Closed Off Soffit Vents

This past winter our attic had a bad moisture problem with some frost accumulation on the roof decking. After looking into it, it seems like it's a ventilation problem. The former owner's father installed a ridge vent when they redid the roof, but from looking around the house I can only find 4 soffit vents, but they were blocked by insulation in the attic, so I figured it was an imbalanced intake/exhaust problem that could be fixed by adding more soffit vents and putting baffles in. However when I went to put the baffles in I found a different problem. The rafters look like they're sitting on boards that are blocking where the baffles should go. On top of that there are boards blocking access to the soffits from between the floor joists. Is there any way to improve ventilation and solve the moisture problem without a major roof/attic overhaul?
Let me know if you need different angles in the pictures to make sense of it.

Part of your problem is that your insulation is upside down. The vapor barrier should be against the heated space.
You could also probably use more insulation also.

I'd suggest taking a cordless drill with a right angle attachment and getting 3" hole saw, then pop a hole in the blocking board in between each rafter bay.

beachguy005 said:

Part of your problem is that your insulation is upside down. The vapor barrier should be against the heated space.
You could also probably use more insulation also.

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There's two layers of insulation in the bays, the bottom one has the vapor barrier facing down with the top one opposite. I've been kicking around the idea of doing blown in fiberglass but wasn't sure if it would fix the problem.

oldognewtrick said:

I'd suggest taking a cordless drill with a right angle attachment and getting 3" hole saw, then pop a hole in the blocking board in between each rafter bay.

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I've thought about doing this as well but wanted to be sure I wasn't drilling into anything structural. I've tried to find pictures of similar construction to get a diagram or at least an explanation for what the boards are but couldn't find anything. Maybe I wasn't searching for the right words. If I drill the holes in the boards between the bays I would have to make a dam for the insulation so it wouldn't crowd the holes right?

Correct, install the styrofoam baffles. Putting a hole in the blocking will not effect the integrity of the structure. It will improve air exchange.

a1cwilkinson said:

If I drill the holes in the boards between the bays I would have to make a dam for the insulation so it wouldn't crowd the holes right?

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Yes.

The circulation has to draw inlet air from the soffits (vents) for the ridge vent to work properly.

Awesome, thank you so much for the help!

When houses are to close together we are not allowed to have soffet vent (new code) so they get ventying by adding box vents just above the wall line and that would work here.

nealtw said:

When houses are to close together we are not allowed to have soffet vent (new code) so they get ventying by adding box vents just above the wall line and that would work here.

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...hmmpf...

Is there an explanation of why and what is a box vent?

THANX!

KULTULZ said:

...hmmpf...

Is there an explanation of why and what is a box vent?

THANX!

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When houses are 8ft appart that are 5ft appart at the roof line. Fire easily speads to the next house as the heat drafts the fire into the soffet vents.
Box vents are the square pills that you see near the peak of a roof.

Not a good picture but try and see that there are three box vent on the roof just over the exterior wall. There were put there because the soffet vents were not aloud.

nealtw said:

When houses are 8ft apart that are 5ft apart at the roof line. Fire easily spreads to the next house as the heat drafts the fire into the soffit vents.

Box vents are the square pills that you see near the peak of a roof.

Click to expand...

nealtw said:

Not a good picture but try and see that there are three box vent on the roof just over the exterior wall. There were put there because the soffet vents were not aloud.

Click to expand...

THANX! for explaining that...

I understand now. Makes perfect sense.

Now does the actual box vent(s) allow enough air entry? I guess there is a formula for how many needed for a particular size roof?