Is inadequate roof or attic ventilation a defect?

Ed_Fako · August 6, 2007, 2:26pm

Brian,

Unless that Certainteed Warranty item you posted has been updated since I last viewed the limitations, I believe that the warranty length is reduced to a total of only 10 years, regardless of which Certainteed Roofing Shingle or Shangle was applied under the circumstances referenced to.

Regarding your most recent post response, how could moisture jump from one enclosed rafter bay to all of the others, even if there had been a bathroom exhaust vent releasing its moisture directly into the attic.

In reality, there was no attic area, becaust this was a vaulted/cathedral ceiling structure for the entire home.

Ed

Brian_A.MacNeish · August 6, 2007, 4:10pm

Not all, Ed

[size=4]Inadequately Ventilated and Non-Ventilated Decks[/size]

[size=2]Any shingles applied to inadequately ventilated or non-ventilated decks, other than the shingles and deck systems described in the paragraph below, titled “Insulated Decks and Radiant Barriers,” shall qualify for a reduced warranty duration of 10 years with no SureStart coverage, with respect to shingle problems related to the absence of adequate roof system ventilation.

[/size][size=4]Insulated Decks and Radiant Barriers
[/size]

[size=2]CertainTeed’s Limited Asphalt Shingle Warranty, including SureStart [/size]™ coverage, will remain in force when its fiber glass asphalt shingles manufactured to meet ASTM D3462 are applied to roof deck assemblies (slopes ³ 2:12) where foam insulation is prefabricated into the roof deck system (often called “nailboard insulation”), where insulation is installed beneath an acceptable roof deck system, or where radiant barriers are installed, [FONT=Garamond-BookCondensed]with or without ventilation directly below the deck. Acceptable roof deck surfaces must consist of either minimum [/FONT]3/8" thick plywood or minimum 7/16" thick OSB. If an alternate deck surface material is being considered, contact CertainTeed Technical Services.

See the following important restrictions.
The design professional is responsible for ensuring

proper quality and application of the insulation and/or radiant barrier,
provision of adequate structural ventilation and/or vapor retarders as determined to be necessary, and
that all local codes are met (particularly taking into account local climate conditions). Special attention must be taken if cellular foam, fiber glass, or cellulose insulations, or other highly-permeable insulation will be used in an unventilated system, or if the insulation/rafter or insulation/joist planes may create an air leak that could lead to moisture transmission and condensation problems.

*All these important factors and decisions, while **not *[size=2]the responsibility of CertainTeed Corporation, are critical to assure proper deck system performance.[/size]

My comments:

what is “structural ventilation”? Never heard of this before; someone’s making up new terms!
the highlighted text in the last paragraph of the warranty restrictions is essntially telling people to not use the attic/roof cavities as a means to ventilate the house. This concept goes back the the 1940-50’s. A bit of history from a 1986 Building Science Insight CE session (1 day; $250) I attended:

Consequences of an Ineffective Air Barrier System
The concept of the building envelope as an environmental separator was first promoted by Dr. Neil Hutcheon, former Director of the Division of Building Research, in a talk to the Engineering Institute of Canada in 1953.¹ Dr. Hutcheon listed the principal requirements of the building envelope, so that each could be addressed separately and in conjunction with its counterparts. He noted that building envelops had to be designed to control air flow and the moisture and energy flow associated with it. To quote from his talk:
“The flow of heat, moisture and air in walls have implications not only by themselves, but for all the other considerations listed. **Air merits major consideration mainly because of its influence on heat and moisture flow.”**Remember, this is 1953 (hell, I was only 3 then), more than a 1/2 century ago! How smart are we really to not listen to or respect those that have much deeper insights into what is really happening in buildings???

aharper1 · August 8, 2007, 8:47pm

Utah does not have a “code” for proper attic ventilation. I have called out "no ventilation many times and still do. But it is per the shingle manufacturers request to honor a warranty on their shingles that has min. ventilation req. Just look on a package of shingles.

Brian_A.MacNeish · August 9, 2007, 1:24am

Here’s where the interesting stuff begins:

In a June, 1994 Energy Design Update article Building Scientists Turning Code and Common Practices Upside Down:
“At the ASHRAE / DOE / BETEC* Thermal Envelopes Conference* in Clearwater, Florida, an international group of building scientists and contractors led by Anne Silberstein of Isover Saint-Gobain of France and Bill Rose of the University of Illinois Building Research Council concluded that unvented cathedral ceilings provide better thermal performance and better moisture protection than conventional vented cathedral ceilings”

Isover Saint-Gobain owns Certainteed!!! Why would a shingle company say this??? Maybe they know something many don’t. They offer a full warranty on some of their products installed without venting!

In the August, 1998, Journal of Light Construction, Bill Rose in the Q&A section states:
“We’ve also found that a vented cathedral ceiling cavity is much hotter than an unvented full attic, other things being equal”

So the unvented full attic is cooler than the vented cathedral!! Why would we want to vent it to save the shingles from heat? It’s already cooler. As I’ve said earlier, vented cathedral ceiling shingles should be failing much faster and more frequently than the unvented full attics since they are hotter.

"So far I find little technical support for the claim that ventilation enhances the service life of shingles. … the temperature difference between vented and unvented is awfully tiny. Shingle colour and latitude make for a much greater temperature difference. In the absence of technical support, I believe that either course of action- venting or not venting- is viable. Those who vent will encounter fewer problems with code officials and shingles warranties. Those who do not are working in the fine tradition of craftspersons who use common sense to challenge accepted wisdom.
Venting has been presented as the key to blissful service life of shingles.

My opinion is that service life is first and foremost a matter of shingle quality. If** ventilation has one ill effect**. it is that it gives shelter to manufacturers who are not investing in shingle improvement."
**
**Why do the shingle companies not publish some actual shingle roof temps from their own studies with the main variables- latitude, orientation, shingle colour and venting- studied. They are huge and have more money than any little university research group!!

I think me smells the truth being ignored or buried!!!

Ed_Fako · August 12, 2007, 5:00am

Brian,

There is much more to the situation than just temperatures. Even in one of your favorite researchers view points, from Joseph Lstiburek, he points out the decrease in a 15 year shingle roof, (How old is this document?), will be about 3-4 years.

The rational for the unvented assembly is to promote higher quality internal health, thereby reducing mold and other moisture related occurrences.

Please review the following link. It is not dated, so I don’t know what era this research paper is from.

Ed

http://64.233.167.104/search?q=cache:kcPfF4acwpAJ:www.noblackmold.com/news_files/UnventedAtticsArticle.doc+prblems+with+unvented+shingle+roofs&hl=en&ct=clnk&cd=2&gl=us

Excerpted paragraph from the above paper:

Unventing roof assemblies in most climates increases the air conditioning load on a typical home by approximately 3-to-5 percent. If the ducts are inside the conditioned space and we are not worrying about mold, humidity, ice-damming or blowing snow issues, vent the roof and don’t give up the 3-to-5 percent.

Remember there is a trade-off. I choose to give up the 3-to-4 years in the life of my shingles **(ed; out of a 15 year shingle warranty. That is a loss of 20% to 27% of the expectet shingle life.), **in exchange for better performance for the entire system and I choose to void the warranty. Not all people will want to make this choice. I already see their logic. Yes, I prefer mold in my house in Orlando, FL in exchange for 3-to-4 years more on my shingle life; and yes, I want my shingle to be black or brown in Austin, TX so that I can install a 1-to-2 ton larger air conditioner.

**Is this some of the logic and rationale that I would like to emmulate and follow? **

Ed

Some More From That Paper:

Now, where the real effect of not venting roof assemblies is felt is the temperature of the underside of the roof sheathing. My field measurements and compute modeling show that the temperature of the underside of the roof sheathing increases between 10 and 20 degrees F. Why the huge difference here and not on the shingles? Well, compare the R-value of a shingle and the R-value of the roof plywood. A temperature gradient can actually exist across the plywood. And, ventilation air on the underside of the roof plywood does remove heat. Take away the ventilation air and you do increase the temperature of the underside of the plywood. But does this matter? Yes and no. Depends on the overall system design.

Unventing roof assemblies in most climates increases the air conditioning load on a typical home by approximately 3-to-5 percent. If the ducts are inside the conditioned space and we are not worrying about mold, humidity, ice-damming or blowing snow issues, vent the roof and don’t give up the 3-to-5 percent.

But if you are stupid enough to put ducts in attics, if you are stupid enough to put air handlers in attics, if you are stupid enough to hire interior designers and architects that design incredibly complicated roof structures that cannot be air sealed at the interior drywall because of jigs, jogs, shelves, coffers, pot lights, valleys, hips, dormers, beams, skylights, etc., give up the 3-to-5 percent. Guess what you gain? You gain between 10-to-30 percent savings from the airtightness of the roof sheathing and lack of conductive gain on ductwork in vented attics.

Ed_Fako · August 12, 2007, 6:08am

Proper soffit to ridge ventilation does decrease moisture content, especially that which has migrated into the deck sheathing.

Brian,

Please read page 10 of the following link.

Ed

http://txspace.tamu.edu/bitstream/1969.1/4545/1/ESL-HH-06-07-34.pdf

Interesting advice from a fellow member:

Other cladding problems may be specific to certain regions. Brian MacNeish, a partner in Atlantic Home Inspections of Sackville, New Brunswick, often sees buckled Masonite hardboard siding on houses built in the Maritimes after 1960. There, the cause of the problem is moisture forcing its way out of the house, not in. “The houses have no ventilation,” MacNeish explains, “so moisture inside gets through the aspenite or clipboard sheathing and into the hardboard. We usually recommend adding vents.

And from the other partner author of this report:

Predictably, we are also finding peeling paint and much wood on several upper-level window sills. We know by now that this is evidence of water seeping in. The solution lies in sealing the windows from the outside and repairing the spalled brick. Had we seen no flaws in the shell of the house, we would have suspected the damage was cause by moisture trying to get out- in other words, an elevated humidity level in a tightly sealed house. In that case, Dunlop suggests putting vents in the roof and/or soffits under the eaves, not too costly a job. A dehumidifier might help too.

Brian_A.MacNeish · August 15, 2007, 3:26pm

Ed Fako:

Interesting advice from a fellow member:

Other cladding problems may be specific to certain regions. Brian MacNeish, a partner in Atlantic Home Inspections of Sackville, New Brunswick, often sees buckled Masonite hardboard siding on houses built in the Maritimes after 1960. There, the cause of the problem is moisture forcing its way out of the house, not in. “The houses have no ventilation,” MacNeish explains, “so moisture inside gets through the aspenite or clipboard sheathing and into the hardboard. We usually recommend adding vents.

Ed:
This was a 1986 interview for a magazine and not a ventilation report:
http://www.homealyze.com/in_the_news/may_june_1986.htm

Notice that in the article, nowhere do I mention attic ventilation… “the houses have no ventilation”. Why would I recommend attic ventilation when the problem was in the siding?

By this time, 1986, I had been airsealing homes and installing exhaust fans / air exchangers / heat recovery ventilators for 5 years, was a US certified residential energy auditor (1981), had a blower door (1981), was an R2000 program inspector / site advisor / troubleshooter / researcher, had been to a couple of National Research Council “Building Science Insights” seminars on moisture problems in buildings. I pretty well understood that exhaust ventilation is needed in newer homes that are tighter simply due to the use of panel sheathing materials (not as many cracks as when using 5-6" board sheathing) and tighter windows and doors.

The interview was 4-5 minutes by phone and I never had a chance to edit my “quotes”. The interviewer seemed stuck on attic ventilation (which I still find in many persons today!!!). Since he had initially talked to Bob Dunlop*, attic ventilation is where he wanted the short conversation to go. The last “vents” should have read “ventilation”
*(partner in Carson-Dunlop, reputedly the best HI training company in North America but, in my opinion, a bit behind the building science of the time. I had a very lengthy discussion about this with other partner, Allan Carson, at their office a few years later.)

True Story: In 1983, we were receiving energy conservation grant funds (Canadian Home Insulation Program -CHIP) through our customers rebates. Due to fraud by some operators, regular inspections were being carried out at 6 month intervals. The item that got us potentially in trouble with them was: We were not installing code attic ventilation. So back to the article- why would I be recommending it 3 years later??? Back to story- We went through 2 inspections where venting was an issue and, with the second report, were threatened with losing our listing # with the program. This would not allow us to receive program $$$- about 25% of our revenue.

When called by the inspector for a third inspection, I asked him if he could take some time after the inspection in the afternoon to view research I had about moisture flows, airealing, my concerns about snow blowing in vents (have you seen the pics of my own attic?) etc. “No can do” says inspector. He comes to our office to check that our files were up to date, contracts were properly filled in, etc. and choose at random, two houses to inspect where we had received gov’t funds. I chuckled to myself since one of the homes (a bungalow) had large triangular gable vents on the short sides of a hip style roof. The attic hatch was directly under the northeast facing vent and it had snowed with winds from the northeast a couple of days prior. When he opened the hatch to inspect attic insulation levels, snow fell on him! We spent the remainder of the day at a local coffee shop.

In 1990, this gent, a certified mechanical engineering technologist, was now a partner in a mechanical engineering design firm and was responsible for bringing me into the firm to set up and manage a new subsidiary doing Indoor Air Quality investigations and [FONT=Arial]air balancing.
[/FONT]

And from the other partner author of this report:

Predictably, we are also finding peeling paint and much wood on several upper-level window sills. We know by now that this is evidence of water seeping in. The solution lies in sealing the windows from the outside and repairing the spalled brick. Had we seen no flaws in the shell of the house, we would have suspected the damage was cause by moisture trying to get out- in other words, an elevated humidity level in a tightly sealed house. In that case, Dunlop suggests putting vents in the roof and/or soffits under the eaves, not too costly a job. A dehumidifier might help too.

If Mr.Dunlop wants to recommend attic ventilation for interior house moisture problems, that’s his issue. (if you notice I have essentially been saying: “Don’t vent the house through the attic; airseal for moisture and energy reasons and install interior exhaust fans”). A humidifier will only bring the interior moisture levels down to 50% RH or so, still way to high to prevent window and potential hidden wall/attic condensation in cold winter temps. We use dehumidifiers here for controlling summer humidities in basements and to help dehumidify after serious water spills/leakage (along with massive house ventilation and heat)

Ed_Fako · August 15, 2007, 5:32pm

Brian,

Since the article was not dated when I was doing my research, I had fugured that it was from some time ago. I know you have a firm stance regarding this topic and it did not seem to jive with your current views.

Did you happen to have time to review my previous back to back posts, excerpted comments, and the linkds they came from yet?

My trouble with your stance is that I have seen the structural devestation on deck sheathing from inadequate ventilation. Although the roof surface temperatures may likely be more influenced by shingle color and orientation to the sun, the interior climate and the resulting consequences are what the real life experiences have shown to me.

Inadequate ventilation has not only shortened the life of asphalt shingles but has also compromised the structural components they are attached to.

I have photos of a home I inspected this week. The 25 year 3-tab shingles are precisely 10 years old. This is an accurate estimate by the home owner, because she put on the new roof when she purchased the home. They are completely deteriorated due to inadequate ventilation installed by another roofing contractor. Additionally, the newly installed OSB decking which was also installed at that time has severe sumps and deterioration occurring as well.

Also, I have photos from a job I did exactly 9 years ago this coming September, which had the proper amount, (more than required), of exhaust ventilation installed. These shingles from the same manufacturer as the degraded ones look as good today as the day they were installed, with the exception of pitted shingles under an antennae, where the bird droppings continually land and eat through the product.

I will post side by side photos for comparison later for review.

I am glad you came back to this thread, but I would be interested in your interpretation of the links and comments from my previously made two posts to see if you feel they have any merit.

Ed

Ed_Fako · August 15, 2007, 5:32pm