Hello 3cityblue, We recommend flipping to radiant ceiling to accommodate cooling. In some climates dehumidification will be needed. You can use a boiler / chiller combination, or a reversing chiller to heat and cool the hydronic water. A Honeywell IAQ thermostat has the dehumidification control needed. Let me know if I can help. Dean

Posted By superplumber_mi on 03 Mar 2011 08:08 AM
I am quoting a 24,000 square foot building for radiant heating & cooling in the floor with some sidewall.  It's a historical building so I am limited on wall space.  I have never done radiant cooling.  I have talked with Radiant Cooling in Chicago yesterday about the project.  They want to use heat pumps from Germany but I want to use something locally.  Do you know of US made heat pumps in the 5 ton range?

How does the dehumidifier handle the humidity load?  I thought about installing a few mini-splits for dehumidification.  I am asking for any advice since I am in a warm and humid Michigan climate in the summer.

If you haven't already, look up Beka USA. They have a lot of good info on their web site. I seriously considered using their in-ceiling radiant mats until I dumped the entire radiant heating/cooling idea for the ICF house I was building for myself.

In my opinion ceiling radiators make sense for radiant cooling.






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Ceiling Heater

I would expect that with radiant cooling, some air circulation (like ceiling fans) would be a big plus. Less condensation, more heat transfer, more occupant comfort.

dmaceld.. Why did you abandon in floor radiant heating in your ICF house? I'm about to build a 2000 sf ICF bungalow and the ICF contractor recommends radiant heating. I beleive that HRV and A/C are still required and will need duct work. I would appreciate any insight you have. Thanks

Posted By kkerr on 16 Mar 2011 08:32 PM
dmaceld.. Why did you abandon in floor radiant heating in your ICF house? I'm about to build a 2000 sf ICF bungalow and the ICF contractor recommends radiant heating. I beleive that HRV and A/C are still required and will need duct work. I would appreciate any insight you have. Thanks

Cost and complexity of installation. To do in-floor radiant you need warm water. I was going to use a direct exchange heat pump from Earthlinked Technologies to provide the heated water. I was going to need 4 wells for the ground loops and it was going to cost on the order of $10k just for those. I also changed from doing in-floor to doing in-ceiling since I wanted cooling and in-floor doesn't work the best for cooling. Both in-floor and in-ceiling require special installation techniques and materials and none of that is simple or cheap.

Then my HVAC contractor told me about the Daikin air to air heat pump he had just learned about. It had pretty much the characteristics I was looking for, efficiency of performance and ability to supply heat down to the design temp, 9°F, for our region. It would also take care of cooling. Since it was a air-to-air system conventional ducting could be used at less cost than the radiant installation.

Since the crawl space was going to be sealed within the ICF shell I decided to use it as the supply plenum. That did two things, reduced the cost of ducting, and provides a slightly heated floor throughout the house in the winter. I insulated the attic with spray foam on the underside of the roof deck so I use the attic for the return duct. I have a duct that goes from the attic space to the air handler which is in the crawl space. I have floor registers scattered around the perimeter of the house, and return grills in the ceiling around the house. I have an ERV. We have ducting from  the laundry, both bathrooms, the attic, and from near the kitchen going to the stale air inlet. The fresh air outlet dumps into the air handler return air duct that goes down to the crawl space. We have no regular exhaust fans in the bathrooms.

The end result is I have a heat pump that puts out heat down to 0°F, constant air circulation throughout the house, a constant temperature in the house, no drafts, no cold spots, no hot spots, a not-cold floor in the winter, and a cool house in the summer, all at nearer the cost of a conventional forced air heat pump system. The only downside is that floors are cool, but not cold, in the summer when the AC is running because of the cold air under the floor. But I couldn't have done it if my HVAC contractor, who is also my nephew-in-law, hadn't been open minded and willing to work with me. I also think I should have increased the insulation on the crawl space portion of the walls since the crawl space goes up to around 85°F during heating.

Hello dmaceld, We've used radiant floors for cooling, they can get the sensible heat out of the space, but aren't really comfortable because the ceiling and walls are still warm. What works is radiant ceiling cooling and heating systems. The xlath radiant ceiling modules use 1/2" PEX and are made for drywall systems. They have been used in over a dozen buildings with great success. In most cases you don't need to do the floors. The Daikin Altherma reversing chiller would be ideal in your climate with these modules.

a well insulated shell should mitigate the "warm wall" issue if you can meet load with an emitter. I do like ceiling though.

Why are you using steel panels though? Aluminum should perform a lot better.

Hi NRT.Rob, Look at the thermographic image on the xlath website. The temperature spread on the steel modules was about 10 degrees F. Notice that the image was taken at 4:30 PM. The outdoor air temp was 103F and that room's mean temp was 78F. That room is a second floor west facing bedroom, the most challenging space we have to work with. The building standard for cooling is 20 degrees below out door temperature. With the steel xlath modules we are maintaining 25 degrees. That is better than standards. Aluminum performs better but costs more. The steel performs good enough and does so at a significant cost savings over aluminum.

20 degrees below outdoor? all the standards I've seen specify a 75 degree indoor temp while cooling, not a floating temp relative to outdoor temp (though I do like that in concept a bit better than a fixed temperature). What standard are you using?

not trying to beat you up or anything but so far most people I know would be pissed if they couldn't get the temp into the 70's at least. I'm mostly curious as my own adventures into radiant cooling are fixed on a 75 degree room temp, so this would impact feasibility of course.

20 degrees below outdoor is an easy number to verify - just turn the AC to max and then measure it. But no idea if this is relevant to existing standards.

The outdoor design temperature here is 95F, and 20 degrees depression hits75F at that temp. For that same house, the homeowner just jams the thermostat as low as possible, the downstairs living / dining and kitchen maintained 67F on the same day.
The chiller was running on for 10 minutes and off for 20 minutes, a 30% duty cycle on a day well above the design temperature.

Radiant Cooling Systems rely mainly on the direct cooling of occupants by radiative heat transfer. Through radiative heat transfer,people in the room will emit heat that is absorbed by the radiant cooling surface!


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SIPs

Radiant cooling depends on careful humidity control. Ceiling fans are not used.

actually, forced convection on a radiant ceiling plane can increase output 10% to 20%. usually you would do this with the indoor air supply diffuser, but a ceiling fan would do the same thing.

The application of a ceiling fan to a radiant ceiling is like wearing a baseball cap with your tuxedo. I think a variable speed air handler would be in order. But if you have a picture, by all means...

In heating mode I would normally agree. but people generally enjoy the sensation of evaporative cooling in the summer. I don't think a ceiling fan is any horrible affront to comfort in that case.

I agree with Rob,
Some air movement really helps comfort in a warm space, and some conditioned outdoor air is nice too. There are three components to comfort: Radiation 50%, 30% Convection and 20% Evaporation. A good comfort conditioning system will address all three issues. In the past the job was to get pretty good comfort at the lowest installation cost. In the future the job will be to get pretty good comfort at the lowest operating cost. We are somewhere in between now.

Glad to see the experts on this forum starting to become more comfortable with radiant cooling. I have learned a lot here and through other research and am convinced that is the way I will be going when I'm ready to build (2 years still). Know it will take some engineering, starting with the load calcs, and then a matter of specing the most cost effective and constructable system (construct-ability is high on my list). Excited to get my plans done and get started. Thanks to all and hope to engage further.

Hi 3cityblue,
It is fun and a bit stressful considering alternative systems like this. Monterrey Energy Group has a lot of experience designing and planning these kinds of systems. They can help with load calcs and system design and will help you get started with a good plan. I"m sure there other engineers out there like dmaceld who could do a great job too, and hopefully we will hear from more of them.

You can really help yourself if you consider the basics of passive building design too. Simply put; make the long axis of the house east-west, limit and shade east and west facing windows, increase south facing windows a bit, but provide an overhang that shades the glass in summer and allows sunlight in winter. Provide for through the house ventilation in summer. Those simple rules will make the house responsive to the seasons and minimize the room loads. This increases comfort and decreases operating costs.

enJoy Dean