By GCP Applied Technologies.
For both residential or commercial structures, ventilation is especially important in situations where poor air sealing lets heat and moisture from inside the structure get into the attic in the winter.
It's common for contractors to add vent holes to an under-ventilated attic. While this is a good idea, ventilation equipment manufacturers say that this is not always done right. Just punching more holes in the space isn't good enough; the holes need to be in the right place.
You want a balance between intake and exhaust, but if that's not possible, then it's better to have more intake vents. A surplus of intake vents will put the attic under slightly elevated air pressure, forcing air out the exhausts on the leeward side of the house.
Another common problem is airflow short-circuiting, which is caused by using different types of vents. For instance, if the attic has a ridge vent and roof louvers, then one will act as an intake and the other as an exhaust, leaving much of the attic essentially unventilated.
In an article in Roofing Contractor magazine, John Nessen of ventilation manufacturer Quarrix Building Products suggests three steps to correcting a short-circuited vent system:
Following these steps will help remove unwanted heat and moisture from the attic, providing uninterrupted airflow across the entire attic space.
Have a question? AskARoofer.
Source: GCP Applied Technologies