Ways to add proper ventilation to attic with ridge vent on roof?

Question

We got a new roof about four ago. The attic is unfinished. It's a split level home, and hot as Hades upstairs.

Unfortunately, the roofers didn't consider attic ventilation. They installed a ridge vent, but the only intake is a gable vent near the peak of the roof. Now we realize that hot air stays at the bottom of the attic in that scenario. So we need to add ventilation at the bottom of the attic. Our soffits are not vented. Seems to me the options are to vent the soffits, or to add a shingle-over intake vent along the lower edge of the roof (then seal up the gable vent). Is either of these options preferable for a relatively new roof? We live in DC.

Answer 1

I would add soffit vents. If it's wood soffit it's fairly easy to cut the holes with a small rotary saw or an oscillating multi tool. Then screw on prefab vents from any outlet supply. If it's aluminum soffit I've replaced solid panels with vented also and you could space them out and put in as only as many as desired. If it's aluminum fascia on front then removing the fascia first makes removing and reinstalling panels is a snap. Just first remove the aluminum fascia (on front) by pulling the bottom nails with pliers. I always like to screw the alum fascia back on with small stainless Phillips screws.

But if it's wood fascia that usually hangs down past the soffit in front, it becomes more problematic. I don't want to try and explain that to you other than give you a heads up that application can be more of a problem replacing alum soffit panels.

Oh and if the gable vents are not leaking in blowing rain, just leave them, they will just give more top level air escape. I see no need to seal up the gable vent unless you see evidence of gable vents taking in water in a blowing rain (some do, some don't) If that is not a previous problem then just leave them. The will have no negative effect on ventilation in any option scenario.

Answer 2

You say, “Unfortunately the roofers didn’t consider ventilation.” Actually, it’s not an option. It’s required by code. I’d cancel the check and have them return to finish the job. (See ICC R806.)

Your attic is required to have ventilation at 1/150 the area of the attic. (See ICC R806.1.) So, If your house is 24’ x 40’ then you need 24’ x 40’ / 150 = 6.4 sf.

However, there is an exception that allows 1/300 the area if between 40% and 50% of the ventilation is in the upper third of your attic. (See ICC R806.2)

There is another exception that deals with your vapor barrier, but you need a Class I or II installed on the warm-in-winter side.

Did they get a Building Permit?

Answer 3

Another option is to put an exhaust fan in your attic, on a thermostat. Which type of fan would depend on the construction of your roof. There are even solar powered attic fans.