# Ridge vent vs mushroom fan



## Windows on Wash (Aug 30, 2011)

You would never use both because they wind up making the other ineffective. If your home has full width intake, soffit, venting a ridge vent is ideal.


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## joecaption (Nov 30, 2011)

A ridge vent vents the whole roof and does not leave hot air trapped in the rafter bays.
Looks a whole lot better.
Not going breakdown on the hottest day of summer.
No noise.
DO let not them install any type of vent that comes in a roll.


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## Nestor_Kelebay (Jun 17, 2008)

There's a general disconnect I've noticed between when people in the USA talk about attic ventilation and when people in Canada talk about attic ventilation. We seem to have differing views as to why you need attic ventilation.

While attic vents do help to get rid of excess heat in the attic in the summer, the real need for attic venting is in the winter. That's because warm mnoist air from your house will always find it's way up into your attic, and the moisture in that air will condense on the coldest surfaces up there, typically forming frost on the underside of the roof sheathing or on the roof rafters. Where I live, that can be a problem because frost can accumulate all winter long in that attic, and come spring, it all starts to melt. Where the problem comes in is that the melt water from that frost ends up getting the insulation between the ceiling joists wet, and insulation works by keeping air stagnant. So, wet insulation takes forever to dry, and that's the kind of condition that promote wood rot of the ceiling joists. And, to add insult to injury, any vapour barrier you have under that insulation is going to prevent the ceiling drywall or plaster from getting wet, lulling the home owner into a false sense of security than there's nothing wrong up there. It's only once the damage is noticed that it's discovered that the ceiling joists are rotted and that there's extensive damage to the house.

(In one newspaper picture I saw, there was an old rented house that was used as a marijuana grow-op, and there was 3 inches of frost covering the roof sheathing in the attic by the end of the winter. I don't know what happened after that to the house.)

The whole idea behind attic venting is to allow cold dry air into the attic in winter, and then having that air warm up as a result of heat loss from the house. As that air warms, any frost or condensation present is absorbed by the warmer air. Then, if that air is allowed to escape from the attic, it takes that moisture with it, thereby keeping all the wood up there dry. Dry wood is happy wood.

Also, venting your attic keeps the roof cold, and that's important at preventing ice damming that occurs on the eves of a house. Without sufficient venting, heat will be trapped in the attic and will cause snow on the roof to melt. That melt water refreezes as soon as it gets over the eves where there's no longer any heat loss from the house to keep the water melted, and it forms ice dams on the eves that can potentially cause water damage to the interior of the house.

Here's how to tell if you have enough attic ventilation: Go up into your attic on the coldest b1oody night of the winter with a flashlight and look for frost or condensation on the underside of the roof sheathing and roof rafters. If you don't find any, then you don't need any more attic ventilation than you already have. Also, look for dirty spots on the ceiling insulation. Those are the result of melt water dripping off a roof rafter onto the insulation below. Check under and around that dirty spot for wet insulation or wood rot.

Finally, everyone touts soffit vents combined with a ridge vent as the ultimate in attic ventilation because THEORETICALLY, it will give you 100% volumetric sweep efficiency as the cold air coming in the soffit vents warms and rises and escapes out the ridge vent. But, in reality, you RARELY get a calm enough day in winter for soffit/ridge vents to work as advertised. MOST of the time the wind blows against the side of the house and you have air blowing in the soffit vents on one side of the house and blowing out the soffit vents on the other side of the house. Go up into your attic and have a cigarette next winter and you'll be able to see the smoke blowing across the attic instead of rising calmly up to the ridge vent.

So, I'm a believer in this: If you don't have any frost or condensation in your attic on the coldest night in the winter, you don't need any more holes in your attic or roof than you already have.

So, while attic ventilation helps to get rid of the heat that can accumulate in your attic in the summer, the excessive heat up there will never do any harm to your house. But, warm moist air rising into your attic in winter could potentially accumulate and cause severe damage to your house's ceiling joists.

Hope this helps.

So, GototheK, if you don't find any frost or condensation in your attic in winter, and you've been happy with the powered mushroom fan you have, then I wouldn't change a thing. Get new shingles if you want, but tell them to work around that existing powered mushroom fan.


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## Windows on Wash (Aug 30, 2011)

No disconnect in this part of the world as far as I can tell. Yes, many roofers will think it is for heat, however, most of the pros on here know the prescriptive benefits and necessities of ventilation for moisture removal and ice dam prevention.


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## Nice Shingles (Nov 26, 2013)

I would try to stay away from mushroom vents and definitely no combining two different ridge-vents.

The best type of ridge vents out there are baffled ridge-vents. I use the Shingle-Vent II by Airvent Company.

If you are having moisture issues in the winter I would check to see if you have clear soffit vents and enough insulation. A well balanced ventilation system will get the warm air out but insulation will also help by keeping the warm air in the living spaces where it belongs.

Hope this helps,

Nice Shingles Roofing & Construction
http://www.niceshingles.com


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## stick\shift (Mar 23, 2015)

Soffit and ridge vent are the ideal combination, regardless of whether the wind is affecting them, as Nestor suggested.


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## Windows on Wash (Aug 30, 2011)

stick\shift said:


> Soffit and ridge vent are the ideal combination, regardless of whether the wind is affecting them, as Nestor suggested.



Am I chopped liver...? Pretty sure I was first on that bandwagon!!

:laughing::laughing:


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## stick\shift (Mar 23, 2015)

Yep, you were. Can't edit now, should have started with, "As Windows on Wash already stated,...."

I mostly wanted to address the wind factor, since that was subsequent to your answer.


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