I plan to build a 2000sf ICF house in Ontario and have been talking to an ICF installer who recommends in floor radiant heating. This is all new to me as my current home has a high efficient forced air gas furnace. My new home will not have access to gas so I am considering propane. I have read an opinion in this forum that mentioned for a "smaller" house, 2000 sf, probably radiant floor heating is not nessecary. To those ICF contratcors, what are your clients using to heat and A/C  thier ICF homes? 
I hope this is the correct forum for this question.    

in floor radiant heat is not the most energy efficient way to heat a house. But it definetely feels the best.

here's an article from EBN


BackPage Primer from Environmental Building News
February 1, 2010

Radiant Floor Heating:
Wrong Choice for Green Homes?

Radiant-floor heating is popular for some good
reasons. It provides very comfortable, uniform
heat, owing to the relatively low temperature and
the large surface area from which the heat is
radiated. It does not interfere with furnishings in a
home as most other heat distribution systems do.
It’s quiet. And, according to proponents, it can save
energy by warming people directly (rather than
heating the air)—thus allowing occupants to keep
the thermostat (air temperature) lower.
Indeed, people living in houses with radiant-floor
heat are often effusive in their enthusiasm. Walking
around with bare feet on warm floors is very
appealing.
Radiant-floor heating systems commonly involve
PEX (cross-linked polyethylene) tubing embedded
in a concrete slab; hot water is pumped through the tubing. The slab warms up and slowly radiates
heat into the room. Radiant-floor heating systems can also be achieved with tubing under wooden
floors.
While radiant-floor heat makes sense in certain buildings, it is not well-suited to highly insulated
green homes for a number of reasons. First, in a home with a tight envelope and a very small heating
load, even a small amount of heat can cause overheating, and the thermal mass in a radiant floor
system (especially with concrete-slab systems) increases the risk of overheating. This is particularly
true in buildings with some level of passive solar gain—the radiant floor may still be delivering heat
even after solar gain raises the air temperature.
Second, when the heating load is very small, the radiant slab has to be maintained at no more than a
few degrees above room temperature to prevent overheating, and this means that the slab isn’t likely
to be warm to the touch. A slab maintained at 74°F (23°C) will be cooler than an occupant’s skin, so
bare feet will conduct heat into the slab.
Third, radiant floor slabs and the mechanical equipment needed to heat them are expensive. For a
typical house, such systems often cost well over $10,000. Again, in a highly insulated house, that is a
lot to spend for a few hundred dollars worth of heat per year.
Fourth, there is little if any evidence that radiant-floor heating actually saves energy. The argument
that homeowners will keep their thermostats set lower with radiant heat is not supported by
(admittedly limited) research. And with slab-on-grade homes with typical levels of insulation beneath
the slab—rarely more than two inches (50 mm)—there may be significant heat going into the ground.
In short, radiant-floor heating is a great heating option for homes with average or below-average
levels of insulation, but it is not well suited to highly insulated homes, especially such homes with
moderate solar gain (passive solar heating).

For more on these issues see “Radiant Floor Heating: When it Does—and Doesn’t—Make Sense” in EBN Jan. 2002.

ICF is by no means a highly insulated house. it can be a very efficient house compared with a traditional 2x4 fibreglass insulated house but the R value of a regular ICF wall is around R22 which is not far from the code minimum in Ontario. by comparison for a house to achieve passive house rating in Toronto for example, the R value of the walls should be around R60 (that's what I'd call highly insulated).

It is hard to determine what are the needs for your house without knowing exactly where your build is going to be (Ontario is prety big and the heating degree days number varies considerably), what kind of attic insulation you'll have, what kind of solar orientation and exposure you'll have, what kind of wall to floor area ratio, how many windows and what kind of windows and so on but I'd venture to say that for an all ICF (regular) the radiant floor heating is probably a good match. maybe not the cheapest but I'm almost sure you'll feel your floors warm.

do a heat load calculation first - it'll be prety easy to see if radiant floors is the way to go.

good luck,
Adi

Adi,

So what design would you use for your R-60 wall? Here many builders will claim the R-value of the cavity as the R-value of the wall. You probably know that this is incorrect as is calculating an average. IF you build a conventional house with a cavity R-value of 22 the conduction of the studs (framing factor) will result in a R-value far lower - say 12. Regards.

Hang on to your britches folks, here we go again.

Posted By kkerr on 16 Mar 2011 08:46 PM
I plan to get a heat loss calculation but not sure what it will show. I suppose that most HVAC contractors would make a recommendation based on gut feel, will the heat loss calculation give a more accurate sizing?

ABSOLUTELY!!!! A recommendation from the gut ain't worth any more than the other stuff that comes out a gut! A complete heat load calculation will give you the heat load for the entire house, and also broken down for each room. The latter is critical to proper duct sizing, or proper tubing layout and water flow parameter selections.

Will the person that does the calculation then make a recommendation on what heating system to implement? Thanks for the input! 

Not only probably make a recommendation but will most likely try to sell it to you, which is to be expected, and which is the usual situation. But if the guy does only forced hot air systems and you want a radiant system you may be in a quandary. It all depends on the competence and integrity of the HVAC contractor. I'm not sure how you can get a reliable review of a particular HVAC contractor in your area. Angie's List maybe. Or comments offline by members here from your area.

Posted By kkerr on 14 Mar 2011 09:38 PM
My new home will not have access to gas so I am considering propane.

From what I have seen and read the cost of heat derived from propane and from electric resistance are on par with each other. Therefore, propane is not your best choice. Look into using a heat pump which will cut your energy cost by 50% to 75%. There are several choices, Daikin or Mitsubishi (and others) air to air HP which will produce heat down to -5°F outdoor air temp, Daikin (may be others also) air to water HP, common branded hybrid HP with supplemental heat from propane, water source HP with output to water which can be used for radiant or in an air coil, or a direct exchange geo source HP with output to either air or water.

kkerr, and others,
My experience from the past two winters with my air heated floor substantiates much of what is in the article from EBN quoted above. DO NOT IGNORE what is written there, especially the comments about floor temperature. It is worth very serious consideration. Is it absolute gospel? Of course not. Nothing is in this business!

Remember, the heat load in the winter in your house fluctuates greatly. A well insulated and sealed house needs the max amount of heat maybe no more than 20% of the time. The rest of the time your heating system needs to input only enough heat to balance the loss. At an outdoor temp of 50°F and higher, which will be much of the time during the heating season, especially the fall and spring, the heat required from the heating system is not very high at all. If you need only 100,000 Btus of heat during a 24 hr period, you stand a high probability of being uncomfortable if your system wants to supply it at a rate of 30,000 Btuh.

Do not ignore the heat supplied from daily living activities such as cooking, watching TV, using the computer, having lights (even CFLs) turned on, and even simply existing (body heat). It will be difficult to quantify, can be highly variable, but it can be a significant part of the heat supply into the house. Except for warm water that goes down the drain, and dryer air that gets vented outside, probably 90%+ of the electricity that comes into your house eventually degrades into heat.

everything boils down to the heat loss. after the heat loss calculation you can make an estimate of how much is going to cost you every year to heat and cool the place. you can decide if a radiant floor is an overkill (very possible) or not. there are asymetrical ICFs out there. you may want to calculate how much is going to cost you to go with thicker foam on the exterior/interior versus how much you can save by downsizing your mechanicals and how much you'll save in energy costs every year.

if you have some computer skills you can get a prety good idea about your structure with the help of hot2000 - free energy modeling software from goverment of canada.

I agree with dmacel on the propane vs electric - I'd go with electric myself - heat pump + some electric radiators back-up and some post heat inline with the HRV (you'll need one in an ICF house). also, look into FIT program for solar PV panels. ontario pays 82 cents a kw for solar electricity fed back into the grid. it can be cash flow positive day one and you can also protect yourself from future power grid problems.

go to R50 - R60 ICF wall and put in some good triple glazed windows and you don't need a heating system anymore. just put a small electric heater inline with the HRV and you're done. it might be cost competitive.....put it on paper.

Adi

Posted By dmaceld on 17 Mar 2011 12:15 AM
kkerr, and others,
My experience from the past two winters with my air heated floor substantiates much of what is in the article from EBN quoted above. DO NOT IGNORE what is written there, especially the comments about floor temperature. It is worth very serious consideration. Is it absolute gospel? Of course not. Nothing is in this business!

Remember, the heat load in the winter in your house fluctuates greatly. A well insulated and sealed house needs the max amount of heat maybe no more than 20% of the time. The rest of the time your heating system needs to input only enough heat to balance the loss. At an outdoor temp of 50°F and higher, which will be much of the time during the heating season, especially the fall and spring, the heat required from the heating system is not very high at all. If you need only 100,000 Btus of heat during a 24 hr period, you stand a high probability of being uncomfortable if your system wants to supply it at a rate of 30,000 Btuh.

Do not ignore the heat supplied from daily living activities such as cooking, watching TV, using the computer, having lights (even CFLs) turned on, and even simply existing (body heat). It will be difficult to quantify, can be highly variable, but it can be a significant part of the heat supply into the house. Except for warm water that goes down the drain, and dryer air that gets vented outside, probably 90%+ of the electricity that comes into your house eventually degrades into heat.

Whether a 30K rate becomes uncomfortable depends on the thermal mass of the house, and to some extent to the thermal mass of the emitter/radiator.  Slabs in high-R houses can be good for stabilzing the temps, but RADIANT slabs as radiators would not necessarily be easy to control but not impossible.  In a truly-R house a lower mass radiant-ceiling approach would be easier to control.  Min-fire on many of the smallest mod-cons are under 15K, so 30K is something of a red-herring.  

A tank HW heater's burner is in the 15K range, but there's no requirement that heat be pumped out at that rate (it can be both higher or lower).  I have lower-mass staple-up radiant zones in my home that draw no more than ~12K at max pumping rate from a fixed-temp buffer tank, works fine even at periods of miniscule load- the thermal mass of the rest of the house and the R-value of the wood flooring limit the room temperature swings just fine.

But radiant floors in truly low-loads aren't particularly cushier than other methods.  In an air-tight home with a whole-house design day load under 10K probably isn't worth the additional expense of radiant heat of any type, unless you restrict the radiant to a limited-area "warm spot" where you want the cats to park themselves.   In a superinsulated home you can put the heat emitter(s) almost anywhere, as long as you haven't created interior thermal barriers such as partition walls containing insulation for sound-abatement.

BTW: It's more like 99.99% of the power used inside the thermal envelope shows up as a heat source, not a mere 80%+.   Figure on a heat source of 3.313KBTU/hr per kilowatt for all uses except exhaust fans and sump/sewage pumps.  Typical US homes are on the order of ~1KW as a background load, which can be a large fraction of the heat load of superinsulated houses. (Typical Japanese homes are about half that.)  But gains from glazing can be many times that figure, which is why designing thermal mass into the interior of the insulation (not just an ICF) and scaling it properly for the passive solar gains is important for comfort when going to R50+.

Posted By Dana1 on 17 Mar 2011 01:56 PM so 30K is something of a red-herring.  

That was a somewhat wild grab out of the air intended to make a point more so than a real number. Although, with a fossil fuel fired hot air heating system that is pretty much what you would have. The one great advantage of a hot water system, modulating furnaces, and variable speed compressor heat pumps is that they can output heat into the living space equal, or at least near equal, to rate it is leaving. That's one reason why my heat system works so great. And another reason why a quality heating system design cannot be a seat of the pants activity. Now, if we keep hammering on that point eventually the new and uninitiated will begin to realize that. I feel sorry for all the home owners who get suckered in by a fast talking HVAC contractor with a fast pencil. Many, but fortunately not all, HVAC contractors are not able to "Dazzle them with brilliance," so they revert to "Baffle them with bulls***!"

BTW: It's more like 99.99% of the power used inside the thermal envelope shows up as a heat source, not a mere 80%+.   Figure on a heat source of 3.313KBTU/hr per kilowatt for all uses except exhaust fans and sump/sewage pumps.  Typical US homes are on the order of ~1KW as a background load, which can be a large fraction of the heat load of superinsulated houses. (Typical Japanese homes are about half that.)  But gains from glazing can be many times that figure, which is why designing thermal mass into the interior of the insulation (not just an ICF) and scaling it properly for the passive solar gains is important for comfort when going to R50+.

I thought it probably is but not having solid numbers in hand I'm hesitant to over reach. Besides, I would expect most people, who are unfamiliar with physics and thermodynamics, will be surprised to learn it's greater than 90%. 3.313 kBtuh/kwh? I've always used 3.416. Based on hourly meter readings from Idaho Power it appears my background load is closer to 2 kw. I don't think I've got excessive background loads, but maybe I'm not near typical either. Solar gains in my house are quite a bit greater, at least as subjectively assessed, than I expected, even though I designed with it in mind. I avoided huge windows and designed for summer shading, but I can really feel the impact during the shoulder seasons.

Typo- it's 3.413 KBTU/kwh not 3.313 (mea culpa!)


Looking at any 1 hour period the load will fluctuate by at least an order of magnitude, maybe two. A 1kw background load works out to 8740kwh/year, which is maybe a bit under the national average of 11-12k kwh/annum.  The 1kw load applies to homes that don't heat (either space or hot water) with electricity and have low cooling needs. 

Places with an ongoing history of efficiency regulation (such as southern CA) the average is more like 6000kwh/year (all uses) per 3-person household which is about 685W average.

My 3-person household is more like an 850-900W background load, (higher in winter due to the piggy air handler duty cycle).  If you're heating/cooling with a heat pump in ID you'd be using considerably more electricity than me (but far less natural gas.)

I expect that shoulder-season passive solar gain impact feels prettty good in March, but not so much in September.  It's always a tough one, but the modeling has gotten much better over the past quarter century.

Some good information here - especially about the heat loss calculation.

Radiant heat works extremely well with ICF wall systems. My own home +3,000 sq. ft. uses electric radiant heat and my heating bill (I have a separate meter on the heating system) cost me just over $500 for last year's heating season. (This season isn't over yet, so the numbers aren't available.) That's at 7 cents per kw. In Ontario you can take advantage of the time-of-use rates and probably heat your home entirely on that rate. Besides, electric radiant systems are a LOT less expensive to install than the hydronic system.

For this I would like to help you..you can get good idea here..the company particularly deals in green energy products..for more visit this... http://www.greenmeetingguide.com

I feel you are looking at this in the wrong manner. first lets look at the "r-value", do you understand by only looking at the insulation you have already failed yourself and the system. look at a window do you ever see a "r-value" attached to it? No, because it is a system you use a "u-value" completly different! r- value measures a single source product while u-value measures the system!! Any building system out there is exactly what it says a BUILDING SYSTEM, you should measure your walls using the u-value method by doing this you will understand how your wall will "preform"! Your right ICF's are only a r-22 however they preform as if they were a r-40 to 60, now with that said, that 2x6 wall that is a r-19 will preform as if it is a r-10.58 huge difference!! you must take into consideration the thermal bridging effect, air infiltration, moisture! i dont blame anyone on here for using the term r-value in fact we have to use it because that is what the goverment has mandated. We need to use the u-value and get rid of the r-value!!

you should measure your walls using the u-value method by doing this you will understand how your wall will "preform"! Your right ICF's are only a r-22 however they preform as if they were a r-40 to 60,

That's good to know.

It's probably not too late for me to recalculate all my heat losses using U-values in order to capture that preformance bonus on this build.

So in well insulated houses with radiant floors, people are going to start applying low emmisivity coatings so that they can have a warm floor without overheating the house :-).

before you redo any of your calculation just google the relation between R values and U values. you'll find probably find that U = 1/R so it doesn't matter which one you use as long as your math is corect.  one is thermal conductivity, the other one is thermal resistance. any material has an R value and any material has an U value. no relation to any system

it is true though that you can measure "clear wall R value or U value" or "whole wall R value or U value", that you can find numbers for "glass U value" or "window U value" and I agree that one should use the entire system U or R values in his calculations and not just the ideal spot in the system.

another thing is the R40-R60 equivalent of an R22 ICF. this is one of those "tricks" apparently still used by some of the ICF industry. I don't understand why they're doing it but I guess it's just bussiness. R22 is R22. an R40 or R60 stick frame full of thermal bridges an air leaks is NOT R40 or R60 - is whatever the numbers say it is after the framing factors and air leackage is measured.

I'll use ICF on my own project so I'm not biased in any way against it but in the heat load calculation, in the input R value box of the software I'll write R22 not R40 or R60.

good luck,
adi

The performance advantage of ICF has nothing to do with the steady-state U-value, it's the dynamic performance of the thermal mass over diurnal temperature swings that matters. But by isolating the mass from the conditioned space with R8+ of foam it's not nearly the advantage it might have were the mass fully within thermal boundary.

The notion that an R22 ICF had the thermal performance of a low mass R40+, even a center-cavity-only R40+ is pure fantasy. Almost all R40 center-cavity stick-built structures use at least R15 of exterior foam, which is a huge thermal break over the framing. Even if you went with R38 batts in a ridiculous straw-man argument 16" o.c. 2x12 studwall you'd still have to use framing factor higher than most to run as low as R22 for a whole-wall number. (And with studs that massive you'd be nuts to use 16" o.c. spacing or full-depth plates & window/door headers, etc. everywhere.)

And, the realistic comparison is never center-cavity R, only the "whole wall" numbers. In the real world of 2x6 framed foam clad house it works about like this:

Crummy R19 batts in a 16" o.c. standard double-plated studwall comes in around R20 center cavity (with wood siding, no foam sheathing) but R14-ish using 25% for a total framing fration.

Adding 2" of cheap EPS sheathing would make it R28 center cavity, but R22 whole wall.

Bumping it the framing to 24" on center reduces the framing factor to under 20%, center-cavity R remains R28, but adds another ~R1+ to the whole-wall number for R23.

If XPS sheathing is used instead of EPS, center-cavity is now R30, whole wall becomes R25.

If iso sheathing is used, center cavity becomes R32, whole-wall, R27.

The cost of air-sealing a frame wall is quite modest, and instead of using crummy R19 batts, a flash'n'fill of 1" closed cell foam + wet-spray cellulose is extremely air-retardent even without a lot of caulking detailing (but air sealing both the structural and insulating sheathing is so cheap is should still be done).

The 1" cavity ccSPF adds another R2 to the center cavity for R34, but only R1 to the whole-wall R making it ~R28.

That's still well under R40 for center cavity R, but there's no chance that R22 ICF is beating it on price/performance (even if the cost of an R28 whole wall stick built as-sketched might be roughly the same or even higher than an R22 ICF.)

Of course the R25 2x6 24" o.c. batt (or spray cellulose, no SPF) + 2" of exterior XPS building isn't anywhere near as structurally robust as an R22 ICF house, but on thermal performance it's beating it measurably, and on price/performance it's KILLING it. At equivalent whole-wall R there's only a ~5% advantage in total cooling/heating energy use for the ICF (and then only in places with the HIGHEST daily temperature swings.) Selling it purely on thermal price/performance doesn't work, but that doesn't mean you shouldn't build with ICF- the premium paid buys a very durable & quiet structure with decent (way over code-min in most places) thermal performance.

In any house with R20+ whole-wall values the glazing fraction and other factors dominates the thermal performance of the wall, since the heat gain/loss of a U0.5 double-pane is literally an order of magnitude higher per square foot than the wall area. A single 10 square foot window in a 9x12 section of wall (a ~10% glazing fraction) would be responsible for about half of the wall's total conducted heat. With ever higher whole-wall Rs, to keep the total performance up, reducing the glazing factor and/or using higher-performance windows is necessary. Optimizing interior thermal mass for the passive solar gain of the glazing also rises in importance.