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Ridge Vents below Valleys


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I am a homeowner in Houston, Texas.  I have a vaulted roof in my living room with no attic space above it.  The home is 20 years old, and the roof was replaced 2.5 years ago.  


In the last few months, we noticed mold forming on the cross beam that spans the length of the vaulted ceiling.  I called the roofer, who suggested water is getting in through the ridge vent as there is a valley two feet above the vent that empties onto the ridge vent.  The explanation makes sense as the mold inside the house corresponds to the impact side from the valley above the ridge vent. The roofer denies liability for the product or workmanship unless I can prove there was not a ridge vent there before.  I don’t know if there was or was not.  I know the roof didn’t leak.   

  • Are there Texas codes and installation standards that would prevent installing ridge vents below valleys.  
  • Why install ridge vents if there is no attic space?  
  • Are there professional services I should consult for damage and repairs?
  • Is the roofer responsible for repair and remediation?

The first picture shows the wet sheet rock and developing mold.  The second picture shows the valley above the ridge vent.  

JamesPW

IMG_3682[1].JPG

IMG_3683[1].JPG

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Unless there has been a storm recently that blew rainwater up into the ridge vent, I'd be suspicious of the moisture level in that room.

Humid air is lighter than dry air and will rise as high as it can get.  Add to that the fact that this is the peak of the summer season when the humidity load on the AC system is at it's highest.

I'm in Lafayette so I'm familiar with your climate.  A house built in 2000 is generally better sealed but an AC not functioning optimally in this hot/humid climate might cool the air just fine but may not remove as much humidity.  You'll feel cool and think it's fine but it isn't. Your AC guy might even miss it.

Get that mold out of your house with a bottle of Tilex, if you can reach it safely. In the meantime, invest in a handheld relative humidity meter and check the moisture level about a foot below the beam in the late afternoon on a hot day.  If it's over 65%, get your AC thoroughly examined by your AC guy.

You may need to do what I'm about to do: invest in dehumidification equipment to supplement the AC.  I've a similar problem in my house.

The ridge vent provides vital ventilation of the upper rafter bays. It isn't needed if the rafter bays are sprayed full with closed cell polyurethane foam. Since you do have a vent, it's likely insulated with fiber glass.

 

Edited by Marc
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JamesPW

google earth pro allows an aerial timeline back to 1995

if you don't have it send email thru the contact button at adairinspection.com with the confidential address i'll snag some before -after screen shots for you

Edited by BADAIR
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2 hours ago, Jim Katen said:

You don't have gutters in Texas? 

some do some don't

many ahj's consider R801.3 Roof Drainage In areas where expansive or collapsible soils are known to exist, all dwellings shall have a controlled method of water disposal from roofs that will collect and discharge roof drainage to the ground surface not less than 5 feet (1524 mm) from foundation walls or to an approved drainage system.

inapplicable for slab foundations

their argument is "foundation walls" slabs don't have walls

ahj around here have pretty much adopted the "good ol' boys play along to get along, keep the builders happy & turn land into tax revenue" attitude

Edited by BADAIR
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Thank you Marc,

Indoor humidity was my first concern.  We did install a new Train AC unit last year.  Perhaps it’s not as effective at removing humidity as my 20-year old Amana.  With an extension ladder I was able to get to the ceiling elevation and did notice a pocket of warm air.  One thought was to reverse the direction of the ceiling fan to get better mixing in the room.  I then started reading that mold from condensation was more likely to form on cold roof surfaces in Chicago than a warm room in Houston.  Thank you for your experience, I will get the humidity monitor today.

There is no attic space between the sheet rock ceiling and roof shingles other than a gap or AC ducting.  One contractor suggested removing 5 feet of ridge vent immediately below the upper roof valley to ensure rain does not get in the house.  Two other contractors said I needed the ridge vent and to add rain diverters or additional gutters to spread the water coming down the valley onto the lower roof.  Any thoughts on these two options?

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Posted (edited)

thank you BadAir,

I thought the same thing about Google Earth Pro and also found real estate listing pictures for the house.  In all cases, I did not have enough resolution to discern ridge vents or not.  

JamesPW

 

Edited by JamesPW
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2 hours ago, JamesPW said:

Thank you Marc,Indoor humidity was my first concern.  We did install a new Train AC unit last year.  Perhaps it’s not as effective at removing humidity as my 20-year old Amana. 

In that case, check the information on your thermostat and see if there's a mode of operation available on your Trane unit that re-directs more btu/hour capacity towards moisture removal.  It does this by slowing down the blower which causes the cooling coil to become colder.  I have that option on my system but when I tried it, it caused the coil to freeze up.

Quote

With an extension ladder I was able to get to the ceiling elevation and did notice a pocket of warm air.  One thought was to reverse the direction of the ceiling fan to get better mixing in the room.  I then started reading that mold from condensation was more likely to form on cold roof surfaces in Chicago than a warm room in Houston.  Thank you for your experience, I will get the humidity monitor today.

 

That's for folks up in northern frigid climates to worry about.  We live in a different climate here.

Hold off on that humidity instrument until until you remove the existing mold, and try leaving the ceiling fan on.  That might be all you need.

Quote

There is no attic space between the sheet rock ceiling and roof shingles other than a gap or AC ducting.  One contractor suggested removing 5 feet of ridge vent immediately below the upper roof valley to ensure rain does not get in the house.  Two other contractors said I needed the ridge vent and to add rain diverters or additional gutters to spread the water coming down the valley onto the lower roof.  Any thoughts on these two options?

Those two suggestions might have merit if the mold growth were isolated to that end of the cathedral ceiling that lies under the upper roof eaves.

A house like yours likely has insulation between the drywall ceiling and the roof deck.  Sometimes it's packed tight with insulation.  Other times it's only partially full, leaving room at the top for ventilation air to pass through to the ridge vent.  This ventilation plays an important role in keeping the rafter bays dry. Same for attic ventilation - it's first about keeping the attic dry. Only thereafter is it about cooling the attic.

Edited by Marc
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It could be a condensation problem or it could be related to the hundreds of gallons of water that are directed right onto that poor ridge vent during heavy rains. 

Install a freakin' gutter! There is no downside to this and it will help you to isolate the problem. 

Running the ceiling fan all the time will just hide the symptom. 

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On 8/18/2020 at 8:11 PM, Chad Fabry said:

But does it say, "You shall not install gutters." Because if the valley is the cause, a gutter will solve the issue.

Why on earth would someone install gutters to prevent rain water from falling onto a roof? Isn't a roof supposed to shed water?

If in fact it is leaking through the ridge vent, it likely has to do with contractor grade products (we had several house here that had snow drifts in the attics because of builder grade ridge vent) or vortex winds induced by stupid roof designs. Pull off the last section of ridge vent and reapply the caps. Far less expensive and more attractive than gutters and convectors. 

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Right, the roofer should be stepping up to fix it.  Every rafter cavity must have a vent, and that vent must keep water out. 

If the lower roof edges already have gutters, then gutters with downspouts on the upper roof sections are one good way to prevent splashing.

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Posted (edited)

Thank you everyone for your thoughtful comments and ideas,  I want to share the current working hypothesis. 

A Houston roofing and construction firm came out to inspect the house.  Not shown in the photograph is the continuation of the cathedral ceiling to an outdoor patio.  Twenty feet to cathedral ceiling is indoors and extends an additional 10 feet outdoors.  The entire length of the cathedral ceiling has soffit vents on both sides.  When the roofer replaced the roof 2.5 years ago, they did not reinstall the last 20 feet of ridge vent, over the outdoor patio and 10 feet into the living room.  As a result, trapped humid air migrates to the remaining 10 feet of ridge vent over the living room and contacts the cool ceiling and surfaces inside the house enabling mold to grow.

The appearance of inside mold seems to be consistent with the missing ridge vent on the roof.  Using Google earth, (thank you BadAir), we were able to confirm the existence of ridge vent on the original roof.  

This is still working hypothesis but it seems to make sense. 

Jim, I’m going to install the gutters for good measure. 

Marc, I mounted a temperature and humidity meter at the peak of the cathedral ceiling.  The air is 7 degrees warmer at ~45% humidity.  We are experiencing dryer than normal ambient conditions currently so I want to keep this test going.   Once  I have a baseline, I will reverse the ceiling fan direction for comparison. 

JamesPW

Edited by JamesPW
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James PW, don't take this wrong but it's clear that you're some kind of a geek specialist. Literally, 2 feet of gutter will fix the issue. You're overthinking it. The house is 20 years old with a recent issue. It's not a building science solution involving sling psychrometers, it's just a roofing issue. Spend  $10, install 2 feet of gutter  

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11 minutes ago, Chad Fabry said:

...it's just a roofing issue. Spend  $10, install 2 feet of gutter.  

I'd bet a nut that would fix it. 

Being at the peak of roofs, ridge vents are only intended to shed the rain drops that fall on it, not hundreds of gallons of run-off cascading from above.

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