, Newburyport, MA


February 11, 2014

The devil is in the details when insulating the attic

This time of the year, I get a lot of calls from homeowners who are flummoxed over issues related to poorly insulated homes, high energy bills and uncomfortable living conditions. One call that I received was from a homeowner who had water condensing and ice on his roof sheathing in the attic. Unfortunately, this isn’t uncommon.

The homeowner had already taken the advice of a contractor who suggested he change the attic ventilation from existing open gables to eaves and a ridge vent. He went along with this and paid to have it done. The homeowner had already treated the attic for mold. Additionally, Mass Save performed an audit and had crews do targeted air sealing and add insulation on the attic floor. An attic hatch cover was added. The condensation persisted, and the homeowner saw no decrease in his heating bill from the prior year for the same period.

A blower door test and infrared scan quickly revealed the source of the moisture problem. While the house was depressurized, infrared showed points of air leakage in the ceiling below the attic. Eight recessed lights directly over the kitchen and right around the corner from a bathroom were open to the attic. Also, the attic hatch cover was not completely sealed to the floor, allowing air to pass under it as seen with the infrared. A family generates plenty of moisture, which in this case was going straight into their cold attic.

Another situation that was a contributing factor to the homeowner having no observable savings was the cold air feeding into the edge of the attic insulation (called wind washing). The wind washing was revealed by testing, easily discernible from the ceiling below using infrared. The eave vents that were installed did not have an air barrier (an eave baffle) to send outside air above the insulation, instead of through it.

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