There is much more to selecting the proper size of HVAC equipment and system than simply the square footage of a home or business. Many companies will use a rule of thumb and estimate one ton of cooling (or 12000 BTUs) per 500 to 600 square feet. This method is quite simply the lazy way to figure out the best needs of a customer. Many factors should be considered in order to find the most efficient and optimally performing HVAC unit for each unique situation.
At ETR, we never use shortcuts or a general rule of thumb. We use a DOE recommended ASHRAE engineering form called a Manual J. Manual J HVAC load calculations determine how much heating and cooling a house actually needs. This expertly created form takes into consideration factors such as insulation thickness and type, window glazing and direction, your home's orientation, window types, areas of all the surfaces that gain or lose heat, and even the presence of overhangs from porches. At ETR, our in-house engineers take the time to carefully and accurately enter all the information to arrive at how much cooling and heating the house needs at peak conditions, in BTU per hour, for each room, each zone, and the entire house.
Any HVAC company that does not utilize a Manual J, usually due to inexperience and time or cost constraints, is performing a disservice to their customer. Yes, whatever they install based on the old rule of thumb will blow cold air, but chances are it will not operate optimally and could actually have a reverse effect. Using an oversized system will often result in the following inefficient and expensive consequences:
- A clammy house because they don't run long enough to remove humidity from the air.
- Shorter lifetime for the system because it turns on and off frequently (called short cycling).
- More expensive to install. That extra size isn't free.
- The ENERGY STAR new homes program requires no more than 15% oversizing of cooling systems.
If you are interested in a new HVAC system, give the expertly trained professionals at ETR a call. We will be happy to discuss how the Manual J software can help us take all the relevant information from your home to help you with your HVAC project. We will ensure that you get the correct capacity HVAC system for optimal performance year round.