Learn the Effects of Humidity on HVAC Performance
The amount of humidity in the air directly effects the efficiency of your HVAC performance. When you’re cooling dry air in the summer, or heating dry air in the winter, your equipment has to perform longer and run harder if there’s not adequate moisture in the air.
Sensible vs. Latent
HVAC equipment heats and cools two ways:
- By lowering or raising the actual temperature (sensible heating/cooling)
- By removing moisture from the air (latent heating/cooling)
In hot, dry climates, ‘sensible’ heating/cooling is beneficial because you don’t need any dehumidification.
Your HVAC equipment works by adjusting the temperature level, but it also removes moisture from the air, leaving it drier than it would be without the system running. Because dry air feels cooler or hotter than moist air, the actual temperature may need to be increased/decreased to change the overall feeling of the air temperature.
Comfort levels
A certain amount of air humidity is necessary for optimal comfort; people are generally the most comfortable when there’s a relative humidity level of approximately 45 percent. For example, 70 degrees at 40% relative humidity feels great, but 70 degrees at 70% relative humidity would be muggy and miserable.
In humid climates, removing moisture helps control the ambient temperature. But in drier climates, extra moisture is helpful.
How it works
A compressor cools the air, and shuts down when the indoor air reaches the desired temperature. However, the indoor coil is still cold when the compressor shuts off, and as it warms, moisture forms on the coil as condensation.
What happens to that condensation?
In a humid climate –the fan should stop right away so the condensation can drip down into a collector pan and drain away. If the fan keeps running, it will cause the water to re-evaporate and stay in the house.
In a dry climate – it’s better to let the fan run a while after the compressor stops so it can help evaporate any water clinging to the coil or sitting in the pan. That evaporation of moisture helps cool the air, and so there’s an energy benefit in addition to the comfort benefit.
HVAC technology addresses humidity issues
Newer models of AC equipment can provide a delay for shutting off the fan, instead of stopping with the compressor, as with older air conditioners. And, of course, installing humidifiers and dehumidifiers to a heating and cooling system is an effective way to control humidity levels in the air.
Effects of humidity (or the lack of it)
Over time, too little air humidity dries out skin, mucous membranes, and the wood in furniture and walls. The result is itchy skin, an increased susceptibility to bacterial microbes, and potential cracks and splits in wood and plaster. Keeping the right amount of humidity running through your HVAC system can not only lower your energy output, but help keep you healthy and comfortable.
Ask a qualified HVAC professional to explain the benefits of adding a whole-house humidifier to help combat the negative effects of extremely dry air.
