Go Back  DoItYourself.com Community Forums > Exterior Improvement Center > Roofing, Gutters and All Waterproofing Anywhere
Reload this Page >

I have vented soffit on a bumpout roof. Should I make it unvented?

I have vented soffit on a bumpout roof. Should I make it unvented?

Reply

  #1  
Old 09-12-10, 08:27 PM
Member
Thread Starter
Join Date: Mar 2008
Location: USA
Posts: 33
Received 0 Votes on 0 Posts
I have vented soffit on a bumpout roof. Should I make it unvented?

I have a two story house with a small bump-out wall with roof and soffit at the back door. I had some air sealing and insulation work done there last year underneath the roof. The soffit is vented; I'm considering either replacing it with unvented soffit or pluging the vent holes with caulking to prevent cold air from entering during the winter. Does this sound like a good idea? Could I be setting myself up for trouble by doing this?
 
Sponsored Links
  #2  
Old 09-13-10, 07:51 AM
Group Moderator
Join Date: Oct 2004
Location: WI/MN
Posts: 19,308
Received 46 Votes on 43 Posts
Bad idea - the vents are to cool the roofing system and plugging them will cause problems
 
  #3  
Old 09-13-10, 09:15 AM
Member
Join Date: Apr 2005
Location: Royal Oak, MI
Posts: 222
Received 0 Votes on 0 Posts
Not just that... Maintaining proper airflow in the attic space is important for moisture management in the attic. In the summer, the hot attic with the relatively cold interior space will put moisture on your wood resulting in rot. In the winter, the warmth in the attic will melt snow on the roof where it will trickle down and freeze at the bottom building an ice dam.

The moisture trapped in the attic will also promote mold growth in your insulation.

Ventilation in the attic needs to be at the top and bottom, so soffit ventilation at the bottom and ridge ventilation are the options available that put the ventilation as far as possible to the extremes of top and bottom, and which are the least visible to disrupt the appearance of the roof. The vents provided at the bottom provide fresh air intake, the vents at the top provide exhaust.

Assuming you have exhaust ventilation in the attic, blocking the soffits would mean the intake is blocked. As the attic warms and cools through the day from the sun and the dark, the air expands and contracts from the heat... So when you cut off intake you may even create negative pressure in the attic, resulting in the attic trying to pull air from inside the house. If you have alot of your stuff sealed off, this may even result in pulling air through the gas vents for the furnace and water heater, pulling CO2 into the home.

In the house we just bought, most of the roof was inadequately ventilated, with the few vents that were present clogged with birds nests. The other sections of roof were not vented at all. The roof had severe shingle deterioration and inch thick moss growth, insulation in the unvented sections was blackened and flattenned, and rafters and sheathing over the dormers were sagging and blackened.

Things may not always be as we might otherwise expect in house construction, but there are good reasons for attic ventilation. If your insulation is good in the ceiling above your home, then you shouldn't need to worry about how cold it is in the attic to keep the house warm in winter.
 
  #4  
Old 09-13-10, 09:56 AM
Member
Thread Starter
Join Date: Mar 2008
Location: USA
Posts: 33
Received 0 Votes on 0 Posts
Originally Posted by WillK View Post
Things may not always be as we might otherwise expect in house construction, but there are good reasons for attic ventilation. If your insulation is good in the ceiling above your home, then you shouldn't need to worry about how cold it is in the attic to keep the house warm in winter.
That makes sense. I never thought of the space under the bumpout roof as an attic, but that's exactly what it is: a miniature attic. It is adequately insulated under there.

I'm glad that the truth matches what I want to hear: I don't have to do anything!

Thanks!
 
  #5  
Old 09-13-10, 05:35 PM
Member
Join Date: Mar 2009
Location: WA
Posts: 1,167
Received 0 Votes on 0 Posts
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
 
Ask a Question
Question Title:
Description:
Your question will be posted in: