Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Roofing/Siding

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 03-04-2012, 06:27 PM   #1
Member
 
Join Date: Sep 2009
Location: BC, Canada
Posts: 249
Rewards Points: 150
Default

Attic mold/venting questions


This is our first house. We bought it about 2.5 years ago and I have a question on the attic section (left hand side). Note the ridge vent on the upper left roof.



Was in the attic today to install a light on the old attic fan line. While up there, noticed a section with a bit of what looks to be black mold. Located on the far left side, only really present where pictured and only on the road side of the roof.





Pictured below is my ridge vent (from inside) and 4" piping leading to the soffits, in every second joist bay.




So, wondering if my ventilation is good enough? Also, took a thermometer up there and it was about 19 deg C in the attic, 20 deg C in the house and about 13 deg C outside.

Thanks! I'd appreciate any comments

burnt03 is offline   Reply With Quote
Old 03-04-2012, 06:32 PM   #2
Member
 
Join Date: Nov 2011
Location: Hartfield VA
Posts: 27,115
Rewards Points: 3,348
Default

Attic mold/venting questions


The ridge vent is fine. I can not see the soffit vents.
Is the insulation laying over them. or is there any?
That's a funky way to frame a roof. Looks like there was metal roofing on that roof at one time.

joecaption is offline   Reply With Quote
Old 03-04-2012, 06:45 PM   #3
Member
 
Join Date: Sep 2009
Location: BC, Canada
Posts: 249
Rewards Points: 150
Default

Attic mold/venting questions


In the last picture, you can see black 4" PVC pipe laying on top of the insulation in every second bay. Those extend down to the soffits. I think the ones without pipe are probably plugged with insulation.

The house used to have cedar shakes, no metal as far as I know.
burnt03 is offline   Reply With Quote
Old 03-04-2012, 06:59 PM   #4
Member
 
Join Date: Nov 2011
Location: Hartfield VA
Posts: 27,115
Rewards Points: 3,348
Default

Attic mold/venting questions


Correct me if I'm wrong. It looks like those rafters are 24" apart. What thickness is that OSB?
I do not see any pipes, And there really is no need for them anyway.
Hot air rises, there needs to be soffit vents where the cooler air is sucked in and it rises and goes out the ridge vent sucking out the trapped moisture as it flows across the underside of the sheathing.
No soffit vents, no air flow, and mold will set in.
joecaption is offline   Reply With Quote
Old 03-04-2012, 07:45 PM   #5
Registered User
 
Join Date: Mar 2009
Posts: 9,968
Rewards Points: 2,000
Default

Attic mold/venting questions


Good news is the OSB is bearing on the 1x4 skip sheathing boards, your truss spacing is fine. Other news; OSB joint does not have a gap in the second pic, to allow for expansion, and it should be breaking on the skip sheathing. Just means you have a lot less shear resistance for the structure.
Mold; yes, I see it there on the road side. The wind is prevalent off the water? That would explain the soffit pipes pictured with darkened areas around them. The ridge is not cut enough on the road side as pictured. Follow the top chord joint up to the sheathing; it should have been cut back (down the roof) to the top edge of that sheathing 1x4 (actually cut 3/4" farther) as that is the center line. You have 1/2 of what you need. Intake is lacking by much.

The mold is moisture from below trying to escape out with the air movement, showing by concentration the escape path out/over the gable end truss is easier than out the partially blocked ridge vent, nd lack of air movement. Your OSB sheathing nails are rusting due to the lake proximity, (A lot of moisture entering your attic) AND from not air sealing the walls below.
Lack of ventilation leaves mold on the gable plywood vertical surface as the "first condensing surface" from warm, moist air rising from the room below: http://www.buildingscience.com/docum...bout-diffusion

Gary
__________________
If any ads are present in my answer above, I do not condone/support/use the product or services listed, they are there against my permission.
Gary in WA is offline   Reply With Quote
Old 03-04-2012, 07:49 PM   #6
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000
Default

Attic mold/venting questions


Five to 60 Air Changes per Hour are recommended for roofs, with 10 being average.

Using mensuration formulas you can figure the cubic foot volume of your space and then size some type of ventilation scheme as to CFM.
Yoyizit is offline   Reply With Quote
Old 03-04-2012, 08:25 PM   #7
Member
 
Join Date: Sep 2009
Location: BC, Canada
Posts: 249
Rewards Points: 150
Default

Attic mold/venting questions


Quote:
Originally Posted by GBR in WA View Post
Good news is the OSB is bearing on the 1x4 skip sheathing boards, your truss spacing is fine. Other news; OSB joint does not have a gap in the second pic, to allow for expansion, and it should be breaking on the skip sheathing. Just means you have a lot less shear resistance for the structure.
Mold; yes, I see it there on the road side. The wind is prevalent off the water? That would explain the soffit pipes pictured with darkened areas around them. The ridge is not cut enough on the road side as pictured. Follow the top chord joint up to the sheathing; it should have been cut back (down the roof) to the top edge of that sheathing 1x4 (actually cut 3/4" farther) as that is the center line. You have 1/2 of what you need. Intake is lacking by much.

The mold is moisture from below trying to escape out with the air movement, showing by concentration the escape path out/over the gable end truss is easier than out the partially blocked ridge vent, nd lack of air movement. Your OSB sheathing nails are rusting due to the lake proximity, (A lot of moisture entering your attic) AND from not air sealing the walls below.
Lack of ventilation leaves mold on the gable plywood vertical surface as the "first condensing surface" from warm, moist air rising from the room below: http://www.buildingscience.com/docum...bout-diffusion

Gary
Thanks for the info. Was hoping to go through and air seal the attic this year as well as install some sort of vapor barrier on the skylight shaft walls and the "half wall" between the attic space and the living space with the cathedral ceilings.

So best thing would be to clear those soffits, maybe install those poly rafter vents if I can get them in from outside and trim out the road side of the ridge vent. Any ideas what I might use to trim back the OSB on the road side?
burnt03 is offline   Reply With Quote
Old 03-04-2012, 08:26 PM   #8
Member
 
Join Date: Sep 2009
Location: BC, Canada
Posts: 249
Rewards Points: 150
Default

Attic mold/venting questions


Quote:
Originally Posted by Yoyizit View Post
Five to 60 Air Changes per Hour are recommended for roofs, with 10 being average.

Using mensuration formulas you can figure the cubic foot volume of your space and then size some type of ventilation scheme as to CFM.
Next time I'm up there I'll take some measurements and see what sort of attic volume I have.
burnt03 is offline   Reply With Quote
Old 03-04-2012, 09:34 PM   #9
Registered User
 
Join Date: Mar 2009
Posts: 9,968
Rewards Points: 2,000
Default

Attic mold/venting questions


They vary per manufacturer, for instance: http://www.ehow.com/how_4478641_inst...idge-vent.html

NFVA: http://www.airvent.com/homeowner/pro...it-specs.shtml

http://www.inspectapedia.com/interiors/atticcond10.htm

Gary
__________________
If any ads are present in my answer above, I do not condone/support/use the product or services listed, they are there against my permission.
Gary in WA is offline   Reply With Quote
Old 03-04-2012, 09:40 PM   #10
Member
 
Join Date: Nov 2011
Location: Hartfield VA
Posts: 27,115
Rewards Points: 3,348
Default

Attic mold/venting questions


Fastest way to cut out the OSB would be a ciruler saw.
Slow but safer way is with an Ossilating saw with a coarse blade.
joecaption is offline   Reply With Quote
Old 03-05-2012, 07:44 AM   #11
Exterior Construction
 
Windows on Wash's Avatar
 
Join Date: Aug 2011
Location: Washington DC Metro Area (VA, MD, DC)
Posts: 6,704
Rewards Points: 2,682
Default

Attic mold/venting questions


Quote:
Originally Posted by burnt03 View Post
Thanks for the info. Was hoping to go through and air seal the attic this year as well as install some sort of vapor barrier on the skylight shaft walls and the "half wall" between the attic space and the living space with the cathedral ceilings.

So best thing would be to clear those soffits, maybe install those poly rafter vents if I can get them in from outside and trim out the road side of the ridge vent. Any ideas what I might use to trim back the OSB on the road side?
Make sure any vapor barriers are on the warm side of the wall.

Also, I don't think it is necessary in this case. Just insulate them very well and seal the seams on the drywall/framing as well as seams in the insulation (rigid foam would be ideal in many of these cases).
Windows on Wash is offline   Reply With Quote
Old 03-05-2012, 01:26 PM   #12
Member
 
Join Date: Sep 2009
Location: BC, Canada
Posts: 249
Rewards Points: 150
Default

Attic mold/venting questions


Quote:
Originally Posted by Windows on Wash View Post
Make sure any vapor barriers are on the warm side of the wall.

Also, I don't think it is necessary in this case. Just insulate them very well and seal the seams on the drywall/framing as well as seams in the insulation (rigid foam would be ideal in many of these cases).
Rigid foam was sort of what I was thinking. They're 2x4 walls so I was thinking about 1.5" rigid foam with joints/edges spray foamed (great stuff). Then, 2x2's screwed on to put the batt insulation back on top of the rigid.
burnt03 is offline   Reply With Quote
Old 03-06-2012, 07:01 AM   #13
Exterior Construction
 
Windows on Wash's Avatar
 
Join Date: Aug 2011
Location: Washington DC Metro Area (VA, MD, DC)
Posts: 6,704
Rewards Points: 2,682
Default

Attic mold/venting questions


Quote:
Originally Posted by burnt03 View Post
Rigid foam was sort of what I was thinking. They're 2x4 walls so I was thinking about 1.5" rigid foam with joints/edges spray foamed (great stuff). Then, 2x2's screwed on to put the batt insulation back on top of the rigid.
That is great approach and well done complying with code.

Windows on Wash is offline   Reply With Quote
Old 03-06-2012, 10:32 PM   #14
Registered User
 
Join Date: Mar 2009
Posts: 9,968
Rewards Points: 2,000
Default

Attic mold/venting questions


"Rigid foam was sort of what I was thinking. They're 2x4 walls so I was thinking about 1.5" rigid foam with joints/edges spray foamed (great stuff). Then, 2x2's screwed on to put the batt insulation back on top of the rigid." -------

The batt insulation will be exposed to wind-washing (degrading the R-value extensively) from the ventilation and they do not meet your "thermal barrier" requirement- if needed, check with local AHJ. Much better to cover the batts with the foam on the outside of the studs to break the thermal bridging there. Then add thermal barrier as said.

Gary
__________________
If any ads are present in my answer above, I do not condone/support/use the product or services listed, they are there against my permission.
Gary in WA is offline   Reply With Quote
Old 03-07-2012, 06:38 AM   #15
Exterior Construction
 
Windows on Wash's Avatar
 
Join Date: Aug 2011
Location: Washington DC Metro Area (VA, MD, DC)
Posts: 6,704
Rewards Points: 2,682
Default

Attic mold/venting questions


Quote:
Originally Posted by GBR in WA View Post
"Rigid foam was sort of what I was thinking. They're 2x4 walls so I was thinking about 1.5" rigid foam with joints/edges spray foamed (great stuff). Then, 2x2's screwed on to put the batt insulation back on top of the rigid." -------

The batt insulation will be exposed to wind-washing (degrading the R-value extensively) from the ventilation and they do not meet your "thermal barrier" requirement- if needed, check with local AHJ. Much better to cover the batts with the foam on the outside of the studs to break the thermal bridging there. Then add thermal barrier as said.

Gary
I think the poster is planning on covering the 2x4 wall with rigid foam, sealing the assembly, and then covering it with the 2x2 battens/fiberglass combination to meet his ignition barrier requirements.

I do agree that a vapor permeable air barrier (i.e. Tyvek) over the fiberglass is advisable to prevent the wind wash issues.

Windows on Wash is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Plywood around attic access kicken Carpentry 3 08-29-2011 01:03 AM
Cellulose Insulation Questions... Master Brian Building & Construction 13 09-07-2010 08:09 PM
Attic Ventilation Question handy man88 Roofing/Siding 10 02-12-2010 10:50 PM
Attic insulation questions. SELLC HVAC 7 10-14-2009 05:29 AM
Attic Ventilation Questions AllGoNoShow Roofing/Siding 4 11-26-2006 12:02 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.