In every house I visit to do an energy audit, the electrical outlets have been a major source of air infiltration. Sealing these holes up in your thermal envelope will reduce your energy usage and make your home more comfortable.
Yes, I realize these are small areas with small gaps. However, there is very little if any insulation behind the box in the wall. There is almost never any air sealing around the box.
The easiest first step is to add child protection covers to the outlets. This stops some of the air moving through the outlet. The next step is to add insulation strips behind the outlet cover. While they are thin and offer very little R-Value – they are better than nothing.
The final step, seal the box tight to the drywall.
All of these steps should be done in order to maximize the effectiveness of the solution. Sealing and insulating all the outlets in both interior and exterior walls is a critical first step in making your home more energy-efficient. To learn more about making your home energy-efficient, read this post.