Roof Vents

Reply

  #1  
Old 04-21-05, 06:56 AM
Member
Thread Starter
Join Date: Dec 2004
Posts: 39
Received 0 Votes on 0 Posts
Roof Vents

I have about 1700 sq ft of attic space (based on 2nd floor sq footage). How many roof vents should I have? I had an air handler installed in the attic and it wasn't cooling properly. The HVAC guy said my attic was getting too hot and needed more ventilation. There are currently 5 vents plus multiple soffit vents. Any thoughts or opinions?
 
Sponsored Links
  #2  
Old 04-21-05, 11:43 AM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Location: USA
Posts: 23,800
Received 285 Votes on 261 Posts
1 sq ft of vent for 150 sq ft of attic when there is no intake...
1 sq ft of vent for 300 sq ft of attic when there is soffit intake.

That's what I've heard, anyway. The following link seems to agree.

http://www.airvent.com/homeowner/products/intakeSoffit-specs.shtml

According to that, you need 5 2/3 sq ft of vent, be it can vents or ridge vent. Ridge vent is more effective because it draw air up each rafter bay, while can vents usually will only draw the hottest air out the rafter bay they are located in.
 
  #3  
Old 04-21-05, 04:11 PM
Member
Join Date: Apr 2005
Location: Royal Oak, MI
Posts: 222
Received 0 Votes on 0 Posts
Whether it's 1/150 or 1/300 depends on whether your attic insulation has a vapor barrier or not (1/300 if you have a vapor barrier and 1/150 if you don't, but check your local codes to be sure in case they might want 1/150 regardless)

And the way I've heard it explained is that the amount of square feet of ventilation you have should be split 50/50 between the top half of your roof and the bottom. A balanced system would have an equal amount of intake ventilation to exhaust ventilation. Ridge vents are exhaust, soffit vents are intake, roof vents could be either depending on where they are placed.

Gable vents can also be either. You could have a gable vent on both ends of the roof, use one end for exhaust and the opposite end can be used for intake by connecting it to the bottom of your roof with ducting.

I was also told to remember that the formula gives you square feet, not number of vents... Typical roof vents, I've been told, are around .75 square feet.

Also, make sure your soffit vents aren't obstructed. You might also have the option of putting in forced ventilation
 
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
 
Ask a Question
Question Title:
Description:
Your question will be posted in: