Hi Guys,

I am building a new house in Saskatchewan, Canada. We get cold winters up here and hot summers.

The house is going to be a walkout basement bungalow house with 1850sq. ft on each floor. The heat system will be a natural gas boiler with in floor radiant in the basement slab and 1.5" of overpour on the main floor. I already have the design, etc. for the radiant system.

What should I do for air conditioning and for an air exchanger and humidity control?

I know I will probably have to run ducting for a/c. Can the air exchanger tie into this ducting?

Any recommendations are appreciated.

Neil

you can check nilan.ca. they're selling a product which combines ventilations with a heat pump that you can use to cool or heat. I don't know what kind of cooling load we're talking here so this product may or may be not enough for you but it may be a solution. other than that - mitshubishi mr slim (or equivalent) for AC and a VENMAR EKO HRV (or equivalent) for ventilation should do the trick.

good luck
adrian

If your house is built for high energy efficiency, you could do what I did. I installed a natural gas fired boiler with radiant heat in the basement floor, but forced air on the main level. Since I needed the ductwork for air circulation/ventilation (HRV) and cooling anyway. I installed an air handler with a variable speed blower. It circulates air continuously at a very low speed (60 watt draw) making it practically silent. When there's a call for heat, the boiler supplies hot water to a heat exchanger in the air handler. The fan ramps up as needed to meet demand. Only on really cold days does the fan run at a speed while is loud enough to notice. The air handler also contains an A-coil for cooling. I run the air only at night when electric rates are low and coast during the day. Finally, I have a whole house dehumidifier tied into the ductwork to maintain indoor humidity at less than 50% year round.

Posted By Clark on 09 Mar 2011 08:21 PM
If your house is built for high energy efficiency, you could do what I did. I installed a natural gas fired boiler with radiant heat in the basement floor, but forced air on the main level. Since I needed the ductwork for air circulation/ventilation (HRV) and cooling anyway. I installed an air handler with a variable speed blower. It circulates air continuously at a very low speed (60 watt draw) making it practically silent. When there's a call for heat, the boiler supplies hot water to a heat exchanger in the air handler. The fan ramps up as needed to meet demand. Only on really cold days does the fan run at a speed while is loud enough to notice. The air handler also contains an A-coil for cooling. I run the air only at night when electric rates are low and coast during the day. Finally, I have a whole house dehumidifier tied into the ductwork to maintain indoor humidity at less than 50% year round.

Where are you located?

I'm located in northern Illinois.

@ Clark... You did just exactly what I am in the process of doing. As a homeowner and DIY type, the equipment is probably the most confusing part. What boiler did you use, what heat exchanger in the air handler, which air handler did you use? I am in Central Illinois, building a 1600 sq ft home over a 1600 sq ft walkout basement. The pex is already in the basement floor and the manifold is on the wall. Lines have been pressure tested and now it is decision making time. I would greatly appreciate any input you could provide. Thank you in advance.

You realize you're responding to a 2.5 year old thread, right?

It's OK to start your own thread (the radiant forum on this site would be good place, given the nature of your question.)

The short answer is: All good heating systems start with a room-by-room heat load calculation, and from that you can spec the size of the boiler, and from there figure out which manufacturers have good distribution & support in your area. Square feet of conditioned space is meaningless- a tent with an open flap will require a very different boiler from a PassiveHouse with R50 walls and U0.12 windows. Your house is probably somewhere in-between.

Yes I'm aware of the age of the post. A new house in the same region should have some comparable traits. The longer the system is in place could make the information that much more valuable. I would agree my house is somewhere in between, as who builds new to those extremes? I would get to that information, but size is already determined. That was not what I ask....

Another thought, most of the boilers I have looked at have a modulating BTU. The "Radiant Ready 30E" unit even says "will heat upto 2,000 square feet". These systems are becoming much easier to size than the old units due to this fact. My last HVAC guy was fired because he talked down to me. He made such a big deal about how labor intense installing PEX was. Well, this old accountant and his wife found the job quite easy. Knocked it out on a Sunday afternoon so the concrete guys could move forward on Monday. Thanks for the input.

Posted By Snooks on 20 Aug 2013 10:18 PM
Another thought, most of the boilers I have looked at have a modulating BTU. The "Radiant Ready 30E" unit even says "will heat upto 2,000 square feet". These systems are becoming much easier to size than the old units due to this fact. My last HVAC guy was fired because he talked down to me. He made such a big deal about how labor intense installing PEX was. Well, this old accountant and his wife found the job quite easy. Knocked it out on a Sunday afternoon so the concrete guys could move forward on Monday. Thanks for the input.

You'd be shocked at how badly people oversize modulating condensing fossil-fired boilers, which DO have a minimum firing rate.  Very few homes in the US require the full output of even the smallest in most vendors' lines, but those aren't the highest volumes they end up manufacturing.

But the The Radiant Ready 30E is a 9kw electric boiler, with ~30KBTU/hr max output. "Up to 2000 square feet" type designations are completely worthless, since the actual load is all that matters, and that load will be different in a 2000' code min building in FL vs a 2000' code min building in MN.  That may or may not be enough output to fully handle the load of a code-min 1600' x 2 home in central IL with a lot of windows (but it might be.) Without running the load calculations it's hard to say for sure. But since you're still in the design phase on the house you have the option of guaranteeing that it is, provided you do carefully calculate the loads as part of the process at every iteration. (Most 3200' code min homes in climate zone 5 have heat loads in the 32,000-45,000BTU/hr range.)

But the operating cost of an electric boiler is about 3x that of ductless air source heat pumps (mini-splits/multi-splits) in a central IL climate.  For the same ~$3.5K purchase price of the Radiant Ready 30E you could buy a couple of pretty-good 1-ton mini-splits and do most of the installation DIY, which would get you air-conditioning to boot.  For most homes in that climate mini-splits sized for the peak air conditioning loads would have a bit of margin on the heating load, so if you intend to air condition the place, DO consider heat pumps (even ducted heat pumps), since the up-charge for heating & cooling versions is pretty small.  With all the ducts inside of conditioned space, even a ducted heat pump would use only half as much power as the electric boiler, while ductless would use only about 1/3 as much power.  If you split the load between a heat pump and the radiant you'd have the nice barefoot cush of the warm slab and still use less power than the boiler alone, but you'd have to figure out your strategy for keeping costs bounded.

For high-R houses heating & cooling primarily with mini-splits and a rooftop PV array is the most common way to get to Net Zero Energy in most climate zone 5 & 6 locations. This is how Carter Scott builds most of his Net Zero houses on the cool edge of climate zone 5. (Central IL is on the warm edge of 5/cool edge of 4, depending on exact location.)  IMHO Scott uses WAY too much of the HFC blown varieties of foam such as XPS or closed cell polyurethane, most of which could easily replaced with far more benign EPS, polyiso, or open cell polyurethane, but his houses DO perform.  Unless you hit pretty close to his whole-assembly R values and design the window type/size/location carefully you probably can't hit Net Zero, but it's not really that hard or expensive to do.

With code-min building envelopes you can't get even close to Net Zero with a PV array that actually fits on the roof, even using  mini-splits that are only using 1/3 the power of an electric boiler.

Posted By Snooks on 20 Aug 2013 05:42 PM
@ Clark... You did just exactly what I am in the process of doing. As a homeowner and DIY type, the equipment is probably the most confusing part. What boiler did you use, what heat exchanger in the air handler, which air handler did you use? I am in Central Illinois, building a 1600 sq ft home over a 1600 sq ft walkout basement. The pex is already in the basement floor and the manifold is on the wall. Lines have been pressure tested and now it is decision making time. I would greatly appreciate any input you could provide. Thank you in advance.

Snooks,

I advise taking the time to estimate your heating/cooling load using software available on the web.  It will factor in things like building R-values, window and door area, quality of construction, geographical location, building orientation, etc.  Proper sizing of HVAC equipment is very important.

I installed an HTP Munchkin T50 mod-con boiler (16k-46k BTU output - now discontinued - see their Elite FT55 boiler) married to a First Co variable speed air handler (Model 24VHBQB).  The boiler has no trouble heating the house in the coldest days of winter in addition to supplying indirect domestic hot water.  In the fall and spring, the boiler usually meets heating demands in the low fire mode and at lower blower speeds.  Keep in mind that my house was built for high energy efficiency (measured at 2.1 BTU/SF/HDD).

This was a DIY installation which worked out very well, but you should be aware that manufacturers' warranty coverage might be contingent upon installation by a certified contractor.  Also, you might want to check first on the availability of parts and service in your area before committing to a product line.  I found a plumbing and heating supplier in Aurora, IL that sells HTP boilers and parts.  After four years, I've had no problems requiring service beyond annual combustion chamber cleaning. 

Just be aware that it's a challenging job to build the hot water circulation piping if it's your first attempt at it.  Don't underestimate the effort and skill needed to do so.  I used a primary-secondary loop piping design with circulator pumps and no zone valves.  I have three secondary loops:  air handler, domestic hot water, and basement radiant floor heat.  The boiler manufacturer (Heat Transfer Products) provides installation instructions, but assumes you are familiar with pipe fitting and boiler installation basics.  For me, there was a lot of reading between the lines to get it designed and built properly.  I'd be happy to fill in the details of my system design, if you think it might help.

Clark

Electric boilers are a bit simpler to deal with than fossil fired mod-cons like the T50, and the Radiant Ready 30E comes with a 5 / 5 manifolds, flow meters, balancing adjustments, and a 3-speed Grundfos circulation pump built into the unit. Hopefully the loop lengths on the PEX were designed to provide reasonable flow for the pump, and reasonably balanced. Hydronic heating is more than a plumbing exercise, to be sure, and there's only so much tweaking you can really do once the PEX is cast in concrete. It's probably enough boiler to deliver the heat, provided the rest of the hydronic design is reasonable.

With any luck he won't have to change out the pump to some monster-pumper to get there from here, but unless at least the napkin-math version was sketched out a-priori some gross hacks like that may be necessary to get it to work. (It would be neither the first nor the last DIY radiant job to have that as an issue, if it came to that.)

edited to add:  According to EIA data residential retail electricity in IL averages about 11.5 cents/kwh. 

Used in an electric boiler you get 3412 BTU/kwh that's  (1,000,000/3412 =) 293 kwh per MMBTU, at a cost of ($0.115 x 293=) $33.70/MMBTU. 

Assuming you get a COP of at least 2.5 out of a bottom-of-the-line mini-split (better ones would deliver about 3) your cost would be ($33.70/2.5=) $13.48/MMBTU.

Residential gas, delivered in IL is running ~$8.22 per MCF. At 1,020,000 BTU /MCF that's $8.06/MMBTU source fuel. Gas burned in a condensing boiler at 95% efficiency that's about $8.48/MMBTU. 

That's quite a bit cheaper than heating with a bottom-of-the-line mini-split, but 1/4 the cost of heating with an electric boiler.  If your primary heat is an electric boiler you really need to tap into some sort of time-of-use off-peak rates deal to get the $/MMBTU down into the affordable range, and improving the the building envelope to 1.5-2x code-min becomes a lot more cost-effective.  In a code-min house the cost of heating with heat pumps would be reasonable, and if off-peak rates apply it could be cheaper than gas.  Electric boilers not so much, except in rare sub-8 cent electricity markets (which do exist, if not in IL.)

Thank you, both of you. Very useful information. My PEX was laid out using Loop CAD 3 D, got the Uponor 1/2 Oxygen Barrier Type A PEX and each loop is between 240' - 255'. I know the whole discussion regarding Insul-Tarp and what the critics have to say about it. Had to go this route for a couple of reasons I won't get into here, but considering most of the basement floor is 6 - 7' underground I am comfortable with my choice. Which always amazes me with some HVAC guys. On one hand there is so much warmth in the ground they talk geothermal and on the other hand they argue you can't get enough insulation under the basement slab. Puzzling to me how both conditions can exist, but I don't want to get into that here. Sometimes good old common sense must be used. I really like the concept of the Radiant Ready 30E, but I would like it more if they would come up with a NG version. You are correct regarding the cost of electric and I certainly was not going that route. I will study your post in more detail when I have more time and it will be very useful in my project. Again, I thank you very much for the input.

No one has to use a blanket under a radiant slab, or any other slab for that matter. We insulate under slabs because we want to heat our room above ground temperature. If you don't insulate under a heated slab--like substituting a blanket for real insulation, then you have to pay to heat the ground below the slab at the beginning of each season, much like heating up a pool.

As for common sense, there is nothing common about radiant floor heating, especially properly designed and installed radiant floors. Give me science.

"Radiant Ready 30E" is clearly a marketing ploy that has obviously worked.

"you have to pay to heat the ground below the slab at the beginning of each season" except that the ground beneath never warms up; it continually draws heat away from the house above.

All that is fine, but don't tell me the ground is warm when trying to sell me geothermal and then tell me the ground is so cold that I need over kill in insulation. The Insul-tarp is said to have an R value of 7.5 and when 7 feet under and the ground is 50 degrees or more, I am comfortable with it. Seems to me a thermal break is more important than pilling up insulation. I am an accountant and not an HVAC pro, so I realize I don't have formal training but there is "common sense" in what I am saying (Science too for that matter). If there is a thermal break then I am not heating the ground. I guess one could argue that I want the geothermal effect in my slab before I turn on the heat. Let that warm ground raise the temp of the slab before the heat comes on. What really is the difference? Global warming is said to be science too, but to each his own. I am just a homeowner trying to make choices in a very confusing and distorted world.

There are at least three definitions of warm that are key to understanding this:

1) warmer than the outside air so it's more efficient to extract heat from it (geothermal)
2) close enough to the inside air so there isn't much heat loss to it (slab insulation)
3) warmer than the inside air so that it feels comfortable on the feet (radiant heat)

except that the ground beneath never warms up; it continually draws heat away from the house

It does warm up quite a bit and soil does serve as insulation. It would be accurate to say that it never warms up to the point where heat loss to it is zero. But that's true no matter how much insulation you use - it's just a matter of how much. And response time from all the mass.

Deep subsoil temps in central IL aren't exactly cozy, in the mid-50sF, best case:

http://www.earthrivergeo.com/img/geothermal-article/geothermal-subterrainean-temperature-contour-map.jpg

That's a temp at which a heat pump can extract heat quite efficiently though.

If all you have is Insul-Tarp for insulation under the slab, scrap any idea of using the Radiant Ready 30E as the heat source- it'll break the bank. Even with natural gas using a basically uninsulated slab on a walk-out basement will be more expensive than heating with mini-splits. To use the slab as a radiator at even 10BTU/ft-peak you'd need at a minimum of R8 between the slab and 55F subsoil (and a sane value would be R12+). Even without using the slab as the radiator there is a good long-term rationale for R8, but there's no going back now. With InsulTarp you have at-best R2. They call it insulation, but without a published and ASTM C 518 R-value they can still stay on the legal side of the FTC, but if they published the validly tested number nobody would actually buy it.

They're never going to come up with a gas version of the Radiant Ready 30E- you can only modulate condensing gas burners, and you get at most about a 4:1 turn down ratio while still maintaining the high efficiencies. (Higher turn downs are possible, but at lower burn rates there isn't sufficient turbulence on the fire-side of the heat exchangers, and efficiencies start to go down.)

The only way to get a handle on what it takes to heat the place is a room-by-room heat load calculation using U-factors appropriate for your construction type & R values, at reasonable indoor temps and the 99% outdoor design temp, which is probably somewhere around 0F for most central IL locations. Peoria's is -1F, Springfield's is +2F.

http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/Outdoor_Design_Conditions_508.pdf

Dana1 - Earlier you did a nice comparison of the costs between a boiler, bottom of the line mini-split and gas burned in a condensing boiler. What would the numbers look like if using a ground sourced heat pump using the same $0.115/kW? Or if this is a silly question please educate me?

Posted By MSG79 on 22 Aug 2013 01:46 PM
Dana1 - Earlier you did a nice comparison of the costs between a boiler, bottom of the line mini-split and gas burned in a condensing boiler. What would the numbers look like if using a ground sourced heat pump using the same $0.115/kW? Or if this is a silly question please educate me?

A ground source heat pump at a "typical" design & implementation in an area with mid-50s ground temps will have an annual average COP of about 3.5 (give or take 0.5) after all pumping and air handler power is factored in.   Best-in class GSHP implementations can hit around 4.5-5, but it take very low radiation temps, best-in-class pumps, and a top-tier system designer to get there. In random third party tested implementations don't count on any better than 3.5.

That means if it was ~$13/MMBTU with the third-rate mini-split averaging a COP of 2.5, the GSHP running a COP of 3.5 would run ($13 x 2.5/3.5=) ~$9/MMBTU.

Mind you, a better-class ductless will come in with a seasonal COP of about 3 in that climate or about ($13 x 2.5/3 =) ~$11/MMBTU, at a tiny fraction of the upfront cost & design-risk of a GSHP system.  (There are many GSHP systems that don't hit that seasonal COP=3 efficiency level due to poor system design/installation, plenty that are running 2.5 or even lower.)

Also note, the seasonal COP of a ductless mini-split varies with climate- these estimates are for a warm edge of zone 5/cold edge of zone 4 climate.

Efficiency is one thing, distribution is another. Not every house is well laid out or sufficiently well insulated for a solely ductless solution, but many can do quite well with ductless slightly overheating the bigger open spaces, and judicious use of supplementary resistance heating to balance temps in the doored-off areas.  (Using cheap radiant cove heaters or somewhat more expensive electric panel radiators rather than electric baseboard, and using occupancy sensor cut out on the thermostats for those heaters can keep the power use to a miserly level without taking a big hit in comfort.)