HVAC (heating, ventilation, and air conditioning) is essential to the comfort inside of your home, but costs can spiral out of control if your equipment is not managed properly. Socket shares tips and best practices that will help make sure you’re not wasting money, while staying comfortable. You should consult a licensed HVAC professional before making any major decisions.
HVAC Units
Making sure that your HVAC unit is sized properly is crucial in ensuring that your home will be comfortably heated or cooled. An AC unit that is either too big or too small will waste huge amounts of energy and money. An oversized unit can lead to short cycling, causing increased energy usage and bills, more wear and tear on your equipment, and high humidity. Undersized units lack capacity to cool the space and may run continuously, missing out on healthy on and off cycles, and increasing wear and tear. Energy Star has a simple guideline to help select the size of the HVAC unit needed based on the floor area of your home. According to the guideline, most residential homes in Nashville would require an AC unit somewhere between the sizes of 2 to 5 tons. You should consult a licensed HVAC professional before purchasing your equipment to make sure it is properly sized for your home. Be sure to ask for a unit that is EnergyStar-rated to ensure you’re getting the most energy-efficient equipment possible.
One important way to determine if an HVAC unit is energy efficient is by looking at its SEER (Seasonal Energy Efficiency Ratio). This rating, which ranges from 13 to 21, informs potential buyers of the energy-efficiency level of the AC unit under consideration. The higher the rating, the more energy-efficient the unit is. Newer units are more likely to be more efficient than older units, due to improvements in technology.
Thermostat Controls
Controlling your thermostat effectively is one of the biggest factors in achieving home energy efficiency. Thermostats activate your unit by sending signals to the equipment based on the indoor temperature, time of day, and, in some cases, humidity levels. Programmable thermostats allow households to vary the temperature settings throughout the day. Homes can save energy by allowing a wider temperature range during times when the home is vacant and at night, while occupants are sleeping.
According to the US Department of Energy, only 1 in 8 homes have thermostats that are properly programmed to save energy. Digital thermostats, installed in 41% of US households, allow users to determine what the room temperature should be at various points of the day.
After having a thermostat installed in your home, the question remains: what should I set the temperature to throughout the day? Ultimately, your level of comfort and zeal for saving energy and money will determine the range you program your thermostat to operate within. In the winter, the Department of Energy encourages home residents to set their thermostat to 68 degrees Fahrenheit and decrease temperature settings down by 7 to 10 degrees when the home is vacant. For the summer, their thermostat recommendations changes to 78 degrees while occupied and an increase of the settings by 7 to 10 degrees when the home is unoccupied. Read more about the recommended temperature settings.
Filtration
Another aspect of home heating and cooling that cannot go unnoticed is indoor air quality (or IAQ for short). IAQ is the measure of how clean the air is from pollutants, viruses, and germs as well as how much moisture is contained. Moisture is typically addressed by the air conditioning unit. Units are typically designed to expel excess moisture from outside air. Moisture issues can be addressed by consulting with a HVAC professional. A licensed professional could also detect possible air infiltration caused from cracks or gaps in your home’s envelope, which consists of the walls, windows, roof, and foundation.
Air filters -- which are positioned in areas where the HVAC unit brings in air -- prevent dust, microbes, and viruses from circulating through the unit and throughout your home. The Minimum Efficiency Reporting Value, better known as MERV, is an air filter rating system. MERV assigns a value for filters, ranging from 1 to 16. The higher the number, the better the filter is at capturing airborne particles. For home air conditioning units, the EPA recommends filters with MERV ratings of 13 or higher. Based on simulations, MERV-13 filters potentially block out three times as many particles as MERV-8 filters.
It is advised to consult an HVAC professional or refer to your HVAC unit’s user manual before upgrading the air filter to a higher MERV rating. If the MERV rating is too high for your unit, it could cause air pressurization issues, which may hurt your home’s energy efficiency. Higher MERV-rated filters may cause the HVAC unit to use more energy to circulate air through the filter.
As a result of capturing contaminants, air filters need to be changed periodically. Most HVAC professionals recommend replacing filters at least every 90 days. For most air filters that are typically 1”-3” in depth, they are recommended to be replaced every 60 days or less. For individuals who suffer from allergies, asthma, or other respiratory conditions, homeowners are encouraged to replace air filters at a higher rate to help alleviate symptoms. For individuals severely affected by pathogens contained in small particles, the EPA recommends HEPA filters, which are between MERV-13 and MERV-16. However, the EPA acknowledges that a trained professional may need to first modify your HVAC system before HEPA filters can be safely installed.
Effects of installing higher MERV-rated filters on energy use largely depend on the age and type of the motor inside of your HVAC unit. Older HVAC units typically use a PSC (permanent split capacitor) motor to operate the blower fan, which pushes air through the unit and home. These units typically operate at a constant power level and fan speed. Newer HVAC units typically have ECM (electronically commutated motors) or brushless DC motors, which varies the energy use and airflow to meet the demands from the thermostat. ECM motors gained popularity in the mid-to-late 1990s and rose to prominence in the early 2000s.
In 2009, the Davis Energy Group conducted a study to investigate the effects of high MERV-rated filters on air flow and energy use by PSC and ECM fans. According to the study, units with PSC motors experience drops in airflow as the MERV rating increases. Units with PSC motors did not experience significant energy use since PSC motors operate at the same power level. On the other hand, ECM motors are better able to handle higher MERV filters and did not see noticeable airflow drops in filters as high as MERV-13. Unlike PSC motors, ECM motors do increase energy use to maintain constant air flow. However, it should be noted that ECM motors are more energy efficient in comparison to PSC motors.
To sum up the findings, older units are not likely to see spikes in energy use, but home occupants may experience less comfort if the MERV filter is too restrictive. Newer units are better able to adjust to higher-rated MERV filters but will likely see an increase in energy use. However, newer units will likely save more energy than older units using the same MERV filter.
In conclusion, by selecting the right equipment and filter and adjusting the temperature wisely, you will maximize the thermal comfort and energy efficiency of your home.
Blog Author
This blog was authored by Freddie Adom, Energy Manager for the Department of General Services Division of Sustainability.