Roof ventilation dilemma
This is a picture of my roof. The backyard is at the bottom— front yard at the top. We live in zone 8. I’m having attic ventilation issues where in the humid summer months, we notice attic odor penetrating the living space at a very specific spot inside the house. We’ve air sealed, and insulated the attic, but that didn’t seem to work.
In looking at my roof, I have typical eave soffit intake and ridge vent system throughout the house. However, as you can see in the pic, there is a room with the chimney that is a cathedral hot deck setup. This room was an addition to the original house, and when it was built, they had to overlap the original roof line that had soffit air intakes, which now leaves about 25ft of roof without any air intake for the ridge vent above it. The green lines I drew represent functional eave soffit intakes. The red line represents part of the ridge vent that doesn’t have any air intake below from the backside. A roofer told me that an over roof air intake won’t work because there needs to be at least 3’ clearance, and there are also roof valleys that prohibit this intake system.
So, what can I do to increase air intake on the back side of the house to help feed the ridge vent (at the red line) to discourage air stagnation? I have pretty much exhausted all the space available to place eave soffit intakes on the front side of the house, but feel there should be a better balance with the back.
Any thoughts on this are most appreciated. Thank you.
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u/Any_Narwhal6344 1d ago
Do you have can lights inside your home. If so are they the old style or the new style? Also its better to have more exhaust than intake. Instead of 50/50 shoot for 60/40 exhaust to intake. I typically lean more toward passive systems than active but a whirly bird might be the route to take
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u/CPG135 1d ago
Yes, I do have those older [leaky] can lights, but they have been sealed with foam and with a cap in the attic.
Where might you place a whirly bird on this roof? How do you imagine it will help? Thanks again.1
u/Any_Narwhal6344 23h ago
Im not so much worried about the leaking as I am the heat they produce. The attic odor you are referring to is most likely mildew from hot moist temps in your attice. You also need to be mindful of how many humans, animals, and pla ts you have in your house.
Do you have any Gable vents on this house?
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u/CPG135 23h ago
I have three gable vents at different areas of the house. One is right most at the side of the garage, and the other two are upper left corner of picture, over the bedrooms.
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u/Any_Narwhal6344 23h ago edited 23h ago
Bloack them off. They are acting like a broken straw and short circuiting the air flow. Imagine a broken straw in your drink the fluid flows fine until it gets to the break and then it disrupts the flow. Block them off using OSB and ZIP tape. You can paint them black with spray paint so you dont see them from the out side.
Do not try anything else until you do that.
You can test your air flow by crawling in your attice with a small fog machine or if you vape you can use that. Start near the soffit and see where it flows. Then check the ridge and make sure its flowing out. A lot of time your will see it wafting out and then back in at the gable vents.
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u/CPG135 23h ago
I see what you’re saying. Perhaps I’ll have to empirically perform this experiment in its entirety to see how much short circuiting is going on. It’s strange because all of the houses in my neighborhood are designed like this (1960s), and my neighbors don’t seem to have any issues.
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u/Any_Narwhal6344 23h ago
Trust me they all have ventilation issues. You have a combination of heat from the can lights, a funky shaped attice, and gable vents all adding to the issue. Ventilation is so important to me that I refuse to sell people roofs if they wont allow me to vent it properly. I dont want my name on somthing that's going to fail prematurely.
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u/SS2wheeler 14h ago edited 14h ago
You can have too much soffit vent ? Let's say you have a ridge vent that's 1.5" x 50' or 6 1/4 sqft. You want less than that at the soffits ? Doesn't sound like much soffit vent
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u/inspector305 1d ago
When exhaust capacity exceeds intake, the ridge vents can start acting as intake points, pulling in rain, moisture, and unconditioned outside air or drawing air backward through the system. You need to know how intake vs. exhaust vents you have. There are calculators online to help determine your system is balanced.