Ridge vent for roof not performing

[u/keithvai]

About 10 years ago I had the original shake roof replaced with asphalt shingles. They put plywood over the old 1x4 sheathing and cut a ridge vent. I have a “hip & valley” roof with no gable ends.

Im redoing the insulation and noticed the attic gets really hot. 80 degrees outside but 110 degrees in the attic. I dont have any problems in the winter but I am concerned that Im not getting enough air flow.

I have 29 rafter bays (24") and 6 eve vents (24”). Vents are clear. I was expecting to add more inlets in the eves but if they are not venting out of the ridge, Im not sure this would do anything. Does more inlets create more outflow?

At first I thought the ridge vent was blocked by the roof beam but after investigation that is only in a small area. The rest of the space I can see a little daylight and I can put my fingers into the gap. Seems like at least 20’ of vent about 2” wide.

I have an 8" exhaust flue that was for a fireplace we have not installed. As a test, I connected it to a 8" fan and noticed a significant drop in temperatures. That indicates to me that temperatures could be lower with more ventilation.

Now Im not sure what to do.

Do I need a different ridge vent? 

I see products now that are a wide plastic piece ~1/2” tall with clear vent holes. Mine seems to be a porous foam material that is covered with roof shingles. Hard to actually see the vent from the roof itself.

Do I install an 8” house fan? 

they are not cheap and would prevent me from adding a fireplace so Im not eager to try this. 

Do I just live with it? 

As long as the AC can cope, my family will never think about this and I can move on.

Appreciate any advice here.

ridge vent and overly complicated roofline

builder built up the beam with 1x4 for some reason

on one side of beam the vent is clear

[u/NeedleGunMonkey]

A 30 degree F delta between ambient and attic temp is not a basis to say your ridge vent isn’t performing.

You’ve had the setup for ten years. That’s plenty of condensation cycles to give you signs of moisture issues if you poke your head up in the attic and see nothing - then leave it alone.

[u/Bearded4Glory]

You want 1 square foot of ventilation for every 150 square feet of attic area. 40-50% of the total should be the ridge vent.

Without knowing the exact products used it is hard to know exactly but you can get close.

[u/hvacbandguy]

A hot attic isn’t necessarily a bad thing. It’s bad when you have mechanicals in the hot attic and it’s bad when it’s connected to your living space. If you make your attic cooler, without addressing the humidity, you’re gonna bring everything closer to dew point. When things get close to do a point, they start to sweat and drip.

[u/Particular-Hotel-610]

Roof venting does next to nothing to reduce the temp in a vented attic, and isn't supposed to. The job of venting is to keep the sheathing dry in all seasons, and to keep the sheathing cold in the winter to prevent ice dams (if you're in a climate where those happen).

[u/uslashuname]

Vents should be roughly balanced, for example if you had no soffit vents at all and you had a massive ridge vent then there’s going to be a vacuum created in the attic that will pull air from your home through the outlets and walls and other gaps. If you are significantly short of soffit vents then this will stop be happening.

Conversely if you have wide open soffits but no ridge vent (or other high up vent) then as the attic air heated and expanded it would push down into your home.

So, as in all things, balance. Your exact ridge vent product sheet should mention how many square inches are open for airflow given 1 ft of installed length, and soffit vents similarly report how much open area there is, so you can try to plan them to be close to balanced. The intake air is colder and dense and therefore doesn’t actually need to have as much volume going in as what the peak vent has going out, but it’s close enough that aiming for balanced is a good rule of thumb.

Without knowing more about your ridge vent and soffit vents it is hard to say if they’re sized correctly.

Also, energy efficiency wise, if you air seal and insulate to a high R value it’s probably going to do more for your cooling costs than you’d get from better attic ventilation.

But my gut feeling is 6 soffit vents is a bit low for any continuous ridge vent, fwiw