More insulation in the attic makes an older house easier to keep at the temperature you want, upstairs as much as down. Together with sealing the air leaks into the attic, it can also help cut down the ice that builds along the eaves in winter. In a house with an unfinished attic, the insulation lies on the attic floor, between the joists and over them. That’s the easiest place to add more, and usually the one with the most to gain.
How a house shows it’s short on insulation
Any of these can mean a house could use more attic insulation: drafty rooms, ceilings or whole rooms that run hot or cold, high heating and cooling bills, and ice dams along the eaves.
The ice is where the attic and the roof meet. Ice dams start with heat collecting in an attic that’s poorly insulated or poorly ventilated, and they’re more common in older homes with less insulation up there. Preventing ice dams in the Lehigh Valley explains how the ice builds, and what to check before the first hard freeze.
Seal before you insulate: air sealing the attic comes first. To see where the leaks tend to be, and what damp air does once it gets up there, read how humidity affects roof shingles.
Is there enough up there?
Look across the attic floor from the hatch. If the insulation is level with the joists or below them, so you can easily see them, it needs more. If it covers the joists evenly, you probably have enough.
Check the edges too. The insulation can be thick in the middle of the attic and thin out toward the eaves. Out there it shouldn’t be stuffed into the soffit vents, though, because badly placed insulation can block the airflow from the eaves to the ridge. See types of roof ventilation systems for how the intake and exhaust vents work as a pair.
How much is enough depends on the climate where you live, and there’s a chart of recommended R-values for each climate zone.
Problems to fix before more goes in
An older attic can hide problems that should be dealt with first. If you find any of these, have a professional put it right before insulating:
- Insulation that’s wet or damp, a sign of a leaking roof.
- Rafters or joists that are moldy or rotted.
- A kitchen, bathroom or dryer vent that blows into the attic instead of outdoors.
- Little or no attic ventilation.
- Old knob and tube wiring, which can be a fire hazard when insulation touches it.
If what’s up there now is vermiculite, a light, flaky gray mineral about the size of a pea, it may contain asbestos. Leave it alone until an approved lab has tested it. Your local health department can give you the name of one.
Damp insulation sends you back to the roof. Our post on how to detect hidden roof leaks helps you work out roughly where the water is coming in, and tell a leak from condensation on the nails.
When the roof is replaced
A re-roof gives you the chance to look at the attic and the roof together and put right what’s wrong while the new shingles go on. Working intake and exhaust vents may also help reduce ice dams, and an ice and water shield along the eaves helps keep out the water they back up.
Help with the cost
For households on a low income, Pennsylvania’s Weatherization Assistance Program can put in air sealing and attic insulation, chosen after an energy audit of the house. Older residents, people with disabilities, families with children and high energy users get priority. You apply through the weatherization agency that serves your county.
Before more insulation goes down, it’s worth knowing the roof above it is sound. A roof inspection from us includes the attic. To set one up, call (484) 553-0213.