cover roof ridge vents in winter?


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Old 11-15-12, 10:56 PM
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cover roof ridge vents in winter?

Would covering our ridge vents from the interior create any potential issues with condensation, heat build up, etc
 
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Old 11-16-12, 01:54 AM
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Yeah it would probably cause more than the usual amount of frost on the sheathing, as the RH would likely increase due to the lack of airflow. When the frost melts as the roof warms up (sometimes on a daily basis, if it's sunny) it can cause it to "rain" on your insulation, adding to the RH.
 
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Old 11-16-12, 02:43 AM
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You want the attic space to be as close to the outside temperature as possible. The insulation on your ceiling is what keeps you warm. Consider all the bad things XSleeper mentioned.
 
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Old 11-20-12, 01:00 PM
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"Wind washing!"

For some time, there has been a move towards having a warm roof.
Having a ventilated roof has advantages and disadvantages.

Advantage: The passing wind created a suction effect that pulls the air through the roof, drying any wet surfaces, moving water vapor outwards. And possibly cooling the roof in summer.

Disadvantage, it also pulls your expensive warm air out of your home raising your heating costs, this is a thing called wind washing, once the wind is moving at more than 4.2 m/s it pulls the air through fiberglass and other open cell products. It can also pull Radon gas from the ground into your home leading to lung cancer.

If you have a sealed air tight roof, you need to seal all the holes and cracks in the ceilings and seal the ceilings to stop water vapor moving into the roof, water vapor is attracted to cold and it is always looking for ways to pass through your ceilings and walls. Once in the roof or walls it will condense and may cause mold and wood rot, if the wood doesn't dry during the summer.

Water vapor in itself isn't a problem as long as the wood has the chance to dry. With most homes the heat of summer looks after that side of things.
 
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Old 11-20-12, 01:19 PM
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If you have a sealed air tight roof, you need to seal all the holes and cracks in the ceilings and seal the ceilings to stop water vapor moving into the roof, water vapor is attracted to cold and it is always looking for ways to pass through your ceilings and walls. Once in the roof or walls it will condense and may cause mold and wood rot, if the wood doesn't dry during the summer.
This applies to hot and cold roofs and would negate 'wind washing' - air sealing from the house into the attic is very important.
 
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Old 11-20-12, 01:29 PM
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I'd have to disagree with pretty much all of that (2 posts up)

Having wet insulation all winter and hoping it dries out in summer is ridiculous.

If it gets wet it will compress and lose it insulation value.

Also.....a warm attic will melt the snow....the water will then freeze at the eaves causing ice dams.

If you're losing all your heat because of the "wind" in the attic.....get more insulation.

If you have radon then that's a separate problem that needs addressing.



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Old 11-22-12, 01:50 AM
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I would ask you to read my blog again, there is no mention of wet insulation, merely wet framing, due to water vapor rising into the roof from the living space below, and condensing on the cold roof.

Not all insulation compresses when it gets wet. All closed cell insulation polystyrene and its various offshoots are impervious to wet and retain their insulation properties.

A normal roof will indeed allow the snow to melt and lead to ice dams, however. A "Warm Roof" is different!

The expression "Warm Roof" relates to the practice of insulating below the roof, to keep the top/outside of the roof cold. In this way any snow landing on the roof does not melt where its in contact with the roof and ice dams do not form, the snow stays in place and/or blows off/evaporates/melts in time.

The idea of sealing the ceilings and/or having enough insulation to keep the heat inside the comfort zone is the main idea. Stopping ice dams and melt entering the attic space is a benefit. The term Warm roof, merely means the roof is enclosed and air tight, and may have insulation between the rafters and will have insulation attached below the rafters to keep the home below warm. Some insulation may be between the ceiling joists and below the ceiling joists, the roof is considered warm because it is not open to the outside cold.environment.

When you have a Wind Washed space inside the attic adding more insulation, if its fiberglass or some other open cell cheap product does not solve the problem as the moving air is able to pull the warm air from the insulation. Thereby causing the rooms to become colder.
 
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Old 11-22-12, 07:26 AM
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You first referred to "fiberglass and other open cell products"

I simply stated that once wet.....this insulation loses its R-Value

Now you refer to
"closed cell insulation polystyrene".....which doesn't apply here.

The original poster simply asked if he can block off his ridge vent.....the answer is no.

Of course there are different ways to engineer a new roof system.

But.....altering an existing home is not so simple.....that is my point.

In this situation the exhausting of the warm moist air in the attic is key.

It is a passive.....most times slow moving......self enclosed system.

The "suction" that would draw air from inside the home is minimal.

Simply because.....like most things.....air travels in the path of least resistance.

That path is from vented soffit to upper roof or ridge vent.

And.....if you stop this air flow.....no debate.....you will have mold.

Of course.....the added bonus will be ice dams, wet insulation and wood rot.




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