No Soffit Vents in Hip Roof

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Old 04-09-08, 06:54 PM
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No Soffit Vents in Hip Roof

Minnesota

I have no soffit vents in my 1900 Hip roof house. What I do have for ventilation is a whirlybird near the peak and one window on the north side dormer (The only dormer).

My question is: Does it suffice to simply leave the window open? (1 whirlybird, 3-4 sqft open window-screened, 1,000 sqft attic)

In the past I have closed the window in the winter and opened it in the summer. Should I leave it open all winter?

I have noticed in the early spring some frost on the attic floorboards just above the outside walls. I think it may be a result of having little or no insulation in the walls and the conditioned air may leak up through them. I am considering getting my walls drilled and filled with insulation, but in the mean time am wondering if I have adequate ventilation or do I need to put soffit vents in (and perhaps? ridgevents)

Thanks for any help.
 
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Old 04-10-08, 04:01 AM
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Do you have any overhang into which you can install soffit vents? If so, it would, by far, be better to install them than leaving a window open in the attic. Air must go in and must go out in the same volume, so let us know what your situation is.
 
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Old 04-10-08, 07:10 PM
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Yes-my soffits extend out at least two feet from the exterior wall.
 
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Old 04-11-08, 04:41 AM
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Then you have the ideal situation to install soffit vents and let the air circulate properly from them to your other exit vents. You need to make sure insulation does not block the area of the soffits and install soffit blocks (styrofoam forms) that keep insulation away from the roof side so air can move freely.
 
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Old 04-11-08, 06:25 AM
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Since the department of energy recommends attic insulation equivalent to R-49 in your area, I would think THAT would be a higher priority than venting right now. But with only 1000 sq ft, you would need roughly 4 sq ft of venting to give you a 1:300 ratio. That 4 sq ft should be divided up, with roughly half (some recommend 60%) for soffit vents (intake) and half (or 40%) for roof vents (exhaust). So you'd just need one 6x12 soffit vent on each side of the house, and one roof louver vent on each side of the hip roof for a total of 4 soffit vents and 4 roof vents. As Chandler mentioned, you'd need to use styrofoam baffles over the top plate to allow an airway from your soffit into the attic. Once the baffles are in, insulation could be generously added to the attic.

But since you mention "floorboards", I'm guessing there is practically zero insulation up there to begin with, which is pretty amazing for a house in Minnesota. Adding more venting without adding more insulation will only serve to remove heat from the home more quickly, I would think. If you won't be adding more insulation just yet, then opening the window in the summer, closing it in the winter makes the most sense to me. Until then, I'd suggest you keep doing what you've been doing. But save your pennies for the insulation.
 
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Old 04-11-08, 06:15 PM
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Thanks for the replies!

Xsleeper--I think you figured it out for me. It is interesting that my house lacks insulation, but I guess houses built in 1900 didn't have the product??? Nor did they worry about the cost of energy.

My efficiency woes start with lack of Attic (not much) and wall insulation and continue w/single pane windows. I'm trying to fix all of these, but I am on a tight budget. I hear you about venting more w/o adding attic insulation...I don't know if that is true, but it certainly makes sense.

We did invest in a high efficiency furnace 2 years ago and it will have paid for itself in 1 more year.

I think you are right, I should include attic insulation as well soffit venting.

Thanks again you guys!
 
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