# Snow coming through roof vents



## carp.780

Make sure the eaves allow enough air in. A possible solution for ventilation is a turbine vent , I call them whirly-birds. Since they are rotating regularly they shed any snow that lands on them, they also circulate a LOT more air than a traditional vent. The one downside i could see is that most of them are not very aesthetic (to my eye anyway).

http://www.askthebuilder.com/NH039_-_Roof_Ventilation_with_Turbine_Vents.shtml


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## jmiller

or just do this:


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## Artworks

*snow*



carp.780 said:


> Make sure the eaves allow enough air in. A possible solution for ventilation is a turbine vent , I call them whirly-birds. Since they are rotating regularly they shed any snow that lands on them, they also circulate a LOT more air than a traditional vent. The one downside i could see is that most of them are not very aesthetic (to my eye anyway).
> 
> http://www.askthebuilder.com/NH039_-_Roof_Ventilation_with_Turbine_Vents.shtml


These things let a lot of snow in & odd bird that get trapped. ( seen 5 gal pail full of snow and couple birds ) & they will pull moist air out of the living space ( if not completely air sealed) & into the attic area (I have seen gobs of Ice in attic because of this) they look UGLY and are noisy.


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## BamBamm5144

Make it simple and right. Remove the box vents, reshingle each area, and put in ridge vent. Ive tried nearly all of them and I believe gaf sno country to be the best.

Seems as if the lower ones are acting as intake vents for the higher ones which makes sense.


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## MJW

Ridge vent will also work as an intake. It may band-aid the problem but it still isn't working correctly. You need to correct the attic space. There is obviously a huge open area in the attic between the lower roofs and the higher roof. Big problem....that will make the lower roofs an intake. The wind outside can make it better or worse also, but it definitely isn't working right.

There are a ton of guys with solutions, but the real problem should be addressed before sticking a bunch more labor and money into it.


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## BamBamm5144

Are we certain about the lower portions not being separated?


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## pardyc

BamBamm5144 said:


> Make it simple and right. Remove the box vents, reshingle each area, and put in ridge vent. Ive tried nearly all of them and I believe gaf sno country to be the best.
> 
> Seems as if the lower ones are acting as intake vents for the higher ones which makes sense.


From what I can tell the attic is getting enough ventilation, and I assume this would not change if the roof vents were removed and replaced with ridge vent. Just an unbalanced air flow would still exist... if that makes sense. Would this be a problem if snow entering was eliminated?

Has anyone had experience with snow entering through a ridge vent? Are they all designed to keep snow out? If I were to recommend to the customer removing current vents and installing ridge vents will he still get snow in? Because without making other modifications the lower ridges will likely still pull air in for the higher sections.

Lower portions are not separated. Roughly 3' of opening between sections.


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## pardyc

jmiller said:


> or just do this:


I think you have a good idea, my concern would be the warm air trapped in the lower section of the attic. The area where you suggested removing the vents is only open to the larger side by approx. 3' of space, leaving a large cavity for air to be trapped. You actually have to crawl on your knees to get in there. In fact it's basically the height of the green arrow underneath the vents.


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## jmiller

pardyc said:


> I think you have a good idea, my concern would be the warm air trapped in the lower section of the attic. The area where you suggested removing the vents is only open to the larger side by approx. 3' of space, leaving a large cavity for air to be trapped. You actually have to crawl on your knees to get in there. In fact it's basically the height of the green arrow underneath the vents.


Then leave those vents and block that 3' space off. It will probably fix this and be far easier than adding/subtracting actual vents. Snow coming in the vents is proving that space is being vented by the main ridge though, so either would work.

The whole attic must remain accessible so make it obvious what to remove to gain access if you cover any holes. If the vent at the far right is 3' below the other two and part of the same attic space, it has to go.

Yes, I've seen ridge vent do it too- more often than box vents.


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## dougger222

I have had a couple turtle vents allow snow in the over the years as has my brother. The only "call backs" are on unfinished garage attics were the home owner can clearly see snow in the garage space. 

Last year we had a lot of snow but never got any calls for snow getting in. 

The vents I use are Lomanco metal box vents. I see some roofs in my area though with lower profile metal vents. 

We used to use plastic Lomanco turtle vents and we never had snow get in. Instead lots of birds and squirels!


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## johnk

pardyc said:


> I noticed you're from B.C. Guess you would know... what brand and model do you find works best?
> 
> Do you have experience with ridge vents and snow?


These are the type we use http://duraflo.com/specs/weatherproroofvent.htm.The best ridgevent I have found is Shinglevent2


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## PA woodbutcher

BamBamm5144 said:


> Make it simple and right. Remove the box vents, reshingle each area, and put in ridge vent. Ive tried nearly all of them and I believe gaf sno country to be the best.
> 
> Seems as if the lower ones are acting as intake vents for the higher ones which makes sense.



What he said:laughing:

Johnk's link didn't work, but I'm thinking it's the same style ridge vent.


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## MrConcepts

I agree with JohnK about ridgevent. I really like AirVent ShingleVent2.

Something that hasn't been mentioned yet is make sure you have correct size holes cut for the intake and exhaust vents. I've seen guys put hatchet chopes in the soffit and roof deck and say they "cut a hole" for the vent.

If you don't cut the correct size hole for your vent you won't get enough air movement through your vent. The net free area of a vent is only valid if you have cut the proper size hole.

If you still have questions about how to calculate proper attic ventilation, google 'how to calculate proper attic ventilation'. The NFA of AirVent ShingleVent2 (4' shingle over ridgevent w/ 'snow and bug' filter) is 18sq in/lineal foot.


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## jeffatsquan

Unbalanced intake - exhaust vents suck --*SNOW*


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## jmiller

MrConcepts said:


> If you still have questions about how to calculate proper attic ventilation, google 'how to calculate proper attic ventilation'.*(removed by moderator)* has a good sheet that walks you through how to calculate your attic ventilation. The NFA of AirVent ShingleVent2 (4' shingle over ridgevent w/ 'snow and bug' filter) is 18sq in/lineal foot.


I did the calculation above, but not for the individual attic spaces. For a 1500 sf attic floor he would need 360sq in intake and 360 sq in of exhaust. 

1500/300 (for 1:300 ratio) =5
x144 to get sq inches =720
/2 
=360 square inches of exhaust AND
AT LEAST that much intake from the eaves.

Now lets install your ridge vent. 
18 sq inches x 60' RV = 1080 sq inches of exhaust. That's a lot of intake to stuff into areas where there's limited soffit.

What happens if you don't have equivalent intake NFA? Conditioned air ends up going out the ridge vent. Not just what floats into the attic on it's own accord, but I've read that it can create a negative pressure that actively sucks air out of the living space. I am a big fan of continuous ridge vent in conjunction with continuous soffit vent and proper baffles in every rafter bay. The air flow is palpable while in the attic on a windy day. But if you're just installing RV willy nilly w/o checking the soffit NFA that air flow is going to cost the homeowner money.


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## MrConcepts

jmiller said:


> I did the calculation above, but not for the individual attic spaces. For a 1500 sf attic floor he would need 360sq in intake and 360 sq in of exhaust.
> 
> 1500/300 (for 1:300 ratio) =5
> x144 to get sq inches =720
> /2
> =360 square inches of exhaust AND
> AT LEAST that much intake from the eaves.
> 
> Now lets install your ridge vent.
> 18 sq inches x 60' RV = 1080 sq inches of exhaust. That's a lot of intake to stuff into areas where there's limited soffit.
> 
> What happens if you don't have equivalent intake NFA? Conditioned air ends up going out the ridge vent. Not just what floats into the attic on it's own accord, but I've read that it can create a negative pressure that actively sucks air out of the living space. I am a big fan of continuous ridge vent in conjunction with continuous soffit vent and proper baffles in every rafter bay. The air flow is palpable while in the attic on a windy day. But if you're just installing RV willy nilly w/o checking the soffit NFA that air flow is going to cost the homeowner money.


Good job JMiller. A quick tip about calculating attic ventilation...take your total attic square footage and divide it by 4. This will give you an estimate for the amount of intake NFA and exhaust NFA. This isn't a perfect 1:300 ratio, but it is a quick way to edit while your in the field.

If you divide by 4 you actually 'over ventilate', which as long as you have a good balance of intake/exhaust, is a good thing..and will save you 5 minutes of time calculating.


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## pardyc

Spoke with the customer today. They said they want this fixed regardless of expense. But will not spend any money on guessing games.

I think we all agree, an unbalanced intake vs exhaust is to balme.

I think the most cost effective option is replace the vents with the "WeatherPro" mentioned by JohnK. The design should keep snow out. If I'm not able to adjust the airflow properly.

That being said, while replacing these I will likely shingle one maybe two over depending on the exact NFA specs. This is where the guessing game comes in. Like mentioned earlier, there are basically four attics which are partially joined and are sometimes feeding off each other. I'm not thrilled about closing off sections of the attic to create four completly seperate sections.

Does anyone have any suggestions in regards to which vents to remove?


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## pardyc

Forgot to post this. Here's the vent currently being used on the home.


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## pardyc

Jmiller has already made some suggestions in regards to this. And I think he has the right idea. I wanted to repost his idea for others to see.

There maybe a key point that I forgot to mention when responding to his suggestion earlier. The last roof vent to let snow in was in the highest portion of the attic. This somewhat goes against some of the logic that has been talked about doesn't it? Why would air be pulled in through these?


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## pardyc

MrConcepts said:


> Something that hasn't been mentioned yet is make sure you have correct size holes cut for the intake and exhaust vents. I've seen guys put hatchet chopes in the soffit and roof deck and say they "cut a hole" for the vent.


Thanks, but not a problem here. The soffits are all vinyl vented soffits and are completly open and free of insulation. Rood vents are cut to size as well... although if they weren't we may not have a problem.


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## jmiller

pardyc said:


> Jmiller has already made some suggestions in regards to this. And I think he has the right idea. I wanted to repost his idea for others to see.
> 
> There maybe a key point that I forgot to mention when responding to his suggestion earlier. The last roof vent to let snow in was in the highest portion of the attic. This somewhat goes against some of the logic that has been talked about doesn't it? Why would air be pulled in through these?


It does go against the logic and does appear to shoot my theory in the foot. Maybe it's just actually blowing in as suggested. It shouldn't be too hard to switch the vents out with what john recommended.

Whatever is going on doesn't defy the logic of proper venting though, so you should probably separate the attics as well. Do both to CYA, and you might get lucky and not have to go back. Trying one or the other is a gamble, and both may not work either.

This would all be free had you used us as subs for the roof. Is that company not around anymore?


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## pardyc

jmiller said:


> This would all be free had you used us as subs for the roof. Is that company not around anymore?


I did ask the homeowner if the roofing contractor gave them a warranty, but got a run around answer. Seems like there's a burnt bridge there somewhere.


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## Roofsafe

SVII is a good vent as well as Tamko's Coolridge vent. I prefer the Tamko product, just like the SVII, the vanes on each side create a negative air flow that draws air out the vent. I have watched during a blizzard last year to see if snow came in as guys have said it does, but there was no snow coming in the ridge or any of the soffet vents. If the intake is the same as the exhaust numbers you shouldn't have any problems with air flow, the SVII has a filter in it, I have found that filter material will plug up with dirt or other stuff that can be blown around by the wind, I always yank the filter in SVII, haven't had any problems.


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## ksw1234

*Solution?*

With that top louver sucking air, was there a gas furnace or house fan pulling air? Love a mystery (as long as it's not snowing in my attic).


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