Systems are sized by considering home size, foundation, building materials, insulation and weather stripping, attic ventilation, and other factors. This sizing is called a heat-loss/heat-gain analysis. Some dealers call this a "Manual J" calculation. Surgi's offers this service free to potential buyers and existing customers.
Proper sizing is important to you because over-sized and under-sized systems can reduce your comfort and increase your utility bill. Oversized systems can cool or heat your home too quickly. A system that is too large will drop the temperature before it can adequately remove sufficient moisture from the air - causing your home to feel warm. Undersized systems will not be able to achieve the desired temperature on extremely hot or cold days.
