Attic insulation and your roof: why it plays a vital role

If your roof has ever leaked, your attic insulation was probably soaked too, and if nobody replaced it, it is worth having it checked. Attic insulation and your roof work as a team. Insulation keeps your home comfortable, but it also protects the roof deck from moisture, helps prevent ice dams and keeps your HVAC system from working overtime. After years of climbing into Tennessee attics, we have learned that old and new homes alike often come up short on insulation, ventilation or both.

Attic insulation and your roof: what it does

Insulation does more than keep heated or cooled air inside. It also keeps summer attic heat and winter cold from getting into your living space. Beyond that, good attic insulation:

• Works with air sealing to keep damp household air out of the attic.
• Helps your heating and cooling system last as long as it should.
• Works with attic ventilation to help prevent ice dams.
• Prevents avoidable roof damage from condensation and rot.

How insulation and ventilation protect your roof

Moisture from bathrooms, the laundry room and the kitchen rises. When it reaches the attic and meets the cooler roof deck, it condenses, and over time that can lead to mildew, mold and soft decking. This is one of the most preventable kinds of roof damage.

In winter, an attic that is well insulated and well ventilated stays closer to the outside temperature. That keeps snow on the roof from melting from below and refreezing at the eaves, which is how ice dams form and damage shingles, fascia and gutters. And when your heated or cooled air escapes easily through the ceiling, your HVAC system runs longer and wears out sooner. Insulation and ventilation have to work together: insulation slows heat, and ventilation carries away the heat and moisture that still get through.

How much attic insulation does a Tennessee home need?

The right amount is measured in R-value, which is how well insulation resists heat flow, not in inches, because different types of insulation give different R-values per inch. Most of Middle and East Tennessee, including Davidson, Wilson and Knox counties, is in climate zone 4A according to the Department of Energy's guide to climate regions by county.

For zone 4A, ENERGY STAR's recommended insulation R-values call for R-60 in an uninsulated attic, or adding R-49 if the attic already has 3 to 4 inches of insulation. Our post on whether you have enough attic insulation explains how to check what you have.

Don't count on insulation that has been wet

If your insulation was ever soaked by a roof leak and your roofer did not recommend replacing it, ask to have it checked. Wet insulation often cannot perform the way it should even after it dries: it compacts, loses loft and can hold moisture against the ceiling drywall and framing. In many cases it needs to be replaced, and after a storm, damaged insulation may be part of your insurance claim, depending on your policy.

Why many homes come up short

The most common reason is age. Older homes were built when recommended insulation levels were much lower, and many attics have never been topped up. Blown insulation also settles over the years, so an attic that was right when the house was built may not be today.

Another reason is a rushed installation. When builders hire out blown insulation, the work is often not closely checked, and an attic can end up with thin spots or less insulation than it should have. Air leaks around attic hatches, recessed lights and plumbing can undercut even a good layer of insulation.

Signs your attic needs attention

• Rooms that are hard to keep comfortable, or energy bills that keep creeping up.
• Ceiling joists visible above the insulation, or bare spots and low areas.
• Ice dams or long icicles along the eaves after snow.
• A musty smell, dark stains on the roof deck or damp, matted insulation.
• A past roof leak that was repaired without anyone checking the insulation.

We can check your attic

When we inspect or repair your roof, we look at the attic too, and we can tell you whether your insulation and ventilation look right. Our renovation work includes attic vents and insulation, so if your attic needs help, we can take care of it along with a roof inspection, roof leak repair or roof replacement. Mobley Brothers Roofing & Renovation has offices in Lebanon and Knoxville, both A+ rated by the Better Business Bureau in Lebanon and Knoxville. Call our Lebanon office at (615) 455-3131 for Middle Tennessee or our Knoxville office at (865) 205-0800 for East Tennessee, or request a free estimate online.