From: rob
Newsgroups: misc.consumers.house alt.home.repair
Subject: Re: Roof vent
Date: Sun, 16 Apr 2006 21:55:48 -0500

On Mon, 17 Apr 2006 01:41:02 GMT, "Moisés Nacio" 
wrote:

>
> wrote in message
>
>> Funny but I HAVE seen them covered on the outside and it's possible
>> that even those not covered might have had some covering / blockage
>> from inside (dunno because I can't see the attic of course).  I agree
>> that if you don't care about cold air getting inside, then no need to
>> do anything.  And usually moisture isn't a problem in winter for
>> unheated areas.
>
>You are misinformed about moisture not being a problem in the winter. When 
>heat escapes from the thermal envelope into an attic, it must exit, or you 
>get condensation in the attic. It is simple physics of when cold meets 
>warm. Take for example a glass of ice cold liquid, sitting on a coffee 
>table at room temperature, it's not leaking fluid from the glass, but 
>sweats (condensation).
>
>I have seen instances where homes had power vents and that's all. The 
>problem is, they don't come on in the winter. This caused thousands of 
>dollars worth of damage to the roof deck, insulation & wallboard.
>
>Never block venting during the winter, unless you want condensation, rot, 
>and mildew.
>
>This link will provide you a better explanation on how a house breathes.
>http://www.airvent.com/professional/whyVent/tools-iceDam.shtml
>

I agree and I should have said it differently.  

I was thinking that usually you wouldn't bother to cover up the
venting unless you had a heated (finished) attic so moisture shouldn't
come about unless the venting was inadequate in either case.