Radiant heat for radiant cooling?

[bmxdad]

Question ... can a radiant heating system be used as a cooling system too? Or would there be a moisture problem? Just a thought question ....

I have a friend who is building a new house, and wants a finished concrete floor with radiant heating ... she's looking for A/C too, but wanted to know if the floor would be able to cool the rooms down. I told her there might be a moisture problem, but didn't really know.

 

[B.C.Biker]

I'm no expert by any means but a friend of mine built a new house about 5 years ago. Cools real nice all summer. Uses wood boiler outside. Circulates all evening and maybe the daytime too. Zero moisture problems , might be climate dependant? About a 1200sqft story and 1/2.

 

[matt_i]

You can take heat out via heat transfer....it could be a challenge to do that. But...

I think you will run into problems unless you also run a dehumidifier.

Simply pulling out heat (reducing temp) makes the air cold and clammy as you move toward the dew point and increase the relative humidity.

 

[NUTTSGT]

I would think if the floor was cooler than the room, it would start sweating much like a garage floor can do.

 

[finn]

If the floor is below the dew point, it will sweat.

Probably not a problem in Arizona, but a disaster here.

It would be inefficient, also, as the delta t between the air and floor would likely be small.

How do you plan to chill the fluid in the floor tubes?

 

[Kaizen]

You could if you were running a compressor with an air to air heat exchanger or geothermal. just running it in heat mode probably not. In theory if the metal outside boiler cools down to say air temp of 60 at night she could run it and remove some of the heat but not like ac she is used to.

 

[yeldogt]

The systems that are able to chill water - I believe start at 5T. I have a neighbor that has his converted barn cooled with his radiant system -- it also has some convectors. The building must have independent humidity control -- but that's installed in high insulation buildings anyway. It requires the correct installer.

His dehumidifier looks like a mini split with a separate compressor -- so he is not adding heat to his building when the dehumidifier is running.

It would be a problem in a garage that open to the outside often.

 

[Firebrick43]

The issue with humidity makes chilled water a silly choice. A dehumidifier is an air conditioner. If your going to spend the money for energy you might as well just use an ac system.

The university here has steam heat/chilled water in the central areas of a lot of the residence halls. The walls sweat and feels very clammy. They have also had mold
Issues at times

 

[yeldogt]

The issue with humidity makes chilled water a silly choice. A dehumidifier is an air conditioner. If your going to spend the money for energy you might as well just use an ac system.

The university here has steam heat/chilled water in the central areas of a lot of the residence halls. The walls sweat and feels very clammy. They have also had mold
Issues at times

That's because of poor humidity control -- a proper dehumidifier will remove more water than an ac unit given the same KW input. With radiant cooling you are not installing ductwork -- the one system is doing both.

Radiant cooling is all about humidity control

 

[bwringer]

Given that Puyallup is on the "wet" side of WA, I'd say nope. Looooooots of humidity thereabouts.

Also, the humidity would be accumulating on the floor, which is rather suboptimal.

A few hundred miles to the east, in the desert on the other side of the mountains, and you might get away with it.

 

[bmxdad]

It would be a problem in a garage that open to the outside often.

I'm not doing this. A friend is building a house and using the radiant heating for the rooms, and will have polished concrete floors through-out. She was wondering why she needed a separate air-conditioning system. 6 or 8" walls, so it's super insulated.

 

[johnnyradiant]

Take all the 'mechanical' issues out of the equation. How comfortable would that be on your legs and feet? Before the floor started working as a cooling surface I think you would be in a feels like it's cold in here scenario and it would be uncomfortable to walk on or work standing up on for any length of time. Your legs can also start aching when working on an over heated floor too.

 

[yeldogt]

Take all the 'mechanical' issues out of the equation. How comfortable would that be on your legs and feet? Before the floor started working as a cooling surface I think you would be in a feels like it's cold in here scenario and it would be uncomfortable to walk on or work standing up on for any length of time. Your legs can also start aching when working on an over heated floor too.

One would think this to be the case --- It's not my experience. Now I have not been in many .. nor have I done one myself. But the OP's friend doing a concrete one -- is the ideal floor covering.

 

[ard]

Take all the 'mechanical' issues out of the equation. How comfortable would that be on your legs and feet? Before the floor started working as a cooling surface I think you would be in a feels like it's cold in here scenario and it would be uncomfortable to walk on or work standing up on for any length of time. Your legs can also start aching when working on an over heated floor too.

Plus cool air sinks- the floor will be cold, your head will be warm- and nothing around to move the air.

She should look int Ground Source Heat Pumps. GSHP.

Crazy AC efficiency.

 

[willymakeit]

Don't think it's done much because of efficiency. The project I'm running would have it if the payback was worth it. This is about 100,000 sq.ft of radiant heat system.

 

[Radiantec Guy]

We have actually tried this by hooking up a condenser and running chilled water through the floor in our office in VT. Many of the comments made by other posters above are accurate.

The number one issue we had was controlling the condensation. We ran a floor sensor to control the slab temperature so that it didn't get too cold. But, this was an office environment and it just felt clammy. The paper in the copier would jam up because of the moisture. After a few weeks we installed a window mounted a/c unit to take care of the humidity problem and it worked. Our moisture problems were gone.

The biggest issue, in my opinion, was that it was an uncomfortable environment. Much in the same way that it's difficult to explain to someone how comfortable radiant heat is if they've never experienced it, radiant cooling was very uncomfortable. Even though it kept the space cool and the system "worked," I really disliked the feeling. It was like being a cold cave.

Our application was in a 2nd story with the tubing installed on top of the subfloor in a 2" slab. Just my $.02!

 

[eddieK]

I'm not doing this. A friend is building a house and using the radiant heating for the rooms, and will have polished concrete floors through-out. She was wondering why she needed a separate air-conditioning system. 6 or 8" walls, so it's super insulated.

To warm a space all you need to do is add heat.

To cool a space you need to remove heat, adding cold does not do that in any form efficiently. Air conditioning is just that, it removes moisture and heat and transfers it to where it is desirable (outside).

If mold is not a concern...try it.

 

[ard]

We have actually tried this by hooking up a condenser and running chilled water through the floor in our office in VT. Many of the comments made by other posters above are accurate.

The number one issue we had was controlling the condensation. We ran a floor sensor to control the slab temperature so that it didn't get too cold. But, this was an office environment and it just felt clammy. The paper in the copier would jam up because of the moisture. After a few weeks we installed a window mounted a/c unit to take care of the humidity problem and it worked. Our moisture problems were gone.

The biggest issue, in my opinion, was that it was an uncomfortable environment. Much in the same way that it's difficult to explain to someone how comfortable radiant heat is if they've never experienced it, radiant cooling was very uncomfortable. Even though it kept the space cool and the system "worked," I really disliked the feeling. It was like being a cold cave.

Our application was in a 2nd story with the tubing installed on top of the subfloor in a 2" slab. Just my $.02!

Great feedback, thx

 

[Brian_WK]

There is radiant Cooling in the works but must be mounted high and also need dehumidification to allow it to work. It is still very much in the developmental stage.
This is a run down from a company with a video on youtube

Also on the condensation and polished concrete floors: Every summer in August they have a county fair here the expo buildings are also the hockey arenas the floors are polished smooth concrete with glycol lines in the slab to freeze the water to create a rink. They attempted to run the cooling system one particularly hot humid day to cool the building the water was running out the doors and the floor was so slick that they closed the buildings for the day and ran barn fans and power squeegees to dry it out.

Brian

 

[Vermaraj]

I have radiant heat/cooling in my house. It works well in some instances and not so well in others. If you have wooden floors it takes a day or two to start effectively cooling. Concrete or tile floors start cooling after 2-3 hours.

Radiant cooling is best at keeping a room cool not at getting down to temperature. To cool the house from 78 to 71 will take 2 days. But, I can keep the house around 72 degrees for 8 hours (9am-5pm) with outside air at 85-90 by circulating just 80 gallons of 38 degree water.

I use a Tekmar 406 controller that reads humidity and temperature to determine the dew point. It controls a variable speed injection pump to adjust the amount of chilled water added to the floor circulation loops.

Radiant cooling is great if you have a lot of East facing windows. The floor will not heat up from the sun, making the room very comfortable. However the system doesn't move any air so its pretty ineffective at cooling the house.

After 4 years of dialing in this how we use it:
1.Turn on air conditioners at 7PM, let them cool house during sleeping period. Floor is always in cool mode.
2.Fill 80 gallon storage tank with 35-38 degree chilled water. (1/2-1 hour of chiller operation depending on outside temperature and floor temp, 5-ton Unico chiller)
3. At 6 AM (house temp 70 degrees) shut off air conditioners and chiller leave floor on circulation
4. On a 90-95 degree sunny day, by 5Pm house temp will have risen from 70 to 72-74 degrees. Humidity will also rise from 50% to around 60% but well below dew point. Storage tank temp will be at 70 degrees which is just below shut down temperature.
5. Repeat (all of this is programmed into control system)

 

[bmxdad]

Good info ... I'll pass it on.

 

[ard]

I have radiant heat/cooling in my house. It works well in some instances and not so well in others. If you have wooden floors it takes a day or two to start effectively cooling. Concrete or tile floors start cooling after 2-3 hours.

Radiant cooling is best at keeping a room cool not at getting down to temperature. To cool the house from 78 to 71 will take 2 days. But, I can keep the house around 72 degrees for 8 hours (9am-5pm) with outside air at 85-90 by circulating just 80 gallons of 38 degree water.

I use a Tekmar 406 controller that reads humidity and temperature to determine the dew point. It controls a variable speed injection pump to adjust the amount of chilled water added to the floor circulation loops.

Radiant cooling is great if you have a lot of East facing windows. The floor will not heat up from the sun, making the room very comfortable. However the system doesn't move any air so its pretty ineffective at cooling the house.

After 4 years of dialing in this how we use it:
1.Turn on air conditioners at 7PM, let them cool house during sleeping period. Floor is always in cool mode.
2.Fill 80 gallon storage tank with 35-38 degree chilled water. (1/2-1 hour of chiller operation depending on outside temperature and floor temp, 5-ton Unico chiller)
3. At 6 AM (house temp 70 degrees) shut off air conditioners and chiller leave floor on circulation
4. On a 90-95 degree sunny day, by 5Pm house temp will have risen from 70 to 72-74 degrees. Humidity will also rise from 50% to around 60% but well below dew point. Storage tank temp will be at 70 degrees which is just below shut down temperature.
5. Repeat (all of this is programmed into control system)

Sounds like a nice system.

Where are you located??

The humidity involved will dictate how well this works in different envoironments. ALSO, you state 'air conditioner'....so you ave both, an aircon (that dehumidifies) and a slab cooling to hold temp?

 

[Vermaraj]

location Westchester, NY. 20 Min north of NYC.

Yes, three separate aC zones to cool then floor holds temperature during the day. I also have chilled water cooling coils on two standalone ERVs. Theoretically the radiant floor and the dehumidified air from ERVs should be able to cool and hold temp. In reality, ERV cooling coils don't make a dent in the humidity. Condensate can be measured in drops.

 

[yeldogt]

latent and sensible heat .. it gets complicated. You can't just lower the temp w/o the humidity being in the 50% comfort range (or lower).

A properly sized AC system is removing a lot of water if you live in a humid part of the country -- same with a very tight house. Radiant cooling is not going to remove the humidity - you need fan coil or a separate dehumidification system to do this.

You can be very comfortable at 78 with 40% humidity and very uncomfortable at 70% with 80%. It takes a lot of energy to remove that water from the air.

As houses get tighter w/ greater insulation the need for dedicated humidity control increases -- but, it's often overlooked. The new VS HVAC equipment works much better but even with those systems .. overcooling is often required to get the humidity down to comfortable levels. At my place in PA it's not uncommon for the dehumidifier to be running along with the AC unit to remove humidity on a cold wet day. There is not much heat to remove -- it's all in the water vapor.

 

[yeldogt]

location Westchester, NY. 20 Min north of NYC.

Yes, three separate aC zones to cool then floor holds temperature during the day. I also have chilled water cooling coils on two standalone ERVs. Theoretically the radiant floor and the dehumidified air from ERVs should be able to cool and hold temp. In reality, ERV cooling coils don't make a dent in the humidity. Condensate can be measured in drops.

5 ton was the smallest air to water system I could find -- when I added up all the additional components required to make everything work for both radiant cooling and heating ... it was more more expensive and still too many unknowns. Too many controls and complexities. I'm doing my latest house with both ducted HVAC and a combination warmbord radiant w/ slab radiant. Makes for a great system -- they all work together. Having the duct work makes incorporation of the make up and fresh air systems easier.