We've been enjoying nice temperatures on our carpeted second floor all winter. We have a dense, low R slab foam rubber pad with a relatively dense, low nap wool carpet on top. It sits over warmboard. We've had no problems with the rooms heating up nicely, generally responding to calls for heat within 30 minutes. We had the carpet steam cleaned this morning. The carpets were very damp when the cleaning was finished. I cranked up the radiant to help the carpet dry. 5 hours later, the rooms are still the same temp. Radiant has run non-stop. Does the evaporation of the water carry away the radiant energy? Is this the same effect as sweating in the summer to cool off? Outgoing water temp is around 100, return temp is around 88, and I can tell heat is being delivered. It's very humid upstairs, windows are fogged, but the area is cool.

The heat of vaporization of water is about 965 BTU / lb, so if the carpet & padding are harboring even a couple gallons (16.66lbs) it can take a few hours to cook it all off at 15-25 BTU/hr per square foot, impeding the rate at which the sensible heat (temperature) gets into the room.

A dehumidifier would speed up the drying by increasing the difference in vapor pressure between the air entrained in the rug and the room air, and convert the latent heat (heat of vaporization) back to the room as sensible heat (temperature), which is the right thing to do.

If the carpet is soaked then you should get the carpet cleaning people back out to vacuum the carpet. Carpet blowers would help and can be rented . If you have a/c turn it on , it will act as a dehumidifier. Also you can pull up one corner and allow air to flow beneath carpet. The carpet will mildew if it doesnt dry in a reasonable amount of time.

That's interesting, and just about exactly what happened. After 6 hours of heavy vapor with the radiant cranking, the temp shot up from 66 to 72. The floors are all dry now.

The carpet wasn't abnormally wet. It would have dried on its own in 24 hours, but I just wanted to speed things up. It seems to be fine now.

Putting the carpet in sun or placing it near the heater would also have helped.  rug pad

Or you could open a window.

Nice explanation of the "heat of vaporization" Dana...you one savvy eng-a-neer.

http://www.kentchemistry.com/links/Energy/HeatVaporization.htm