There is nothing more annoying than hot and cold spots in your home! (Well, except for maybe your whole home being hot when you want it cold, or your home being cold when you want it hot … )
First off, what constitutes a hot or cold spot? Here in the HVAC industry we usually consider it a true bad spot if there’s a temperature difference of more than four degrees.
There are a lot of different things that could be the root cause of hot and cold spots in your home, but usually, it has to do with air flow…Namely, the hot or cold spot is not getting enough airflow. But why isn’t your HVAC system getting air to that area?
Small/Large Ducts (We Said “Ducts,” Not Ducks!)
Usually, the issue is not your air conditioner or furnace, but the ductwork. The problem could be that your ducts or duct boots (which are hinge pieces of your ducts that connect other ducts together, or connect a duct to a register / vent) are not the right size.
How do you know whether you have the right duct size? You really don’t, but there is a manual published by the Air Conditioning Contractors of America (ACCA) that is all about making sure you connect the correct ducts to your system. It’s called Manual D, and it’s one of the manuals that every HVAC technician has with them when they evaluate your home!
A poorly designed ductwork system can also contribute to hot and cold spots in your home. You may be wondering, “How is a ductwork system ‘poorly designed’? This isn’t part of the interior decorating, is it?”
No, not exactly! It’s not about how pretty the ductwork looks, but about whether it’s laid out properly. Your ducts must be located in the right spots, must be close enough to your air handler, shouldn’t have too many bends or not enough air will get through those bends, and must be designed in such a way as to withstand static pressures. Again, this is where the strict guidelines of Manual D come in, whether an entirely new ductwork system is being installed, or an existing one is overhauled / added to.
Speaking of adding on, if you’ve built an addition on your house, but you’re still trying to use the same HVAC system…that’s a very easy explanation for hot and cold spots. Your HVAC system is not equipped to handle the new addition!
The fix may be simple, just adding adapt and a supply that to his face that’s either too hot or too cold. But it may be more complicated and involve a Manual J load calculation … yep, you’re getting the manuals involved again! And that probably means you’d better leave things up to the techs …