We have a 3 year old house with a forced hot water heating system. The second story has three bedrooms and two baths (master bed & bath with two additional bedrooms and one full bath). The thermostat for the the upper level is in just inside the master bedroom from the hallway. All the bedroom doors on the second floor are closed at night, but the problem is that the thermostat does not equally regulate temperature to all the room upstairs. If we set the thermostst to 64 degrees and we close the master bedroom door, then the bedroom on the south side of the house ends up at about 75 degrees, while the larger bedroom on the north side of the house is about 60 degrees. We have been told by our builder that the length of heating registers is proportional to the size of the rooms. But, then why is there such a temperature differential? Our solution has been to turn the thermostat to about 66 degrees, so that the large kids bedroom is warm enough for children. Then we open the windows in the master bedroom, and close the baffle to the other smaller kid's bedroom on the south sie of the house. There must be a better answer. This is not economical or efficient. Any advice would be appreciated.