Radiant Cooling

James Day_2

I have a customer that is very interested in a radiant heated and cooled house in New Jersey.  Is it really feasible to install radiant cooling with such humid climate.  I have many concerns about humidity issues.  Also, does anyone know where to find info on sizing the floor or ceiling for the cooling. Do I have to increase the size of the pipes, or can it run the same size as I would need for the heat.  Any info would be appreciated.

Brad White

Uponor

has literature and design information. It is becoming more common on commercial and institutional projects.



Radiant cooled floors are strictly a sensible cooling means and this goes for chilled beams and radiant-cooled ceilings. Your surfaces must always be above the space dew point. Even with the large areas, there are few BTUs per SF they can absorb. But with modern lighting (LED's and low Watt fixtures of all types), the interior loads drop enough to give it a shot.



To make these systems work,  the entire team has to buy-in. The electrical engineer/contractor has to specify efficient lighting fixtures, the architect specifies the appropriate glass plus materials for sequencing the construction. The GC also has to be fully on board.



To control dew point, a separate air system, often a DOAS (dedicated outside air system) is used. Because this system does more than just cool, it has to dehumidify not only the outside air but more deeply to absorb the room humidity. Lots of people, such as an auditorium? Could be a large system and with energy recovery.



We typically design such companion air systems to have a dew point (leaving air temperature in this case) of 47 degrees F. saturated. Only then will you have a shot at humidity control in most spaces. A unit using hot gas reheat (free energy) is a good way to temper that and not over-cool during low load periods. In winter, not a problem. But this is a DX process, not chilled water. If you DO have chilled water available, great. Use it for the first stage and trim it to 47 degrees with a refrigerant coil. For a residence, I suspect DX only unless the house is large enough to warrant a chiller.

James Day_2

DOAS

What can I use as a DOAS?  Would you use an ERV or is there a specific piece of equipment or brand you can recommend.  I tried doing a search on DOAS and it comes up with alot of explanations, but no equipment.  Thanks    James

Brad White

DOAS

Hi James,

A DOAS is really an air handling unit and the term is just how it is set up. At the core of most is an air to air heat exchanger, in many cases a total energy or enthalpy exchanger which will transfer moisture in each direction. In NJ you may or may not be in this category, on the edge. Personally, when mechanical cooling dominates, I would do this and deal with defrost issues separately.



One can purchase units set up for this application (DesChamps, Venmar and others), or you can cobble your own with a separate air to air exchanger ducted to an AHU which will finish the conditioning.



In our K-12 work for displacement ventilation these can be too complicated to describe here, but a typical process path would look like this:

Supply Path Flow Left To Right:



OA intake - Air Filter Bank-HRV or ERV Wheel or Core-DX Cooling Coil>Optional HG Reheat Coil-Fan and Discharge to Ductwork.



Exhaust Path Flow Right to Left (Counter-flow to Supply)



Discharge to Atmosphere-Exhaust Fan-HRV or ERV Wheel or Core-Air Filter Bank-Exhaust Ductwork



There are more details and refinements such as bypass dampers to avoid HEX pressure drop when free cooling is available. Balance energy savings with simplicity in any project but especially in a house where costs are keener to be felt.



Brad

radiantdave

same except

got a customer who is adding a salt spa wants to heat with and cool with radiant .

here are the problems i have with this job

1) built like a cave salt blocks salt covered ceiling decorative but still everywhere even on walls.stalagtite type salt formations on ceiling for effect.lighting is fiberoptic and possibly salt lamps.maybe even low volt led not much heat gain there unless they use salt lamps theese things heat the salt surounding them .

2) one complete air exchange every hour.not a big deal for heating but humidity issues abound

3) floor is covered in 3" of sea salt and sand r-value for this would be 2-3 again not a heating problem i can adjust for that but cooling ? what can i do that wont completly corode dry salt in suspension is in very high amounts in the air until air exchange . help what equipment should i use to cool this and maintain a 20 minute recovery between uses?

all in the name of good health

CMadatMe

Where in NJ

Uponor has radiant cooling. I can tell you though that needs to be slab or lightweight pour. Where in NJ are you? Luck has it that Uponors East Tech guy lives in the NJ market. Drop me a e-mail. Would be able to get you together with him and the local reps.

Nick Ciasullo

I have a few commercial jobs running locally

Our company did the Comcast Building in Philly and Microsoft School of the Future.  You can pick up most of the load with the tubing, and there is the big payoff for operational cost.  You will dehumidify the space, but now your horsepower requirements for air movement are reduced dramatically.



Nick

NRT_Rob

we're doing this

with the DOAS strategy in our residential-scale and style shop.



radiant ceiling is best, or high output flooring (warmboard/tile, uncovered slabs).



If you already are using a heat pump (geo, altherma, etc) it's even easier.



If you can remove the latent load in the incoming air and keep all distribution water above your controlled dew point you're good, but we recommend condensation sensors and positive pressurization.