Measuring tape

How to Size a Heating and Cooling System

How to Size a Heating and Cooling System


If you’re in the market for a new heating and cooling system, you may think bigger is better for battling mercury that can range from 20s in the winter to 90s or above in the humid North Carolina summers. But the truth is, your best bet for maintaining comfortable indoor temps is choosing a correctly sized system for your specific circumstances.

Outdated information and performance specifications often lead to bad advice from HVAC contractors to homeowners — who then can end up with oversized systems that don’t work efficiently and cost too much to operate. For optimal heating and cooling in Raleigh, NC, choose a correctly sized system that will work well with your space and needs for many years to come.

Size Right for the Raleigh Humidity

The U.S. Department of Energy notes that choosing correctly sized HVAC equipment is particularly important in humid climates like Raleigh’s. In extreme humidity, air conditioning equipment can “short-cycle,” resulting in poor control of indoor humidity. Excessive starting and stopping increases wear and tear and can lead to a shorter useful life for equipment.

Use Standard Sizing Procedures

If a contractor estimates your needed system size based on experience alone, it’s time to find another contractor. Your HVAC service professional should use the Air Conditioning Contractor’s Association of America Manual J and Manual S procedures for sizing your equipment. The procedures specify equipment that is compatible with the load calculation for your home.

Consider Built-in Efficiency

The procedures in Manual J use various factors — including your home’s insulation value, air duct leakage, building envelope and area of walls, ceilings, floors, and windows — to calculate your heating and cooling loads. Your home’s orientation, roof color and number of occupants also can make a difference in load. Calculations for newer homes consider the improvements in efficiency that have occurred in new construction in recent years.

Calculate how much Energy your Home Will Lose

A contractor providing you with a bid for a new system should calculate your estimated peak-hour heat loss. This number represents the expected amount of energy loss during the year’s coldest hour; your new system must compensate for the loss. If your contractor uses old guidelines for calculations, you could end up with a system that is too big — and inefficient — for your needs.

Plan your System Appropriately

Along with your new system, plan for a programmable thermostat that allows for adjusting the temperature remotely and setting schedules. By controlling the cooling and heating of your home for your specific needs, you can avoid the temptation to purchase an oversized system. In the long run, you’ll reap the benefits of better system performance and energy savings.

Work with a Contractor you Trust

If you need a new heating and cooling system in Raleigh, NC, choose a reputable, experienced contractor who won’t try to upsell you on a system that’s too big for your needs. Delta Heating, Cooling & Plumbing is a family-owned business serving Raleigh and surrounding areas. For more information or an estimate, call us today at (919) 256-5120.