Select the Right HVAC Equipment for Optimal Humidity Control

Controlling the temperature is pretty straightforward, but when it comes to humidity, things tend to get a little complicated. As it gets cooler or warmer, the relative humidity (RH) changes rapidly, so balancing them both can be tricky.


Relative humidity plays a vital part in comfort-Too high, and the body's ability to lose heat through perspiration reduces, and this environment even promotes the growth of mold. Too low, and an otherwise comfortably cool temperature starts feeling too cold, and could even cause sinus irritation.

The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) recommends RL levels be maintained below 65% for improved indoor air quality (IAQ).

Factors to Consider While Selecting HVAC Equipment

An HVAC (Heating, Ventilation and Air Conditioning) system can help you maintain a comfortable temperature in your home, as well as regulate humidity for optimum comfort. When you're looking at different kinds of HVAC equipment, here are some of the factors that you should take into consideration:

1. Stage Compressors-Match Cooling Capacity to Load Requirements

HVAC equipment that uses staging compressors can better balance the cooling capacity needed at various times with cooling load requirements. This reduces the likelihood of the system overcooling, which it does in an attempt to lower the RH levels indoors.

  • If you’re using an HVAC system with a single compressor, try to find a two-stage compressor.
  • For systems that use multiple compressors, opt for an HVAC controller that switches off some of the compressors when they aren’t needed.

Apart from controlling the humidity, multi-stage compressors and HVAC systems with multiple compressors have many other advantages, like improved efficiency through fewer on-off cycles, less temperature spiking, and more.

2. Select HVAC Equipment with Integrated OEM-Designed Dehumidification Systems

HVAC equipment like liquid reheat and hot gas can be integrated with other types of dehumidification systems to improve IAQ.

Typically integrated dehumidification systems work by first cooling the air to reduce humidity through condensation. A reheat coil is installed close to the evaporator, which utilizes some of the exhaust to heat either gas or liquid. The medium is then used to heat up the dehumidified and cooled air to prevent overcooling.

This type of system for dehumidification can have significant advantages over add-on ‘third party’ dehumidification systems. Some of the benefits include:

  • They are less complicated and easier to install
  • The temperature and humidity are easier to control
  • Troubleshooting is simpler, as is regular maintenance

3. Choose an Appropriate S/T (Sensible to Latent) Air Ratio

Sensible cooling load is the try bulb temperature and latent cooling is the wet bulb temperature. S/T Air Ratio is used to determine the available capacity of an HVAC system for both cooling and dehumidification, expressed as a ratio.

You should look for:

  • A system with a flexible S/T ratio, which can optimize comfort by balancing humidity and cooling loads.
  • OEM engineering data to match the S/T ratio of the system to that of the building or space where it is installed.

4. Opt for Systems with Independent Integrated Dehumidification Controls

Look for HVAC systems that have an integrated dehumidification system, but independent controllers for adjusting the temperature and humidity levels separately.

This allows the home's occupants to set them according to their own preference, and also provides a more flexible system that can be adjusted to accommodate for varying external and internal environmental factors. There are a few more advantages, like:

  • Lower installation costs and total cost of ownership
  • Fewer parts, which leads to reduced down-time and maintenance costs

Picking out the right HVAC for your needs is crucial, since it will last you for years to come, and the comfort of your home depends on it!

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