Soffit venting one side of home

I came across a 2019 house with almost no soffit venting on one side and all soffit vents on the other, between every truss. The other side has 3 vents on front porch (with air access to main attic) on one end, no vents for 40 feet then soffit vents above garage (with air access to main attic). To me this seems problematic for good air flow. Has anyone else come across this situation? I’m trying to look up Washington state code but haven’t found a definitive answer I’m looking for yet.

Welcome back Don! Pictures sure do help us trying to help you! :wink:

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There are way too many unknown variables in this question for anyone who was not there to determine if it might be an issue. Did you see any indications in the attic of poor ventilation, like frost, mold, discoloration, staining, etc?

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Did you calculate for this typical code requirement?:

The IRC requires 1 square foot of net free ventilation area to every 150 square foot of attic floor space (1/150), but does not specify the location of intake vents or exhaust vents, nor does it specify the ratio of intake to exhaust.


I’ve seen many homes that were designed in such a way that good attic ventilation was problematic for certain areas. There is a formula for determining the amount of intake & exhaust venting that is required, and as long as the calculated numbers are complied with, it will pass inspection, even though there are areas that obviously don’t have “adequate” ventilation IMO as a home inspector.


Oh yea sorry, no nothing wrong with attic.

Rough guess without measuring, it appears to be 50% intake 50% exhaust proper. Just doesn’t seem like it would make for good air flow on one side. Thank you Kevin

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Ok. I know you are just asking mainly for your own learning, etc. But in this case, if you did not see any signs of inadequate ventilation, and if you are not prepared to perform the calculations mentioned above, I would just stick to the SOP.


Yup, the home does cover the intake/exhaust numbers but I have never come across a home with all on one side and couldn’t find anything on line about my situation. Thank you Larry

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Thank you Ryan

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You’re welcome, Donald. :+1:

Sometimes on these “one off” situations that appear to be performing, it is best to make sure you get plenty of good CYA pictures, in case it ever stops performing, lol.

Attic ventilation is not a black and white issue. Many, many older homes perform perfectly with just two small gable vents that are 50% plugged with debris. Lots of variables, and that is why the SOP excludes it.


Home ventilation is not as simple as most home inspectors may think. As others have mentioned above, there are many factors that may dictate placement, such as prevailing winds! I lived in the PNW for 20 years, and there are definitely areas that have strong, predominate, directional winds. This also affects venting for the HVAC, WH, and other appliances. Did you notice if there was any unusual separation, including intake and exhaust on opposite sides of the home, for other vents for the home?


I’ve seen this where the house is too close to the neighbors home and the city required the soffit vent be filled with Sheetrock to reduce the chance of fire being spread.

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Was there by chance a smart vent system where the other side had inlets for air flow cut into the roof and above the insulation?
I am in WA and see this quite a bit where one side is with traditional soffit vents and the other has the smart vents… Sometimes dictated by wind and sometimes dictated by prints for new construction based on the orientation of the home. Not sure if “smart vents” is the correct technical term, but it is what many of the roofers at new construction sites have referred to them as??? :man_shrugging:t2:

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I did not see any

Thanks Jeffrey, that is something that I will keep in mind that I often forget about

Haha yea prevailing winds like in North Bend I-90 on way up to Snoqualmie pass

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I could understand that but the vents were on the side closest to another house. Thanks Martin

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Look at the distances between homes on either side. Then look at the other home on the side where the soffit vents are. Did that home have missing soffit vents on that side? If so, and the distances are within required fire separation distances then Martin provided the answer.

Not sure if Washington has amended the codes but this would be under R302.1 in the 2018 IRC. Also look up any local amendments to the codes as they might have increased the space requirements between houses.

If it is not a fire separation issue then there is no explanation why. The building codes do not specify where the vents are suppose to be just that they have the balance you have described if they are low input and high output for 1 Sq. Ft. net free opening for every 150 Sq. Ft. of attic space.