Before You Upgrade, Have A Load Calculation Done

If you are getting ready to upgrade your HVAC system, make sure you obtain an accurate load calculation in writing from your contractor or utility company selecting a new unit.  The U.S. Department of Energy warns that oversizing is the most common mistake made by inexperienced or unprofessional HVAC installation firms. For a variety of reasons, simply matching your old unit in size can result in more furnace and air conditioner than you need. Residential Load Calculation, or "Manual J," published by the Air Conditioning Contractors of America (ACCA) is the industry's standard guide for determining size.  Manual J describes what should be considered when doing a load calculation, such as :

•   the design of your home, including roof overhang, ventilation, tightness and type of insulation

•   measurement of your home's square footage, room-by-room

•   ductwork and registers -- their design and condition, routing, joint seals and insulation

•   window square footage, location, age and condition

•   your family's size, age and comfort requirements

•   the climate, vegetation and lay of the land, and position of your home on the site affects exposure to the sun and wind   

•   the number and types of lights and appliances and how much heat they generate


State-of-the-art software and worksheets can help technicians evaluate everything and avoid miscalculation. Accurate load calculation saves you the added expense and inefficiency of purchasing too large an HVAC system for your home. Bigger is not better. In addition to costing more at purchase, an oversized HVAC starts and stops frequently, shutting down too soon. This causes incomplete dehumidification and leaves the air clammy when the AC is running. Frequent cycling also burns energy unnecessarily and shortens the equipment life.

For more information about upgrading your HVAC, contact Comfort Services. We have experts ready to help you make this important investment for your family and your home.