box vents, turbines or ridge vent

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Topic by Darell posted 07-13-2011 06:25 PM 10590 views 0 times favorited 3 replies Add to Favorites Watch
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2 posts in 3590 days

07-13-2011 06:25 PM

Topic tags/keywords: question attic

I would like some input from members here on attic ventilation. After the hail storms of a month ago here in central Oklahoma I’m getting different views from different roofing companies as to the best way to vent my attic when I have my roof replaced. Last year my son had his roof replaced and had ridge venting installed. So far he’s pleased with it citing lower attic temperatures than with his old box vents. I’ve had turbines on my roof for the entire 26 years we’ve lived in ths house with no problems other than some icing up during ice storms. The roofing companies I’ve had out don’t recommend ridge vents citing increased possibility of snow blowing into the attic during snow storms. Yes, we’ve had some snow storms around here the past couple of years despite the 100+ degree temps during the summer. One guy prefers box vents over turbines or ridge vents, another says turbines are the way to go. I have the standard 8×16 soffit vents every 8’ around the entire house. You can feel the heat being expelled from the attic when standing next to one of the turbines so I’m pretty sure I’ve got adequate venting now. The question is, what to folks here prefer and why? Thanks in advance for your opinions.

-- Darell

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139 posts in 3635 days

07-16-2011 02:16 AM

Darrell, I live in Duncan, OK. I have had turbines and I currently have ridge vents. My son has (I think what you are calling box vents) turtles (what the roofers call them around here). I have installed ridge vents in Minnesota where they get real snow. I have seen snow blow into homes here locally. So what is the best and why? I have ridge vents on my home today and I have been happy with them. I have had one problem. Smoke from my chimney will go into them and the attic when conditions are right. This has happened 2 times in 11 years. I don’t think that is the fault of the ridge vent. I think the chimney is too short. I have a contractor friend that installed ridge vents on a new home he built. Snow blew into the attic of that home. The insurance man told him it should never happen so leave them on. I think the snow gets in when there are several roof elevations and you have high pressure or low pressure areas. Some roofs seem to stop a lot of tree leaves and snow. I have an “L” shaped house with a ridge going east to west and a ridge going north to south. I have 80 feet of ridge vent. I have had 2 roofing companies look at replacing my roof in the past. both said they could reuse the ridge vent if it was the kind that came in 4 ft. lengths. If it was the stuff that came in a roll they throw it away. They both said the roll kind was junk. These folks didn’t know each other. Wind turbines have moving parts and they do make noise. Turtles and turbines depend on a certain size hole through the decking. If it is small then they cheated you. I am a licensed home inspector so I see all kinds of things on homes. I see 8 inch square openings under a 12 inch turbine. That is only 64 sq inches when it should be 113 sq inches (12 inch dia opening). In those cases the contractor stole half the vent available. The “Principles of Home Inspections” book tells us that an attic should have 1 sq. ft. of vent opening for every 150 sq feet of attic floor space. This should be considered a minimum. Screens obstruct air flow through soffit vents. Metal louvers obstruct more air. Wood louvers obstruct a great deal of air flow. Vinyl soffits offer very little air flow. I learned most of this when I installed a whole house attic fan many years ago. I see many home (especially those with dark shingles) that have nearly new shingles that look decades old. The “Principles of Home Inspections” also states that when attics are too hot the volitail materials will evaporate and the life of the shingles will be shortened. If an attic is over ventilated this can create a negative pressure and warm moist air can be drawn from the living area into the attic. This book also states that attic temps can approach 130 degrees. I have personally used my infrared thermometer to record 175 degree attics. That was in 2010. This year has be miserable and I haven’t taken any temps. I like 8×16 open screen vents when they are possible. In some of the new homes with the 12:12 pitch on the roof the soffits are small and 4×16 vents are being used. I like my ridge vent. It is at the very top of the attic. There are no moving parts and the opening is 1 inch on each side of the ridge pole. I have 80 ft of ridge vent. that gives me 13 sq ft of opening. Of course when you put the ridge vent on it obstructs a lot of that space. With all this said, do you have air chutes in the attic? They can be made of many things but polystyrene (foam)is the most common around here. These staple to the under side of your decking. This allows air to flow from the soffits past the insulation and into the upper attic. These devices keep insulation from covering the soffit vents. You need these and they need to be at every soffit vent. Work on these areas with your calculator and see what you have. I have given you my feelings and preferences and my observations. I like ridge vents.

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2 posts in 3590 days

07-16-2011 07:01 PM

Thanks Grandpa for your input. We’re still deciding on what we want to do. I don’t have air chutes but my soffits are clear with no restrictions on airflow. I made sure of that when I had insulation added. I like the look of the ridge vents, less stuff sticking up out of the roof. Turbines tend to ice up during freezing rain and ice storms but so far I’ve not noticed any damage. I’ll have to check and see which kind of ridge vent the contractors use. Thanks for the heads up on roll type versus sectioned vents.

-- Darell

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