Repair of a Leaking Attic High Vent, Employing A Roof Penetration Adapter

This post of an action in 2016 is important in a Year-2025 campaign for broad employment of "roof penetration adapters" in residential roofing. Click the hyperlink to find a reverse chronology of all of my writing on this subject, in this blog.

Clarification is needed, whether penretration adapters are needed at attic high vent caps. They do have virtue. Please read on.

Here is a leaking condition that had recurred about once a year when high winds and driving wind would create a siphon under an attic high vent:

March 13, 2016

See that this attic vent was blindly cut in by roofers, without awareness of roof joist locations, as a new requirement on a home built in 1970. It would not have happened with a shingle tear-off.

A new problem was introduced in a re-roof, with cap misalignment from the shingle and sheathing cuts.

There are solutions against these misalignments. Immediately defy the siphon by stuffing a shingle bridge under the roof cap.

Better with a new venting opportunity on an already-shingled roof, let the vent locations be piloted from within the attic. Let all holes be circular, cut from the roof about the pilot hole. Insert a penetration adapter then to divert water flowing down-roof. Thereafter in a tear-off, center the adapter on the roof cut.

An imperative of easy and safe freedom in-attic to place high vent pilot holes would have been served by my self-funded campaign of Mandatory Attic Access Walkways. Know that vents clog over time from the inside. Circular high vents might have more promise of long unobstructed service, than roof-peak slots. A high vent cap should be easily removable for cleaning, from the roof,  without pulling any shingle nails.

Get the idea of the new-roof high vent installation process from rework of a found 4"  roof cap, now to serve a strong kitchen exhaust fan with 7" ducts. My roof adapter has bore 7 1/2" ID, 1 1/2" tall, formed of spun aluminum. The available roof cap is Famco 8". The 2x8 board has deck screws that when worked into composition shingles about the pilot screw will enable a well-defined sheathing cut by Sawzall. This is the same-size adapter plate that was tried by a very competent roofer under my instruction, to fix my leaking roof high vent.

Construction Metals RV38 Vent Cap Over Added 7.5” Roof Penetration Adapter

The penetration adapter is one shingle row deeper than the roof cap. A lower shingle bridge stops possibility of siphon action, even without the penetration adapter. The penetration adapter is redundant except as a can’t fail locator of the sheathing and shingle cuts. The adapter is locked in posution where it is attached to a duct. For a non-ducted roof cap, set it permanently upon the sheathing cut using upper-edge screws or nails. With a firm-set adapter rim, cut replacement composition shingles by stabbing-around with an awl; then breaking away the divots.

A further virtue of the adapter is in allowing a powered fan to be set in place of a static vent, without disturbing roof shingles, tiles or metal sheeting. Want all powered fans to be freely removable for service or replacement, without disturbing roofing.

The leaking vent was repaired including employment of a 7 1/2” spun-aluminum duct penetration adapter. Opportunity of better alignment with the roof cut was missed, and the use of shingle bridges is unknown. There has been no return of leaking. If respected, this will be an example to a roofer someday of ensuring alignment with the sheathing cut. Wish that better alignment of the adapter will be chosen. Wish the cut of plywood ang skip sheathing had not been excessive. Sharp corners are stress risers for lumber splitting.

We find that very many bath fans and kitchen exhaust fans are badly, even dangerously ducted. In any existing home the rather frequent retrofit of a new fan is not subject to building codes/ permitting review. Awful access to the attic contributes to the problem. I see this as a unique engineer/ inventor/ contractor/ technical writer. From age 60 twenty years ago, I have been a general contractor focused mainly on attics and crawl spaces. I know that dirty, awful work, delegated, is without learning and practice with ever-better materials, methods and procedures. I demand that practice of myself and am unaware of another like-minded attics person anywhere.

A roof penetration adapter is very useful when a roof cap is served by a through-roof duct. We shall want that all roof caps and roof-top powered fans are removable for service or replacement, without need af attic entry.

A ducted roof cap with a stem invites others to bond the duct to the cap; then removable only with attic entry. My preference is that ducts shall be galvanized steel "warm air" pipes. The crimped end is upward toward the roof, engaging often as an elbow, to full, tight penetration of the adapter plafe throat. Slight maneuvering of the adapter in a reroof shall not decouple the duct somehow strapped-up.

There shall not be compromise aiming of a duct pipe or flimsy plastic thing toward an existing attic high vent cap. There shall be no capping over framing or roof sheathing at a static vent cap, with a common "duct starter" plate, the usual practice wrongly taught to weatherization contractors.

 At 2025 there is a wrongful trend to offer duct-served roof caps only with long stems that reach into the attic. There is at least one cap manufacturer with thinking somewhat like mine.

 InOvate/ BetterVenting 

Product RoofNeck

Employed with 4" stemless caps for clothes dryer ducting. This is a rolled-in plate with a pipe length necessarily reaching both directions from the plate. I do not want a rolled-in pipe engagement.

Where the adapter has a stem penetrating roof sheathing, it is securely indexed to the roof cut, but there is likelihood the pipe below will be locked to the stem by screws and tape. The RoofNeck is likely to be a nuisance in a re-roof, requiring roofer access to the attic. Roofers do not want this.

For an adapter without sheathing penetration, as I  offer of spun aluminum, some other means must index the plate to the duct. A crimped pipe end protruding through sheathing, works. I do not prefer an adapter with a long stem. It is so very much harder to interleave with shingles, requiring more nail pulling in an insertion through already-placed shingles.

Want one-piece adapter plates with a simple neck at least 1 1/4" tall, as formable in stamping of aluminum. If a short neck protruding downward is needed as a location index, let it be a separate galvanized steel pipe length, crimped end, inserted from the attic. The stamped upper protrusion has needs of leak-free permanence. The downward-extending 

Who do you call, for through-roof ventilation exhaust ducting?

Who do you call, for through-roof ventilation exhaust ducting ?

A Google AI Overview answer is:

For through-roof ventilation exhaust ducting, you should call a licensed roofing contractor. They have the expertise and experience to properly install ventilation systems on your roof, including assessing your needs, choosing the right type of vent, and ensuring it's installed correctly to prevent leaks.

If that were true, roofers would be constantly willing to work in attics to create the majority of that ducting and the installation of the fan appliances served. Roofers do not have this interest or capability.

Consider my need of a kitchen exhaust fan in the major remodel of the kitchen of the home I own.

I chose a Panasonic in-line fan, pivoting from flooring over thorough R49 insulation with only a small-bend 6" warm air elbow to complete the path through-roof. Here I drilled a pilot hole through-roof at the center of a tracing of the placed elbow. Duct completion is in several traverses between roof and attic, enabled by a strong attic ladder, and by good lighting and flooring in the attic

Cut through shingles with a wood block propelling sharp deck screws, preserving a hole saw. Drill a hole starter and complete the cut with a sawzall. Pry shingles and pull nails as needed. Collect wood debris in the attic upon a sheet.

12/5/2018

Here is the fan, ready-to-use.

My vast attic flooring is useful. It adds to insulation value and serves as the top element of extremely strong box beams of the 12" thickness floor over the remodeled kitchen.

The insulation is protected forever.

I had to anticipate all of this in placing the register and duct from the kitchen ceiling over the electric (not gas!) stove.

At much of a four-foot periphery the insulation is protected just by being off-path. See top-layer R30 Rockwool insulation except R30 fiberglass at the extreme periphery, accommodating plywood attic ventilation inlet baffles.

9/27/2018

See the kitchen fan register in-line with an operable window, over the kitchen stove. Upon a steamy or stinky cooking adventure, lift the window a bit or a lot, and turn on the fan. The view is from the archway entering the kitchen from the living room. The fan switch is the right-most of a 4-gang switch group. The lighting constellation chosen here is Passing Through,  4-Way switched at each of the three entries.

In this, my now-modern and clever 1955 home, I could not imagine calling a Licensed Roofer, for greater competence at the through-roof ducting of the kitchen fan. Roofers by my experience see an attic as merely a trash heap. They will not go there. Roofers will benefit in a new regime where other Trades, or a general contractor, will just stay out of their way. And, that is what I have practiced here.

This illustrates a customer installation of kitchen exhaust ducting similar to my own. See that the ideal location of the penetration adapter is in hinging at the high end upon the roofing membrane. That is one shingle-layer deeper than a common roof cap. The better roof cap is minimally tucked under shingles. The screwed-down roof cap safely anchors disturbed surrounding shingles against driving wind and rain.

As a inventive Weatherization Contractor and General Contractor, I almost always confront really-awful ducting of bath and kitchen exhaust fans surely not the work of roofers. I am not taught to call a roofer, but to do what I can, myself. With bath fan ducts, the best and awful practice of weatherization contractors is to just plug the plastic or flexible-aluminum found duct, to a 4" take-off stabbed into a plate that covers a found roof high vent. I know better. That installation then lacks a backflow check and diminishes the needed attic ventilation. The duct probably obstructive of discharge from a crummy fan that is only a noise-maker, continues to do harm.

Here is a photo album sampling my jobs employing penetration adapters, in chronological order, showing evolution of methods.

Search  Label: Roof Penetration Adapter , at this blog, and find posts including these:

Roof Caps For Bath and Kitchen Exhaust Ducts  (January 15, 2017)

Note then this post describing the shingle-over of my roof in Spring 2023, being the roofer confronting this roof cap. I could venture into the attic, but there is no need:

 Roof Penetration Adapters and a Composition Shingle Overlay  (April  3, 2024)

Turn out four gasketed deck screws to reveal the roof closure with a 6" penetration adapter and its' transferred flapper, riveted to the adapter rim.

With little nibbling of new shingles, the rain barrier  hinges down, perfectly aligned with and coupled to the duct and fan below.

There was the same accurate simplicity at three 4" plastic Air Vent caps without stems.

Learn an important lesson. Lay down all covering shingle rows before screwing down the roof cap. The shingles will be more-strongly retained including fullest engagement of tar strips. Let the cap not be tucked under shingles anywhere if that is how it works out. Remember, the cap is only a rain cover. There is never a need to cut shingles as more than the circular hole. Shingle material lapping over the top of the roof cap has no purpose. It is not more pretty.

What, really, is needed in a roof cap?

code requirements for ducting a bath fan through a roof

Google AI Overview: 

when ducting a bathroom fan through a roof, the primary requirement is to exhaust the air directly outdoors, not into the attic or any other interior space, meaning the duct must be routed to the exterior of the building and terminate on the roof.

There is reference to International Residential Code (IRC) Chapter 15, Exhaust Systems.

code requirements for ducting a kitchen fan through a roof

Google AI Overview:

According to most building codes, when ducting a kitchen fan through a roof, the exhaust duct must terminate at least 12 inches above the roof surface, with some regions requiring even greater heights to prevent snow buildup, and the ductwork should be positioned at least 18 inches away from the roof surface where it attaches to the fan; the fan discharge itself should be at least 40 inches away from the roof surface.

This is surprising in the matter of elevation at discharge!   And, never met in my discoveries. Who offers such a discharge path above the roof? It seems to be concerned about flame in a grease fire, or discharge burial under snow.

I find nothing offered, in this Google search: image: 12" tall kitchen exhaust roof cap

Smarter now, I could replace the squat Famco cap with this: 

Goose Neck Exhaust Roof Vent – Painted Famco, $99.95. 

The lesser flow resistance makes sense. Nibble out the stem and flapper, or convince Famco to offer separate cap without stem, and flappered penetration adapter.

Want the elevated discharge for a bath fan too, to tolerate snow.

Let even a not-ducted attic ventilation high vent be only a rain cover. Where placement is set with a penetration adapter, avoid misalignment of the sheathing cut and the cap.

Now move on to report an incident that inspires this post:

Violence against bath fan ducts in my row home residence, July 17, 2024!

In this job photo album, I share the awful and typical conditions of fans and ducting that I found and fixed in a now-pretty and useful attic.

On July 17, 2024, the two bath fan roof caps were ripped off, leaving broken ducts to dump moist air into the attic, blackening the roof sheathing.

We were not consulted We were not informed.

New steel caps with manually-crimped stems were left to again defy roofers, at the next roofing replacement, if we were smart enough to reattach the ducts..

10/30/2024

The steel ducts with new elbows are now screwed and taped to the foolish roof cap stems. At next reroof, workers might curse the now-captured roof caps, again breaking the ducts in refusal to enter the attic.

See that this space directly off the  wonderful attic ladder is the convenient repository of long ducts and other sheet metal I keep in reserve for my unique A-rated business of Attic Access.

With this post and that album, please understand that a roofing company is not the superior owner of well-performing bath fan ducts, entitled to demolish them for no apparent reason and without notice. The roofing repair company of this incident is identified as  NW Roofing. We must learn whether NW Roofing routinely breaks ducts bonded to roof caps, without thought of repair. In most cases, attics are hostile of access, and in many there are no safe walkways to points where it is known that service will be needed at intervals not longer than 25 years. See my proposal that attic access walkways shall be mandatory to expected service points.

This blog, Sunday, October 30, 2016

Mandatory Attic Access Walkways

At my own expense I defended ten thoughtful proposed revisions to 2016 International Energy Conservation Code. All ten were unanimously disapproved in a codes process rigged by National Association of Home Builders. In a bad regime of service access, it is very important that roofers shall not be required to enter attics. Roofers must come to understand the impossibility of their responsibility for and superiority over ducts. With roof penetration adapters and their permanent attachment to ducts, roofers may do only what they do best.

As a unique and valuable weatherization contractor/ engineer/ inventor, age 80, I have given much exemplary service to existing homes for twenty years, in metro Portland, Oregon. Here is the job album of one good example in SW Portland, with mending of awful bath fans and a kitchen microwave exhaust without ducting even to the attic. Safe, lighted access and removal of interfering and not-needed beams were  imperative. Awful, dangerous conditions in a home often need considerable investment to do right.

Job Album C-L Attic Access, November-December 2016.

 

I know of no one else on Earth doing the important work I inspire. I need allies including most-competent roofing companies. Specifically at January 2025, I need the support of Pacific West Roofing, the installer of the current roofing of the townhouse complex where I live, and where my penetration adapters known to them, were misunderstood and violently discarded. I ask that Pacific West Roofing shall support my timely product improvement requests to roof cap manufacturers Famco and BetterVenting. Where BetterVenting begins with a focus on the small market of through-attic clothes dryer ducts, they shall know that dryer caps must be cleaned often, off-roof. BetterVenting (Inovate) offers an adapter similar to mine, called RoofNeck. They don't seem to value the device as a water barrier or as an asset to cap cleaning. Dryer ducts must be thoroughly cleaned very often, more easily in soaking, off-roof.

BetterVenting RoofNeck with smallest-possible sheathing cut:

Install above or below the roof deck. 

The plate is too small to mend sheathing hacks or misalignment with shingle patterns. The neck at 4 1/8" ID does not securely engage with warm-air steel ducting 4" OD.

The downward neck invites capture in the attic, which is OK only if  this is a permanent part of the roof. Atttachment holes should then be only at the top edge, allowing hinging tuck of membrane and shingles in a reroof..

BetterVenting imagines a dryer cap thoroughly bound by surrounding shingles. If there is a RoofNeck here, it is not being employed to best advantage.

I have learned that the best use of a cap primarily a rain cover, is to anchor the surrounding shingles, with just four gasketed deck screws. Don't be breaking tar strips and pulling nails to clean a cap/.screen/ backflow flapper.

At 2/12/2025, Google this:

penetration adapter for ducted vents of a house roof   

Find some foolishness in caps with stem jabbing through-roof, and this:

Roof Cap Vent Adapter · Metal Ducting · Galvanized · 6" (RVA6) 

By PrimeSource Building Products

Dunn Lumber Store SKU

559176

Price at 8/22/2025: $16.40 plus shipping.

(Not an economical availability.)

Any local good sheetmetal shop can improve upon the Dunn cost and availability. Specify  stem ID that of standard HVAC round pipe. Custom-form the stem as a  weldment of strip 3" wide. Roll-form the stem centered in the hole-cut plate. Let the plate be round or square at say 3x stem diameter, or maybe stem diameter plus 8". Any economical producer would set a plate shape standard. A plate-centered 3" stem would pilot both the round minimum sheathing cut, and divert water flow under the roof cap.

Better but without the piloting in roof sheathing, form penetration adapters by stamping aluminum plate to form a 1 1/2" upward stem. Let there be competition for least-cost distribution of a penetration adapter for every roof cap. Let the penetration adapter have a hinged flapper for backflow prevention even at high statc vents, to combat embers in wildfires. Just get on with smartness and an uncoupling of roofers from needs of attic entry.

A Drop-Down Attic Access Hatch

Crawling eight feet into this small attic space to connect bath fan ducts will be a challenge. There was no access and I must invent and build my own hatch cover. Employ this opportunity, to invent a well-insulated airtight hatch cover that drops out of the ceiling. With ducting and tools pushed ahead, I must not share space with and perhaps break the cover.

At 3/11/2025, at last edit that claim about safety with 7:12 roof pitch.

This is the Search Labs  AI result of Google search: 

What range of roof pitch is safely walkable?

Generally, roofs with a pitch of 6/12 or lower are considered relatively walkable, while anything steeper, like 7/12 or higher, requires caution and potentially specialized equipment or professionals. 

At 7:12 pitch I was roped and harnessed whenever without  secure piping-above or roof-above constant  hand holds. The danger with a shift of balance not restrained,  is evident. It is good to know pitch reliably measured with pitch gage overlay on a photo. I do the overlay in Adobe FrameMaker. I hope you can do likewise somehow.

Finding the best ceiling cut is error-prone. Excess demolition is resolved with an easy plaster patch. Easy if you have learned to employ Scructolite plaster, and other patching techniques. A fifty pound bag is perishable and a burdensome investment for occasional patching. I apportion a bag to a couple-dozen airtight plastic jars, then lasting indefinitely.

Here is the prepared opening for the invented hatch cover, with neat plaster applied up to steel-angle edges. The outer frame is a tight-fitting part of the hatch assembly and is pinned in place at best centering in the edged rough opening, by wood shims.

Here is plaster smoothed with my tough flexible grout, and the inserted hatch cover. The cover is securely held by two pull-push latches of European origin, purchased from Fakro USA. I have trimmed excess dimensions of the cover face, GP Densarmor drywall, to overall clearances of 3/8".The cover is not heavy, but be under it upon a ladder while attaching or detaching.

Here is the rough frame, a maximum of found space between ceiling joists and 1x3 that cross the joists and support the plaster lath.

And here is the assembled cross section with latching.

The latch pair was purchased from Fakro USA, where it is employed in several families of Fakro attic ladders. The eye bolt is found to be unsuited to its job, where movement at the nutted end is not linear and the latch slot it engages is too small to accommodate its movement arc with the bolt near-vertical. I conclude that the pull is intended to be small-diameter wire rope. There is no need for the pull to be rigid, of beefy 3/16" OD. By measurements and trial & error, know that the pull center must be 2.5" from the latch edge. Enlarging the slot for the bolt is a workable but poor solution.

At 6/9/2024, I have ordered this wire cable set that should serve better with the Fakro latch if employed in a current attic ladder project.

In fact for the attic ladder project, I think there will be a better latch,

Let every project be a shared learning experience, and a ready resource for recall of my own learning. 

My attic access job continues with achievement of the customer motives of fixing dysfunctional bath fans.

The bath fan with bad ducting must be replaced, to achieve proper ducting. Choose Panasonic FV11-VQ1, 

The found fan discharged through this:

Except that flow is entirely stalled in a squirrel-cage fan with an immediate 90° bend, flow resistance is not much different from the new installation, just losing all velocity head of developed flow in a 4" pipe, K = 1, resistance beyond a bend.

If K = 0.5 for a 90° entry bend and K = 0.15 for a 30° entry bend, then add K = 1 in either case, the flow resistance comparison is not telling.

8" aluminum flex ducting was bonded not-at-all airtight, into an existing Norwesco NWE RCV-4 static vent, 50 sq in net free area. There was no backdraft damper! The untrained fan installer thought it would be a good idea to cut out the screen. The fan backdraft damper remained functional stopping cold air and warmth-seeking bugs, but too many "American" fans have failed backdraft dampers.

Here is the completed new duct installation, an elbow set to 30°, a two-foot length of smooth pipe, and an elbow mating with a roof cap through an about-60° bend. Not much resistance, and no flow stall.

I always employ a Roof Penetration Adapter for a through-roof duct. I accomplished this tuck with removal of only two roofing nails.

On occasion, as here, the roof cap can't be tucked under a shingle row for appearances-sake. No matter. The cap is only a rain cover.

Know that discharge through proper new ducting with 30° bend, is strong. There was no noticeable flow from the now-scrapped Broan fan. Blame the foolish elbow placement, and foolishness of  all bath fans vs. thoughtful always-learning design of Panasonic fans. I can readily call a Panasonic technician in New Jersey, at 866-292-7292. I have done that here, reporting (again), that fan installation should always be as retrofit. No serviceable appliance may be captured, demanding demolition for replacement. Well, that is what I believe, but I don't find confirming building code. Still, to trap a bath fan above drywall is really mean and stupid. Panasonic should presume installers will insert the fan body though a drywall cut prescribed by a template in the fan packaging, body flange then below drywall. The Panasonic instructions badly mislead all who will suffer consequences at a future replacement. See that graphics are those of a compact ceiling, not attic, fan, for all fan models. The compact fan is less efficient and should be avoided.

One compact fan Panasonic FV11-VF1 was installed in a basement, in this job. A basement overhead will usually allow a full-height fan, but some non-structural 2x4s reduced the headroom. Builders should want Panasonic fans and they should not be constrained by allowed obstructions.

View the flappered outlet of the fan adapter assembly, before insertion of the fan body

Being a Diligence Reporter

This post is a further service to my customer, giving a succinct, durable record of interesting query and innovation in his service.  Please read more upon the subject of Diligence Reporting , collecting writing by Label. A blog post is not always part of the diligence. A blog post is inspired by seeing something new, discovered in the job.