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Air Conditioners and Heat Pumps

If you are building a new home, you have many decisions to make. Choosing your indoor comfort system is a big one. To help in this process, AHRI provides the following guidance to help homebuilders make the right choice for their homes.

How do I find the right system for my new home?

The best systems operate efficiently with minimal electricity to reduce utility bills. They provide steady, dependable performance for many years when correctly sized for the home, properly matched, correctly installed and regularly maintained. Good systems are quiet, long-lasting and low in service needs. They also have been performance certified. Central air conditioners and heat pumps that are performance certified bear the AHRI Performance Certified® mark and are listed in the AHRI Directory of Certified Product Performance. Heating equipment such as furnaces, boilers, water heaters and hydronic equipment bear either the GAMA Efficiency Rating Certified or I=B=R marks and are listed at AHRI Directory of Certified Product Performance. These marks are your assurance that the manufacturer’s efficiency claims have been tested and verified by an independent third party.

How can I be sure my system is the right size for my home?

Homeowners should ask their air-conditioning installer to size the equipment to meet the specific needs of their home. If a system is undersized, it will struggle, and even freeze over, on the warmest days. If oversized, the system will cycle on and off too frequently, greatly reducing its ability to control humidity. It will also be less efficient.

To properly size a system for a home, trained technicians will use an equation that factors the home’s age, the number and quality of its windows, how well it is insulated, how many stories it has, its total square footage, and local energy rates. Homeowners should ask their technicians to perform a Manual J analysis, the industry’s term for the standardized equation for sizing an air conditioning system.

Your technician will specify the cooling capacity of the system in either Btu/h (British thermal units of heat removed per hour) or refrigeration tons (one ton being equal to 12,000 Btu/h).

How do I know if my system was properly installed?

When building a new home, you have the opportunity to be part the HVAC system design. Understanding the basic characteristics of a quality installation will help you ask your installer the right questions. You should expect your air conditioning installer to take the following steps:

  • Determine room-by-room loads and air-flows using ACCA Manual J calculation procedures (or equivalent).
  • Lay out duct system of floor plan, accounting for the direction of joists, roof hips, fire walls, and other potential obstructions. Determine register locations and types, duct lengths, and connections required to produce layout given construction constraints.
  • Size duct system according to ACCA Manual D calculation procedures (or equivalent).
  • Size HVAC equipment to sensible load using ACCA Manual S procedures (or equivalent).
  • Install equipment and ducts according to design specifications.
  • Charge the system appropriately, and verify charge with the evaporator superheat method or subcooling method (or equivalent).
  • Check for proper furnace burner operation and fire-box drafting.
  • Test the system to ensure that it performs properly by determining that the system is properly sized, it does not leak substantially, and has either proper air handler fan flow, and proper plenum static pressures, or proper room and return air flows, and proper plenum static pressures.
  • Provide an AHRI Reference number or AHRI Certificate of Certified Product Performance, which verify the technician has installed a properly matched system.

How will I know if my system is properly matched?

Split air conditioning and heat pump systems (with indoor and outdoor units) need to be properly matched to achieve the energy efficiency and longevity that you expect from your system. When improperly matched, the efficiency and longevity of these systems are significantly compromised. AHRI tests thousands of indoor and outdoor units each year to verify that they will work together as a system to achieve a given energy efficiency rating.

The easiest way to verify that the system is properly matched is to ask your installer for an AHRI Reference Number or an AHRI Certificate of Certified Product Performance. The reference number and certificate verify the outdoor unit (condenser) and indoor unit (evaporator) combination has been certified as a matched system by the Air Conditioning, Heating and Refrigeration Institute (AHRI). The reference number can be entered into the or an AHRI Directory of Certified Product Performance to obtain a Certificate of Certified Performance. For higher efficiency systems, the certificate can be used in some areas to obtain a rebate from your utility or local municipality.

To locate your air conditioning system in the AHRI directory without an AHRI Reference Number, you will need the manufacturer’s name, model name, and model number, for both the indoor and outdoor units. This information should be on the equipment’s warranty, your sales invoice and on the units themselves. Then, click on the directory for your equipment.

What should I look for in an installer?

Knowledge and experience. One way to identify a knowledgeable technician is to look for one that has been certified by the North American Technician Excellence (NATE). To become NATE-certified, technicians have to pass a nationally recognized test to demonstrate they have the knowledge to properly size, install and repair today’s increasingly sophisticated heating and cooling systems. Find a NATE-certified technician in your area.

What measures can I take in designing my home to reduce air-conditioning usage?

Many factors affect a home's heating or cooling requirement, or “load.” When designing your home, you may want to discuss with your builder the right combination of energy efficiency measures. A combination of proper insulation, energy-efficient windows and doors, daylighting, shading, and ventilation will usually keep homes cool with a low amount of energy use in all but the hottest climates. Although ventilation should be avoided in hot, humid climates, the other approaches can significantly reduce the need to use air conditioning.

Which air conditioning systems are energy efficient?

Air-conditioning manufacturers are required by law to evaluate and rate their equipment according to its energy efficiency. This rating is known in the industry as a SEER, or Seasonal Energy Efficiency Ratio. The higher the SEER, the more efficient the equipment. Generally, the higher the SEER of a unit, the higher the cost, but the difference often can be recouped through reduced home energy bills over the long run. As of Jan. 23, 2006, the minimum SEER of an air conditioner or heat pump manufactured in the United States today is 13.

Using an independent, third party laboratory, the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) certifies that a manufacture’s efficiency claims are accurate. However, homeowners need to be aware that while air conditioning and heat pump units may bear the AHRI Performance Certified mark, the mark is only valid for a split system if both the indoor unit and outdoor unit are properly matched to work together to achieve the AHRI Performance Certified efficiency level.

Homeowners should ask their installer to provide them with a Certificate of Certified Performance to provide assurance that the system is properly matched and will achieve the efficiency rating claimed by the manufacturer.

What are two-stage and variable-speed motors?

Air conditioning systems are designed to cool your home, even during extremely hot temperatures. However, weather fluctuates, and even winter days can be somewhat mild.

While most single-stage units are either “on” or “off,” two-stage central air conditioners can run at two speeds. Most of the time, the unit runs at 80 percent, kicking into high gear only on very hot days. This saves on wear and tear, since the unit cycles on and off less frequently. Two-stage systems are also better at maintaining a consistent temperature and you won’t have to keep adjusting the thermostat.

A variable-speed motor can actually save you money on your energy bill as they consume less electricity than standard motors. Also having a variable-speed air conditioning system as part of your home’s comfort system means you will gain air conditioning efficiency or SEER. The higher the SEER (Seasonal Energy Efficiency Ratio) the more energy efficient the unit. This means even more energy savings for your household.

What is a scroll compressor?

The newer compressor designs, called scroll compressors, have fewer moving parts and may therefore break down less often than the older, reciprocating type. Two-speed compressors are very efficient, but they're also more complex than single-speed compressors, and manufacturers have less experience with this design.

What do I look for if I want a quiet air conditioning system?

Look for sound-dampening features such as vibration isolation for the compressor and insulation. Also, louvers or heavy-duty wire grids and caps protect the unit from weather and impacts from sports or lawn equipment.