Attic Ventilation: How Much Do You Need?

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We just finished installing 23ea 16X8 eave vents in our home. Last year we had a new metal roof installed on our home. Roofing contractor sold with the metal roof a ridge cap. When I look at the roof plan from the insurance company they list the ridge as 65lf. Two weeks ago I added blown-in insulation in the attic, it took me a week to get ready for the insulation job. When in the attic I finally had noticed that the roofer had never cut an opening for the Ridge cap. I contacted the roofer and he sent out a crew and they said they cut a 2" opening 20' long, I have not went back up in the attic yet to verify. My question is will 20' be enough. Attic space is roughly 2250 sq feet. The vents we installed have 3ea 3" holes cut out for ventilation. Insulation I added is about 24" deep in the attic. I have vaulted the ceilings in two rooms in our ranch style house. Roofplan shows roof area is 3910sf. Last winter we had ice dams at every valley on house and snow would be melted off our roof in just a few days. I hope I have given you enough information.

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The good news is, you can never have too much attic ventilation.  If you have continuous soffits down both sides of your house, you should have a continuous ridge vent – because they work together.  If you only have a ridge vent in the center, it wont be as efficient as having it end to end.  The roofing contractor clearly missed this and needs to come back to complete the job. 

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