Buying a new HVAC system

Step one

Your heating, ventilating and air conditioning system — HVAC for short — accounts for nearly half of the typical home’s energy use. Its operation is fundamental to a home’s indoor air quality, and the comfort of its occupants. Because of the importance of an HVAC system to the overall performance of the home, there are some very important considerations to make if you are purchasing a new HVAC system to replace your existing system or as part of a new home under construction.

Choose a licensed contractor to assist you. HVAC systems range from complex to very complex in terms of proper installation, sizing and testing. A highly qualified contractor is essential.

When choosing a contractor you will want to take your time and choose carefully. Remember, you won’t benefit from even the best HVAC system in the world if it is not installed properly. To help with this decision, follow these important steps when choosing a contractor:
  1. Consult the HVAC listings in the Green Building Directory for a list of contractors.
  2. Ask your friends, family and neighbors for recommendations.
  3. Ask contractors for references — be sure to find out about installation, performance and if the job was finished on time.
  4. Find out about any special offers from your utility providers, potential contractors and state tax incentives. For example Progress Energy offers rebates for a number of energy-efficient HVAC options.
  5. Make sure the contractor is licensed to work on the type of system you need or want. Without a licensed contractor you will most likely void the system’s warranty and be unable to claim insurance if something goes wrong.
  6. Be sure that your HVAC contractor is knowledgeable and encourages the use of energy-efficient HVAC systems. Ask them if they will perform a “Manual J” and use mastic to seal the ductwork to start with.
  7. Get estimates! Request itemized bids from different contractors and compare overall costs as well as long term energy costs for operating the system.
  8. Protect yourself by signing a proposal or contract which specifies total time, cost and warranty information.

Step two

While you are choosing a contractor, you will gain an idea of what kind of HVAC system you will most likely need for your home. Keep in mind that there are a number of different HVAC options each of which you will want to consider according to your needs:

  1. Heat Pumps are the most common systems in our area and can provide both heating and cooling. Heat pumps use refrigerant to transfer heat from one place to another and include both an outdoor and an indoor unit. Heat pumps require a back-up heat source below about 40 degrees.  Commonly, heat pumps use electric coils to operate at low temperatures, which will send your electric bill sky high. If you have an outdoor thermostat installed, the electric coils won’t kick in until absolutely necessary. Or, consider using a furnace as a back up heat source instead. An even better option is to install a dual-fuel heat pump. When choosing a heat pump, look for a minimum efficiency of 14 SEER and 8.5 HSPF. Because Western North Carolina’s moderate climate more often requires heating than cooling, the HSPF-efficiency is the most critical number.
  2. Furnaces are the most commonly used heating system in the U.S. today. Depending on your needs, furnaces typically operate on natural gas or fuel oil. Fuel oil units can run on biodiesel if it is available in your area. Keep in mind that if you are combusting gas or oil you will want to be sure to install carbon monoxide detectors and adhere to building code when installing the system. If you decide on a furnace be sure to purchase a high-efficiency model of 90 percent AFUE or above.
  3. Boilers generate heat by burning natural gas or fuel oil to heat water. Like furnaces, you will want to take proper precautions to limit the potential dangers of combusting fuel in your home. Boilers circulate hot water or steam through baseboards, radiators, or radiant floor systems so they do not require duct work. Look for a minimum efficiency of 90 AFUE.
  4. Central air conditioners are one of the most widely used systems for cooling homes in the U.S. Proper sizing and installation are critical for the performance of this type of system to both cool and dehumidify properly. Look for at least a 14 SEER.
  5. Geothermal heat pumps are very efficient and reliable heating systems. They are expensive up front, but with the many tax incentives currently available it is a great time to consider installing one. Because the ground maintains a constant 55-60 degrees below the surface, drawing heat from beneath the earth is an efficient way to utilize a heat pump system.
  6. Solar thermal heating utilizes the sun’s radiant energy through solar collectors and a heat exchange unit. The heated water can then be used in a radiant system of with a heat exchanger in forced air systems. The systems can also supply domestic hot water.

Step three

Once you have decided on a contractor and a particular HVAC system, you will want to make sure that all the steps are taken to properly size and install your system. There are a number of issues to take into consideration to assure your system is performing to maximum efficiency.

  1. Properly sizing your HVAC system is absolutely critical to the overall efficiency and performance of the system. Without properly sizing your HVAC you will most likely run higher energy bills and have a hard time making your home comfortable. In order to size your system, your contractor will have to do a Manual J calculation. This is usually required by code, but it is often overlooked, so be sure to request the calculation from your contractor. Keep in mind that oversized equipment is not better, and will cost more upfront, will shorten the system’s lifespan, perform poorly and will not properly dehumidify.
  2. Sealing your duct-work to minimize leakage is essential for ducted systems. As seen in the following graphs, leaky ducts will dramatically and negatively affect your HVAC performance. Be sure to have your contractor use mastic adhesive around all duct joints — not duct tape. Consider hiring a third party auditor to test the system’s leakage with a duct blaster.
  3. Refrigerant charge is important for systems like central AC or a heat pump. Proper refrigerant charge will assure quality performance, and will reduce your energy costs and improve the system’s efficiency.
  4. Airflow optimization is critical for HVAC performance. The air circulating in your duct system must be the proper amount. Ask your contractor about performing a Manual D calculation to make sure your ducts are properly sized and test for proper air flow to allow your system to maximize home comfort.
  5. Install a programmable thermostat. These come in a number of variations which can best suit your needs. A programmable thermostat is easy to use and can improve your HVAC performance and lower energy costs.

Typical Furnace Installation

With your new HVAC system installed, you will want to make sure to take care to properly maintain it and maximize its performance to receive the most possible benefit. Keep in mind these tips once you have your system up and running:

  • Change your return air filters regularly for ducted systems
  • Have your contractor perform routine tune-ups
  • Tighten electric connections
  • Lubricate moving parts
  • Check gas and oil connections
  • Clean the coils
  • Clean the blowers
  • Have your contractor test the refrigerant charge
  • Check your condensation drain for stoppage

Jake Sadler is the Residential Outreach Coordinator for the WNC Green Building Council. You can reach him at or (828) 254-1995