Low Airflow Rooms
It seems that almost every house, whether it's brand new or 100 years old; every house has at least one room that just doesn't seem to get comfortable. The rest of the house can be the perfect temperature, but that one room is too cold to use in the winter and too hot in the summer. And fixing it, well that is not cheap! You'd almost have to give your first-born for a contractor to come in and reroute your ventilation to solve the problem. Yeah Right!
What's Really Wrong?
If we take a closer look, the problem is either that the Heating and A/C unit (furnace with central air) is undersized, or the ventilation is poorly designed and does not provide the proper airflow to each room. Let's visit each of these individually:
Undersized Furnace - Hopefully you don't have an undersized furnace. If you do, the reason your room(s) aren't getting to a comfortable temperature is because the unit is not powerful enough. An undersized furnace is not capable of outputting enough heat at a fast enough pace to actually raise the temperature of the room(s). If your furnace isn't properly sized, your only solution is to replace your furnace.
Poor Ventilation System Design - Designing and installing efficient ventilation systems is not a trivial undertaking, as the ducts need to ensure there are enough bends and turns to provide the proper back pressure, without also having too many leading to too much resistance. In addition to getting each duct run just right, the ventilation designer has to also make sure the whole system is load balanced. Without proper load balancing, there will be more airflow in some parts of the house than the others.
Enter - The Register Fan
If you're not sure of the cause of the low quality airflow in some rooms of the house, or if you've determined that it's due to poor ventilation system design, there may be an inexpensive and easy fix. A register fan may be just what is needed to improve the level of comfort in your room(s).
The register fan is an inexpensive (~$40) fan that is specially designed to fit right on top, or even replace, the registers covering the vents in the room(s) with low quality airflow. The fan operates by blowing upward - by pulling the air into the room. This pulling effect efficiently provides for a better airflow into the room, allowing you to get the temperature just right.
There are two types of register fans available - they are designed to either sit on top of the existing register; or to replace the register and sit flush with the floor. Because of the size restriction of the fans that replace the register, these fans are usually less effective.
Maybe a register fan isn't going to miracuously fix your airflow problems, but with the price and availability, it's worth a shot before spending big bucks with a contractor. Register fans are available on the web and at your local home improvement stores.