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Attic Insulation Prep is Key

February 15, 2015 | Posted by Mitt Jones
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attic_prep.pngAs with most things in life, insulating your attic isn’t as simple as it may seem. Most attics need at least some prep work before insulation is added, and prepping the attic often takes longer than insulating it. This prep work nearly always provides a boost in comfort and energy efficiency. It also protects you and your family from potential health and safety challenges, such as old wiring or potential moisture related problems.  

Attic prep is a key difference between what you get from a home performance company and from a low-cost insulation contractor. Most high-volume, low-cost insulation contractors schedule each crew to insulate multiple attics each day, so prep work is minimal at best.

Decommission Knob-and-Tube Wiring

In the Portland area we often find knob-and-tube wiring in homes built in the 1920s and before. Knob-and-tube wiring buried in insulation is considered a fire hazard, and building codes forbid insulating around knob-and-tube wiring. The good news is that it’s relatively inexpensive to have knob-and-tube wiring replaced and removed from accessible attic spaces. 

We also recommend considering any planned updates that would require an electrician to work in your attic, such as replacing or adding light fixtures, electrical outlets, or light switches. These upgrades will probably cost you less if you have them done before you increase attic insulation.

Air Seal the Attic Floor

Insulation will reduce the heat loss through your attic floor, but it doesn’t stop warm air in your home from escaping into the attic through gaps, penetrations, recessed light fixtures, and other openings. These leaks cause comfort and energy efficiency problems in both winter and summer. They can also cause condensation problems in your attic and contribute to poor indoor air quality. For more information, check out our Air Sealing FAQ.

Properly Ventilate the Attic

Attic ventilation is less important if your attic floor is properly sealed, but it’s generally still a good idea to improve attic ventilation to current building code requirements. Improving your attic ventilation may help protect your attic from condensation problems. It can also help reduce ice damming after heavy snow falls, though for now at least we get few of those here in Portland, OR.

Seal Heating and Cooling Ducts

It makes sense to seal any heating//cooling ducts that run through the attic. Sealing the ducts is relatively quick and inexpensive, and it provides the same benefits as air sealing.

Correct and Seal Exhaust Ducts

Many bathroom exhaust fans are improperly ducted at best. This can affect fan noise and operation and can create moisture-related problems inside your attic. A reputable home performance contractor knows how to duct exhaust fans to optimize fan operation and prevent moisture-related problems.

Improve Spot Ventilation

Given that most exhaust fans install in the ceiling, it makes sense to add or replace exhaust fans as needed before you add insulation. If you wait until the attic is insulated to improve bathroom or kitchen ventilation, chances are the new fans will cost more to install or will be installed poorly. Replacing exhaust fans later would also mean having somebody move through the insulation, which would likely reduce its efficacy.

Install Insulation Dams and Ventilation Baffles

Insulation baffles and dams should be installed to keep the insulation where it belongs. For example, there should be a simple insulation dam around the attic hatch to keep loose-fill insulation from falling out when you open the hatch. An insulation dam should also be installed at the border between the house and garage, to keep insulation in place over your living space.

Insulation baffles create a channel for air to flow up though soffit or eave vents and keep insulation from blocking these vents. To guard against fire, we use another type of baffle to keep insulation away from old recessed fixtures and from metal furnace or fireplace flue pipes.

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