Mold is common in buildings with lots of moisture and it poses health risks to those who live and work inside those structures. According to the Centers for Disease Control and Prevention, mold can cause allergic reactions that irritate the eyes, nose, throat and lungs. Coughing, wheezing and swelling of the throat are among the symptoms a person can present.

Keeping relative humidity between 40-60% is ideal, says Chris Roman, an energy industry professional at Conservant Systems, since viruses, bacteria and mites don't like to live in those ranges. 

Roman is an expert in HVAC systems in healthcare working to help prevent surgical site infection (SSI) at hospitals. SSIs are the leading cause of hospital readmission, but HVAC technology can help reduce this issue through air-handling units (AHUs).

"These air handlers really allows for better indoor air quality while de-carbonizing facilities, which typically in the energy world if you get better indoor air quality, you're usually using more energy because something was broken or the boxes weren't opening like they should or the valves weren't opening and closing like they should," Roman says.

However, that’s not the case with AHUs. Energy costs go way down, in addition to therm savings. "It's funny how important relative humidity becomes but most people only pay attention to temperature, but you have to do both," he says. 

Air handlers look like a big box car from the outside. In the inside, you have coils, vents. "We remove the heat from the building and then we use the heat from the building to do heating," he says. 

When it comes to keeping relative indoor humidity in range, Roman offers some suggestions.

"The process we have in most buildings is called sub-cool reheat, which means they cool the air down so low that moisture condenses and it falls off the coils into a drain pan, which collect the condensate and then it puts it in the pan and it is funneled outside. This doesn't go into the air handler any further," he says. 

With everyone after therm savings, they are turning off their reheat, which means they are cooling down but they are not reheating it up.  They want to reduce the natural gas consumption and they are going to shut off their reheat but the water could end up with more moisture, which could be in the walls, floors and ceilings — and then everyone could be breathing it in and not knowing it. 

What you're left with is black mold, which is a big problem. 

Find a way to eliminate the reheat or something that can provide heat without natural gas. If you want to get rid of that gas reheat, you have to replace it with something else, Roman notes. 

"A lot of people want to turn off the ventilation, but you should keep the minimum positive pressure requirements to force the water out. Pressure matters and if more people could keep their ventilation on over the weekends, when you come back in on Monday, you'll have so many less problems," he adds.