Useless Ridge Vent?

the roofing god · 10-22-2007, 02:23 AM

NEVER question TRG,unless I`m wrong of course(perish the thought)

lol

tinner666 · 10-22-2007, 06:43 PM

Musta been 1/2 asleep. Missed the width post.

**Ed the Roofer** · 10-22-2007, 08:29 PM

Without knowing which brand of Ridge Vent is being discussed, I looked up the manufacturers specifications for the ridge vent slot opening, even when you come across a wide ridge board.

This method I previously suggested would certainly make more sense and be less costly than additionally having to remove or lift up the decking near the ridge and the shingles already attached to the decking, just to place shims under it.

TRG, you had me doubting myself for a little while, but I should have known better and stuck to my guns sooner.

By the way, how thich of a shim would you feel is necessary to elevate the decking enough to achieve the rated 18" NFVA per lineal foot?

My thoughts would seem to indicate shimming the deckin up by 3/4" per side to perform similarly to a total of 1 1/2" wide slot cut on truss construction.

Ed

Air Vent’s ridge vent installation instructions
require the following when cutting the
ridge slot.
Slot Width:

— If it’s ridge board or ridge pole
construction,

cut 3⁄4" on each side
of the pole or board
— If it’s truss construction, cut a

1
1⁄2" opening

Slot Length

— Cut the slot length along the ridgeline

6"

from the end wall or hip intersection
— Cut the slot 12" from a chimney or an
intersecting ridgeline

Cutting the Slot Wider

Here’s a common question we receive about
slot width:

Can I cut the slot wider to increase
the Net Free Area?

Cutting the slot wider
will not increase the
Net Free Area because
the NFA will be restricted
to the openings on the
ridge vent.
For example, ShingleVent II is specified at
18 square inches of NFA per linear foot.
If you cut the slot 2" wide (instead of the
required 1

1⁄2") it may seem logical that the
NFA would increase to 24 square inches
per linear foot. However, keep in mind that
the air that passes through the wider slot
must now pass through the openings in the
ridge vent itself. Although the slot is wider,
the ridge vent’s openings remain the same.
There’s no benefit to cutting a wider slot.

A word of caution:

There is the potential
for weather infiltration if the slot is cut

too wide. The vent needs to fully cover
the slot to protect the attic from weather
infiltration.
C A N Y O U
N A I L ¡ G U N
S H I N G L E V E N T

® I I ?

the Ridge Vent Slot

Cutting

W I D E R I S N O T B E T T E R

T I P :

The slot width is designed to match the amount of Net
Free Area provided by the ridge vent itself. For example,
ShingleVent II has openings that total 18 square inches
of NFA per linear foot. Over the span of 1 foot, a 11⁄2" slot
width equals 18 square inches.
Likewise, a 3⁄4" slot on both sides of the ridge board or pole

also equals 18 square inches over the span of 1 foot.

the roofing god · 10-22-2007, 10:33 PM

seems like you just bolstered my point,I would shim it up a 1/2",so the air would reach the normal cut out,I don`t see where it says to cut it past a 4 1/2"beam to 5 1/2-6",what I see is

A word of caution:

There is the potential
for weather infiltration if the slot is cut

too wide. The vent needs to fully cover
the slot to protect the attic from weather
infiltration. ( which is one point I made)
the Ridge Vent Slot
Cutting
W I D E R I S N O T B E T T E R
T I P :
The slot width is designed to match the amount of Net
Free Area provided by the ridge vent itself. For example,
ShingleVent II has openings that total 18 square inches
of NFA per linear foot. Over the span of 1 foot, a 11⁄2" slot
width equals 18 square inches.
Likewise, a 3⁄4" slot on both sides of the ridge board or pole

also equals 18 square inches over the span of 1 foot.(which was the other )

the roofing god · 10-22-2007, 10:35 PM

so anyway thanks for cutting +pasting to prove what I was saying

**Ed the Roofer** · 10-22-2007, 10:44 PM

There was more in the document, which stated that you would need to add a bead of tri-polymer sealant under the ridge vent.

It does not specify widths of ridge beams, just how far to cut past them when they are in place.

On the roof common sense should dictate if youy have to cut too far.

The width of the SV II is 14" across including the external baffle, yet they still specify the slot to be cut the same for the SV II-9 and SV II-7, don't they?

Whoops, I better go look that up, before I stick my foot in my mouth.

I sure hope that nobody heard that last comment. Shhhh!

Ed

the roofing god · 10-22-2007, 10:47 PM

remember the cap is only 12",I know about using the sealant

**Ed the Roofer** · 10-22-2007, 10:57 PM

I correct myself.

The width is only 13 3/4" wide including the external baffles.

Ed

10-22-2007, 02:23 AM	#16
the roofing god Member Join Date: Aug 2007 Location: Pomona,New York,10970 Posts: 876	Useless Ridge Vent? NEVER question TRG,unless I`m wrong of course(perish the thought)lol __________________ "If it`s worth doing,It`s worth doing right!!" To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts. *To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.*

10-22-2007, 06:43 PM	#17
tinner666 Pro Slate Roofer Join Date: Mar 2005 Location: Richmond, Va. Posts: 1,426	Useless Ridge Vent? Musta been 1/2 asleep. Missed the width post. __________________ Frank To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

10-22-2007, 08:29 PM	#18
Ed the Roofer Super Moderator Join Date: Jan 2007 Posts: 2,384	Useless Ridge Vent? Without knowing which brand of Ridge Vent is being discussed, I looked up the manufacturers specifications for the ridge vent slot opening, even when you come across a wide ridge board. This method I previously suggested would certainly make more sense and be less costly than additionally having to remove or lift up the decking near the ridge and the shingles already attached to the decking, just to place shims under it. TRG, you had me doubting myself for a little while, but I should have known better and stuck to my guns sooner. By the way, how thich of a shim would you feel is necessary to elevate the decking enough to achieve the rated 18" NFVA per lineal foot? My thoughts would seem to indicate shimming the deckin up by 3/4" per side to perform similarly to a total of 1 1/2" wide slot cut on truss construction. Ed Air Vent’s ridge vent installation instructions require the following when cutting the ridge slot. Slot Width: — If it’s ridge board or ridge pole construction, cut 3⁄4" on each side of the pole or board — If it’s truss construction, cut a 1 1⁄2" opening Slot Length — Cut the slot length along the ridgeline 6" from the end wall or hip intersection — Cut the slot 12" from a chimney or an intersecting ridgeline Cutting the Slot Wider Here’s a common question we receive about slot width: Can I cut the slot wider to increase the Net Free Area? Cutting the slot wider will not increase the Net Free Area because the NFA will be restricted to the openings on the ridge vent. For example, ShingleVent II is specified at 18 square inches of NFA per linear foot. If you cut the slot 2" wide (instead of the required 1 1⁄2") it may seem logical that the NFA would increase to 24 square inches per linear foot. However, keep in mind that the air that passes through the wider slot must now pass through the openings in the ridge vent itself. Although the slot is wider, the ridge vent’s openings remain the same. There’s no benefit to cutting a wider slot. *A word of caution:* There is the potential for weather infiltration if the slot is cut too wide. The vent needs to fully cover the slot to protect the attic from weather infiltration. C A N Y O U N A I L ¡ G U N S H I N G L E V E N T ® I I ? the Ridge Vent Slot Cutting W I D E R I S N O T B E T T E R *T I P :* The slot width is designed to match the amount of Net Free Area provided by the ridge vent itself. For example, ShingleVent II has openings that total 18 square inches of NFA per linear foot. Over the span of 1 foot, a 11⁄2" slot width equals 18 square inches. Likewise, a 3⁄4" slot on both sides of the ridge board or pole also equals 18 square inches over the span of 1 foot.

10-22-2007, 10:33 PM	#19
the roofing god Member Join Date: Aug 2007 Location: Pomona,New York,10970 Posts: 876	Useless Ridge Vent? seems like you just bolstered my point,I would shim it up a 1/2",so the air would reach the normal cut out,I don`t see where it says to cut it past a 4 1/2"beam to 5 1/2-6",what I see is *A word of caution:* There is the potential for weather infiltration if the slot is cut too wide. The vent needs to fully cover the slot to protect the attic from weather infiltration. ( which is one point I made) the Ridge Vent Slot Cutting W I D E R I S N O T B E T T E R *T I P :* The slot width is designed to match the amount of Net Free Area provided by the ridge vent itself. For example, ShingleVent II has openings that total 18 square inches of NFA per linear foot. Over the span of 1 foot, a 11⁄2" slot width equals 18 square inches. Likewise, a 3⁄4" slot on both sides of the ridge board or pole also equals 18 square inches over the span of 1 foot.(which was the other ) __________________ "If it`s worth doing,It`s worth doing right!!" To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts. *To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.*

10-22-2007, 10:35 PM	#20
the roofing god Member Join Date: Aug 2007 Location: Pomona,New York,10970 Posts: 876	Useless Ridge Vent? so anyway thanks for cutting +pasting to prove what I was saying __________________ "If it`s worth doing,It`s worth doing right!!" To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts. *To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.*

Useless Ridge Vent?