Why You're Losing Money - Air Seal Your Attic
Air Sealing the Most Common Attic Air Leaks
Electrical, plumbing and HVAC contractors use your attic to conceal the wires, pipes and ducts that comprise the mechanical systems in your home.
During the construction of your home, they drill and cut holes through the walls to run these pipes and wires. Follow the interior and exterior walls and look for the holes. You'll also want to look for chimneys, furnace flues and lights. This is where most of your largest leaks can be found.
Looking up at the ceiling underneath your attic should help you find the holes. Before you go up into the attic, try to get familiar with your home's layout or just sketch out a floor plan map. This helps you keep your bearings as you ascend into the attic.
While you are in the attic, carefully move over to the areas you've identified and pull back the insulation. If the insulation is black and dirty, you know you've definitely found an air leak. As the warm air rises through air leaks in your ceiling it carries dust which is filtered out by your insulation. Leaving behind a black or brown stain like the one in this video.
Air Sealing the Attic Perimeter
Air sealing the wall plate around the perimeter of your attic blocks air from escaping around the outer edges of your home. It's usually the hardest place to air seal because the cramped space underneath the eaves (where the roof rafters rest on the outer wall) makes it hard to move your hands and head.
Start in the back corner of your attic working on one section at a time. Remove the insulation so you can see what your doing and lay some plywood down for a work platform. Crawl into position under the eaves and seal up the gap between the drywall and exterior top plate with some Great Stuff.
This can be easier said than done because the can of Great Stuff needs to be held upside down and the little hose that comes with the can is tough to maneuver. So I jam a 2 foot piece of 5/16" clear tubing onto the end of the hose and duct tape a piece of pvc pipe or wood to the tube. That way I can reach back into the tight spaces under the eaves.
Air Sealing the Top Plates and Electrical Wires
While the Great Stuff is drying, try to find the top plates of any interior walls that are nearby. Remove the insulation and squirt some Great Stuff in between the drywall and the framing. You'll probably find some wires piercing through the plate. Stick the tube down in the hole and squeeze the trigger until the foam comes out of the hole. Keep moving around uncovering more interior wall plates until the Great Stuff skins over and is no longer sticky. Then put the insulation back into place and move on.
Air Sealing Ceiling Light Boxes
There's usually a light in the center of most rooms. From your vantage point inside the attic, all you see is an electrical ceiling box with wires sticking out of it. This hole in the ceiling needs to be sealed with either Great Stuff or caulk. Seal around the light box where it touches the drywall and all of the wiring holes on the top and sides of the box. Note: Don't squirt the Great Stuff into the box.
Air Sealing Plumbing Pipes and Attic Chases
Plumbing vent pipes typically have excessively large holes cut around them or they enter the attic through a framed opening known as a plumbing chase. Pipes coming up through holes in drilled through the top plate can usually be sealed off with a few squirts of Great Stuff. For the large plumbing chase you need to cut a piece of drywall or foam insulation board large enough to cover the hole. Then seal around the perimeter with Great Stuff
Air Sealing Around Ductwork
Some of the largest holes I see are usually from the HVAC contractors running ductwork. You might be able to get away with Great Stuff, but some of the gaps are just too big.
If you run into large gaps, cut a piece of drywall or foam board around it and screw it into the framing. It doesn't have to be perfect because you finish it off with Great Stuff.
Air Sealing Dropped Ceilings
Some bathrooms and kitchens have dropped ceilings. This is a space over the tub, shower or kitchen cabinets that's lower than the rest of the ceiling. They may be hard to spot up in the attic if there's already insulation up there. So get your bearings from below to zero in on them.
Pull the insulation back to uncover the ceiling and look for black or discolored insulation. These black marks should guide you to the gaps and cracks that are leaking air into your attic. You can seal these leaks with Great Stuff or you can enclose the entire dropped ceiling with foam board insulation or drywall and air seal around the perimeter with Great Stuff.
Pay Careful Attention to Heat Sources
Heat sources in your attic include chimneys, furnace flues and recessed lights. Air sealing around these ceiling penetrations can be a little more challenging because they can start a fire. Chimneys are usually create the least heat, but Non-IC (non insulation contact) recessed lights and furnace flues can reach temperatures of 300 degrees farenheit. So you need to keep the insulation at least 3" from these high temperatures.
Air Sealing Chimneys
Cut a few pieces of sheet metal or roof flashing to cover around the opening in the framing and nail it into the framing. You may need to bend a few pieces to create a nailing flange. Bending flashing or sheet metal is easy if you sandwich the metal between the floor and a scrap 2X. Mark a line where you want the bend the flashing and put the 2X on that line. Then pull up on the ends of the sheet metal and press it against the 2X, creating the bend. Seal off the remaining gaps with Great Stuff Fireblock or high temperature caulk.
Sealing the Chimney Top with an Air Tight Removable Seal
If you have an open wood burning fireplace that your rarely use, you may want to consider sealing the chimney top with a removable seal. Open fireplaces cost the average homeowner $300 dollars a year by sucking the heat out of your home. Even with the glass doors closed, your fireplace exaust warm, heated air out of your home at an alarming rate. Sealing up your chimney is cheap and easy.
Air Sealing Furnace Flues
The first step in air sealing a furnace flue is to approximate the diameter of the flue. It's almost always similar in size to a coffee can which is what I use to draw a circle on a piece of sheet metal. Try to make the hole a little bigger just to be safe. Cut the sheet metal to fit between the ceiling joists, then cut it in half right through the middle of the circle. Now cut the circle out and check for a fit. Place one half on either side of the flue and make adjustments if needed. Secure the flashing to the drywall with a bead of caulk around the flue. Press the sheet metal into place and seal it off around the flue with high temperature caulk.
Air sealing recessed lights can be a little tricky. Non-IC rated lights build up a lot of heat and are not rated for direct contact with insulation. IC rated recessed lights are rated for insulation contact. They are less than $15 at Lowe's and the Home Depot. If you have some electrical skills, you may want to consider replacing them or calling in an electrician for a few hours.
Air Sealing Recessed Lights
If you decide to air seal the recessed lights, keep the insulation within 3" of the light and don't put insulation on top of them. Use high temperature caulk around the rim where the light penetrates the drywall. It's usally tough to get the caulking gun to squeeze in around framing. Try taping a 6" piece of 5/16" clear tubing to the end of the caulk tip to increase your reach in the tight spaces around the light. Electrical tape works great for this.
Air Sealing the Attic Door
Your attic door or drop down attic stairs are a major source of air leakage. It's by far the largest hole in your ceiling and it's probably costing you a fortune. Blocking the air from leaking through the attic door is one of the most important things you can do.
Your options for air sealing the attic door are:
1. Buying an attic door
2. Building an attic door
Building an Insulated Attic Door
Building an attic door cover is easy if you have the right tools. All you need to do is:
- Cut a piece of plywood to the size of your attic door.
- Cut a few pieces of foam board insulation the same size and screw them to the plywood with long 4" screws.
- Install a piece of weather stripping around the access hole in the attic.
- Drop the attic door over the weather stripping and mark around the perimeter of the attic door with a marker.
- Take the attic door off and install a couple of hook and eye locks near the perimeter marking on the plywood side of the attic door.
- Reinstall the attic door and install the eyes of the hook and eye lock so they pull down on the attic door. This creates an air tight seal.