When it comes to maximizing the indoor comfort and energy efficiency in your home, it’s essential to have a correctly sized furnace professionally installed. Installing an HVAC system is a technical challenge, but it’s guaranteed to fail if the initial load calculation isn’t carried out. This requires a very specific skill set, experience, and knowledge of how HVAC systems work in domestic and commercial locations. If the initial load calculations are incorrect, it can lead to poor HVAC system performance, a reduction in energy efficiency, and even equipment failure. Let’s take a closer look at the importance of using the right furnace size in your home.

The Drawbacks of a Poorly Sized Furnace

Many homeowners understand the importance of properly sized air conditioning system to keep their home comfortable and energy efficient during the hotter summer months. If the air conditioner is too large, it can cool the home too quickly; this will lead to frequent cooling, short cycling, and premature wear and tear to expensive equipment. If the air conditioner is too small, it will run constantly as it attempts to cool the spaces, and this will use a great deal of energy. But, many people are less aware of the importance of size when it comes to choosing and installing a furnace in their homes.

When you have a furnace that’s incorrectly sized for your home, you will encounter similar problems to a poorly sized air conditioner system. A furnace that’s oversized will make certain rooms in your home too hot, and this is particularly noticeable if the rooms are closer to the furnace. An oversized furnace will also cycle on and off frequently, this causes considerable wear and tear, leading to equipment failures and unnecessary repair bills. An undersized furnace will need to run constantly as it attempts to reach the temperature set on the thermostat. This will overwork the furnace leading to frequent repairs, and the system will rack up huge energy bills.

As you can see, both an undersized and an oversized furnace have considerable drawbacks. The level of indoor comfort will be inconsistent, and your expensive heating equipment may be damaged. This will lead to frequent repairs, and in extreme cases, an early replacement may be needed. The energy efficiency is also a concern; in both cases, the furnace will use far more energy than it should, and this will drive up your energy bills.

A Professional Load Calculation 

If you visit certain HVAC manufacturer websites, you may notice that they have an online calculator or chart to help you make a load calculation for your home. They invite you to input the square footage of your home to help you find the right size of furnace to meet your needs. Although these tools may be useful to get a ballpark figure, they are essentially useless when it comes to an accurate calculation.

A professional HVAC technician has the skill, expertise, and knowledge to make a load calculation that will provide accurate data. There are many factors that need to be considered if the load calculation is going to be correct, and these are not even considered in a simple online tool. There are eight main areas that need to be factored into a load calculation if you want the correct size of furnace for your home:

  1. The square footage of your entire home.
  2. The indoor air space measured in cubic feet.
  3. The current integrity of your homes envelope
  4. The efficiency of the ductwork.
  5. The type and quantity of insulation present in your home.
  6. The level and orientation of sunlight exposure.
  7. The climate zones in your home.
  8. The R-values and U-values of the doors, windows and any other entry ways.

These measurements need to be taken by a trained HVAC technician, and this will allow them to make an accurate assessment of your furnace size needs. This is the first step in choosing a furnace that will heat your home comfortably and efficiently for a long time to come.

Evaluating Your Furnace

If you’ve noticed that your current furnace is exhibiting any of the problems discussed earlier in this article, it may be the incorrect size for your home. The best way to confirm your fears is to contact a local HVAC technician and get them to check your furnace. If they discover that your furnace is the wrong match for your home, the most cost effective solution is to replace the furnace. This may seem disheartening if the furnace is relatively new, but it can be a blessing in disguise. The latest furnaces are far more energy efficient compared to units made only a few years ago. Many people find that their initial purchasing cost of a new energy efficient furnace is quickly recouped in the medium to long term with lower energy bills.

The heat output of a furnace is measured in British Thermal Units (BTUs). When you look at the specifications for a new furnace, there are two numbers to look out for; they are the efficiency rating and the input BTUs. The efficiency rating is expressed as the percentage of generated heat that actually gets to your indoor living areas. The input BTUs is the amount of heat that your prospective furnace generates when operating under normal conditions.

As an example: let’s say you buy a furnace with an efficiency of 90 and an input BTU of 100,000. This will deliver around 90,000 BTUs of heat into your home (90% of 100,000 is 90,000). If you have an older furnace with an efficiency rating of 75 and an input BTU of 120,000, the heat delivered into your home would be exactly the same. But, the older furnace will use far more energy to achieve the same level of heating performance.

Hopefully, you now understand the importance of a professional load calculation before you install your next furnace. Without accurate data, you cannot make informed decisions, and this can cause problems in your home and cost you a lot of money at the same time.