Far too many homes have HVAC systems that are not sized right. Quite often, an HVAC consultant will simply calculate the size of a new system based on what was in the home previously or based on square footage. While square footage of the home is one factor that should be considered in calculating HVAC size, it shouldn’t be the only one.
Here’s what frequently happens with a wrong-sized HVAC system: 1. If it’s too small, it will run continuously in an effort to cool or heat your home. Parts will overheat and wear out before their time. 2. If the unit is sized too large, it will short-cycle, which means it will run for a while, then turn off, then turn on again, once again running inefficiently in a way that wastes money and wears out parts.
Correctly Calculating HVAC Size
Unless you’re a trained HVAC tech, it’s probably best if you don’t try to size your own HVAC system. Hire a reputable HVAC company to do the job — preferably someone who has experience and testimonials from customers who are pleased with the consultant’s ability to calculate the right size.
Some of the factors to be considered in determining HVAC size, beyond square footage, are:
- How many people live in the home
- The number, age, condition, and orientation of windows and the direction that windows face
- Presence of natural shading
- Climate (in our case, that would be hot!)
- Ductwork configuration
- Heat-generating appliances in the home
- Insulation
- Air leakage of the home
An HVAC tech should make note of these factors, then enter them into industry software called Manual J. The consultant should then get a pretty clear notion as to the number of BTUs (British Thermal Units) you need to warm or cool your home. If the dealer doesn’t have your exact BTU size, talk to the consultant about installing an in-between size unit (probably a bit larger capacity to ensure it will do the job). The consultant may also use Manual S software to calculate the size of the equipment.
For more on HVAC size, contact Hansberger Refrigeration and Electric Company.
