Ridge and Box Vents Working Together?

I am re-roofing my 20-yr old 33 square gable roof which has 8 box vents and no gable vents. Upstairs of my house is 5 to 8 degrees hotter in summer even with the new AC I installed last year (I am in lower Michigan). I was hoping for your input for better venting of my attic.

My attic area is 40 ft by 40 ft. A roofer who gave me quote talked about a power vent (PC15 model). However, if he does that, all box vents need to be closed to prevent short circuiting. I was wondering if installation of a ridge vent and keeping my all (or some) box vents (instead of an electric vent) will do a much better job? OR installing one power vent with a thermostat set at 95 deg is a better option? I want to save on electricity if I could. I also noticed that the “saw dust” insulation I have in my attic seems to be covering my soffit vents. I am not sure may be below the saw dust they have a filter or glass wool so the soffits are breathing. I did not smell mildew in my attic so my guess is that it is doing OK over the last 20 yrs.

Thank you in advance!

You probably would be better off with ridge vent.

Take a look here ; roofingcontractorreview.com/Roof … -Myth.html and some of the associated roof ventilation pages.

Yes, and make sure to leave the box vents in too.
Dont close them off.

Don’t leave the box vents in or they’ll act as an intake and can draw water in. Best method is eave vents double to ridge vent. What style roof do you have? Not all roofs are a good choice for ridge vents. Some hip roofs and other style don’t have enough length for a balanced system

Yes, the advice is based upon 40x40 gable roof.

If it was 40x40 hip roof than it would only be less than 20 feet of ridge and a good answer would have been power vent.

Leave the box vents in.

ridge vents and make sure all soffits are open,get rid of boxed vents.

The “Net Free Ventilation Air-Flowage” from your soffit vents has been compromised. How much? Hard to tell from here.

To be sure, you need to increase your Intake Ventilation. Are they aluminum soffit panels with either lanced or perforated ventilation holes in them or are your soffits wood, with either rectangular aluminum vents spaced ot or do you have a continuous 2" wide strip soffit vent now?

Any Powered Attic Ventilator will need sufficient Intake Air Flowage to not suck out the interior conditioned air from the points in the walls or lighting and fan penetrations in the ceilings to work properly. Too little Intake and the motor burns out and also the houses internal air gets caught up in the stream of sucked air and gets vacuumed out.

If you do not want to provide additional air flowage from the soffits, you can add an under shingle Intake Vent, either the Smart Vent by DCI Products, Inc., or TheEdge by Air Vent Corp.

You most definitely should remove the other can exhaust vents if you are choosing a better exhaust vent system.

I recommend closing off the box, mushroom style vents and installing a continuous Ridge Vent, which should contain an External Baffle, such as the Shingle Vent II or the Cobra Snow Country imitation style ridge vent.

Make sure you have an equal amount of Intake Ventilation or Greater amount, than the amount of Exhaust Ventilation. These products are all rated by NFVA per inch.


Thats what i meant 8)

Roof lover, if you leave the cans in what happens is the ridge vent will pull from the cans rather than the soffit. It will bascially cut the roof in half and cook the lower half.