By David Muir

It’s a typical Summer in Florida – yup, it’s hot and humid outside.  You’ve got your high-efficiency, whole-house air conditioner running.  So, it seems comfortable inside.  Your modern house is well-sealed against the elements and it’s likely you haven’t opened a window in months.  That means, without proper ventilation, the air inside could be polluted and may even be unhealthy.    

Engineers and health agencies recognize that indoor air contains more kinds and higher concentrations of pollutants than outdoor air.  Common home indoor air pollutants include biological pollutants (mold spores, dust mites, bacteria, viruses/SARS-CoV-2, pollen, animal dander); combustion pollutants (including carbon monoxide); lead from old paint or lead-tainted soil; volatile organic compounds (VOCs) emitted from many paints, glues, and other building materials (this is called “outgassing”); and, in some areas of Florida, radon. 

Mattresses, carpets, wood flooring, furniture, and appliances all outgas VOCs.  Then there’s all the who-knows-what from kitchen and bathroom drains.  The other contributor to poor indoor air quality in Florida is moisture.

When done correctly, proper ventilation will assist in pollutant and moisture removal and control.  This can be accomplished by, what I call, ‘blowing the place out’.  It’s recommended to do so regularly… more often than you might expect to maintain a healthy indoor environment.

Here’s an approach to ventilate the house – especially in the summer when just leaving windows open is not an option:

“Blow-out” Ventilation (best performed on a breezy day in the afternoon when humidity is lower)

• At the thermostat(s) turn the HVAC fan on high (don’t change the temperature setting)
• Turn on all ceiling fans
• Turn on all bathroom and kitchen exhaust fans
• Open at least one window (with a screen) on each floor or wing, far from the exhausts
• After at least 1 hour, close the windows and turn off the exhaust fans
• Let the HVAC and ceiling fans circulate, filter, cool and dehumidify the new air before reverting to normal programming

Frequent Ventilation is highly recommended as well.  This can be as simple as regularly turning on exhaust fans in the bathroom and/or kitchen.  Leave them on for several hours and often.  You might chose to do this when you leave the house, if the noise is a bother.  Exhaust fans create a negative pressure inside the house that draws outdoor air in through small gaps around doors and windows.  This is not a substitute for periodic “blow-out” ventilation but does achieve a beneficial partial air exchange.

There are numerous considerations for house ventilation.  Outdoor air is moist and carries allergens.  Fortunately, our HVAC filtration systems mitigate these quite well.  Modern systems have HEPA filters, some with carbon capture and even UV disinfection or ozone generators.  To me that means I can ventilate or ‘blow the place out’ and then further clean up the new air inside.  There are whole-house ventilation systems that are highly recommended and I’m considering having one installed.  In the meantime, my house, although equipped with state-of-the-art HVAC and filters, does not have a dedicated ventilation feature.  Therefore, I must rely on natural ventilation and a concerted effort to manually use the mechanical equipment it does have. 

There is abundance information about house ventilation on the internet. 

Click here for a link to the fundamental considerations in Florida.

Ventilation

Dave Muir