radiant heat,radiant cool??

[randydupree]

on my loft style warehouse home we put the pex tubing in the fllor so we can heat it.
but i'm wondering if i can cool the building too by running cold water through the pex in the summer,i'll bury 10,000' of pex underground to cool the water,using the geo-thermal effect.
any thoughts?

 

[djjsr]

Radiant heat works because heat rises. Cool doesn't. You may be able to cool down the concrete, but given the humidity in Fla, I think you'll just have a very wet floor from condensation.

 

[PAToyota]

As an architect, I've seen radiant cooled floors proposed. But as djjsr states, I'd think the single biggest problem is that it would attract condensation and you'd have to have a whole separate dehumidification system.

 

[randydupree]

i never thought of that.
hmmm,anybody else?

 

[sneezer41]

that is the answer

 

[Jaguar Fan]

As an architect, I've seen radiant cooled floors proposed. But as djjsr states, I'd think the single biggest problem is that it would attract condensation and you'd have to have a whole separate dehumidification system.

Hey PAToyota,

How about in the desert of Las Vegas? 8% to 10% relative humidity with 115 degree summers? As an architect, would you suspect/guess it is also inappropriate in the desert?

 

[randydupree]

i was reading on the net about cooling big office buildings and hospitals with cold water,and they are running in through the concrete floors and ceilings,that way they don't spread germs with air blowing through ductwork.
Randy

 

[djjsr]

Since cold air sinks, I guess cooling the ceiling would be better than cooling the floor. You would still have an issue with condensation in high humidity like Fla.

 

[Stuart in MN]

As mentioned, if you had a good enough dehumidification system it may work, but only if there's enough radiant surface on the floor to counteract the summer heat gain. I design water treatment plants for a living; they have big water tanks inside that are full of 45 or 50 degree water, and even in the hottest weather the buildings stay very cool inside, but we have to put in industrial strength dehumidifiers or else every surface would be dripping with condensation.

However, radiant floors aren't designed to react very quickly to changes in temperature, so I would guess using it for cooling wouldn't be very suitable for living space - as the outside temperature goes up and down during the summer, you may have periods where it's either too cool or not cool enough inside.

 

[PAToyota]

How about in the desert of Las Vegas? 8% to 10% relative humidity with 115 degree summers?

Well, obviously the lower humidity will help. Basically, think about what happens to a cold glass of water sitting out. Around here you'll have a puddle on the counter from what condenses on the outside of the glass. A cooled floor is going to do the same thing. If you don't have the condensation problem on the glass, you won't have it on the floor either.

 

[randydupree]

i would have a heat pump ac unit as well,i would not be depending on the floor for all of the cooling,but i sure as heck don't want my house sweating..

 

[dps]

Assuming you have floors that are not hurt by moisture such as concrete or tile, you would have a very effective program used in conjunction with a dehumidifier.

Heat does not rise, as one poster claims, warm AIR rises, and radiant warmth does not work on that principle. Neither does radiant coolth. A large cool mass will even out temperature swings and lighten the load on a heat pump or a/c system.

 

[djjsr]

Heat does not rise, as one poster claims, warm AIR rises, and radiant warmth does not work on that principle.

WHAT? Whether you call it heat or you call it warm air, it rises, unless a blower is forcing it in a different direction. Radiant heat in a floor doesn't have a blower and the heat rises off the floor to keep the room warm. Am I missing something in the laws of physics?

 

[dps]

Radiant heat works by radiation, not convection or conduction. Imagine walking outside on a calm day with a clear sky. It is 50 degrees (F). Walk in the shade and you will feel cool. Turn the corner into the sun and you will instantly feel much warmer. The air is 50 degrees either way. In a house, similar situations exist. In front of a fireplace you will get warm mostly from radiant heat. Move into the "shadow" of the fire (toward either side) and even though you are closer to the fire in feet and inches, you are no longer in its line of site, (which is how radiant heat is transmitted) and you will be much cooler. On a cold night stand in front of a large window and you will feel a heat loss from your body as it radiates out toward the cold glass. Draw a drape in front of it and the effect will be gone.

Warm objects can conduct heat to the air, and the air will rise, but the heat radiates equally in all directions.

 

[randydupree]

ok,heres a question for you guys,if i keep the slab at 75 degrees all winter with hot water,then in the summer keep it at 75 degrees,basicly keeping the slab the same temp all year,will the slab sweat in the summer?

 

[djjsr]

I think it will sweat. I keep the AC in my workshop around 75 in the summer, but keep the doors closed. On humid days, if I open the doors for a while to move something in or out, I get condensation. I found that if I open the doors when the AC is running (maybe creating positive pressure?), it helps keep the humid air from getting into the shop and I don't get the condensation.

 

[dps]

It depends on the temperature and the humidity of the air above the slab. Hot and (relatively) dry air won't condense. Cold and wet won't either. Hot and wet will.

However, running just a de-humidifier would be cheaper than running an a/c compressor. Of course you're also paying something to run at least a circulating pump.

 

[djjsr]

Florida, right? Do you have many hot humid days?

 

[randydupree]

not many humid days here,no more than 250 per year!
thanks for the help.
Randy