How to Insulate Electrical Boxes

Duplex Receptacle with Weatherproof Cover

According to an article by Dan Thompson, "Reducing Heat Loss in Residential Construction: The Insulated Electrical Outlet Box", posted on the E Building Envelope Forum, as much as 20 percent of all air infiltration into homes occurs around electrical boxes mounted in external walls. The Insulated Electrical Box® invented by the Insulation Business Consultants of Brevard, NC has gone a long way towards eliminating this problem and many buildings now require these boxes to be used in new construction. You can reduce your heat loss without replacing your old outlet boxes by using minimal expanding foam insulation around the outlet boxes and installing foam gaskets between the box and the receptacle or switch cover plates.

Things You'll Need

• Screwdrivers
• Two inch wide masking tape
• Scissors
• Safety goggles
• Rubber gloves
• Old paint brush
• Minimal expanding foam insulation
• Razor knife
• Foam gaskets for duplex receptacles
• Foam gaskets for switches

Instructions

1. 

   Screwdrivers

   Turn off the circuit breaker protecting the branch circuit that you will be working on and remove the switch and receptacle cover plates.

2. 

   Paintbrush

   Remove any dirt or loose wall finish material from between the outside edge of the device boxes (electrical boxes) and the wall using an old paintbrush.

3. 

   Masking tape

   Mask off the front of the receptacles and switches. Cover the front of the box completely from edge to edge with tape but don't allow the tape to cover the gap between the box and the wall. You don't want any of the minimal expanding foam aerosols to enter the boxes or get on the duplex receptacles or switches but you do want to fill the gap between the box and the wall.

4. 

   Safety Goggles

   Put on your safety goggles and rubber gloves before proceeding further.

5. 

   Rubber Gloves

   Using the straw applicator that came with the aerosol can, run a small bead of minimal expanding foam insulation between the outside edge of the boxes and the wall finish. Minimal expanding foam expands five to ten times in volume so a little bit goes a long ways.

6. 

   Razor Knife

   Allow the minimal expanding foam to set up for 12 to 24 hours before proceeding. Minimal expanding foam will appear solid and be tactless after 15 or 20 minutes but it won't be cured all the way through until 12 to 24 hours have passed.

7. 

   Switch with Faux Wood Cover Plate

   Trim the cured foam flat with the wall surface using the razor knife. Trim a foam gasket to fit the outlet or switch opening and fit in place.

8. 

   Duplex receptacle

   Replace cover plates and turn on the circuit breaker.

Tips & Warnings

• Always turn off the power to the circuits you are working on. The gas used to pressurize minimal expanding foam aerosols is highly flammable and any accidental arcing in an electrical box could ignite it.

• Always wear protective eye wear and rubber gloves. Minimal expanding foam is an irritant. The vapor can damage your eyes. Minimal expanding foam that gets on your skin and sets up will be there until it's forcibly peeled off or it wears off.

References

• crcindustries: Technical Data Sheet Minimal Expanding Foam
• greatstuff.dow: GREAT STUFF™ -- Directions and Safe Handling