In the second part of our look at the attic portion of a home inspection, we’ll be examining the importance of proper ventilation and pointing out some of the common defects that the certified inspectors at A-Pro have reported on over the last 27 years. As we noted in Part 1, correctly installed venting works in coordination with having the right amount of insulation and sealing all attic bypasses to:
· Prevent harmful moisture buildup and excessive attic heat, which can accelerate shingle and roof underlayment deterioration; cause the roof sheathing to expand, leading to premature roof covering failure; dampen insulation (which reduces its effectiveness); result in the formation of mold mildew; spur wood rot on framing; cause the temperature to rise throughout the home, making living spaces uncomfortable and contributing to high energy costs; lead to frost in the attic; put a strain on HVAC systems; and make areas inviting to wood-destroying insects
· Allow cool air to enter the attic—a critical step in balancing winter attic temperatures so an overly hot attic caused by inside treated air doesn’t melt roof snow and cause harmful ice dams, which form at the gutters
From a “prudent homeowner” perspective, many manufacturers of shingles require specific levels of roof ventilation for proper installation of their products, so you risk voiding your roof-covering warranty if you don’t follow their guidelines. It is important to note that many other factors come into play when determining energy efficiency, home comfort, and roof component lifespan, including quality of roof covering, roof covering color, degree of sun exposure, and amount and type of insulation—all of which play a likely larger role than attic venting in the overall home-health equation. Further, inspectors understand that roof ventilation is not a “one-size-fits-all” proposition. The types of venting systems installed in your area of the country should reflect your climate and may be quite different than what you’d find employed in other regions.
Bottom line: A neglected attic can result in many thousands of dollars in repair and replacement costs both on the exterior and interior of a home. It’s one of many reasons why evaluating the attic, when possible, is such a vital part of a home inspection.
Your inspector will check both kinds of ventilation systems: active (e.g., thermostat-, switch-, or manual-controlled fans; whole-house fans) and passive (e.g., soffit vents, turbines that spin via wind power, gable vents, roof or “turtle” vents, continuous ridge vents).
As we’ve discussed in previous articles, a good inspector uses all of their senses to assess a home. Even before checking for the presence of venting, the inspector will be able to answer a couple of questions that will lead to further investigation: Does the space feel overly hot? Does the air feel moist?
According to the International Association of Certified Home Inspectors (InterNACHI), the minimum amount of venting in an attic should be 12 square inches of net free area for every 150 square feet of attic space, or 300 square feet if there is a vapor barrier. It’s also important to remember that when it comes to venting, “more” isn’t better. In fact, over-venting of the roof system can lead to too much air circulating, high moisture content, roof damage, and higher utility bills. A lack or overabundance of venting may be noted in the home inspection report.
For passive systems, many of the common defects come in the form of venting that doesn’t provide the right balance of intake vents that allow air in (located lower in the system) and those that exhaust air out the roof at the ridge. For example, inspectors often find a lack of soffit vents in the lower portion of the system. Also, the use of dissimilar types of vents can inhibit the proper cross-flow of air in the roof system. As discussed in our last blog post, your inspector will make sure that insulation is not blocking soffit vents—a condition that most often occurs with blown-in insulation. While the inspector can confirm the presence of soffit vents, the only way to check to see if they’re working as they should (or have been properly installed so the vent’s baffling extends through the exterior) is to feel if the air is coming through.
Occasionally, the inspector may find a bathroom or laundry vent that terminates in the attic rather than being exhausted through the roof. Your inspector will note this in the report since such a condition can contribute to an attic’s heat and moisture content.
Other possible venting issues include improperly installed ridge vents that allow insects to get inside; affixing thermally reflective radiant barriers to rafters, which will trap heat in the rafter bays; the use of perforated soffit vents which have been installed over solid wood; wood blocking used between rafters at the eaves that restrict airflow; ventilation openings that are too small and not protected with a corrosion-resistant wire mesh; and leaky roof vents—a potential issue with any roof penetration. Your inspector may remind you that turbine-type vents and electrically powered vents will need periodic checkups to ensure that they are working.
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