Steps to adding A/C to an existing HVAC

Got AC? If not, You needn’t be left out in the (Not) cold

According to Boston Globe writer Leon Neyfakh, “Since the technology was invented in 1902, and the first window unit was brought to market in 1939, air conditioners have become ubiquitous in the United States. Today, almost 90 percent of American households have one—as do the vast majority of restaurants, stores, museums, and office buildings.” 

That article was written back in 2013, so our guess is the percentage of air-conditioned homes is probably even higher today. Of course, if you’re in that less than 10 percent bracket that still doesn’t have air conditioning you’re no doubt sick of suffering through the summer months and looking into the improvement of adding air conditioner to your home will bring.

The good news is you can beat the heat once and for all with your existing HVAC unit. In this post we’ll cover a number of things for you to consider including: 

  • Window air conditioners pros and mostly cons
  • Benefits of central AC besides cool air
  • Is adding AC to an existing central heating system practical
  • Extra components to add to your existing heating system
  • Sizing your AC system for air conditioning installations
  • The importance of energy efficiency

Window air conditioners—Pros, but mostly cons

A quick and relatively easy fix to beat the heat is to install a window air conditioner. While suitable for a single room or small areas, there are drawbacks. The cons of air conditioners include:

  • Window units are loud
  • A portion of the window is blocked, which means there is no possibility of letting in outside air when temperatures drop (besides operating the unit’s blower) and you’re also blocking out natural light
  • Expensive to operate over time; even units rated energy efficient cost more to run than central air conditioning
  • Their bulky design doesn’t exactly add to the aesthetics of a room 

Most important of all, a single-window air conditioner does not cool your entire home. Nor is installing window air conditioners in all the rooms of your house energy- or cost-efficient.

Not just cool air, But better air

A central air conditioning system attached to your furnace not only keeps you cool, it improves your indoor air quality by filtering out dust, allergens and other airborne particulates that at the very least can irritate household members, and in some cases can even threaten their health. Moreover, the air filtration system doesn’t just work with your air conditioning system. Because it is connected to your furnace or air handler, it keeps air circulating throughout your house clean year-round. 

Is it practical to add AC to your existing central heating system?

Whether it is practical to add air conditioning to your home’s central heating system or pre existing HVAC system depends on a number of factors. These include whether:

  • Your house has adequate ductwork
  • Your house is sufficiently insulated
  • You want to pay the price


If you have forced air heat, you have ductwork that distributes heated air throughout your house that might work for cool air as well. The keyword here is “might.” The ductwork must be in good shape without leaks or breaks, which it should be anyway regardless of whether or not you decide to add AC. If you have leaky ductwork, sealing and possibly even cleaning in certain situations may be warranted.

The other issue is whether your current ductwork, as well as your existing furnace blower are sufficiently sized, meaning there is adequate airflow to efficiently distribute cool air throughout your home. 

How do you know if your current HVAC and ductwork are sufficient? A professional certified HVAC (Heating Ventilation Air Conditioning) technician can perform the necessary test to confirm if they are adequate.

How old is your house?

Homes over 20 years of age typically were under-insulated. That means circulating air is leaking out through cracks in the walls and ceilings, as well as leaking in. In addition, insulation that is 20 years old or older does not have a sufficient R-Value by today’s energy efficiency standards. Without efficient insulation, it takes more energy, and more money, to condition a house. 

Chances are if you are reading this, you probably have an older home, as most new constructions include air conditioning. You may want to consider upgrading insulation, at a bare minimum in the roof, if only to improve your heating efficiency, as well as seal any detected leaks.

Is it worth the added expense to add AC?

If you have to repair, or worse, replace ductwork and/or insulation, you may be wary of adding AC because of the cost. Keep in mind that if you intend to stay in the house for any length of time, adding AC to your HVAC unit will improve the efficiency of your existing system and reduce your utility bills. 

Also, even if you foresee selling your home in the near future, upgraded insulation and the addition of AC improves your home’s resale value. So in many ways, the cost is an investment.

What components do you need to add?

Assuming your ductwork and insulation is up to the task, the addition of two components to your existing forced-air furnace provide central air conditioning to your home:

  • Indoor air handler. Houses the AC evaporator coil and blower. Mounted in the attic or a dedicated HVAC closet. In some retrofit situations, the evaporator coil can be installed in the furnace itself if the existing furnace blower is considered capable, or the furnace blower is replaced with a model that is capable.
  • Outdoor condenser unit. Comprised of the AC compressor, condenser, coil, and fan. Located behind or to the side of the house. Two insulated lines that circulate refrigerant are connected to the indoor air handler. 

Sizing your AC system

This added equipment must be properly sized to effectively cool your house. An undersized unit will have to work too hard to cool your entire house, and may struggle to regulate the right temperature levels in every room, while an oversized unit cycles on and off constantly, which causes temperature swings while failing to extract humidity. In both cases, you are wasting energy and increasing utility costs. Most importantly, you won’t be comfortable. 

A certified HVAC technician performs a load calculation that determines the capacity of the AC unit needed to cool the house on a typical hot day. They perform this calculation using BTUS or British Thermal Units (the heat energy extracted from a house every hour). Getting the right unit size is absolutely essential to efficiently add AC to your house.

How much does it cost to run air conditioning?

The final factor in your cost calculation is how much it is going to cost to actually run the air conditioning. AC energy efficiency is determined by its SEER (Seasonal Energy Efficiency Rating). This is a ratio of the amount of electricity required to remove BTUs of heat. 

Some states, such as California, mandate a minimum SEER of 14, which you should probably consider the minimum rating for your house. The higher the SEER, the more energy-efficient. As you might expect, higher SEER units cost more. The payback is that more energy-efficient models consume less energy, lowering your utility bills.

Consult the  HVAC experts

Ongaro and Sons design AC add-on systems using a diagnostics approach to provide the highest levels of efficiency and comfort, in addition to full AC and furnace replacement services. Ongaro and Sons’ technicians are trained for all residential makes and models of forced air and air conditioning installation. If you’re wondering “can you install HVAC yourself?”, it is highly discouraged. Do it yourself HVAC installation and do it yourself HVAC replacement can lead to a ton of headaches and added costs when you’re not fully trained in properly performing HVAC work. Ensuring the efficiency of your entire HVAC system also includes a thorough inspection of your duct system. If needed, we can do a thorough and effective cleaning, repair or even replace leaky ductwork in your HVAC setup. 

Ongaro and Sons put the “V” back in HVAC. Ventilation is the process of bringing fresh air into your home to replace stale air filled with indoor pollutants such as cooking smells, pet odors and/or tobacco. Proper ventilation is not only key to the efficiency of your home heating and cooling system, but to your indoor air quality and your family’s health. 

Ongaro and Sons offer a number of solutions (electrical and plumbing service too) to increase the quality of your indoor air, including everything from a filtration system to a complete home purification system and fresh air exchanger system for a noticeable HVAC upgrade to your home. We’re a family-owned business, so we understand the importance of protecting your health and the health of your family. 

Contact us and speak with our friendly customer relations team for a service call or with any questions about how you can add AC to your existing HVAC system (qualifying HVAC system required), inquiries on a replacement unit, or on an entire system. We guarantee 100 percent customer satisfaction and great customer service with every job you entrust to our expert team.