How do I add in-floor heating to a small area?
There are small radiant heat mats commonly used under tile in  bathrooms. These are electric and can be thermostatically controlled. They are safe to use under carpet and thin type wood flooring.  The mats are apx 30inches by 15 inches and can be connected together to cover the desired area. Both the heater mats and controllers are avail at the home improvement stores or any flooring specialty store.