Snow & Ridge Vents...bad Combination?

 
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Old 01-09-2005, 09:39 AM   #1
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Snow & Ridge Vents...bad Combination?


Well, this is the first winter for my new roof. After much research I increased the intake ventilation (soffits, approx 12 sq. in/ft) and installed a highly recommened ridge vent (Smartridge, 18 sq. in/ft).

We've had a couple moderate snow falls (couple inches to 1/2 foot) in which the roof has done great. When it is below freezing, no melting on the roof!

We had another 1/2 foot yesterday, but this time it seems to have clogged the ridge vent. When it was about 20 out, the snow could be seen melting off the roof. I then checked the attic tempature, and it was close to 40!! I can only assume that the ridge vent has been clogged. I was told that the warm air would make tiny holes for the attic air to escape...I've given it a day but this hasn't happened.

When I did the roof, I sealed the gable vents so I wouldn't short circuit the flow. As suggested I have a soffit and ridge vent system.

I just tried unsealing the gable vents, to see if that will bring the tempature down.

What are people's thoughts about ridge vents and snow?

Thanks
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Old 01-09-2005, 11:28 AM   #2
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Re: Snow & Ridge Vents...bad Combination?


Did you ever measure the temprature before you installed the ridge vent?

What is the slope of your roof? Anything less than 3/12 and I gurantee it is clogged. Anything between 3 and 6/12 and it's 50/50 Anything greater than 7/12 and it's probably not clogged.

Do you feel air flow in the attic? Light a match and hold it about a foot away fromt he ridge vent. This will tell you if there is any air flow.

Do you have any soffit vents? If not you should have never installed the ridge vent. Ridge vents only work in combination with soffit intake ventilation.

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Old 01-09-2005, 12:38 PM   #3
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Re: Snow & Ridge Vents...bad Combination?


The widely accepted formula for intake ventilation is one square foot of net free vent space for every 150 square feet of attic floor space. Same for exhaust ventilation.

You will get some thaw no matter what, you just hope it doesnt thaw faster than it can exit the roof before re-freezing, thus creating ice dams at the eaves
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Old 01-09-2005, 12:41 PM   #4
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Re: Snow & Ridge Vents...bad Combination?


Quote:
Originally Posted by Grumpy
Did you ever measure the temprature before you installed the ridge vent?
Yes, the tempature difference between the attic and outside is currently matching the the days before I improved the ventilation.

Quote:
Originally Posted by Grumpy
What is the slope of your roof? Anything less than 3/12 and I gurantee it is clogged. Anything between 3 and 6/12 and it's 50/50 Anything greater than 7/12 and it's probably not clogged.
The roof is 5 or 6/12 (I can't remember).

Quote:
Originally Posted by Grumpy
Do you feel air flow in the attic? Light a match and hold it about a foot away fromt he ridge vent. This will tell you if there is any air flow.
I can feel air flow from the soffits...I'll have to try the match trick.

Quote:
Originally Posted by Grumpy
Do you have any soffit vents? If not you should have never installed the ridge vent. Ridge vents only work in combination with soffit intake ventilation.
Yes, in fact I improved the soffit ventilation (see original message).

Thanks for your thoughts. I'm going to let the gable vents do their thing for a bit longer today. They have been open for about 3 hours and I haven't see much of a tempature difference. In fact I think the tempature may have gone up (a couple of degrees or so). I don't know if the ridge vent hadn't had a chance to create vent holes (from the warm air) or what. If I don't see any change in temperature in the next couple of hours, I may seal the gable vents up again...
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Old 01-09-2005, 12:47 PM   #5
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Re: Snow & Ridge Vents...bad Combination?


Quote:
Originally Posted by AaronB.
The widely accepted formula for intake ventilation is one square foot of net free vent space for every 150 square feet of attic floor space. Same for exhaust ventilation.
I can't recall the numbers, but I'm above the 1/150 ratio. I have a little bit more intake then exhaust.

Quote:
Originally Posted by AaronB.
You will get some thaw no matter what, you just hope it doesnt thaw faster than it can exit the roof before re-freezing, thus creating ice dams at the eaves
This is what I've observed for the other snow falls...and I've been pleased with the results. What's different about this one is that icicles have begun to form and there is a bigger tempature difference then average between the attic and outside air.
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Old 01-09-2005, 01:14 PM   #6
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Re: Snow & Ridge Vents...bad Combination?


Did you improve the ceiling insulation?
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Old 01-09-2005, 02:47 PM   #7
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Re: Snow & Ridge Vents...bad Combination?


Quote:
Originally Posted by AaronB.
Did you improve the ceiling insulation?
No.

Correct me if I'm wrong. I'm thinking insulation wouldn't have much to do with my issue. We've had colder days, with snow on the roof and the attic temperature has been closer to the outside temp. That's why I'm thinking the ridge vent may have been clogged.

Has anyone experienced a clogged ridge vent before?
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Old 01-09-2005, 03:10 PM   #8
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Re: Snow & Ridge Vents...bad Combination?


The reason I asked is if you blow in insulation (which will improve thermal efficiencies, you will sometimes get insulation blown over your intake ventilation. Also, greater heat loss from the building envelpoe will cause more sever melt, causing more severe ice damming.

What type of ridge vent?
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Old 01-09-2005, 03:37 PM   #9
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Re: Snow & Ridge Vents...bad Combination?


FYI
Quote:
Originally Posted by AaronB.
What type of ridge vent?
Quote:
Originally Posted by findwaldo
I installed a highly recommened ridge vent (Smartridge, 18 sq. in/ft).
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Old 01-09-2005, 04:15 PM   #10
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Re: Snow & Ridge Vents...bad Combination?


Ah yes. I have not used this particular ridge vent.
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Old 01-09-2005, 06:30 PM   #11
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Re: Snow & Ridge Vents...bad Combination?


Quote:
Originally Posted by AaronB.
The reason I asked is if you blow in insulation (which will improve thermal efficiencies, you will sometimes get insulation blown over your intake ventilation. Also, greater heat loss from the building envelpoe will cause more sever melt, causing more severe ice damming.
I have rolled insulation. When I installed the new soffits this summer, I had a chance to make sure that there was no insulation blockege.

It is on my list to increase the insulation in the attic.
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Old 01-09-2005, 11:28 PM   #12
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Re: Snow & Ridge Vents...bad Combination?


I have not been real comfortable installing ridgevent on any roof and am even more uncomfortable now this is the 5th time i have heard of it plugging up in 3 years.

I would probably make sure you have at least 12 inches of insulation in the attic all heat bypass areas sealed trp door, furnace pipes, recessed lighting etc....Install air chutes between rafters before adding insulation so your soffit vents won't clog. If you still have a problem cut some turtle vents in the back of your house as close to the peak as you can. The have been venting houses 50 years plus.
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Old 01-10-2005, 10:23 AM   #13
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Re: Snow & Ridge Vents...bad Combination?


Do not cut additional vents in your house unless you remove the ridge vent. You should NOT mix ventilation types...

which reminds me as soon as the snow melts off tha ridge vent you need to cover your gable vents.
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Old 01-10-2005, 03:21 PM   #14
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Re: Snow & Ridge Vents...bad Combination?


I agree. I use GAF Cobra vent and never had this problem.
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Old 01-10-2005, 06:08 PM   #15
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Re: Snow & Ridge Vents...bad Combination?


Sorry yes you shoud remove ridgevent prior to cutting any turtle vents in. The only ridgevent i will use is GAF snow country and only on or above a 7 pitch. with my experience i will still try to convince the homeowner to use turtle vents at the peak unless they have made their mind up to use ridgevent. I just have'nt seen it being used long and often enough. i have seen similar problems including bugs, cottonwood,squrills chewing through it and now snow. Although i have heard about problems that may arise because of snow and a low pitch.
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Old 01-10-2005, 07:00 PM   #16
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Re: Snow & Ridge Vents...bad Combination?


Quote:
Originally Posted by minnesotaroofin
with my experience i will still try to convince the homeowner to use turtle vents at the peak unless they have made their mind up to use ridgevent.
What if it is a vaulted/cathedrial ceiling?
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Old 01-10-2005, 09:15 PM   #17
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Re: Snow & Ridge Vents...bad Combination?


I have seen a few like this that are truely vaulted ridgevent may be the most economical option. Although most of the houses i have roofed Have Scissor trusses. http://minnesotaroofing.com/24612a.gif There is still room at the top for venting.
I have also seen on some new construction where if it is truely vaulted the space between the rafters is completely filled with spray in foam. I have also roofed houses truely vaulted with 1 inch toungue and groove wood interior held in place by 6x6 beams. this type of vaulting rarely has enough space for insulation and no room for venting we applied 2 layers of 3 inch ISO Than 1x4 firring strips to create air space we left 10 inches space on top and every 10 ft vertical. Installed 1/2 inch plywood Ice and water shingles. Just finished a 12 pitch metro shingle steel roof last week attic was finished we installed 2 inch ISO with 1x4 firring strips then 1/2 plywood but did vent it with ridge vent. We had a hard time venting soffits we did cut holes low into attic space and punched holes between rafters to allow some venting from soffit area.
http://minnesotaroofing.com/before.JPG
http://minnesotaroofing.com/after.JPG
Looks like snow is melting evenly if Ice is still aproblem we may have to find and alternitive for the soffit venting. We hope to finish porch this week

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