Pressure drop in attic ?


  #1  
Old 02-15-23, 01:25 PM
B
Member
Thread Starter
Join Date: Jul 2007
Location: Arizona
Posts: 1,398
Upvotes: 0
Received 13 Upvotes on 13 Posts
Pressure drop in attic ?

I'm not sure I posted this in the right forum. It might belong under architecture or something.

This happened in my house years ago. I came home from work one night and noticed the attic hatch was open and ajar. It's not hinged or anything like that. I checked for signs of forced entry or wild animal intrusions. No signs of that.

There was a violent thunderstorm a couple nights before with 80 mph plus winds. Did this cause a pressure drop or vacuum in the attic through the vents? This attic hatch sits in a recessed cut-out in the ceiling. So it would have to lift this 2 pound hatch maybe 5 inches upward and cast it off to one side.

Is this likely what happened?
 
  #2  
Old 02-15-23, 01:27 PM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Posts: 27,256
Received 1,963 Upvotes on 1,760 Posts
Yes, high winds can cause negative air pressure in an attic.
 
  #3  
Old 02-15-23, 01:48 PM
B
Member
Thread Starter
Join Date: Jul 2007
Location: Arizona
Posts: 1,398
Upvotes: 0
Received 13 Upvotes on 13 Posts
When this originally happened many years ago, I sent a few inquiries over the Internet but never heard back.
I immediately suspected this was the cause.
 
  #4  
Old 02-15-23, 03:40 PM
P
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 28,173
Received 2,272 Upvotes on 2,024 Posts
My attic access is in the garage. On windy days if the garage door is open the wind will lift the cover and often slam it down quite loudly. One of these days I'll do latches or something to hold it down...
 
  #5  
Old 02-16-23, 11:48 AM
B
Member
Thread Starter
Join Date: Jul 2007
Location: Arizona
Posts: 1,398
Upvotes: 0
Received 13 Upvotes on 13 Posts
Wow. In my case, it's kind of hard to imagine the force of nature required to lift the cover upward and off to the side
in an enclosed structure.
 
  #6  
Old 02-16-23, 01:02 PM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Posts: 27,256
Received 1,963 Upvotes on 1,760 Posts
It's pretty much the same force that allows a jumbo airliner weighing 100 tons to defy gravity and fly. Just by the difference created between high pressure and low pressure. (Aerodynamic wing shape and flaps) So when you think about it, a light attic cover isn't much weight. It's sucking air out of the house, which lifts the cover. Doors with no latches (outswing with hydraulic closers) can get sucked open in a similar way.
 
  #7  
Old 02-16-23, 02:38 PM
B
Member
Thread Starter
Join Date: Jul 2007
Location: Arizona
Posts: 1,398
Upvotes: 0
Received 13 Upvotes on 13 Posts
Good example Sleeper.
 
 

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