Ross and Witmer 
The heating and cooling loads in your home drive how much your HVAC system has to run to keep you comfortable summer and winter. The term “load” refers to how hard any system has to work to moderate the temperatures to livable levels. HVAC engineers calculate the loads based on factors that directly influence comfort.
Design Load
Of the three different loads, the design load is the one that’s the easiest for architects and homeowners to manage. The design and construction of a home impact how much energy it will use. HVAC contractors use Manual J software to learn the design load of homes when determining the best size for new systems. The more energy efficient a home is, the lighter its design load is.
The degree of insulation, construction materials, amount of air leakage, orientation to the sun, and quality of windows and doors impact how much conditioning it will need season by season. Even homes with high design loads can be made more energy efficient through home improvements that vary in cost from inexpensive to those requiring a substantial investment.
Extreme Load
The extreme heating and cooling loads take into account factors like the highest and lowest air temperatures for the home’s particular location. Of the three types, the extreme load has the lowest impact on the size, or capacity, of an HVAC system, since extreme temperatures rarely last long enough to make a measurable impact.
Part Load
HVAC contractors base the capacity of the system to keep homes cool or warm primarily based on the combination of the part and design load. The part load takes into account the normal temperature swings throughout a 24-hour period. A well-insulated and tight home doesn’t require as much conditioning during part-load periods because it resists temperature change better, compared to inefficient homes.
To learn more about heating and cooling loads and how they influence your HVAC system, contact Ross & Witmer or call us at 704-392-6188.