Homeowners know when they're cold and they know where their cold. They may not know how to light a pilot light, or air seal an attic floor, or balance a home heating system, but they know when they are cold. Bedrooms are often the coldest room in the house and most often people just live with it. Stick the kid in the cool bedroom, throw a couple extra blankets on the bed and tell them to finish their homework.

Dealing with a cool bedroom is frustrating. If you turn up the heat to warm the room, the rest of the house gets too warm. Shut all the heating registers except the bedroom and it puts too much back pressure on the furnace. Too often I see a household try to adjust the temperature of walk in freezer one room by closing heating registers in other rooms and soon they have half the registers in the house closed and the home heating system working overtime to satisfy the heating request at the thermostat.

Usually, the home heating system is designed by a professional Heating Contractor that went to HVAC school for several hours a week for a number of years. A Heating contractor must pass an apprentice program before he or she can even take the test for their journeyman license.

HVAC Education

During the educational phase of the heating and cooling training, they are taught how to do a heating load calculation on a home. They take the heating load and develop a designed heating system that includes furnace size, fan capacity, duct size, air flows, and register size. In other words, heating systems are designed to heat all rooms evenly and to work as a system with all registers open.

If you have one bedroom that is cooler than the rest of the house, one of two things has happened:

The heating system was designed by a contractor that barely passed the test, or

the heating system is broken.

Recently, I had a homeowner complain that they got very little air flow out of the heating register in their dining room. The dining room was cooler than other parts of the house. With a flow hood, I registered a 75% decrease of air flow at the register as compared to the register in the living room. I removed the register grill, took a flashlight and mirror and looked down the inside of the heating duct.

With the mirror to see around the initial elbow, I could see that a flow damper valve was installed in the heating duct. Further inspection showed that all the heating ducts in the home had a flow damper installed near the registers. The damper in the dining room was the only one that was closed most of the way. The homeowner was not aware that flow dampers were a part of the homes heating system.

Heating Duct Damper

Flow dampers are a bit unusual in my neck-of-the-woods, I don't see them very often. Flow dampers are added to a heating system to allow manual adjustment of the flow of air to the registers. With dampers, the flow of conditioned air can be balanced so warm and cool areas of the home can be eliminated. To keep from putting increased pressure on the furnace fan motor, when one damper is closed down another damper should be opened up.

Sometimes, I believe a heating contractor may throw in a bunch of flow dampers when he looses his pencil and can't be sure of how big to make the heating ducts or how many registers need to be in a room.

6 Ways to Boost the Heat in a Cold Bedroom.

Repair Heating Duct:

There is always the possibility that the duct system has a problem that can be fixed. Ducts can become partially or totally disconnected and flexible ducts can become pinched off or collapsed. This is the first and most important fix considering the cold bedroom. This fix will not only warm the bedroom, but also increase energy efficiency and energy savings.

The first step is the inspection of the duct leading from the plenum to the register to be sure it is securely connected. Also, look for holes, crimping, or collapsed areas. Heating ducts damaged by animals is also a possibility that you should be looking for.

Disconnected heating ducts can be reconnected, but damaged heating ducts most often need to be replaced as they are difficult to repair.

Check for a Damper:

The sneaky heating contractor may have placed a damper in the heating duct and kept it a pretty good secret. Look and feel inside the duct by removing the register cover. Also, remove insulation from the outside of the duct, especially near the register and check for the telling signs of a damper. A metal rod with a small handle and a few anchor screws indicate a damper inside. Open the damper and your cool room problems maybe over.

Balance Room Pressure With a Cross Over Duct:

Now we need to talk about room pressure and balloons. Crack the bedroom door open about an inch, turn the furnace on and see if the pressure builds up in the room and closes the door.

The heating system is a circle of air. Air is heated in the furnace, pushed through the heating ducts into a room and then sucked by the same furnace, out of the room, back through the return air duct to the furnace. If the air in the room cannot get back to the furnace, the room builds air pressure, like a balloon, which restricts the flow of conditioned air into the room in the first place.

With an increase of pressure in the bedroom, the conditioned air is forced through a different duct and into an adjoining room.

To fix the potential problem, many homes have cross over ducts installed in the ceiling or over the door that allow the air in the room to get back into the hallway even when the door is closed. In some larger, higher priced homes, they may have eliminated the room pressure problem by installing a return air register in every room.

To balance the room pressure and stop this problem, the two most used repairs are installing a cross over duct through the wall over the door or simply cutting the bottom of the door off so there is a wider gap between the door and the carpet.

Increase the Size of the Duct:

Maybe the Heating Contractor ran out of 8 inch ducting so he decided 6 inch was close enough. There is a real possibility that the back bedroom is cool because the heating duct system was not engineered correctly. When this happens, the best fix is to correct the mistake and replace the duct with a larger one. If the home is fairly new and the Contractor is still around, you might get this done as a freebee.

In this way, the cool room will get a larger share of the air coming from the furnace. This repair can still be a do-it-yourself'er if your willing. Heating duct material, both ridged and flex, can be purchased at your favorite home store. Some zip ties, a few sheet metal screws, a sharp knife and a pair of tin snips should do the trick.

If the heating duct size is simply too small to service the room, besides replacing the duct with a larger one, the only other fix that might work is installing a booster fan in the duct or adding a complete second duct and register.

Duct Booster Fan

Place a baffle in the heating plenum:

This adjustment can be very effective - especially in a manufactured home. A section of the main heating trunk ( the plenum ) needs to be opened up so a metal baffle or shield can be placed in the main trunk line that will direct more air into the heating duct that goes to the cold room. This is a very effective way to grab more of the conditioned air that passes down the main heating trunk and direct it in the direction you want it go. This is an inexpensive and permanent fix that works very well.

Install a Booster Fan in the Duct:

This $30 part won't create more heat, but it will pull more heat to the cool room. The booster fan should be installed as close to the offending room as possible and can be wired directly back to the furnace fan so the booster fan will run each time the furnace comes on. Installing it can be a pain. A section of round metal duct either needs to be dropped down or added to the system. Be sure the duct system is air sealed or this added fan will pull unconditioned air into the system and lower your energy efficiency.