Snow Blowing Into Attic Through Soffit Vent

[Bruce Breedlove]

Yesterday we had snow and high winds. On an inspection yesterday I noticed a water stain in the corner of the garage ceiling. There were no obvious roof problems (although I did not walk the roof with snow on the roof). When I looked in the attic above the stain I saw snow that had blown into the garage attic through the soffit vent. That explained what had caused the water stains.

Does anyone know of a simple solution to prevent snow from blowing into an attic through soffit vents?

[Rick Hurst]

How about installing some baffle material. That should prevent it from entering the attic space if installed properly.

rick

[Jerry Peck]

Yep.

Baffled soffit vents. Baffled such that the wind cannot easily blow past the baffles.

Simple solution, yes, at time of construction. Now? Not so sure.

[Jim Luttrall]

Does anyone know of a simple solution to prevent snow from blowing into an attic through soffit vents?

Move to Texas;)

[Ted Menelly]

Move to Texas;)


That's funny Jim. I was going to reply the same. Don't want snow in the attic move out of the snow.

[Bruce Breedlove]

Baffled soffit vents. Baffled such that the wind cannot easily blow past the baffles.


Thanks. That's what I have recommended.


Move to Texas;)

Thanks, Jim. But I don't want to do anything drastic! :D

[John Arnold]

Speaking of baffled, I see you have installed F-Rod as your avatar?

[Richard Pultar]

replace the soffit material with holes with soffit with no holes.

[Jerry Peck]

replace the soffit material with holes with soffit with no holes.

Question Richard: What do you do about the attic ventilation which was through the soffits?

[David Wood]

In a northern climate, you really don't need a lot of attic venting. Blocking some of the soffit vents could be acceptable.

As demonstrated here, sometimes attic vents can let more moisture into the attic than they let out - and in a northern climate, the main purpose of attic venting is to keep it dry.

Moore vents (baffles) would be a good solution in this case.

[Rick Hurst]

Bruce,

If you'd been with me today you could have picked up some baffle material. Seems the contractors didn't know what do to with them so they just tossed them in the attic space.

rick

[Billy Stephens]

Seems the contractors didn't know what do to with them so they just tossed them in the attic space.

rick
.
Along with The Vent to Nowhere. :D
.

[Door Guy]

replace the soffit material with holes with soffit with no holes.

I agree. Just replace the area where the snow is blowing in. You could verify the required ventilation to make sure you won't be under ventilated. That's a much better solution then the baffle. The snow and wind comes from the outside, not the inside. How would installing an insulation baffle keep snow from blowing in? It's coming through the soffit. It will still end up inside the structure.

Does this area intersect with another roof line such as a valley?

[Jerry Peck]

I agree. Just replace the area where the snow is blowing in. You could verify the required ventilation to make sure you won't be under ventilated. That's a much better solution then the baffle.


Depends on what type of baffle you are talking about.

You brought up INSULATION baffle and I mentioned SOFFIT VENTS which have baffles, i.e., the baffles stop the wind from blowing rain (and, yes, snow) up into the soffit area.

Sure beats your reducing the ventilation.

[Door Guy]

Depends on what type of baffle you are talking about.

You brought up INSULATION baffle and I mentioned SOFFIT VENTS which have baffles, i.e., the baffles stop the wind from blowing rain (and, yes, snow) up into the soffit area.

Sure beats your reducing the ventilation.

Your going to have to enlighten me Jerry, I have never seen a perforated soffit with a baffle. Will you provide a link? Rick's post sure looks like an insulation baffle to me.

[Dennis Crookshanks]

Try something like the ridge vent material in roll form. Heavy mesh filter material that is installed under ridge shingles. Cobra vent is one. It can be cut to size and easily inserted between the rafters at the exterior wall.

[Jerry Peck]

Your going to have to enlighten me Jerry, I have never seen a perforated soffit with a baffle. Will you provide a link? Rick's post sure looks like an insulation baffle to me.

Not perforated soffits with baffles, but baffles which go in and are used for ANY type of soffit venting - keeps the wind out, which includes wind driven rain and wind driven snow.

Building Products Brentwood Industries - Specialty Products Group (http://www.brentwoodindustries.com/spg/building-products/index.aspx)

http://www.brentwoodindustries.com/spg/Files/Accu%20Sl%20Sht%20103807.pdf

[Dennis Crookshanks]

Jerry , I've not seen those before. Thanks for the link.

[Door Guy]

Not perforated soffits with baffles, but baffles which go in and are used for ANY type of soffit venting - keeps the wind out, which includes wind driven rain and wind driven snow.

Building Products Brentwood Industries - Specialty Products Group (http://www.brentwoodindustries.com/spg/building-products/index.aspx)

http://www.brentwoodindustries.com/spg/Files/Accu%20Sl%20Sht%20103807.pdf

Looks like a plain old insulation baffle to me... I don't know if you have ever lived in the northern states? When the the temps get below zero, wind driven snow as fine as flour will blow in through the vents and actually get driven straight up between the insulation baffle and roof deck. Once there, it will eventually melt, and presto a wet spot.

If you look closely at the orginal pic, it appears that someone already block off the truss space with blocking and snow still is making its way in. The ventilation is already compromised.

Thanks for the link Jerry.

[Donny G]

Starting off. This is a very common problem where I work. I am with a builder in the extreme windy cold Midwest and fight with this issue yearly. Fortunetally we have found solutions, guaranteed some may/may not work depending on location of home/vents/soffits, roof pitch, materials used ect.

What we have found to work best is using ridge venting. This allows for minimal intrusion of the fine wind blown snow. Yes, some will still get in the attic, but it helps signifigantly. As far as coming in through the soffit holes. One response was to use a non vented soffit. We have successfully elliminated 3 homes with this procedure when the area was facing to the NW.

Another step we are now taking is to install a switched outlet in the attic as a inexpensive method to provide the home owner with the option to hang a fan for air circulation. We noticed it was on the warm days, after extreme cold conditions, that the accumulated attic snow would melt, causing water spots, damaged ceillings, ect.

If anyone has any other ideas, PLEASE LET US KNOW!

Thanks

[John Kogel]

If anyone has any other ideas, PLEASE LET US KNOW!
Thanks:cool:

What we have found to work best is using ridge venting. This allows for minimal intrusion of the fine wind blown snow. Yes, some will still get in the attic, but it helps signifigantly. Hang a metal trough under the ridge vent? One that evaporates dry in the spring. :)



Another step we are now taking is to install a switched outlet in the attic as a inexpensive method to provide the home owner with the option to hang a fan for air circulation. We noticed it was on the warm days, after extreme cold conditions, that the accumulated attic snow would melt, causing water spots, damaged ceillings, ect. Fans are bad news if they get left on.
Would you install a humidistat so the fan only comes on when the attic humidity rises? That's the only time you need to move air out.



As far as coming in through the soffit holes. One response was to use a non vented soffit. We have successfully elliminated 3 homes with this procedure when the area was facing to the NW. There is a soffit design which has vent slots hidden behind the ridges. Have you tried those?
If they're putting a fan in, they need all the soffits open, IMO.

[Door Guy]

:cool: Hang a metal trough under the ridge vent? One that evaporates dry in the spring. :)
Fans are bad news if they get left on.
Would you install a humidistat so the fan only comes on when the attic humidity rises? That's the only time you need to move air out.


There is a soffit design which has vent slots hidden behind the ridges. Have you tried those?
If they're putting a fan in, they need all the soffits open, IMO.

John, do you have a link to the soffit vent. I would like to see it. Thanks!

[chris mcintyre]

John, do you have a link to the soffit vent. I would like to see it. Thanks!


http://www.variform.com/NapcoWebDocument.nsf/OtherDocs/UltraSpan/$file/UltraSpan-Soffit-bro.pdf

This is one, but as far as I know all siding manufactures have a version of this.

[Door Guy]

:cool: Hang a metal trough under the ridge vent? One that evaporates dry in the spring. :)
Fans are bad news if they get left on.
Would you install a humidistat so the fan only comes on when the attic humidity rises? That's the only time you need to move air out.


There is a soffit design which has vent slots hidden behind the ridges. Have you tried those?
If they're putting a fan in, they need all the soffits open, IMO.


http://www.variform.com/NapcoWebDocument.nsf/OtherDocs/UltraSpan/$file/UltraSpan-Soffit-bro.pdf

This is one, but as far as I know all siding manufactures have a version of this.


Thanks Chris, I can still see blowing snow making it's way through this and any soffit material I have ever seen. I think the hidden slots are more for appearance than function?

[chris mcintyre]

I think the hidden slots are more for appearance than function?

I agree, I have not checked the specs but it does not appear to be much ventilation.

Fortunately I have no idea what snow blowing into an attic is all about :D.

[Roger Hankey]

I believe ridge vents are the answer when the opportunity is available. (new construction, or during reroofing) Good ridge vents such as the Cobra utilize a random weave plastic mesh material AND a filter fabric to cover the ridge opening. I've not seen dry powder snow enter attic when this material is used. Nearly any other type of roof or gable vent is vulnerable to window blown powder snow. Around here (MSP), during the past 34 years, this typically happens only once every 3-4 years, but with climate changes, who knows what to expect.

As for soffit vents, baffles and "wind wash barriers" are needed to manage soffit vent air flow, although I rarely see any snow blown into attics via soffit vents. The main problem I see at soffit vents is displaced blown fiberglass insulation. The worst cases are where the soffit vents are placed close to the wall instead of near the fascia.

In attics with a plastic vapor barrier on the ceiling or foil faced drywall ceilings, we rarely see enough snow to cause ceiling stains. The snow melts, evaporates, and leaves a dimple in the insulation, which of course reduces the effectiveness of the insulation, but usually does not damage the ceiling.

[Glenn Duxbury]

Hi, All &

Greetings !

Am thinking - positively pressurize (fan-forced) that attic space (don't see a problem if it's just a garage) & keep that /those roof vents blowing-out (exhausting), whenever the snow flies...


CHEERS !

[Matthew Klein]

I want to take the discussion in a different path. Why is the attic even ventilated? The purpose for attic ventilation is temperature and moisture control Attics get hot--no news there. However, when the attic gets hot, the materials facing the living space also get hot and radiate heat into the living space. The occupants feel this as radiant heat, one of the four methods our bodies receive and give off heat. In the winter, probably not a problem; but in the summer, a problem. Therefore, if they want to feel cooler in the summer, they lower the A/C. This attic space is over a garage. Now, assuming that the garage attic is properly isolated from the residential attic, who cares if it gets hot? As far as moisture control, attic spaces over residential areas get moisture mainly from the activities of the occupants, washing, cooking, etc. Again, this space is above a garage where those activities do not occur. So, assuming that the slab has a vapor barrier under it, as it is supposed to, it should not have the moisture problem that requires ventilation. My feeling is that the eave vents can be eliminated without much consequence.

[Joe Klampfer]

If snow is blowing in from the soffit vents and it always or only happens on the one side, there's no harm in blocking off the soffit vents on the wind-ward side as long as the minimum venting requirements for your area are still met. (up here the venting we req is 1/300th of the attic space served).

I have seen soffit vents blocked off on the wind-ward side of homes facing a bluff or waterfront, to prevent the attic loose-fill insulation from being blown to the other side of the attic space.

[Door Guy]

I want to take the discussion in a different path. Why is the attic even ventilated? The purpose for attic ventilation is temperature and moisture control Attics get hot--no news there. However, when the attic gets hot, the materials facing the living space also get hot and radiate heat into the living space. The occupants feel this as radiant heat, one of the four methods our bodies receive and give off heat. In the winter, probably not a problem; but in the summer, a problem. Therefore, if they want to feel cooler in the summer, they lower the A/C. This attic space is over a garage. Now, assuming that the garage attic is properly isolated from the residential attic, who cares if it gets hot? As far as moisture control, attic spaces over residential areas get moisture mainly from the activities of the occupants, washing, cooking, etc. Again, this space is above a garage where those activities do not occur. So, assuming that the slab has a vapor barrier under it, as it is supposed to, it should not have the moisture problem that requires ventilation. My feeling is that the eave vents can be eliminated without much consequence.

Except now you have probably just eliminated your shingle warranty. This will bake the shingles on the roof in hot weather.

[Jerry Peck]

If snow is blowing in from the soffit vents and it always or only happens on the one side, there's no harm in blocking off the soffit vents on the wind-ward side

I have seen soffit vents blocked off on the wind-ward side of homes facing a bluff or waterfront,


Regardless the reason for doing so, or the amount of venting still open, doing that violates the intent and reason of using soffit vents, they should be on all sides, or at least on opposite sides, of the roof.

From the 2006 IRC (which I know does not apply up in Canada) (underlining and bold are mine)
- R806.1 Ventilation required. Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters shall have cross ventilation for each separate space by ventilating openings protected against the entrance of rain or snow. Ventilating openings shall be provided with corrosion-resistant wire mesh, with 1/8 inch (3.2 mm) minimum to 1/4 inch (6 mm) maximum openings.

[Door Guy]

I want to take the discussion in a different path. Why is the attic even ventilated? The purpose for attic ventilation is temperature and moisture control Attics get hot--no news there. However, when the attic gets hot, the materials facing the living space also get hot and radiate heat into the living space. The occupants feel this as radiant heat, one of the four methods our bodies receive and give off heat. In the winter, probably not a problem; but in the summer, a problem. Therefore, if they want to feel cooler in the summer, they lower the A/C. This attic space is over a garage. Now, assuming that the garage attic is properly isolated from the residential attic, who cares if it gets hot? As far as moisture control, attic spaces over residential areas get moisture mainly from the activities of the occupants, washing, cooking, etc. Again, this space is above a garage where those activities do not occur. So, assuming that the slab has a vapor barrier under it, as it is supposed to, it should not have the moisture problem that requires ventilation. My feeling is that the eave vents can be eliminated without much consequence.


Regardless the reason for doing so, or the amount of venting still open, doing that violates the intent and reason of using soffit vents, they should be on all sides, or at least on opposite sides, of the roof.

From the 2006 IRC (which I know does not apply up in Canada) (underlining and bold are mine)
- R806.1 Ventilation required. Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters shall have cross ventilation for each separate space by ventilating openings protected against the entrance of rain or snow. Ventilating openings shall be provided with corrosion-resistant wire mesh, with 1/8 inch (3.2 mm) minimum to 1/4 inch (6 mm) maximum openings.


Jerry, I think the point some of us are trying to make is just blocking off the problem area. Like an area where a dormer would intersect the larger roof line. Snow tends to enter these kinds of areas. We are not talking about eliminating the soffit venting all together, just maybe one or two pieces. If your still within the required amount of ventilation you solve the problem and no harm done to the ventilation.

-806.2 Minumum area. The total net free ventilating area shall not be less than 1/150 of the area of the space ventilated...

By the way a 1/8" or 1/4" screen won't keep blowing snow out.

[Jerry Peck]

Jerry, I think the point some of us are trying to make is just blocking off the problem area.

I understand that.


We are not talking about eliminating the soffit venting all together, just maybe one or two pieces. If your still within the required amount of ventilation you solve the problem and no harm done to the ventilation.

-806.2 Minumum area. The total net free ventilating area shall not be less than 1/150 of the area of the space ventilated...

I was pointing out, and apparently I missed the target, that "and no harm done to the ventilation" is incorrect.

Proper ventilation IS NOT just meeting minimum ventilation area, it is ALSO meeting the "shall have cross ventilation" requirement.

[Door Guy]

I understand that.



I was pointing out, and apparently I missed the target, that "and no harm done to the ventilation" is incorrect.

Proper ventilation IS NOT just meeting minimum ventilation area, it is ALSO meeting the "shall have cross ventilation" requirement.

Apparently I missed the target, one piece of unvented soffit where two roof lines meet will not eliminate cross ventilation. When a crawl space is vented, is it necessary to vent the entire top of the foundation? "NO" you can get the required area and cross ventilation required without doing that. Why would it be necessary to vent every piece of soffit?

[Cobra Cook]

looking at the two pictures it looks as if the soffits are already completly blocked off with 2x4s installing baffels , how are they going to help? the baffles are supposed to be installed to prevent insulation from blocking off the soffits so that ventilation can pass through, in this case there is no insulation so that is not the problem.Can you take a picture on the outside up at the soffits or does this portion or the roof join another, if that is the case I would suspect a flashing problem.

[Patrick McCaffery]

In a northern climate, you really don't need a lot of attic venting. Blocking some of the soffit vents could be acceptable.

As demonstrated here, sometimes attic vents can let more moisture into the attic than they let out - and in a northern climate, the main purpose of attic venting is to keep it dry.

Moore vents (baffles) would be a good solution in this case.

It would have been nice to see a picture of the outside of the house, to see what the soffit vents looked like. As the area indicated in the picture is at the very corner of the roof, are we sure that the soffit vent is the problem. As to not needing much ventilation in the North, I live in Rochester, New York along Lake Ontario. In the past two days I have done inspections where there are ice cycles hanging from the gutters. The cause is not enough ventilation. I did not notice any snow on the interior of the house from the soffit vents. At the time of the inspections the temperature was about 15 degrees F. and it was snowing. Just some thoughts.

[Jerry Peck]

Apparently I missed the target, one piece of unvented soffit where two roof lines meet will not eliminate cross ventilation. When a crawl space is vented, is it necessary to vent the entire top of the foundation? "NO" you can get the required area and cross ventilation required without doing that. Why would it be necessary to vent every piece of soffit?


Again I missed my target, apparently, ... it is not necessary "to vent every piece of soffit", but one must take into consideration THE LOCATION of the vents and not just THE AMOUNT of the net free vent area, which is what you said:

(underlining is mine)

If your still within the required amount of ventilation you solve the problem and no harm done to the ventilation.

Which is what I pointed out was incorrect.

I guess that takes us back to square one where *YOU* said "If your still within the required amount of ventilation ... " and I replied "Proper ventilation IS NOT just meeting minimum ventilation area, it is ALSO meeting the "shall have cross ventilation" requirement."

Whack!

Balls in your court now ... and within bounds ... :rolleyes:

[chris mcintyre]

In the past two days I have done inspections where there are ice cycles hanging from the gutters. The cause is not enough ventilation.

Patrick, you lost me there, what is the relationship between attic ventilation and ice "sickles" hanging from the gutters.

[Patrick McCaffery]

Chris,
Improper attic ventilation,(not enough) will cause the attic to be too warm. This melts the bottom layer of snow, causing ice damming in the gutters. If the attic temperature is cold enough, the snow will not melt, thus no ice cycles.

[Door Guy]

Again I missed my target, apparently, ... it is not necessary "to vent every piece of soffit", but one must take into consideration THE LOCATION of the vents and not just THE AMOUNT of the net free vent area, which is what you said:

(underlining is mine)


Which is what I pointed out was incorrect.

I guess that takes us back to square one where *YOU* said "If your still within the required amount of ventilation ... " and I replied "Proper ventilation IS NOT just meeting minimum ventilation area, it is ALSO meeting the "shall have cross ventilation" requirement."

Whack!

Balls in your court now ... and within bounds ... :rolleyes:

I totally agree cross ventilation is important and is a code requirement. I would not advocate using solid soffit on one complete side of the house (hence no cross ventilation). The point I was trying to make was you can satisfy both, and hopefully eliminate problem areas.

In my opinion, attics need as much, or in some cases more attic ventilation (with cross ventilation) than warm climates. Maybe that's because I live in one? If the attic gets to 32 degrees, guess what? Ice build up.... that's why we also have the Ice and Storm requirement.

Attics in cold climates can also produce a lot of condesation. If not properly ventilated warm moist air making it's way into the attic will condense in the cold attic space. You know the rest of this story.

I think we are on the same court now. :D How about you? I wouldn't want to get "whacked" again...:eek:

By the way, I may not be able to dunk anymore. But I can still knock down a trey now and again.

[Jerry Peck]

I think we are on the same court now. :D How about you? I wouldn't want to get "whacked" again...:eek:

By the way, I may not be able to dunk anymore. But I can still knock down a trey now and again.


I was thinking tennis when I whacked ... with the tennis racket, but I don't play tennis or Bball ... but I think we are on the same court now, and in Bball that would be half court?

[Bruce Breedlove]

It would have been nice to see a picture of the outside of the house, to see what the soffit vents looked like. As the area indicated in the picture is at the very corner of the roof, are we sure that the soffit vent is the problem.

Patrick,

It's been a year since that inspection but I was able to find the following photos. Unfortunately I did not take a photo of the soffit vent. The soffit vents were the rectangular type. The location of the soffit vent in question is at the rear of the garage. The rear wall and soffit are short; the layout apparently channels the wind (and snow) into the garage attic through the soffit vent.

First photo - View of house. Soffit vent is located at right-rear of garage.
Second photo - View at rear of garage.
Third photo - Intersection of garage rear soffit and wall of house.

[Cobra Cook]

The house has no soffit vents as it looks like they are solid, mostly because it is a two story house and the first story does not have to be vented or as much as the attic. To me the pictures are a little confusing with the description numbers. I mentioned earlier that it is possible that the flashing where the two walls meet is not correct. One would have to really look at the ice cycles on the gutters to see why they are forming but the usual cause is when there is snow or ice on the roof in the day the sun starts to melt which runs down into the gutters and if the gutter is stopped up they overflow and if the temp is below freezing ice cycles are formed just like on trees. I would suggest cleaning the gutters. Just a thought from a home owner who has already had this happen.:) .

[Patrick McCaffery]

Hi Bruce,
Thanks for the additional pictures. The picture of the back of the garage indicates that the way the house juts out, there is probably a lot of wind turbulent in this area. This could be enough to blow snow through the soffit vents. I would agree that installing the baffles shown by Rick Hurst would be a good place to start.

[Cobra Cook]

why do you need baffels when there is no insulation installed to block off the vents that are not inslalled in the first place?

[Bruce Breedlove]

why do you need baffels when there is no insulation installed to block off the vents that are not inslalled in the first place?

Baffles are normally used to prevent soffit vents from being blocked off by insulation. In this particular case a baffle may be useful to prevent snow from blowing through the soffit vent into the garage attic. The lack of insulation is irrelevant in this particular case. (Many things can be used for more than their primary purpose. Have you ever used a wrench as a hammer?)

[Door Guy]

Baffles are normally used to prevent soffit vents from being blocked off by insulation. In this particular case a baffle may be useful to prevent snow from blowing through the soffit vent into the garage attic. The lack of insulation is irrelevant in this particular case. (Many things can be used for more than their primary purpose. Have you ever used a wrench as a hammer?)

No... but I have used a hammer as wrench and in conjunction with a wrench:eek:

[Jerry Peck]

Have you ever used a wrench as a hammer?)


No... but I have used a hammer as wrench and in conjunction with a wrench:eek:


Yep, and used a screw driver as a hammer, and the claws on the hammer as a screw driver ... whatever is available and will do the job is what gets used. :D

[Cobra Cook]

just curious, how do you install the baffels with no insulation to hold them in place? nail them to the underside of the roof I guess. And oh brother a pipe wrench makes a nice hammer, pry bar and much more:D

[Door Guy]

just curious, how do you install the baffels with no insulation to hold them in place? nail them to the underside of the roof I guess. And oh brother a pipe wrench makes a nice hammer, pry bar and much more:D

They get stapled the the underside of the roof decking. They could be nailed I guess. Just make sure the nails are shorter than the roof decking. Otherwise you'll need that pipe wrench to pound them back down once they penetrate the shingles above.:D

[George W Derby]

If snow is blowing in from the soffit vents and it always or only happens on the one side, there's no harm in blocking off the soffit vents on the wind-ward side as long as the minimum venting requirements for your area are still met. (up here the venting we req is 1/300th of the attic space served).

I have seen soffit vents blocked off on the wind-ward side of homes facing a bluff or waterfront, to prevent the attic loose-fill insulation from being blown to the other side of the attic space.

You seem to be the one who understands "my problem" which is on the windward side (NE) one mile from the ocean. Although my soffit vents are above the gutter. ( ie; a drip edge vent) How can I baffle this arrangement? Thank you all for the education I have received by reading the posts on this site. Thanks again. George

[Griffen]

Here's my take. I inspect tons of attics. I see frost and snow in attics all the time. As long as there is a vapor barrier on the underside of the drywall and its properly installed, and there is sufficient insulation, here its around 19", the ceiling should not get wet. The insulation may feel damp, but as soon as it warms up that moisture will evaporate and all is good. Attic baffles are great for making sure soffits dont get blocked. But I have never seen a moldy attic due to snow infiltration is the above was installed prior.