How Foam Insulation Affects Air Conditioning and Comfort

Every week we receive inquiries regarding the use of foam insulation in new construction and existing homes.  Often, these questions are from customers referred to Surgi's by their foam insulation vendor.  We frame our advice by discussing the home as a system.

A home is a system consisting of the envelope, the insulating barrier, ventilation, occupants and their lifestyle and a comfort control system.  A change in any of these components affects most or all of the others.

  • Envelope - windows, walls, ceilings, floors
  • Insulating Barrier - house wrap, foam, fiberglass, weatherstripping
  • Ventilation - bathroom vents, kitchen hoods, dryer vents
  • Occupants and Their Lifestyle - size of family, heating/cooling/humidity preferences
  • Comfort Control Systems - air conditioner, heater, humidifier, dehumidifier, filtration and air purification devices.

Adding foam insulation to an existing home without modifying the other components will decrease utility bills, increase humidity and increase pollutants in the home.  Why? 

Lower Utilities.  Depending on how much of the envelope is coated with foam, the amount of air conditioning required to cool the home is reduced.  Without changing the size of air conditioner, the system will run less.  You might think that this is a good thing and it is regarding your utility bill.  However....

Humidity: An air conditioner is a giant dehumidifier.  When it's not running it is not dehumidifying.  Higher humidity in a home can make the house feel "muggy" and encourage mold growth.

Pollutants: Homes breathe through vents, cracks around windows and doors, electrical outlets, attic doors, etc.  This infiltration of fresh air causes your air conditioner and heater to work harder but it flushes out humidity, germs and pollutants.  Anytime you lessen the infiltration of outside air you increase the amount of pollutants in the home.

How do you take advantage of the benefits of foam without affecting comfort and health?  (Again, this depends on the amount of the envelope coated in foam.)

Install Two-Stage Air Conditioning.  Newer high-efficiency air conditioners run at 50-70% capacity on low speed and 100% on high.  Since air conditioners are sized to cool a home on the hottest days of the year, they are oversized for all other times.  By running on low speed most of the time, two-stage units use less electricity and have longer run times.  When a system is running, it is dehumidifying.

Introduce Fresh Air.  By intentionally introducing a small amount of filtered fresh air from outside to the return air of a system, you can create a controlled version of infiltration.  This will help decrease carbon dioxide and other pollutants in the home.

Add Advanced Air Purification.  Depending on how tight your envelope is you will have to add some type of air purification to the home.  One-inch disposable filters were designed to protect your air conditioning equipment but have little effect on the health and comfort of occupants. Newer purification systems use various combinations of  4-5" filters, ionization and ultra-violet to purify air.

Consider Dehumidification.  Can't replace your air conditioner at this time?  A whole house dehumidifier can reduce humidity to acceptable levels.  Some of these units will introduce outside air and process it before it enters the envelope.

Conclusion:  Foam is a wonderful product.  But, if you wish to have a completely sealed, energy efficient foam home, you are responsible for the future health and comfort of the occupants.  You can plan for it in advance or you can call us to fix the problems that foam has created in your home.

Surgi's Heating and Air Conditioning offers free consultations for homeowners considering an upgrade to the efficiency of their homes including the addition of foam insulation.  If you live in southeast Louisiana, including the Greater New Orleans area, call Dale Neumire at 504-469-4232 to chat or schedule an appointment.

© 2011 Surgi's Heating and Air Conditioning, Inc.