My mom’s go-to phrase anytime my sister or I left a door open on the house is one many will recognize: “Were you born in a barn?!” 

From a building science perspective, I need to talk to you about opening your doors and windows during the summer months and how my mom — and your parents too — may have been right to call you out.

I can’t think of one person who doesn’t love to open their windows and get fresh air in the house when the weather is nice. But there is a hidden problem with that. 

During the warmer months, the amount of moisture in the air greatly increases. Meteorologists refer to this as humidity, and humidity is the enemy of air conditioning. 

When the humidity is higher than 50% approximately, the air becomes increasingly less comfortable. You know the feeling when it’s muggy out. When you open your windows and doors on muggy days to get fresh air, you are allowing the moisture in the air to saturate any material in your home that can absorb it. 

When it becomes too hot and humid to keep your doors and windows open, you close them and turn on your air conditioning. Your A/C now has to dedicate the majority of its function to removing that humidity before it can efficiently cool the air. This adds extra cost to the operation of your A/C. 

As a general rule of thumb, if the outside air temperature is at a level that you enjoy and the relative humidity is at or below 50%, then open up those windows and doors. If, however, the relative humidity is above 50%, I would suggest you keep the windows and doors closed and allow the A/C to maintain a comfortable climate.

If you have questions about your cooling system or our rebate programs for heat pumps, then give me a call. I would love to answer them for you.