

I works but not up to my expectations. When it gets below 0* the master gets too cold, about 12* below GR.

Next summer I am repiping near boiler again using 3 zone valves so each of my zones will again have control.