More insulation: A hot idea -- or not?

Jim Mallery | Improvement Center Columnist | July 18, 2013

Are you concerned that your energy bills are running too high and think the answer is more insulation? While you might achieve big energy savings by popping some additional batts of insulation into your attic, your lack of energy efficiency can continue to drive you batty if poor insulation is not the cause of your problem.

Before you jump to the conclusion that you need more of a good thing, consider the possible causes of your particular home's energy problems. Just because your cousin in Maine has insulated his roof to R-60, doesn't mean you should rush to do the same to your home in Miami. Insulation needs differ by regional climate. And some investigation and analysis into your own home's energy weaknesses is necessary before deciding what actions to take.

Do an energy audit

First, if you have concerns about your escalating energy costs, consider an energy audit. A certified auditor can comb your home for all issues energy-related and opportunities for improved efficiency, including your usage habits.

A house is really a closed energy system, explains Craig Olson, a certified energy auditor with Washington Energy Services in the greater Seattle area. "An audit may find that your insulation is fine, but you have a multitude of other problems -- windows, doors, air leaks, furnace, etc. -- that are wasting energy," says Olson.

A comprehensive energy audit typically costs $300 to $500 but can be higher. Your local utility may offer free energy checks; however, they are usually less thorough.

Unless a house was built before 1960, Olson says, you can concentrate your search for answers on the top and bottom -- the attic and crawl space. That's because heat rises, he explains. It's much less likely to travel horizontally through walls, unless there is absolutely no insulation in the walls, as was likely to be the case before 1960.

Examine insulation in the attic

Investigating your attic can turn up a number of insulation-related problems -- everything from uninsulated space, ventilation issues and rodent damage to wiring considerations if you plan to add insulation.

  • Cathedral ceilings and low-pitched roofs -- These can be problematic for insulators because there may not be room in the trusses to add more insulation. A traditional roof/ceiling system has to have ventilation above the insulation to prevent moisture buildup. If the cathedral ceiling has room for more insulation but no access, you could increase insulation during reroofing, or a contractor may be able to cut holes in the ceiling drywall and insert more insulation. Olson says a contractor can eliminate the need for venting the area above the ceiling by densely packing the insulation so that the space from ceiling to roof is solid insulation to prevent moisture transfer. As with steeply pitched roofs, very low-pitched, or flat roofs also can pose space problems.
  • Rodents -- Even if you have enough space to add more insulation in the attic, rodents may have ruined your insulation either with their droppings or by packing it down and rendering it ineffective. In this case the insulation must be removed and replaced.

  • Wiring -- You must not insulate over a junction box -- an electrical box where wires are spliced together. If you've rewired the attic, those junction boxes should be visible above the new insulation. If your house is especially old, built in the 1940s or '50s, you should have an electrician inspect for degraded wiring before you add insulation. If the house was built before 1940, you might even have the ancient knob-and-tube wiring that you are not supposed to cover with insulation. In that case, you would have to rewire.
  • Air sealing -- Olson emphasizes that any insulation project should include air sealing, shutting off passages where air can travel between the living space and the attic, such as wiring holes, light cans or chimneys. An energy auditor can detect air gaps with heat monitors and air-pressure testing. Olson points out that a homeowner may be able to detect some air gaps by looking for patches of dirty insulation -- the insulation can act as a filter for dusty air as it passes from the house to the attic. In parts of the country where roof eaves develop ice dams in winter, sealing is an important measure to help prevent them.
  • Knee walls -- A knee wall is a vertical wall in the attic, such as you might find in a dormer bedroom. Knee walls don't present stumbling blocks for insulators other than they require proper methodology, of which some contractors and most DIYers might not be aware. That includes insulating the wall as if it were an exterior wall, assuring that there is proper ventilation throughout the system -- including above the bedroom ceiling -- and proper air-sealing between the bedroom floor and the ceiling below. A dormer bedroom that is too hot in the summer and too cool in the winter probably has not been insulated properly.

knee wall insulation

Knee wall insulation

Explore the crawl space

crawl space hole

Courtesy of Washington Energy Services: This large plumbing hole in the crawl space should be covered.

Your floor also needs to be insulated, though not as much as the ceiling. The biggest problem with insulating the crawl space is that you have to go down there to investigate. It's probably a homeowner's least favorite place.

As with the attic, you need to seal all air penetrations. If you own a newer home, don't be freaked out to discover that you have no insulation under your floor. You may have a sealed system, recommended by the Department of Energy, in which the crawl space is closed off as if it were a basement. The foundation and crawl-space walls are waterproofed, sealed and insulated, and a waterproof membrane covers the dirt. A sealed crawl space uses less insulation, and you do not have to insulate your ducts.

Add adequate insulation to walls

If your home was built pre-1960 and the walls are not insulated at all, you can cut holes in the drywall between studs and blow in insulation.

If you want to increase the insulation in walls that are already insulated, you have some options, though the effort may not be cost-effective.

  • You can remove the siding and cover the exterior of the wall with insulative wall sheathing, which can add an R-value of 3 or more. You would then cover that with new siding.
  • You can also install insulated vinyl siding, which would add a minimum of R-2.
  • If you were remodeling a room, you could remove the drywall and fur out the wall with a 2-by-2 to create more depth for thick insulation -- old wall construction used 2-by-4s and modern construction uses 2-by-6s.

Insulate forced-air HVAC ducts

If you have forced-air heating and cooling, the ducts must be insulated. If you've been thinking your home's insulation is inadequate, a big portion of your problem could be uninsulated ductwork running through the crawl space or attic.

Insulation is a good thing, and sometimes, more is better, especially if you have none or very little. But adding more may be very difficult and may not help in every situation. If you have other issues -- things like air leaks, an antiquated furnace, single-pane windows -- rectifying them could be just as, if not more, important than adding insulation first. But if you do decide to add insulation, keep in mind -- poorly installed insulation could actually do more harm than good for you and your home. Do your research and seek out professional advice to avoid the pitfalls.

About the Author

Jim Mallery, a semi-retired journalist and onetime registered contractor, has extensive experience remodeling, repairing and rebuilding homes.