Your New Furnace: All About The Sizing

Your HVAC system is the most important system in your home when it comes to energy efficiency, comfort and indoor air quality. The wrong-sized heating system will have a noticeable effect on all three of these factors. Prior to the last decade or so, contractors used rule of thumb calculations, determining furnace size by square footage and/or the number of rooms in the house. Now, to compensate for stricter building code modifications, rule of thumb measurements are no longer acceptable.

If you’re replacing your furnace, it’s imperative that your HVAC contractor use accurate load calculations before recommending the best make and model for your your home. Here are some of the things your contractor will take into consideration when using load calculations for accurate furnace sizing.

Manuals J And D

Often HVAC manufacturers have established load estimating procedures used to size HVAC equipment. Alternately, the Air Conditioning Contractors of America (ACCA) – a national contractor trade association – has also created Manual J and D that make load calculations much easier. Your HVAC technician will be able to plug in various pieces of information about your home, and the load calculations will be determined via the software. Manual J deals specifically with heating and cooling equipment. If you have an older home, your contractor may use Manual D (or similar program) to re-evaluate your duct design. Though often somewhat involved- it might be worth it to redesign your duct system if your current layout and/or duct equipment are inefficient.

Factors That Affect Heating Load

Your contractor will do a thorough inspection of your home during a load calculation appointment. There are a variety of factors that affect how well a particular furnace will heat your home. These factors include points like:

• Your home’s orientation
• The types of windows and window treatments used
• R-value of home insulation and whether the quantity of insulation is sufficient
• Air leakage rates
• Number and types of heat gaining appliances
• Occupancy

Once these and other factors have been entered into the Manual J software, your contractor will complete the furnace sizing process by recommending the makes and models that are best suited for your home.

Contact P.K. Wadsworth Heating & Cooling for precise load calculations and to accurately size the furnace replacement for your Cleveland area home.