Hip Roof Ventilation issue (finished interior space)

Hey all, I’m having issues discussing this with a vendor that I trust, and hoping someone here has seen this issue before.

We purchased an older home (1916) in the Chicago area that was never modernized for ventilation & insulation. Second story is a finished living space, with two bedrooms and a bathroom. Knee walls create a 30" perimeter crawlspace around the entire second floor. Small attic space at the very top of the hip roof. We’re renovating the second story to make better use of the footprint.

Before interior work, we’re replacing the roof. The problem is the roof design blocks rafter chutes from feeding into the attic space, as many of the rafters terminate into the HIP rafters, rather than feeding into the attic itself. I’m not sure whether this issue is best solved with roofing (hip vents & ridge vents? etc?) or interior work (preserve interior ventilation channel by eating into the living space?), or some combination of both.

    1. Vendor suggests edge vents throughout (there are no soffit vents currently)
    1. Ideally looking for a passive system, and few/zero mushroom vents if possible.
    1. Hip & ridge vents SOUND ideal to me, versus a bunch of mushroom vents and ad-hoc vents in the corners… but would hip vents create issues with our climate and roof angle?
    1. Are there general hip & ridge vent issues we should know before going with that route?
    1. R-value is very flexible for us, as long as we don’t end up with snow issues. The house has been TERRIBLY insulated most of its life, so literally anything is an improvement here. Just trying to ensure we don’t create humidity pockets or other issues that will lead to mold or leaks in these pesky corners!
    1. Only able to embed one photo, so I’ll attempt to reply with additional photos for clarity.

Any words of wisdom would be hugely appreciated. I’m afraid vendor will do whatever I ask, even if I’m wrong!
Matt

Additional photos, part one.

Additional photos, part two.

Not a photo of my home, but illustrates the problem from a wider angle.

Cold roof it. no ice dams either.

1 Like

Hip roof by design can be difficult to vent properly however hip/ridge ventilation systems designed to be installed on the diagonal slope are effective when properly installed. The biggest issue I see when hip/ridge vent are used is they are often not used correctly. I’ll see zero intake vents and to many exhaust vents, or they are used with other types of vents such as power vent fans , or turbine vents. More isn’t always better.
As long as your not mixing ventilation systems and using vents designed for use on the hip or diagonal slope, properly balanced with enough intake vents I see no issues, as far as functionality but as always check your local code requirements.

As long as you don’t insulate the rafter cavities, it’s all good.

2 Likes