Ridge Vents Extend Life Of Roof Structure
Q. My neighbors just got a new roof. The contractor installed something called a “ridge vent.” What is this for?
Could I or should I install one on my house, which was built in the ‘40s? And if so, which type of ridge vent is the best?
A. Ridge vents are an excellent way to achieve attic ventilation, but ridge vents are only half of the system. You also need eave vents.
Since your home was built in the ‘40s, it may or may not have adequate attic ventilation. The building codes and standard practices in your area may not have called for attic ventilation.
The primary purposes of attic ventilation are to keep the attic cool during sunny periods and to vent moisture that could accumulate in the attic. The objective is to protect and extend the life of the structural components of your roof.
This is done by placing screened vent holes through and around the roof structure.
Optimum ventilation is achieved when half of the vents are placed high (on or near the ridge) and half are placed low (in or near the eaves). The vent area should be one square foot of vent to every 150 square feet of ceiling area. However, if you have half the vent area split between high and low vents, a ratio of only 1 to 300 is required.
For new construction, additions and remodels (where the roof is being redone), I would highly recommend ridge vents as an attic ventilation component.
But in your case, you should ask yourself a few questions first.
Do I already have attic ventilation? Is the attic ventilation system working?
Inadequate attic ventilation is evident if you notice any heat or moisture damage problems in the roofing material or structure (curling shingles, dry rot, mold or moisture stains). Sometimes by design or accident, the attic ventilation in older homes is just fine.
If you decide that you want to add ridge vents to your attic ventilation system, two types are typically available.
One is a metal piece that is placed on top of the ridge. It replaces the roofing material cap.
This vent can run full or a partial length of the ridge and has a screened vent slot running the length of the vent.
The other type is a plastic material that is laid down over the ridge, and the roofing material cap is placed on top and nailed through to the roof. The plastic ridge vent should run the full length of the ridge.
The plastic material is in a honeycomb with about 1/16-inch diameter holes.
Both types do the job. The metal ridge vent has more free vent area per linear foot (more ventilation), and the plastic ridge vent is less noticeable, fitting in better with roofing materials and colors.
It is also very important to check the eave vents and be sure they are clear. Eave vents should be baffled to prevent blockage by the insulation in the attic.
Another worthwhile precaution is to seal all attic penetrations (around light and fan fixtures, attic hatches). Warm air from the house is the prime carrier of moisture into the attic.
For the final choice of which type of ventilation system will best suit your home, consult with a roofing contractor and see what is available in your area and what experience the roofer has with the different vents.
For a free fact sheet, “Attic and Crawlspace Ventilation,” call the Energy Hotline at (800) 962-9731 (in Washington) or (509) 324-7980.
xxxx
The following fields overflowed: SUPCAT = COLUMN, QUESTION & ANSWER - Homewise