Hey guys. so not simple question, but looking for simple answer : ) we are doing an addition to our small 800 sq foot house, we are lifting and adding a basement and pouring the walls with the ICF. i will put down the 2" dow foam under the cement. the houses new footprint will be under 1200 sq, with a 400 ish sq foot attached garage. the house already has a furnace and will heat the entire house and addition, not the garage. i plan on doing the floor heat in the garage also. i am going to run 1/2" pex, and was told a 40+ gal water heater with 60000+ btu rating. just wondering how big of a pump i will need to run the system. I was going to either run 2 pumps, one for the garage and one for the basement...or get an automatic valve for 2 zones....thinking that the 2 pump method would be easier. sorry for rambling, just want to give as much detail... the floor heat is just for comfort really, i dont plan to heat the entire house with it, so that being said any suggestions on a pump size for each zone, and if you use 2 pumps/2 thermostats, the water will only flow in whatever zone pump comes on correct? (unless there both being called for thanks guys oh should have mentioned, the garage will have a basement under it also, that is where im going to run the tube...i have a forced air heater to heat it up real fast when i want to work out there, so the in floor heat is basically to keep the garage above freezing. thanks again

i was looking at this small pump to run each zone. (basement and garage)
http://pexsupply.com/Grundfos-59896341-UPS15-58FC-3-Speed-Circulator-Pump-1-25-HP-115-volt-4701000-p

All decent heating system designs start with a heat load calculation, from which the rest of the design flows. Unless this is an uninsulated garage in Antarctica there's no way you need a 60,000BTU/hr burner to keep the place at a comfortable temp.

The pumping specification depends on the amount and diameter of pipe, the head-resistance of the heat exchanger (assuming you're not doing something dirty like running it with potable water, which opens a whole other can o' design worms), the range operating temperature difference between outgoing & incoming water that you need to keep the boiler/burner happy, and the amount & type of radiation.

If there's any chance that the water in the garage slab could freeze you need to run anti-freeze in that loop, which is yet another design issue.

Basically, you're a LONG way from being able to spec a pump at this point. Even if you do all the work as DIY sweat-equity, hire somebody who knows what they're doing to design the system, or take the time to learn enough about it to design it yourself. Radiant heating design is NOT a back-of-napkin or lipstick on the mirror kind of deal (unless you have really big napkins/mirrors. :-) )

Indpendent of BTU input/output, if using a hot water heater for the heat source you'll better off using a condensing hot water heater, since it's likely that continous use in this type of application would result in destructive condensation issues on the flue & heat exchanger using a standard water heater (unless you design it to NOT do that, which is again, another design detail that needs attention.) A condensing HW heater is designed to tolerate and make use of the condensing combustion gases for increased efficiency.

What Dana said.

This is a good candidate for a combination system using a high efficiency condensing water heater to provide space and domestic hot water. Not a DIY design project.

Heat load calculation.

Heat source consideration.

Distribution/radiation specified and sized to the load.

Pumps, controls, air elimination, water quality and quantity.

Is this simple enough?

ok i guess i wasn't clear enough...
its like a secondary heat source, just for comfort...my high efficiency furnace is enough to heat the entire house when its done....the floor heating is just like what i have in my kitchen/bathroom, just extra for comfort.
the garage isn't a slab, like i said its going to have 9' basement walls just like the house...it too is like i said, extra heating, ive got a large corner hang forced draft natural gas heater for the main heat...
all i want to know is, will this pump, pump water to and from my hot water tank. not too fast not too slow, it has 3 automatic speeds for demand which is nice, but im sure isn't imperative.
there will be between 1200 and 1600 foot of 1/2" pex tubing in the floor. (not sure yet with the permits not final)
i guess i just wanted like i said an easy answer, im not asking for written hard copy quotes, just like, yep that will work, but perhaps u could consider this...
im keeping my on demand system i have now for the potable water so its seperate
imalso considering 3 pumps with 2 basement zones to keep the bedroom/utility room cooler

If you use a dedicated tank-type water heater (not recommended) you will need to control temperature in the tank (higher) and the floor.

You are asking for a reel without knowing the rod, the line, the hook or the fish.

Your radiant designer will have the pump or pumps you may need. In winter you will not want the forced air to heat anything.

Sounds like corzy just wants to keep his toes warm and NOT heat the building with the hydronic radiant floor heating. Seems like that would be an expensive toe warmer.

Sure enough. But, as you know, you can't do one without doing the other.

huh ok, well i priced out the entire system and its 3-400 for the pex, 1500 ish for the insulation (that is needed anyways) 500 ish for the tank and 100 per pump...lets say 100 for fittings/staples, i dunno 3 G isn't overly expensive for comfort, and its certainly going to warm the basement more than just the feet.
anyways, guess this site doens't have any shade tree plumbers, no worries...lots of other sites out there
maybe forced air is the wrong name for it, its the type that hangs in the corner, you fire it on, its on/off and blows hot air out with a fan...its definately used for the winter, not really sure what other time of year you would want a heater going...

The type of heater you are suggesting is called a unit heater.Reznor,Modine are two manufactures that make these type of heaters. As pointed out earlier without a proper load calculation ,you are just guessing.

Posted By corzy on 22 Jan 2013 09:32 PM
huh ok, well i priced out the entire system and its 3-400 for the pex, 1500 ish for the insulation (that is needed anyways) 500 ish for the tank and 100 per pump...lets say 100 for fittings/staples, i dunno 3 G isn't overly expensive for comfort, and its certainly going to warm the basement more than just the feet.
anyways, guess this site doens't have any shade tree plumbers, no worries...lots of other sites out there
maybe forced air is the wrong name for it, its the type that hangs in the corner, you fire it on, its on/off and blows hot air out with a fan...its definately used for the winter, not really sure what other time of year you would want a heater going...

I'm  more in the class of shade-tree plumber/designer, and am definitely not a hydronic heating professional. 

But I do at least the first-order math before diving in, so as to neither overspend nor under-design stuff.  (BadgerBoilerMN & NRT.Rob can attest to the numerous kludge-factors of my hot-water heater based heating system, having run it up the flagpole here to more jeers than cheers. :-) )

You're looking for shade-tree numbers without specifying the species, size or age of the tree, but some of what you HAVE shared throws up a lot of warning flags.  You don't have to do the hard math to get something that works, but you have to do at least SOME math other than what the presumed hardware costs.

Do NOT do this one with a ~$500 tank HW heater, unless you plan on replacing it every few years due to heat exchanger corrosion issues, (especially if you over-pump the sucker and are doing it without mixing valves & isolating heat exchangers.)

It's not tough to do an I=B=R type spreadsheet heat load estimate using U-factors based on your construction details, and your 99% outside design temp.  It doesn't have to be super-precision to get to something that works, and will determine whether simple staple-up sans heat spreaders will buy you enough comfort to make the project worth while at reasonable HW heater storage temperatures. (Even the cheaper bent sheet metal heat spreaders make a real difference in how much heat you can get into the floor with 130-140F water. Higher storage temps end up with much higher standby losses, and cut into condensing efficiency when a condensing heater is used.)

Loop lengths, water temps, and staple-up vs. heat-spreaders have a DIRECT bearing on the delta-T and pump sizing.  Most shade-tree hacks end up overpumping (sometimes by a LOT), others will staple up 1000' of half inch PEX in a single loop and wonder why there isn't enough flow. If you're not going to try and address first-principles, it's going to be very hard to get satisfactory results (unless a dumb-luck strategy always works for you? :-) )  No designer worth ANYTHING is going to even hazard a guess as to how much pump you need without a better description.

the basement was going to be 4 loops each 300' long 1/2" tube, however, im open to doing 6 @ 200' if thats better. the garage was going to be 2 loops at 200'....
its not under a main floor, its under the cement slab of the basement of the house and basement of the garage...(stapled down to the 2" dow foam before pouring the concrete)
I was planning on having 1 3/4" headder for the basement and one for the garage, but ive also considered doing 2 for the basement and have 2 zones so i could keep the bedroom in the basement as well as the utility room a bit cooler than the rest...so was going to use either 2 pumps or 3...
If i get 2,3 or lucky and 5 years out of a hot water heater, i'd be happy with that, but if your suggesting a different heat source (keeping in mind, that its only for the floor heat) i would love to see a link to one to check them out.'
like i said before, the basement walls will be poured in ICF so i'd say about the solidest in insulation possible...(same for the garage basement walls)
what else can i tell ya? were in SW ontario so the coldest days of the winter are maybe -20 C ... but really it stays closest to -5 in the dead of winter....
still open for suggestions, let me know what else you would like to know...

You need U-factors and surface area for ALL exterior building elements, including windows, doors roof, etc, not just walls, but you still haven't given us the R value of even the wall. "...ICF so i'd say about the solidest in insulation possible..." is not enough description to design anything to, since ICFs range anywhere from R16 to R28 and even much higher, with dramatically different U-factors.

SW Ontario is a big place, with a wide range of 99% outside design temps- wanna pick a nearby town from the ACCA list I linked to? It could be than -20C is the right number, but it could be wrong too.

Nobody is going to design it for you for free, but we can point you to some methods.

feel free to shoot holes thru my idea.
this heater ... http://www.homedepot.com/Plumbing-Water-Heaters-Residential-Gas/h_d1/N-5yc1vZc1tz/R-202959675/h_d2/ProductDisplay?catalogId=10053&langId=-1&storeId=10051#.UQBHuo6bLbU
3 3/4" manifolds out of the tank each with there own pump/shut off manual valves, i was thinking about using this pump http://pexsupply.com/Grundfos-59896341-UPS15-58FC-3-Speed-Circulator-Pump-1-25-HP-115-volt-4701000-p
the 3 zones would be basement main,4 200' lengths of this 1/2" pex tube http://pexsupply.com/Rifeng-050-1000-OXY-1-2-Oxygen-Barrier-PEX-Tubing-1000-ft-Coil
the utility/bedroom zone 2 200' lengths of the same tube...and the garage the same as the last, 2 200' lengths again.
not sure if the pumps are usually on the supply or return to the tank?
oh and each zone would have its own thermostat, was thinking about this one.... http://pexsupply.com/Wirsbo-Uponor-A3030101-Wirsbo-Radiant-Thermostat-WT-1-Heat-Only-Two-wire-2063000-p
each thermostat wired to its own pump for that zone.

please feel free to add/subtract anything

the closest place on that list is sarnia an under heating 99% dry bulb is 3.
lets assume R-16 (like i said were in the middle of getting permit approval from the conservation authority due to cliff erosion issues so it still up in the air)
so even though im heating the entire main floor and upstairs with my furnace, you still need the u values? im sure the basement will have a few windows and we plan to use the best ones we can, however my wife likes the metal window look, so not too sure the u values....

Badger and Dana have given you very good advice…you first need to do a proper building heat loss analysis and it will be problematic integrating these two very different styles of heating systems. Feel free to use the DIY calculators on our website, but my sense is that you would be much better served just to hire a knowledgeable/capable company in your area to sort this out for you.

R16 ICFs are getting somewhat rare, but they're still out there. Most vendors these days start at R20-R22 (2.5"/63mm of EPS on both the inner and outer surfaces.) Find out what it is- and ignore any performance claims related to thermal mass- just the total thickness of the EPS, and give it R4.2 for every 25mm of thickness. The U-factor will be roughly 1/R.

Sub-grade heat loads are difficult to calculate with any accuracy due to the wildly varying thermal conductivity of soils (which will also vary with seasonal/site-specific moisture content.) If using a spreadsheet method of calculation, only count the portion of the wall area down to about a foot below grade. While there IS still a heat load from the rest, it's comparatively small, and doesn't vary with the hourly outdoor temperatures very much.

The conducted heat loss in BTUs/hr is: square feet of area x U-factor x temperature difference. So if you assume you'll be keeping it ~20C/68F, with a 99% design temp of +3F that's a 65F difference. With an R20 SIP the U-factor is is (1/20=) 0.05 BTU/degree-foot-hour, so every square foot will be losing 65F x 0.05 = 3.25 BTU/hr.

Do a similar calc on window & door areas. If it's conditioned space above, count the ceilng losses as zero. If it's an insulated ceiling/roof, we need to know the R-values and construction type.

Add it all up, then multiply by a ~10% fudge-factor to cover ventilation & infiltration and you'll be in the right ball park.

When you know the room's total load, you can calculate the BTU per square foot of radiant floor tells you the temp the floor needs to reach to deliver that heat, from which the water temp and pumping specs flow...