Radiant Cooling, Sun on the floor

NRT_Rob

When calculating a cooling load and figuring out a radiant floor cooling performance, one thing that's tricky is that performance can go WAY up when sun is shining directly on the floor.



Anyone have an easy way of accounting for this when estimating a radiant floor cooling panel's performance???? Head, spinning...

NRT_Rob

also

all the lit says radiant ceiling should be able to do over 20 BTUs/sqft for cooling.



Yet it should also be about double its heating output at an equivalent Dt.



I can't find anything showing radiant ceiling out put at a 20 DT to water temp for heating at over about 5 BTUs/sq ft, which would put cooling output around 10 BTU/sq ft.



thoughts? Head, really spinning..

icesailor

Radient Cooling:

How do you keep a radient cooling panel from sweating and turnng to a mold panel?

NRT_Rob

easy

control your humidity and your water temps.

icesailor

Radciant Cooling:

Easy? The easiest way to control humidity is through air conditioning. Where I work, the humidity is always high. There's a fog factory just off shore and the dew on the leaves can provide up to 40% of water to plants in the summer. Standing under a tree in the summer at night may require an umbrella or a rain coat.

It must be expensive to run two systems. 

NRT_Rob

no real AC involved

we maintained a rock steady 50% RH in our shop all last summer with just a chilled water coil. That's pretty easy.



no AC ductwork at all, just our trusty ERV.

Gordy

control the sun

 Through proper soffit overhang designs, Low e glass, and window treatments.



A radiant cooling systems design goes farther than the system itself. There needs to be building design involvement. But then I'm sure you know that already Rob.



I would still like to see total operating costs for a well designed radiant cooling system verse a standard forced air cooling system. I'm not sure there is much of an edge...yet by the time you add it all up. Dependent on the climate of the dwelling the system is operating in. Example in the south west region yeah low humidity. Southern, and midwestern regions would be tough here in the states.



Gordy 

Bob Gagnon plumbing and heating

Radiant Cooling

I shut all my curtains when running my radiant cooling. With the sun shining in it doesn't get cool that fast. Ice Sailor, to reduce humidity and cool and move the air I simply send cool well water through a fan coil unit I made out of baseboard element, it works great. When the temperature outside is 100 degrees the temperature in my house stays about 70 degrees. I have been using this system for 10 years and have had no mold or humidity problems. Where in Ma. are you, I'm in Lowell.



Thanks, Bob Gagnon

Gordy

Bob

 Are you running the same temps through your radiant panel as you are through your coil unit?



 Would you be running a constant circulation on the panel side of the system?



 What kind of delta t's are you experiencing on the panel side?





 I have a ceiling radiant set up. But I have no duct work. Contemplating radiant cooling. But I have city water, I'm quite sure your well water is much cooler. I see from your schematic when you are cooling you are watering the lawn? Not sure if I condone the use of precious resources like that.



  All though I have read that Phoenix AR. day, and night temps have risen since its build up with all the pavement, and ac units running now compared to when it was just a hole in the wall. Makes sense in other big cities also. I guess water the grass, and help cool the atmosphere or run the ac, and help heat it up, and increase the load.





Gordy





Gordy

Bob Gagnon plumbing and heating

Radiant Cooling Questions

Gordy, I run the well water first through the fan coil, so it is a couple of degrees cooler than when it goes through floors and ceilings. The well water temperature is about 56 entering the house and I get about a 4 or 5 degree delta tee when it leaves the house, the lawn watering works good because when it's hot and you need air conditioning, that's when you need to water your lawn and garden more. It's fair to say that I would be running the well pump for my lawn and garden anyway, so I'm getting nearly free air conditioning, except for running the circulators. My well is only a 12' deep point driven well. The comfort from this system is unbelievable, I highly recommend it.



Thanks, Bob Gagnon

NRT_Rob

well

if you discount the actual cooling/dehumidification energy used which should be similar in either case, our entire distribution energy load (and most normal sized homes would be) a 25 watt dehumidification pump, a max 45 watt circulator, one regular 90 watt circulator, and 40 watts of fan. and the regular circulator is just because that's what is built into the altherma we're using.



that's 200 watts for total dehumidification, fresh air, MERV 12 filtration, and cooling distribution. Compare that to any typical HVAC system blower PLUS an ERV or HRV fan energy draw. should be a significant improvement. and with a radiant ceiling install I think I can pencil out a complete radiant based and IAQ mechanical solution at less than 2x the cost of a good quality air system. Not too bad. Might even have a payback calculation on that compared to most typical AC systems.

Mark Eatherton

It wouldn't work in Denver....

The Denver Water Board has outlawed outside use of water between the hours of 10 AM and 6 PM...



We ARE on the edge of the Great American Desert, and there IS a water shortage issue world wide. Hard to tell that looking at the flooding going on around the world (Australia and South America), but it is here to stay.



Interesting proof of concept tho. There are a LOT of ways of being able to produce cool water temperatures, including mechanical (vapor compression) and evaporative (Coolerado) http://www.coolerado.com/



We have the technology, we just need to marry these technologies to make them work.



I also agree with keeping it out of the envelope in the first place, so you don't have to reject it mechanically. There are dynamic windows available that can virtually eliminate the solar gains that come through windows. See http://www.sage-ec.com/



and Raven Brick makes a neat window product, see http://www.ravenbrick.com/ and click on Raven Windows.



We have had discussions about marrying their window technologies with our heated window technologies and have determined that it is physically possible.



These ain't your Grandpas windows :-)



ME

Bob Gagnon plumbing and heating

In Denver

Would you be able to pump the water out and through a heat exchanger and back into the ground? Or you could run a closed loop system underground, like a heat pump, which would be more efficient because you would be circulating the water instead of pumping it, but you wouldn't have the water available for lawn watering, if you lived where they do allow it. Thanks for posting the raven window site, this could be BIG, if it pans out. I have been waiting for windows like that for a long time. Windows that shade the sun out during the warm weather and allow it in when the weather gets cooler will turn every window into a solar collector.



Thanks, Bob Gagnon

Mark Eatherton

We don't have wells in this city...

at least we aren't SUPPOSED to have well in the city limits. All water is supplied by the Denver Water Board, and it comes from the mountains. One of the largest underground water utilities West of the mississippi.



And yes, direct burial of ground loops is another way of providing base cooling. You shouldn't have to worry about exceeding the dew point using THAT system :-)



ME

Gordy

Hmmmm

 I live in town, and I'm on municipal water, but I do have a dry well on my property for storm water managment. It was put in when the house was built before storm sewers were in this area.  I asked the city about it because it is close to the alley that runs behind my house. They say its my baby....of course.



 Its about 20' deep with a foot of water in it most times. This coincides with the level of the river across the street. I think I will be doing some temp readings this summer to see what that water tends to be through out the season. May be some potential there. Problem is its about 70' from the house. If the water temps are marginal to be of any radiant cooling benefit I may have a pretty good temp rise before the water gets to the house.





Gordy

Bob Gagnon plumbing and heating

Well, Well, Well

Gordy, I drove  a point down through my basement floor and the water is 56 degrees at the end of the summer, a little cooler in early summer. It seems to be about the right temperature to cool the house without condensing on the radiant surfaces.



Thanks, Bob Gagnon