Dormer ventilation

Are dormers typically ventilated on a Cape Cod style? The dormer soffits had vents, however there was no ridge vent on the dormer peak. Modular house built in 2004.


Look at the total attic vent.

It has to do with ? sf per?sf of floor space.
I’ll let you look that one up.

Where they are located has to do with elevation.

The total net free ventilating area should not be less than 1 to 150 of the area of the space ventilated except that the total area is permitted to be reduced to 1 to 300 provided mechanical ventilators are used.

Was the decking cut to allow the air from the dormer to the main roof ? I’ve seen some that were not and they would need separate ventilation.

More pics.

Look it up!

Your area may be different.

You may not even need ventilation…

Yes, I am not joking!

I don’t believe I’ve ever seen a dormer that wasn’t connected to the main attic. How did they install the windows if it wasn’t connected?

If the floor space below the roof is heated then it should be vented in some fashion; the way we frame our dormers it is naturally vented…simply because you do not see ridge or gable venting does not mean its not vented. If you were able to access the attic then you would be able to tell how it was vented.


Some modular home companies will install dormers separate and then apply siding after the fact. As I was driving home a couple weeks ago I saw one of the local modular home companies do just that…what always blows me away is that they brag about how fast modulars go up…yet many of them take just as long to finish out. It takes me about 12 - 16 weeks to build a custom home up to 2500 sq ft… and I can do it less than what a modular cost in the end with more quality and value… its amazing that they sell…but then again, hardly anything is selling around here.

Nice sharing,
Its really very good informative post about dormers ventilation. I am a newbie for this forum site, and I hope that i will get so useful information here.
Thanks for sharing this.

They over-frame onto existing roof sheathing instead of tying directly into the roof framing.

Kind of like the illustration, only imagine the rafters and sheathing cut out hand headed off, flush with the inside of the ledger. Structural ridge supported by posting down to window header at the outside wall so no rafter ties (ceiling joists). If the dormers had flat ceilings, they were probably vented into the attic. If the ceilings were vaulted, they had intakes but no exhaust and faulty ventilation.