The most important step in selecting the right HVAC system for your home is sizing it correctly. HVAC contractors use Manuals J and D to do the load calculations, which take into account the energy efficiency of your home, along with other contributing factors. System sizing is critical for your comfort and the durability of the equipment you choose.
A load calculation using Manual J determines the size of the system, while Manual D calculates the size and capacity of your ductwork. Both manuals are interdependent and use these characteristics of your home to arrive at the right size:
- Cubic footage you condition;
- Amount of insulation, including walls, the attic and floors;
- Windows, their efficiency and exposure to the sun;
- Levels of air infiltration;
- Floorplan design;
- Heat-producing appliances indoors and your lighting types;
- Number of household members and their ages;
- Preferred indoor temperatures; and
- Landscaping factors.
Once the HVAC contractors assess your home, you’ll know where you can improve its energy efficiency, which could lower the size of the equipment you need, which saves money initially and throughout the life of your system.
Load calculations are so critical because systems that are too large run for shorter cycles more frequently. In the summer, they won’t remove as much humidity, decreasing your comfort. They also don’t trap as many airborne particulates on the air filter, which could aggravate allergies or asthma. Frequent starts and stops also increase the wear on your equipment, causing premature part failure.
During the winter, the system will heat your home too quickly and the solid objects won’t have time to absorb the heat. Some areas may also stay chilly. A system that’s too small won’t be able to keep your home comfortable during weather extremes.
Proper duct sizing is crucial for your comfort as well. If they’re too small, the noise load increases. If they’re too large, the velocity coming through the ducts will be slower.
If you’d like to learn more about load calculations, contact Team Bob’s Heating Cooling Plumbing. We’ve provided HVAC services for Grand Traverse and surrounding counties for more than 30 years.
Our goal is to help educate our customers in Traverse City, Michigan and surrounding areas about energy and home comfort issues (specific to HVAC systems). For more information about load calculations and other HVAC topics, download our free Home Comfort Resource guide.
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