Bathroom fan venting

[Brian A. MacNeish]

Originally Posted by bdoles2

Ditto that..

That may work in warm Atlanta but in cold areas, this is a recipe for part of the condensation that may be found in an attic and can lead to mould growth/sheathing rot.

[David P. Valley]

Originally Posted by Brian A. MacNeish

That may work in warm Atlanta but in cold areas, this is a recipe for part of the condensation that may be found in an attic and can lead to mould growth/sheathing rot.

I've seen hundreds of these bathroom soffit vents and never once found condensation issues on the sheathing above relating to the bathroom vent below.

They are fine.

[Brian A. MacNeish]

Originally Posted by dvalley

There's nothing wrong with venting your bathroom fans into the soffit area.

A roof penetration would be susceptible to leaks.

David:
Went back to the beginning of the thread and saw that I was talking about a different situation. When your post said "into", I assumed it was not vented down through the soffit material to the outdoors but up above the soffit into the triangular cavity formed by the eave extension. I have seen problems with this, even with venting soffit materials

I have only seen minor condensation problems or mould twice with the air vented down through the soffit to outdoors.

[David P. Valley]

Originally Posted by Brian A. MacNeish

David:
Went back to the beginning of the thread and saw that I was talking about a different situation. When your post said "into", I assumed it was not vented down through the soffit material to the outdoors but up above the soffit into the triangular cavity formed by the eave extension. I have seen problems with this, even with venting soffit materials

I have only seen minor condensation problems or mould twice with the air vented down rough the soffit to outdoors.

No, I did not intend make it sound like it is OK for an installation in the soffit interior. I should have stated "into and out of". That just doesn't make sense. An interior type of vent installation is definitely conducive to MOLD build-up.

All vents must extend to the exterior, no matter where it is.

[Ed Fako]

I disagree with the venting of the moist humid air to the soffits, which have fresh air intake vents installed in them. It would depend on how close the next intake vent inlet were to be placed, but all in all, I think it is bad practice and asking for trouble.

I copy/pasted a recent response I made in the JLC Forums regarding the same topic.

Please check out the link for "Scary Stories From The Attic, Part 1".

Ed



The Soffit Intake Vents, by their very design and nature is intended to promote the flowage of exterior air back into the attic cavity.

By expelling the moist humid air content from the bathroom exhaust directly to where the adjoining intake opening are located suggests that moisure and mold problems will occur.

I will find a link to and article by Ron Hungartner, and he completely captures this scenarion in several well written articles with illustrative photos included.

http://www.ronhungarter.com/articles.html

Read the article, "Scary Stories" and "Attic Heat" first, if I recollect correctly.

Ed

[bdoles2]

Originally Posted by dvalley

All vents must extend to the exterior, no matter where it is.

Ditto that!

That is my recommendation in each and every report that I complete.

[Brian A. MacNeish]

Originally Posted by Ed Fako

I disagree with the venting of the moist humid air to the soffits, which have fresh air intake vents installed in them. It would depend on how close the next intake vent inlet were to be placed, but all in all, I think it is bad practice and asking for trouble.

I copy/pasted a recent response I made in the JLC Forums regarding the same topic.

Please check out the link for "Scary Stories From The Attic, Part 1".

Ed



The Soffit Intake Vents, by their very design and nature is intended to promote the flowage of exterior air back into the attic cavity.

By expelling the moist humid air content from the bathroom exhaust directly to where the adjoining intake opening are located suggests that moisure and mold problems will occur.

I will find a link to and article by Ron Hungartner, and he completely captures this scenarion in several well written articles with illustrative photos included.

http://www.ronhungarter.com/articles.html

Read the article, "Scary Stories" and "Attic Heat" first, if I recollect correctly.

Ed

Hi Ed:

So we're at again!!!

To quote Ron:

"Energy costs and conservation have us building tighter and tighter homes, but unfortunately, a tight home is not necessarily a healthy home."

This statement scares people away from seeking out a truly well built energy efficient home and a contractor that can do it without problems. It's the street talking!!!! Here's the line on airtightness from the "Health House" guidelines from the American Lung Association......those very healthy people with no lung afflictions:
"Blower door testing on the final product must meet airtightness standard of
1.25 square inches ELA (Equivalent Leakage Area) per 100 square feet conditioned aera space or 0.25 cfm per square foot conditioned area"
(note: Joe Lstiburek was the co-chair of the original Technical Committee that wrote the first guidelines........no slouch ......this guy!!)

This is a very tight house and it's being recommended by the Lung Association. Are they nuts or what??? ...........Or do they know something that most others don't? I choose the second answer!!!!!!! See

http://www.healthhouse.org/build/200...guidelines.pdf

From another of his articles:Now you know things not to do, so let's discuss things to do about excessive heat. First, confirmed that every roof has continuous soffit inlet vents that are fully open and functioning. If your home was designed and built in the 1950's, without any soffit overhangs, making the installation of conventional soffit inlet vents impossible, there is new hope. New products now provide inlet air at eaves without overhangs, by bringing the air in from behind the gutters, and under the shingles and sheathing.
Second, confirm that every roof has functional outlet vents, (9" roof vents, or gable end vents, or ridge vents). Since excessive heat rises to the peak of the roof, the best outlet vent is a ridge vent. Third, you must eliminate excessive heat sources from entering your attic, as discussed above.

Really, firstly you should eliminate heat and moisture from getting to the attics by good design/ execution of energy efficient features including comprehensive airsealing. Then the need for large amounts of ventilation is significantly reduced. I feel that many are trying to lead the horse by its ***.

His "
"Scary Stories From The Attic, Part II
Is your home dying?" is almost laughable......ventilate the attic to get rid of most of the moisture problems in the home. Don't believe me........send this to Building Science Corp. or Advanced Energy Corp. to critique......he'll have to crawl under a stone!!!

My comments may seem harsh but I will quote Gus Handegord- an Old Guard at Canada's NRC Division Of Building Research, a passionate building science researcher and mentor to Joe Lstiburek- speaking to the Alberta Building Envelope Council a few years ago "It was once suggested that one problem in transferring technology in the building industry is that nobody reads anything. It may be equally valid today since practitioners, as well as many researchers in building and construction seem to have neglected to read or re-read the Canadian Building Digests, even those that fall into their respective areas of interest."

IMHO, that statement still stands!!!

[Ed Fako]

Brian,

I call them as I see them. I moderate a DIY site and a recent poster submitted photos of his soffit vents actualy having icicles forming from within just one of them.

It came out to be that a bathroom exhaust fan was ducted to the soffit intake vent.

Now, in that scenario, the home owner did not show me any photos of the interior, nor was I able to automaticaly assume that wet insulation or decking was occurring, but from the icicles which were up to 12" long extending out of the one soffit vent, I would be reasonably confident that my assumption would be correct.

My reasoning for providing the link to Ron Hungartners article, was primarily due to his extensive photos of interior damage due to attic moisture that was not properly vented out.

I have not yet personally seen a house built to the air tight details that is espoused by your learned colleagues. There is good theory and there is real world actual circumstances. The real world takes priority in my book. Maybe where you live, they build to a higher degree of specifictions, but not in the Chicago region that I service.

Ed

[Brian A. MacNeish]

Originally Posted by Ed Fako

Brian,

I call them as I see them. I moderate a DIY site and a recent poster submitted photos of his soffit vents actualy having icicles forming from within just one of them.

It came out to be that a bathroom exhaust fan was ducted to the soffit intake vent.

Now, in that scenario, the home owner did not show me any photos of the interior, nor was I able to automaticaly assume that wet insulation or decking was occurring, but from the icicles which were up to 12" long extending out of the one soffit vent, I would be reasonably confident that my assumption would be correct.

My reasoning for providing the link to Ron Hungartners article, was primarily due to his extensive photos of interior damage due to attic moisture that was not properly vented out.

I have not yet personally seen a house built to the air tight details that is espoused by your learned colleagues. There is good theory and there is real world actual circumstances. The real world takes priority in my book. Maybe where you live, they build to a higher degree of specifictions, but not in the Chicago region that I service.

Ed

For the past 15 years here, houses have been, by code, required to be airsealed, although not to the R2000 tested levels. For the past 10 years, they have been required to have general ducted ventilation to all major rooms.......this is usually an HRV with dedicated ducting or piggybacked onto a forced air heating system. Contractors are also installing bathroom fans ducted to the exterior. These are required to be on a switch separate from the bathroom lighting so that they can stay on when the lights are shut off. When I install a bathroom fan, it is always controlled by a timer, never a switch.

In this age group of houses, I can not ever remember seeing moisture staining/mould on roof sheathing under normal conditions. The only time I was called to a newer house with an HRV with just beginning mould (a few spots) was after a hurricane. The soffits facing the storm winds blew off and wind driven rain entered up through the openings. Since it was very warm in the days after the hurricane, the extra moisture in the attic allowed the mould to begin. The wet insulation was removed and no progress was ever seen in the few mould spots.

The Canadian Building Digests that Gus Handegord was talking about began being published monthly in January, 1960. He wrote #9 on vapour barriers. He must be very frustrated to see that even today, very few truly understand (or have read) what he was espousing then. Two generations of houses have been built and had moisture problems in walls/attics due to warm, moist air leakage after he said this CBD #9: (my emphasis added)

"The importance of avoiding all unnecessary openings through the vapour barrier cannot be overemphasized. These openings may not only provide a means for water vapour to pass into the wall by diffusion, but if associated with a crack or opening in the interior cladding they may also allow moist air to flow into the wall under the action of air pressure differences. Tests have shown that a vapour barrier which barely meets the permeance requirements, but has no openings, will perform satisfactorily under severe conditions. Openings in the most impermeable barrier, however, will result in excessive condensation within the wall."

" The same basic principles of vapour control in frame walls apply to insulated ceilings and roofs. There is a greater possibility for more openings to exist in vapour barriers in ceilings of frame construction than in walls. Not only are electrical ceiling fixtures common, but openings occur around plumbing vents, ductwork, and chimneys. Of even greater significance is the tendency for moist interior air to flow upward through these openings due to the chimney action of the building itself. The danger of excessive amounts of moisture accumulating in the attic space is therefore more acute than in exterior walls."

And his concluding lines:

"The most important general principle to be followed in both design and installation is to reduce to a minimum the number of openings in the barrier. Where such openings are necessary, special care should be taken to seal the barrier so as to approach complete continuity."

So 48 years later, he watches as most people still have not a clue of what he correctly said in 1960! He must feel like Galileo trying to tell the pope that the earth is not the center of the universe. The Vatican finally acknowledged this formally in 1992!!!!!!

From Wikipedia:

"Galileo was eventually forced to recant his heliocentrism and spent the last years of his life under house arrest on orders of the Inquisition."

"On 31 October 1992, Pope John Paul II expressed regret for how the Galileo affair was handled, and officially conceded that the Earth was not stationary, as the result of a study conducted by the Pontifical Council for Culture."

WOW!!!!!! 400 years later!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[Ed Fako]

Originally Posted by Brian A. MacNeish

The Canadian Building Digests that Gus Handegord was talking about began being published monthly in January, 1960.

He wrote #9 on vapour barriers. He must be very frustrated to see that even today, very few truly understand (or have read) what he was espousing then. Two generations of houses have been built and had moisture problems in walls/attics due to warm, moist air leakage after he said this CBD #9: (my emphasis added)

"The importance of avoiding all unnecessary openings through the vapour barrier cannot be overemphasized. These openings may not only provide a means for water vapour to pass into the wall by diffusion, but if associated with a crack or opening in the interior cladding they may also allow moist air to flow into the wall under the action of air pressure differences. Tests have shown that a vapour barrier which barely meets the permeance requirements, but has no openings, will perform satisfactorily under severe conditions. Openings in the most impermeable barrier, however, will result in excessive condensation within the wall."

" The same basic principles of vapour control in frame walls apply to insulated ceilings and roofs. There is a greater possibility for more openings to exist in vapour barriers in ceilings of frame construction than in walls. Not only are electrical ceiling fixtures common, but openings occur around plumbing vents, ductwork, and chimneys. Of even greater significance is the tendency for moist interior air to flow upward through these openings due to the chimney action of the building itself. The danger of excessive amounts of moisture accumulating in the attic space is therefore more acute than in exterior walls."

And his concluding lines:

"The most important general principle to be followed in both design and installation is to reduce to a minimum the number of openings in the barrier. Where such openings are necessary, special care should be taken to seal the barrier so as to approach complete continuity."

I do agree with these concepts entirely too, yet I do not see strict adherance to following the guidelines during the construction process in my part of the country.

One explanation for my field results being vastly different than yours may be due to the fact that I rarely install a roof on a relatively new home, with the newest roof systems being applied to homes that are at least 12 years old, while most are more than 40-50 years old and many from the 1920's and earlier.

This obviously would skew my field observations, yet I tend to believe that the tract home builders are the scourge of the industry when it comes to "Strict Adherance" to any fundamentaly sound vapor reduction techniques.

In the Chicago market, 2 very large buiders have recently filed bankruptcy and a 3rd is in the prepatory stages of doing so. If any work does follow up on these under capitolized mass quantity subdivisions, quality control issues will be the last thing on their priority lists, including vapor permeance.

The entire system it would seem, is only as good as its weakest point. This may be my strongest arguement against this ventilation and vapor transmission theory, since the pieces of the puzzle must inevitably be constructed properly from the onset and remain financially feasible. If the builders do not gain additional rewards from following these specifications, they wil not be adhered to.

With the cost cutting tendencies and mass production business model being espoused by so many builders with craftsman who hardly qualify as being called so, the entire premise is flawed from the get-go.

I particularly liked your analogy to Galileo, especially since I recently watched a documentary on the man and his admonished philosophies.

Ed