Once you start to consider your home’s energy efficiency, particularly as it relates to heating and cooling, you realize that there is a whole world of acronyms out there that may not make a lot of sense. Trying to figure out what they mean often leads into rabbit-holes that rely on even more jargon. With this guide, you will have a better understanding of the ratings and common jargon used to describe Heating, Ventilation and Air Conditioning systems, and how they affect your home comfort.
HVAC refers to the broader system of temperature control in your home. It stands for Heating, Ventilation and Air Conditioning. Many people have a central HVAC system that takes air from outside, cools or heats it based on the season and sends that treated air through the ductwork into separate areas of the home. Other homes have different types of heating and cooling systems, such as electric baseboard heaters or room air conditioners. The last part, but no less important, is ventilation. Ventilation allows the HVAC system to exchange air pulled inside with air returned outside, and provides necessary ventilation for exhaust-producing appliances such as stoves, furnaces and gas dryers.
The amount of insulation in your home can significantly affect your home’s energy efficiency. Insulation in the attic and under the floor reduces the rate at which warm air passes through the home. In the winter, better insulation prevents the heated air escaping to the cold outdoors. The country is divided up into regional zones with recommendations for insulation thickness and efficiency based generally on the climate. Insulation is measured in R-values. The R-value of your insulation depends on the type of insulation, and ranges from about R2 per inch for blown fiberglass insulation to over R8 for spray foam insulation.
To determine how much insulation you need in Louisville, Cincinnati or Indianapolis, you simply refer to the guidelines and divide the total R-value by the type of insulation. For example, a Zone 4 uninsulated attic requires R-value insulation of R38-R60. If you have blown fiberglass insulation at R2.5 per inch, you should have 15-24” of insulation in the attic to meet the current recommendations.
There is a portion of the HVAC system that must handle the air that is brought inside, and blow it through the ductwork. That component is called the Air Handling Unit. Each AHU must have three components:
- Filtration (i.e. the air filters)
- Heating or cooling coils to alter the air’s temperature
- A blower fan to move that air through the ductwork
Many furnaces contain the air handling components needed to run the system. If you have a heat pump instead of a furnace, you may use a separate AHU for heat transfer.
Energy Star Ratings
When you go shopping for new appliances, fixtures and equipment for your home, you may see that some products have an Energy Star label on them. This label is established through the United States Department of Energy and shows consumers that a particular model demonstrates notable efficiency greater than minimum standards. For example, in order to earn the Energy Star designation, gas furnaces must maintain a fuel efficiency of 90 percent for the south, and 95 percent for the north. That is noticeably higher than the 80-85 percent required for furnaces without the label. Energy Star air-source heat pumps and air conditioners must have a Seasonal Energy Efficiency Ratio (SEER) of 15 or higher, compared to a SEER rating of 13 for standard air conditioners.
While fuel efficiency is comparatively easy to calculate as a simple percentage, SEER ratings are a bit more complicated. The SEER rating of your air conditioner is a number based on the amount of cooling that comes from the air conditioner related to the energy consumed. The output is measured in British Thermal Units (BTUs) and the energy usage calculated in watt-hours. When you look at your energy bill for the month, you will see a number of kilowatt-hours (1,000 watt-hours) consumed for electricity. Those watt-hours power your air conditioner, which is sized by output in BTUs per hour. If you have an air conditioner sized at 10,000 BTUs and you used it 10 hours a day for 100 days per year, the air conditioner would produce 10 million BTUs in cooling over the course of a year. An air conditioner with a SEER rating of 13 would consume about 770,000 watt-hours per year. An appliance with a SEER rating of 16 would use 625,000, almost 20 percent less consumption.
If you or your family members suffer from seasonal or chronic allergies to environmental contaminants, changing your indoor air quality through filtration may be an excellent idea. High-efficiency particulate air (HEPA) filters are able to filter particulate matter from the air extremely effectively. Although dust, debris and pollen may first come to mind when you think of particulates, you should also think of bacteria and mold spores as well. HEPA filtration systems often contain two filters. The first filter catches much bigger particulates, like dust, dirt and pet dander. The second filter, the true HEPA filter, uses electrostatic charged plating to trap contaminants between glass fibers.
Since maintaining your furnace air filters is a fairly simple maintenance task for homeowners, you may have switched them out or cleaned them from time to time. Those air filters are rated to a Minimum Efficiency Reporting Value (MERV), which tells you how much they can filter out of the air coming through your ductwork. MERV ratings range from 1-20, with higher ratings providing better-quality filtration.
The ratings are divided up into five categories: 1-4, 5-8, 9-12, 13-16 and 17-20.
You almost certainly do not need filters with the highest numbers, which are usually reserved for clean rooms and hospital operating rooms. A rating of 9-12 is about the greatest you would need for a residential home, and many people do just fine with a filter rated 1-4 or 5-8. If you notice that your indoor air quality is not ideal, you may observe quick improvement by increasing the MERV rating of your air filters.
ASHRAE Air Quality Standards
Since people spend so much time inside homes and other buildings, indoor air quality is crucial to their health. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) is a worldwide organization that promotes research on energy efficiency, sustainable building and healthy construction practices, as well as the creation of standards based on that research. The accepted national guidelines for air quality and proper ventilation in residential homes are based on standards ASHRAE updates once a year. This standard ensures that there is adequate ventilation between indoors and outdoors to prevent the infiltration of outdoor particles and to allow the release of indoor contaminants (e.g. furnace exhaust) out of the building.
When you read through an instructional guide or an informational article about using your HVAC system, it may feel a little like alphabet soup with all the technical jargon and industry acronyms. You can use this guide as a reference to keep the terms fresh in your mind, helping you to know more about how your HVAC system works and what you can do with it to increase its efficiency or the comfort of your home.