It happens every year. I get a few calls from customers who say “I installed AtticFoil® – it’s a great product and I could really tell a difference in the summer, but now I am having trouble getting my house to cool off at night. Is the radiant barrier working right?”
Remember heat ALWAYS flows from hot to cold. So, if it is hotter outside than inside your home, heat is flowing IN – typical summer weather. Or, if it is cold outside and warm inside heat is flowing OUT – typical winter weather. The problem is that there is typically a period in the spring and fall when the heat flow FLIPS in the middle of the day. Example: It may be warm – 80º in the afternoon and heat is flowing IN, then it cools off at night down to 50º heat is now flowing OUT of the house.
The challenge is that radiant barrier does not know that you want your home to cool off on nights like this. It is just doing its job. Radiant Barrier will ALWAYS reduce heat flow from hot to cold – even if you don’t want it too. In the afternoon, AtticFoil® radiant barrier is reflecting heat OUT of the home to keep the home cooler; at night it will help KEEP the heat inside to maintain a warmer home.
Yes, it is true. There are some days each year when an installed radiant barrier will cause the opposite effect of what you may want, but the solution is usually pretty easy to solve. In the evening, once the air temperature cools off, you need to flush out the heat your home is holding inside. The best way to do this is to crack open some windows and run bathroom exhaust fans and/or a kitchen vent hood fan to help pull out the warm air and heat inside the home. I even heard of one customer who would pull down their attic staircase in order to allow air to enter through the windows and escape through the attic.
Fortunately, this uncomfortable period usually only last for a few weeks before the weather changes to consistently hot or cold. Therefore, the overall benefit of installing a radiant barrier far outweighs this short-term inconvenience.
Interestingly, we have many customers who do not have air conditioning. They live in mild climates or higher altitudes that cool off significantly at night. However, even in these areas there are usually a few weeks of the year where they wished they did have air conditioning. We often hear that installing a radiant barrier has made a huge difference during this period and keeps their home comfortable by not heating up as much – even on the hottest days.