Hi Guys,

I am building an 1850sq. ft. walkout style bungalow home in Saskatchewan Canada. I am doing radiant for both the basement and the main floor. The main floor will be an 1 1/2" overpour.

What do I need for acceptable air conditioning in the house and what are my options. The floor will be engineered web trussing.

Neil

A ductwork system like any normal forced air house. Not much getting around that part.

There are lots of options. Mini split systems are a very good choice for your size home. Mitsubishi, Fujitsu, Daikin are a few mfg. If ductwork is desired then any air handler with outside condensing unit could be used. If running ductwork is a problem, and that is the type of system you are after, then look into Unico, Space-pak or Hi Velocity..Radiant cooling is also possible.

distributed chilled water fancoils works, if you're doing a water to water heat pump or something it can make sense to go that way. radiant cooling can work too if the cooling loads aren't too high. but no matter what you do you should have a ducted air system... just maybe smaller ducts for an HRV/ERV instead of a full fledged air conditioning system. Fresh air is important and putting it where you want it is best.

So is radiant cooling starting to take hold in the U.S./Canada? Assuming that one lives in a relatively dry climate, loads are not overwhelming ( shouldn't be if house is well insulated and tight) and proper attention is paid to IAQ and indoor humidity, is radiant cooling a viable option? Is it possible to find someone to do the design for both the heating and cooling in radiant.

I am getting close to staring a build in Boise and wrestling with this. Really want to go radiant ceiling but if I have to also install a separate ducted AC (or mini-split) system, don't think that makes sense. Ducting for HRV/ERV is no problem, would need to do that anyway. Have any of our radiant heating experts ever tried their hand with the cooling side?

not really: it's still (b)leading edge. We are doing radiant heating/cooling in our office/shop and have the design particulars down fairly well but we haven't done many combo designs for clients yet... just a few... Happy to work on that, for those willing to venture off the beaten path, and radiant ceiling is very powerful in cooling. but it's not "mature" design in the residential market at this time. also note radiant cooling is great but it's not fast response... you dial in a temp and let it ride.

Step one is to check the room by room loads and make sure it's viable and how much, if any, supplemental cooling is necessary. generally if any supplemental is necessary it can be a small fancoil in a great room or something like that... not a fully ducted system.

Rob is right.

For residential - light commercial radiant floor designs we recommend top/down cooling using dedicated conventional duct work and DX compressors, as this is common, available and competitive. We design and integrated system which includes Energy Recovery Ventilation.

Moviing air is counterproductive in cold weather but increases comfort in heat of summer.

I am hoping new heat pumps will start killing DX, frankly. I love being able to hit latent and sensible loads independently, and I love being able to zone with impunity. But we're still early in that fight.

I'm with you, but the scale will hardly warrant the investment in our lifetimes...

I'm not so sure about that.

Posted By 3cityblue on 04 Jun 2012 10:35 AM
So is radiant cooling starting to take hold in the U.S./Canada? Assuming that one lives in a relatively dry climate, loads are not overwhelming ( shouldn't be if house is well insulated and tight) and proper attention is paid to IAQ and indoor humidity, is radiant cooling a viable option? Is it possible to find someone to do the design for both the heating and cooling in radiant.

I am getting close to staring a build in Boise and wrestling with this. Really want to go radiant ceiling but if I have to also install a separate ducted AC (or mini-split) system, don't think that makes sense. Ducting for HRV/ERV is no problem, would need to do that anyway. Have any of our radiant heating experts ever tried their hand with the cooling side?

Latent loads are all but nonexistent in Boise (from a Manual-J design condition point of view the latent loads are negative, even at 45% interior RH) making that climate more amenable to chilled-floor cooling than anywhere in the eastern US. 

In  a well insulated home in Boise you can get a lot out of nighttime ventilation strategies.  Even in July overnight lows hit the high-50s/low 60s regularly, and the dew points rarely exceed 60F.  The midsummer mean dew points are in the mid-40s, so indoor humidity during the heat of the day are readily managed via HRV ventilation rates. 

But well insulated and tight isn't the same as "low gain" from a summertime heat gain point of view.  Even in moderately insulated homes solar gain accounts for the lions share of sensible cooling load. If you're dedicated to it, you can chill the floor or ceiling to as low as 60F without risk of condensation on all but the most-humid days, which is quite a bit of coolth. Whether that's enough to counteract the gains from sun exposed windows requires a more detailed analysis.

But the principles of managing solar gains are the same everywhere- limit the amount of east & west facing  glass, and shade the (useful in winter) south facing glass with either overhangs/awnings or operable exterior shades.  Any east & west window glass needs to be low-E and shaded on the exterior.  That's the first 75% of the cooling load in a well-insulated house- the rest are mostly from interior sources (plug-loads, mammals & birds, cooking/showering, etc.).  Conducted heat through roofs count, but walls, not so much.

With sufficient internal thermal mass and sufficiently low gain (external & internal sources) you should be able to cool solely by nighttime ventilation in that climate, but it takes forethought and designing the house to the site-factors on solar orientation & existing natural shading.

Dana is right...in theory.

Few people can appreciate a cool floor, regardless of the weather or latent heat. Better candidate for a evaporative cooler I think, but would start with an ERV as keeping the rH steady would be my goal. I still have the floor going in my basement bath.

Come to think of it, the heat was on in the basement and the cooling going upstairs (with all the glass) just yesterday. Such is the nature of the shoulder months.

Given a choice, and highly depend on climate of course, I would more likely heat and cool from the ceiling, which appears to be the commercial trend.

we do like our cool floor, but ceiling is better.

I did specify "...floor or ceiling...", didn't I?

I kinda like 60F floors under bare feet on hot days, but odds are it would never need to be that cold if the house was designed & oriented for low summertime gain, but for sure 60F ceilngs would never be an issue.

The 1% design temp for Boise is 94F, but even on the 1% days the nighttime lows are below 70F. I've summered near there in decades past (Ontario OR/Payette ID), and the diurnal temperature swings can be gia-normous on killer-hot days which usually correspond with clear-air/low humidity days for maximal nighttime radiational cooling, unlike the eastern seaboard with 75F fog at night on 95F days. But even with not-so-well insulated houses exterior shading and night ventilation can work pretty well if you're willing to actively manage it. It's not the same as setting a T-stat, to be sure, but with window gains designed-out and some interior mass designed in it could be dead-easy.

The mid-40s summertime dew points are pretty comfortable too- not nearly as drying to the skin & eyes as in parched desert areas, and nowhere near the steam-heat 65-70F+ dew points of the mid-Atlantic. No need for ERV- HRV under dehumidistat control would work (in any season- crank it down to 30% for winter, up to 40-45% for summer.)

The Coolerado variation on swamp coolers keeps the humid air separated from the conditioned space air and would work extremely efficiently in Boise but I suspect simply designing out load would make even that less attractive as a solution- it depends on the actual load. But if the load is substantial, you won't beat it on efficiency with any compressor based system in that climate:

http://www.coolerado.com/products-files/2012/M30/M30_brochure_2_2012.pdf

60F exceeds the limit for acceptable thermal comfort underfoot anyway.. you don't really want to be below 65 degree floors, residentially. Floors are weak until the sun shines right on them. Of course if the sun isn't shining on them, the load isn't that high. it's complicated.

Ceilings, much easier.

I am extremely unimpressed with the coolerado. having to dump all your cold air after one pass around the building isn't exactly the most efficient thing you can do. Any standard ECM fan would negate most of their fan energy comparison claims and run circles around it for efficiency.

I sure appreciate everyone's responses. Reading in between the lines I come up with the conclusion that Boise would be a very good candidate for a radiant heat/cooled ceiling, but we are a little hesitant with delving in to some areas we don't have a lot of hands on, practical experience with. My architect and I are at the stage where we are trying to complete the envelope stack-up and the window placements. Orientation is not a factor we can really play with for a number of reasons but window specs we can. I am all for using shades to limit heat gain.

Once I get my unresolved envelope questions hammered down, would anyone be interested in doing the radiant design? I'm not looking for a freebie here. I am willing to pay the going rate for the load calcs and a design. What's the best way for me to arrange/communicate with someone who is willing to do this type of design without tying up the forums (although I'll bet there are a lot of interested people in this subject).

If some of you respected experts are interested, my email is [email protected]. Hope I am not breaking any forum rules here. Thanks. This is all very encouraging.

I am extremely unimpressed with the coolerado. having to dump all your cold air after one pass around the building isn't exactly the most efficient thing you can do.

I didn't get that from reading the specs. Inside air can continue to circulate and stays separate from outside air via the heat exchanger.

I don't know what you're reading. the primary unit they advertise is 100% fresh air unit: that means every Cubic foot of air into the building must come out.

http://www.coolerado.com/products/how-it-works/

The ECM fans in the Coolerado move far more air than is removed from the building (about 1/3 of the volume moved by the fan ends up in the building, but it's a tweakable ratio that can be optimized for the application) but yes, what's coming out of the ducts is 100% fresh ventilation air in the most basic units. Fan speed is variable and load-tracking fan speed control with PID type T-stat feedback is the standard "-A" option. (It's not that different from the PassiveHouse approach to heating with 100% ventilation air.) Some of their commercial-sized units have air recirculation with variable mix volumes though.

Fan energy issues aside, it's the compressorless aspect is what gives the Coolerado double-digit COPs on grid power expenditure. Ductless mini-splits can probably meet or beat it in more humid climates, but in Boise a Coolaroo with load-tracking control would do better.

Kevin: It's always worthwhile to use an energy use modeling too like DOE2 or BeOpt when trying to nail down the true load, and optimizing the glazing type & sizing to manage those loads, and give better numbers than a Manual-J type estimation. (BeOpt uses DOE2 underneath, but is designed for cost-optimizing the performance of the building. It's a freebie download. See: http://beopt.nrel.gov/ )

But the basics won't change- if you have big un-shaded west-facing windows (even heat-rejecting low-E) it will raise the peak loads. Minimizing the size helps, but operable exterior shades or even insulating shutters can decimate the magnitude of those gains.

There are variations on insulating shutters that might suit the architecture with benefits beyond just shading the most convenient of which are rolling venetian-blind types that can be obscuring (or not), and can be a great wintertime performance-booster, but have the limitation of cutting significant daylight when fully deployed:

http://www.enviroblind.com/rollingshutters.html

But there are hinged & sliding versions that look more like traditional hinged shutters too.

Exterior shades come in a variety of translucency & colors & textures too. Coolaroo has a big chunk of the US market, but there are many others. They're pretty good at killing solar gain with less reduction in daylighting function, but don't have the winter season benefits of an insulating shutter.

Yes, it has great efficiency. but when you factor in the lost energy in exfiltration it looks a LOT less attractive. it's like comparing atmospheric to sealed combustion boilers: the air losses are not factored into the traditional efficiency calculation, but they are real and need to be seriously considered. Frankly, this unit is "cheating" by putting its losses into factors that are missed on a COP energy calc.

Heating a passivehouse for 1 week a year with 95% efficient heat recovery using an ERV and duct heater is a *wee* bit different than doing your primary cooling via this method. in comparison with the worst parasitic electrical offenders, this may make sense, but as an actual energy solution, frankly, it sucks.

The whole point of DOAS ventilation in commercial is that your airflow rates are for air quality, not cooling-level airflows.