Do I need soffit vents for my knee wall attic?

Question

I purchased a 55 year old home that has no soffit vents. The attic space consists of a knee wall attic space and peak attic space. The peak attic space has vents at each end and a ridge vent at the top. I checked for signs of moisture and mold and found none. I live in the Fort Worth, Texas area. I always hear Mike Holmes talk about the necessity of soffit vents, but I know his show is in Canada which is a very different climate from mine. It seems to me that if the house was OK for 55 years without soffits, then I don't need to do anything and that it's OK.

What do you guys think?

Answer 1

Soffit vents ensure a continuous flow of outside air on the underside of your roof.

In cold climates, this prevents two critical issues. First, from condensation on the underside of the roof from moist air in your home or from earlier in the day that has made its way into the attic. And second, from snow that falls on the roof from melting at the top, and refreezing further down creating an ice dam that causes melt water to backup into your roof and ultimately into your home.

In warm climates, the main benefit is to cool the attic space to reduce your heating costs. Some building products break down in extreme heat. Insulation in your ceiling is only slowing the transmission of heat, but when you have a 120°F attic, you'll have a lot more heat transferring through the insulation than if it is only 80°F.

That said, older homes, and those built in warmer climates are less likely to have soffit vents. Between the gable vents and ridge vents, you likely have enough ventilation for your climate (not that more wouldn't be better).

For more details on roof vents, see tester's fantastic blog post.