Last week I inspected a new build in the Madison, MS, area. The builder used HardieSoffit, a perforated product designed for soffit installations, for his cornice venting.
Net free venting requirements for residential construction state that we should provide a “balanced” airflow for attic ventilation. 50% of the opening space needed to cool your attic should enter the attic at the roof’s eave. 50% of the required openings should be installed as high as possible, preferably at the top of the roof.
I recommend a ridge vent for the high part of the venting. The ridge is the highest peak of the roof line. Since hot air rises, if you place roof venting at the top, you’re more likely to vent ALL the hot air from the attic. Here’s an in-depth booklet on roof ventilation written by the great folks at Airvent.com.
Care should be taken when using the pre-drilled holes of the HardieSoffit. See the HardieSoffit Warranty.1HardieSoffit Warranty
As you can see, newly painted holes and framing/blocking (see the lightly shaded area in the photo) can “stop up” the vent. Laying down too much paint and adding too much framing behind this product can adversely alter the balance of the attic ventilation.
Run the numbers on your ventilation requirements. If left completely open, the product pictured will allow five sq inches of net free venting per linear foot.
Homeowners, if you have this venting in your home, take care and don’t allow the painter to clog up the vent holes. It can defeat the purpose and affect the attic’s air balance. As a result, the attic can overheat, driving hot air into the ceiling and creating higher cooling costs.
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