Air Sealing a Drafty House

Learn techniques to more than double your home walls' energy-efficiency rating.

Insulation and Air Sealing 03:06

New insulation greatly increases the r-value of the Wilsons' house.

A leaky house can run up hefty energy bills. So rather than continuing to heat and cool a 70-year-old home with virtually no insulation, the Wilson family embarked on a Deep Energy Retrofit (DER) that will eventually bring the operating cost of their house down to zero.

Imagine not paying to heat or cool your home.

"I'm hoping we can save 50 to 90 percent on our energy costs from the process, which is a combination of air sealing, insulation, windows and doors and new off-the-shelf HVAC technology," says Jeff Wilson, who jump-started the DER on his Athens, Ohio, home with a thorough energy audit and assessment to pinpoint leaks.

Air Sealing and Insulation for Maximum Efficiency

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Homeowner and carpenter Jeff Wilson hopes to save 50 percent to 90 percent on energy costs through his Deep Energy Retrofit (DER) project. To achieve this goal, Jeff must air seal his 70-year-old home and ensure the new garage/addition envelope is tight. He used two air sealing methods: one in retrofitting the original home and another involving new construction techniques for the garage/addition.

Using the original painted redwood siding as a foundation for new insulation, Jeff began creating a curtain wall by nailing 2x3 framing to the exterior.

Jeff and the crew worked on the original siding while building the new garage/addition. Here you can see 2x3 framing installed on the original siding and the frame of the addition, which will be insulated from the interior.

The original house was insulated from the exterior. About 2 1/2 inches of Foam-It Green spray foam insulation was applied between the 2x3s.

The spray foam will reinforce cellulose insulation that was blown into the walls of the original home five years ago. On top of the foam, sheathing was applied. This surface was covered with house wrap before SmartSide ready-to-paint engineered wood siding was installed.

Jeff and the crew demolished the old garage that was attached to the original home and built a new garage/addition, applying today's energy efficient best practices.

This photo shows the crew insulating the floor of the yet-to-be-built addition. It's a floating slab surface cradled with foam insulation four inches thick on the bottom and two inches thick on the sides. The slab doesn't touch concrete block or dirt; therefore it doesn't transfer heat or cold air into the space.

After the foundation and first floor are finished, rafters are put in for the addition's second level.

Framing goes in for the area above the new garage, which will serve as an office or apartment.

The new structure was seven feet wider than the old garage and had higher ceilings (13 feet) to accommodate a second level. Jeff had to raise the roof angle of the entire back of the house (both old and new). This also created a flatter surface to support solar panels.

This is the view of the back of the home as sheathing is applied to the new addition's exterior.

Jeff installs radiant sheathing on the rafters of his home and the addition. This prevents heat generated by sunlight hitting the roof from entering the structures.

The interior walls of the new garage/addition get Foam-It Green treatment. Because the wall cavities are deeper, Jeff has room to install three more inches of fiberglass batting to further insulate the wall.

Jeff's goal was to boost the R-value of the new garage/addition. Jeff double-insulated, using spray foam and batting, achieving R-27 — twice the efficiency of his original home's walls when they were only filled with cellulose.

Air sealing is a key component of the DER and what will allow the Wilsons to live comfortably in their home.

"The idea that you have to freeze in the dark in the new energy economy is wrong," Jeff says. "We want our houses to be more responsive, healthier and cheaper to run. We can have that."

Before Air Sealing the Home

Five years ago Jeff began exploring ways to improve the insulation in his home. Like most old houses, the construction left a gap — a big air pocket — between the plaster wall and the original redwood exterior siding. (The previous owners had slapped aluminum siding on top of this damaged surface.)

Jeff hired a company to blow cellulose insulation into the walls to fill that gap. Cellulose is essentially chopped-up newspaper treated with a fire retardant. Pieces of exterior siding are removed, and holes are punched into the surface to make room for hoses that force insulation into the wall. The damp cellulose expands in the wall cavity and prevents air passage. The price of this service was $1,200 in 2005.

Immediately afterward, Wilsons' heating bills dropped 10 percent to 15 percent. "And there was less noise from outside," he adds. Because the front of the home is brick, cellulose was blown in through interior walls. Jeff patched up holes in the plaster wall after the project.

Still, after this additional padding, the average monthly cost of heating and cooling the home was $160. Jeff intended to slash this price, tighten the home and improve indoor air quality with air sealing.

Air Sealing Two Ways

Jeff used a combination of green retrofit technology and new construction techniques on his home air sealing project. The original home needed a "curtain wall" — layers of insulation enveloping the home. The new garage/addition was insulated from the interior, using the same products but a different application technique.

House: Air sealing efforts focused on insulating the exterior of the home. This required removal of the aluminum siding, which revealed rotted redwood siding. Underneath the siding was plank sheathing fixed to the home's skeleton — 2x4 framing. Cellulose filled the cavity between the framing and the plaster interior walls.

Jeff used the redwood siding as his starting point, fixing 2x3 studs (the skeleton) into the redwood siding that looked like a grid. Then, Jeff filled those gaps with 2 1/2 inches of Foam-It Green spray-foam insulation. Over the foam, Jeff fixed standard sheathing. On top of this, he applied house wrap. "The house wrap was a little redundant because the air sealing from the foam would have air sealed the house, but we were concerned about making this last," Jeff says.

Siding was the last step, and Jeff opted for SmartSide, which is ready-to-paint engineered wood siding treated with nontoxic resins.

New Garage/Addition: Jeff employed new construction techniques on the garage/addition, building 2x6 walls for a deeper cavity to hold more insulation. (By comparison, the original home's walls are a true 2x4.) Sheathing was applied on top of the new addition's framing, followed by house wrap. Then, Jeff worked on insulating the interior wall since he had complete access to this surface — unlike with the original home, which already had painted plaster walls in place.

Jeff filled between the framing with 2 1/2 inches of Foam-It Green spray insulation. That gave him three more inches of wall cavity to add more insulation, so he chose fiberglass batting with an energy efficient rating, or R-value, of R-13. Finally, interior walls were installed. (Remember, the original home's cavity is filled with less-efficient cellulose and air sealing was accomplished by insulating the exterior.)

Garage Floor: Rather than laying a basic concrete slab floor, Jeff opted for a floating slab that is cradled with foam insulation four inches thick on the bottom and two inches thick on the sides. "The slab doesn't touch concrete block or dirt," he explains. "It sits on foam, and there is plastic underneath to keep moisture from seeping through."

Why bother insulating the floor? By doing so, Jeff will prevent heat loss and cold air entry through the cement. "Even though it's a garage, it's still a workshop and upstairs is space we'll inhabit as an office or bedroom," he says.

DIY Tips

The insulating techniques Jeff used will give the home a long-lasting air seal — at least 70 years, and probably longer, he estimates. "We're not only making the house last longer, we're adding something to it that's just not going to go away," he explains. "The payback is dependent on what energy costs do in the coming years."

  • If you want to beef up the insulation in your home, start by finding out where the leaky spots are by getting an energy audit. That way you can focus your dollars on trouble spots.
  • Blown-in cellulose insulation can fill empty wall cavities and decrease heating bills. Jeff realized a 10 percent to 15 percent savings immediately for the $1,200 project.
  • When planning a new addition, investigate off-the-shelf technologies that will boost your home's R-value. Jeff double-insulated using spray foam and batting, achieving R-27 — double the efficiency of his home's walls when they were only filled with cellulose.
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