Venting, letting off steam … whatever you call it, the idea is the same. When things get heated, you have to get it out. Out of your head AND out of your attic space.
There is a lot more science behind attic ventilation than you might think. Experts suggest that a key consideration is to have a balanced system, meaning that a home’s ability to intake fresh outside air matches the ability to discharge overheated attic air. In a passive ventilation system, the heat rises and naturally pulls fresh air into the attic space, but if that system is out of balance with too little or too much intake for the amount of exhaust ventilation, the whole process becomes dysfunctional.
Exhaust ventilation gets most of the attention, and often even that gets precious little. Most of the time, whatever is there just gets replaced with a new version of what is already there without much deliberation. Contractors have some definite opinions on the efficiency of box vents versus ridge vents, whether or not rigid or flexible rolled ridge vents can beat whirlybirds. But it all comes down to the particulars of the house and how to best balance the intake.
In order to use a common language, experts use the term net free ventilation area. This is the number of square inches of unobstructed area that air can pass through some type of vent.
Every type of vent has an NFV rating, and every attic space has a calculated NFV need. There are several calculators online that allow contractors and homeowners to research the ideal ventilation needs of their home. Owens Corning’s site is our personal favorite.
There are two categories of products (intake and exhaust) and two balance ratio guidelines (1:150 or 1:300) that you can try out to see how to best achieve the perfect balance for your attic. Be careful not to include the square footage of the whole house if a 2-story – only the area of the attic that needs to be vented!
If only balance were so easy in other aspects of life!
If you find that your home is inadequately ventilated and you would like to discuss options with a trained estimator, feel free to call us anytime at (502) 749-7663.