Insulation without rodents?

The mission: Write about the importance of replacing or adding insulation to keep a home warmer and lower its energy costs. Bonus points for finding a type of insulation that is not attractive to rodents.

Person to talk to: Chuck Henrichsen, owner of Clean Crawls in Marysville and a licensed pest controller. He’s seen pretty much every critter there is that can wreak havoc in an attic or crawl space. Mice, rats, skunks, mink, otters — he has dealt with them all.

So, let’s tackle the energy efficiency issue first. Simply put, by setting aside some extra time now to improve your home’s energy efficiency, you can feel comfy cozy during the cold fall and winter months, plus save quite a few dollars in heating costs when the icy winds blow.

The effectiveness of insulation is rated by an R-value. The higher the R-value, the greater the material’s ability to insulate. New homes are required to have minimum amounts of insulation, but older homes have little or none. In fact, just in the past few years the R-value of insulation required throughout a home has increased.

“It was about 2002 when codes changed and construction went from two-by-four construction to two-by-six construction, allowing you to put R-21 insulation into the walls instead of an R-13,” Henrichsen said. The R-value codes for floors, attics, ceilings and heat ducts also increased.

For older homes with no insulation in the walls, cellulose insulation can be blown into the void between wall joists.

“On the outside of the home, we drill two-inch holes spaced between each wall joist, then inject cellulose insulation,” Henrichsen explained. The new insulation gives the walls an R-15 value. The holes, which are generally drilled just under the eaves, are then plugged by the insulation company, with the homeowner providing the paint touch-up work.

If your home is made of brick or stucco, adding insulation to your walls is a bit more complicated. The project will need to be tackled from the inside. The procedure is messy, but it can be done.

Insulation in the attic is especially important. Since heat rises, every effort should be made to keep it from leaving the home. Blanket or batt insulation is a popular choice that can be tackled by a homeowner. Fiberglass or cellulose insulation can also be blown in.

“Cellulose insulation is made from recycled newspaper and is fire retardant,” Henrichsen said. “It is very common to use cellulose because of the green movement we’re experiencing. Its cost and effectiveness are about the same as fiberglass.”

When upgrading an attic’s insulation, cellulose insulation should not be placed on top of existing fiberglass insulation.

“The cellulose is heavier and will compress what you already have up there,” Henrichsen said.

He also cautions homeowners not to walk across the attic’s insulation. “With people going through an attic and tromping through the insulation, if they’ve done it 10 times in the lifetime they’ve had the house, they’re probably losing a lot of heat,” he said.

The same goes for storing boxes in the attic. It condenses the insulation and reduces the R-value, Henrichsen said.

Heat ducts are another huge source of heat loss. Today’s code requires R-8 insulation to be applied to heat ducts, which translates to four to five inches of thickness. The utility companies prefer you have R-11 insulation. Ten years ago, insulation with a value of R-3 or R-4 was used and only measured one half inch or less.

“To add insulation to heat ducts, buy an R-11 batt and basically do a spindle wrap around the ductwork,” Henrichsen said. “Use twine to secure it but not condense the insulation. Squishing the insulation is what kills your R-value.”

Insulating the heat ducts provides a second important factor. “When you’ve got heat going into a crawl space, it attracts rodents,” Henrichsen said.

Ah, yes, rodents. If the heat’s not escaping the heat ducts in your crawl space, then you’re not providing a nice warm condo for the critters.

“A rat’s number one instinct is survival,” Henrichsen said. Rats want food, water and a nice place to nest. Most types of insulation provide a rat the perfect nesting ground.

Once the rats have made your attic or crawl space home, things won’t look — or smell — too wonderful. “The urine scent attracts more rats,” Henrichsen said. “If you plan to remove the insulation, make sure to deodorize the area, because that scent will continue to attract more rats. Leaving the insulation and not deodorizing the area is a recipe for disaster.”

Spray deodorizers can be purchased at the hardware store, but in the long run may cost as much, if not more, than hiring a professional to deodorize the space. “We personally use a fogger that creates a real fine mist,” Henrichsen said. “I can spray a 20 square-foot area in seven or eight seconds.”

A spray foam insulation may be your best bet in the quest against critters. “This is one of the things that has been found to be less conducive to rats,” Henricksen said. “They don’t like the material. They might chew or scratch at it here or there, but they’re not going to just destroy everything.”

According to Henrichsen, the professional spray foam is much like the ready foams available at hardware stores, but it’s a much more scientific mixture. “The base can have soy added to it so it has the green aspect going on instead of having a petroleum-based product added to it,” he said.

There are two other pests that can ruin your insulation: water and mold.

“Homeowners should be checking their crawl space and attic spaces on a regular basis, a minimum of every six months,” Henrichsen said. Water from a slow leak can weight down insulation. Wetness or improper ventilation can lead to mold. And check for critters. Always check for critters.

To save money on your insulation project, check with your utility company.

Snohomish County PUD, Puget Sound Energy and Cascade Natural Gas all provide generous rebates to qualifying customers. Loan programs may also be available.