Warm Up Your Home's Walls

Adding insulation to your walls always improves your home's comfort. Based on economic analysis by E-Star Home Energy Rating System, insulating your wood-frame walls is nearly always a cost-effective cure anywhere in Colorado. Insulating brick walls, while also a proven comfort and energy winner, is a tougher call.

To determine what action makes the most sense in your home, have your walls checked by a certified E-Star energy rater, plus have the house tested for tightness and your home's other energy features evaluated for possible improvements. Then call the Denver Home Builders Association (303-7781400) for a list of their insulation contractor members; get several bids as well as a good description of how each would do the job.

Insulating frame walls

Empty stud cavities can be "blown" with loose-fill insulation, but this isn't really a do-it-yourselfer type of job. Here's how a contractor typically will do the work. First, depending on the type of siding or other exterior finish, a 2.5-inch hole is drilled from either indoors or outside into each wall cavity. Then a long 1.5inch diameter vinyl tube is stuck through the hole down to the bottom of the wall cavity. The tube is hooked up to a four-inch hose that snakes out to machinery in an insulation truck.

Bags of compacted loose insulation are dumped into the mixing machine that loosens up the insulation. Then air pressure blows the insulation through the hose and into the bottom of the wall cavity. As insulation is forced through the hose by high air pressure, it packs densely into the entire width of the cavity, slowly pushing up the hose as it packs in. Once the cavity is filled, the holes are plugged with material that matches the surrounding surface (wood, drywall, stucco, etc.).

Two common insulations

The two most common types of insulation blown into walls are cellulose and fiberglass.

Cellulose is made from ground-up newsprint and wood-fiber material (85 percent) that is mixed with a fire retardant (15 percent). Denver-based About Saving Heat Co. (ASHCo) and Sun Power Inc. normally use cellulose. According to Sun Power's Charlie Wright, he can pack the cavity to a much higher density (about 3.5 lbs per cubic foot) with cellulose, and that helps reduce air leaks in the home. ASHCo.'s Dennis Brachfeld also says it costs more to pack walls with loose fiberglass than with cellulose.

Since you can't see the wall, how do you know it's filled with insulation when the workers are finished?

Using a hand-held infrared device that measures surface temperatures, Brachfeld takes numerous before-and-after temperature readings with the homeowner present to prove to them that the inside wall surface is warmer in winter (or cooler in summer) than it was before being insulated.

A fair indicator of whether the walls were densely packed with insulation is to check the number of bags used on a job; you can figure it takes one bag per 2025 square feet of wall area.

Sun Power and ASHco. say holes for installing insulation are usually drilled from the outside. However, the choice of outside vs. inside depends on the type of siding as well as on customer preference. With wood siding, drilling from the outside is usually faster, but you'll need to paint the sanded wood plugs to match your paint job. On homes with brick veneer, good insulators can drill half inch holes through mortar joints so that you will hardly notice once they have filled the holes with mortar. Going through the interior drywall is a good option if you plan to paint the inside soon. On homes with metal siding, the holes for insulation must be drilled through the interior surface; if that surface is wood paneling, you're simply out of luck.

Re-insulate frame walls

Homes built during the 1960s and early 1970s often had thin batts (1.5-2inches thick) installed in the walls.

By today's standards, that provides very minimal insulation-between R-5 and R-7 insulation, compared to either R-13 or R-15 batts installed in today's new homes. (The higher the R-value, the better the insulating benefit.)

Furthermore, allowing air to circulate on either side of a batt within a wall cavity can further reduce the batt's insulating benefit. So Brachfeld recommends re-insulating those partially insulated walls.

The technique is the same as described above for an uninsulated wall. A vinyl tube shoved down to the bottom blows insulation into the cavity, compressing the batt against one side. The installer needs to be careful to move the tube around in order to completely fill the cavity. Once the wall cavity is filled, the resulting wall should be insulated to R-13 and the home should be both tighter and less drafty.

Because of homeowner comfort complaints, Brachfeld reports that he even re-insulates 1980s homes with R-11 low-density fiberglass batts. For skeptical homeowners with comfort complaints, Brachfeld makes the following offer: "If you're not sure about this, let us just re-insulate your coldest room. I guarantee that after we re-insulate it, the room will be warmer, and I'll prove it will the infrared sensor. In fact, the reinsulated room should become your warmest room." About 10 percent of ASHCo's customers start by re-insulating just one room or one wall; within a year, he says every one of them has reinsulated the rest of their home.

Costs

The most common range of costs is between $0.90 and $1.25 per square foot of total wall surface, including windows and doors. Drilling and insulating through smaller holes in brick veneer takes longer, so the cost is on the high end of this range.

Brachfeld says that for the average home where he insulates walls, the typical cost range is between $800 and $1000.

Save energy

Insulating your walls should cut your annual heating bill by 15 to 30 percent. Here's a quick case study, reported by Mountain View Electric Association, after a major reinsulation upgrade in 38 townhomes they own in Limon. These 1975-vintage electrically heated units were already insulated and had double glazed windows, yet tenants were moving out because of comfort problems and high heating bills. The primary upgrade was re-insulation by Insulation Services and ASHCo. In the attic, four inches of cellulose was blown over the top of R-30 fiberglass. The contractors blew cellulose into the 2x6inch walls which already had R-19 batts in them. Common walls between the townhome units were insulated with cellulose, as were the in-floor spaces around the perimeter of each unit. This re-insulation package, in combination with storm doors and windows, significantly improved comfort in each home while cutting heating bills by roughly 50 percent.

Insulating masonry walls

Uninsulated double-brick or blockbrick walls offer poor insulation (R-3) and are very cold in winter. Insulating them can be much more expensive than frame wall insulation, but the energy savings should be comparable and there will be a dramatic improvement in comfort. If your exterior brick is covered with peeling or flaking paint, or the unpainted brick needs a major facelift, instead of repainting consider covering the outside with a three-inch layer of foam and applying a stucco finish over that. This isn't cheap; expect to pay $4 to $5.50 per square foot. Yet besides better comfort and energy savings and low maintenance, the finished product provides a fresh new look that adds value to tired exteriors.

If you want to preserve the brick exterior and the inside needs a major rehab, you can frame out the interior side with 2x4's, insulate the cavities with baits or sprayed insulation, and then just drywall over the frame. If you need to save space, use a skinnier foam and furring strip system that takes up only two total inches while providing up to R-12 insulation.

Steve Andrews consults with builders for E-Star Colorado and writes on energy issues (sbandrews@att.net). E-Star (www.e-star.com), is a nonprofit home energy rating system that works with both new and existing homes statewide.

2008 Built Green Colorado

Home Builders Association of Metro Denver, 9033 E. Easter Place, Suite 200, Centennial, CO 80112
(303) 778-1400 fax: (303) 733-9440  info@builtgreen.org

Last Updated: 10/05/2007