Sizing your next furnace accurately will help you increase both comfort and durability in your home. The most accurate way to size a gas furnace is to bring a trusted HVAC contractor into the process early on. Too small or too large a furnace can contribute to higher energy bills, increased maintenance costs and unequal distribution of heat.

A qualified contractor will assess these factors during the sizing process:

  • Attic and wall insulation levels;
  • Cubic feet under roof;
  • Number of windows, their placement and energy efficiency;
  • Overall air infiltration rates;
  • Home’s floor plan design;
  • Heat-producing activities indoors;
  • Family size and ages; and
  • Your temperature preferences.

The HVAC professional will then input this data into a software called Manual J, laying the groundwork for the next steps, which includes the furnace’s capacity and efficiency.

Furnace capacity is measured by the number of BTUs (British thermal units) they use. However, not all BTUs translate to heat for your home. The most efficient furnaces use nearly all of the heat they create to warm your home. Their AFUE (annual fuel utilization efficiency) ratings are close to 99, which means they only waste 1 percent of the fuel they consume.

A furnace with an AFUE rating of 80 wastes 20 percent of the fuel that it uses, typically as heat and combustion gases that go up your chimney. A system with an AFUE of 99 will deliver more heat to your home than one whose rating is 80, even though both may have the same number of BTUs.

If you opt for a more efficient furnace, you can choose a smaller system, since it doesn’t waste as much heat. You can also reduce the size of your furnace by improving insulation, sealing air leaks and upgrading your windows.

The pros at Around the Clock Air Conditioning & Heating can help you size a gas furnace to enhance your comfort and reduce energy costs. We’ve provided top-notch HVAC services for homeowners in Greater L.A. since 1967.

Our goal is to help educate our customers in Los Angeles, North Hollywood and surrounding areas about energy and home comfort issues (specific to HVAC systems). For more information about sizing your furnace and other HVAC topics, download our free Home Comfort Resource guide.

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