Ridge Vent . . . and Nothing But the Ridge

Can anyone convince me that this picture shows anything other than the fact that the ventilation provided here is effective only in the first five inches down from the ridge? And yes, there is continuous soffit venting that is baffled and open to the outside.

Views: 7894

Comment

You need to be a member of Home Energy Pros to add comments!

Join Home Energy Pros

Comment by Bob Mariani on December 29, 2011 at 3:30pm

Still more natural air flow should persist.  I believe the soffit venting is insufficient.  The air movement should be equal between the ridge and the soffit vents.

Comment by Ed Voytovich on December 29, 2011 at 2:55pm

Bob . . . I'll refer to the black snot as "mildew" in hopes of assuaging to the extent possible the anxiety of the homeowners and the desire of their lawyers for a new Mercedes.   

Thanks for pointing out the fact that the cut-out is somewhere around an inch or less on each side instead of the manufacturers' recommended inch and a half.  Still, could another 3/4" on each side make that great a difference?

There are no gable end vents, and the same pattern of mildew extends the entire length of the ridge.

I suspect that this condition is more typical than not of ridge vents.  When the wind blows across the roof  and the ever-popular Bernoulli's Law (http://scienceworld.wolfram.com/physics/BernoulliEffect.html) comes into play, the downwind side of the vent sucks air out of the attic.  I suspect that it is most likely to take the makeup air from the nearest source (which is the other side of the ridge) than from either gable vents or vents in the soffit.  My thinking is that the high-moisture conditions in this particular house created an interesting experiment, but I am grateful for other thoughts and possibilities.

Comment by Bob Mariani on December 29, 2011 at 1:52pm

Ed, is that mold on the discolored section of the sheathing?  The vent opening should have been larger.  Only a small air flow is occurring.  Also be sure no gable vents are still opened that will short circuit the soffit to ridge vent airflow.

Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy,) and brought to you in partnership with Home Energy magazine.  Home Energy Pros is sponsored by the Better Buildings Residential Network.

Latest Activity

Lars olsen posted a blog post
36 minutes ago
Eric Kjelshus replied to Rod Fox's discussion Does altitude affect AFUE? or just the input/output BTUs?
"The heat exchanger gets burnt out, if presser is to high or if mix is to rich, then I see holes in…"
11 hours ago
Hans Joachim Preiss replied to Rod Fox's discussion Does altitude affect AFUE? or just the input/output BTUs?
"Good discussion. I came across this comprehensive presentation by Gas Consultants on the effects at…"
12 hours ago
Dale Pickard replied to Rod Fox's discussion Does altitude affect AFUE? or just the input/output BTUs?
"Excellent reply Hans. I think that there isnt' a good general answer to this question but that…"
15 hours ago
Mary Desilva posted blog posts
16 hours ago
David Heslam joined David Eggleton's group
Thumbnail

1000 Home Challenge

Linda Wigington distinguished between deep retrofits & deep energy reductions, thus expanding…See More
17 hours ago
Jose Macho commented on Charlie Hewitt's blog post Revisiting Heat Pump Water Heaters
"I am aware of homeowner dissatisfaction of hybrid units not performing due to location,…"
18 hours ago
KC Brown added a discussion to the group Job Board
Thumbnail

Job Opening: SR. ENERGY ENGINEER - CLEAResult, Energy Efficiency Leader (Pennsylvania)

POSITION:  Sr. Energy EngineerREFERNCE CODE:  2015-2197 JOB DESCRIPTION:CLEAResult is a leading…See More
20 hours ago

© 2015   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service