*
Dear Mr. Fusco,
Thank you for your comments and questions, having to do with venting and shingle service life. In my research, I measure the temperature of various roof system components under various conditions. I know of at least one researcher in the roofing industry who is working on describing and modeling the links between shingle temperature and shingle service life. The most current working model asserts that the hydrocarbon chains will be more or less volatile depending on their length and chemistry, and that the rate of diffusion of the short-chain molecules is temperature dependent (using the Arrhenius equation), and that the rate of embrittlement of the asphalt correlates with the loss of the short-chain molecules, and the shingles go bad as they become more brittle. This model makes sense to me, though we should be open to others.
If the world were a world of pure research, we could then look at temperature profiles and assign a shingle service life to different temperature profiles. Assuming we could control some of the wild variables (such as the soup that is asphalt), we could say that temperature profile A will lead to a service life of, say, 10 years, and temperature profile B will lead to a service life of, say, 20 years. Then we could begin to assign a dollar value to the temperature reduction associated with the cooling effect of venting.
I don’t expect that will happen, for reasons of commerce. If we rank the factors that affect shingle temperature, color may be at the top, framing type (truss-framed v. cathedral) is very high, geographic location is very high, and venting is relatively low. If we say that temperature control is the key to shingle service life, then the industry and consumers alike must begin to contend with the consumer options that are the strongest determinants.
You also deduce from reading the Issues article that the net effect is pro-venting. To some extent I agree. Venting certainly cools shingles, though not as strongly as does choice of color. Venting can dilute moisture that enters the cavity, though the aerodynamics of complex roofs can be counterproductive in terms of moisture. I hope no one presumes from reading the recent work on venting that we should go around and close up vents. There are many cases where venting is undesirable, inadvisable or impossible. I hope our research can help lift such constructions out of the limbo they presently occupy.
Instead, through ASHRAE, we are working on a method to do improved moisture design of building envelope assemblies. To design a floor system to resist gravity loads, for example, we have a method that is not too complex: 1) determine the occupancy load, say 40 psf, 2) analyze the design using formulas or span tables, and 3) check the result against some criteria such as L/360 deflection. In this ASHRAE effort we are asking 1) what moisture loads should be used (interior humidity, weather conditions, and accidental wetting), 2) what analytic tools and tables derived from those tools should be used, and 3) what distinguishes acceptable from unacceptable building envelope assemblies (Preliminary answer: mold growth). From this point of view, we should be able to analyze the performance of any assembly for any load and climate and determine whether or not it is acceptable. This is likely to provide a new view on which assemblies are acceptable and which are not, though you can be sure that field experience will continue to serve as a validator. I believe that many of the builders and others who build and advocate assemblies that make others uncomfortable, are proceeding from such a perspective.
Replies
*
Mr. Rose,
Joseph Fusco
View Image
"Whenever, therefore, people are deceived and form opinions wide of the truth, it is clear that the error has slid into their minds through the medium of certain resemblance's to that truth."
Socrates
*Hey Joe, happy millenium. I've been wondering where you've been. Now, here you are posting away, but all I see are attacks on others. First, it was FredL, now Mr. Rose. I'm kinda' disappointed in you Joe. Another thing, let's keep venting over on the venting page, agreed?
*Anyone with roof venting knowledge,I have a hard time reading all this drivel regarding shingle lifespan as a function of roof ventilation.Oh great roof ventilation sorcerers, please explain the following phenomenom:1. unvented shed roof that dies into wall, living space below, 3/12 pitch, 20 plus years old, southern exposure, no noticeable difference betweeen these and other shingles on multiple other vented pitches, same house. 2. unvented porch roofs, no living space below. any age, with no appearant difference in shingle wear.3. rake over hangs with no venting, shouldn't there be a difference in the ageing in relation to the rest of the roof? Again, any age roof.4. many, many unvented roofs exceeding rated life spans of shingles. 5. i'm sure that you guys can think of many other examples relating to roof longevity vs. venting.Now if you want to talk moisture problems or ice damming, I am conducting field studies on my own house as I write this. The jury may still be out on these.Tom
*Tommy, in all of the threads relating to this question I have read, all mentions of the shingle life thing are "What if" about the warranty. I can't recall anyone saying that they had actually had a warranty problem that was refused due to non-vented structure.Obviously I can't recall every word of every post each time a thread has swung off track to rock & roll about who knows their a** from a vent. Do you remember a specific instance?Venting my curiosity, from Southern Cal, the land of zero insulation mostly. Joe H
* Hey Rich,
Joseph Fusco View Image "Whenever, therefore, people are deceived and form opinions wide of the truth, it is clear that the error has slid into their minds through the medium of certain resemblance's to that truth." Socrates
*Rich,I don't see anything in Joe's comments that could be viewed as an attack on Mr. Rose.Seems like just questions to me.Vince
*Ditto.It sounds like some legitimate questions to me.I downloaded both the article, and Joe's questions. Read them both, and it will be interesting to see if any answers are given.Just my opinion...James DuHamel
*Gentlemen. For many years now, the Asphalt Roofers Manufacturer's Association(ARMA)has been asked to provide documented evidence to support their claims that shingle longevity is a funstion of attic ventilation. The asnwer provides is: "If you knew what we know about shingles you would know that we are right." What has alkways bothered me in these posts is that few if any ask ARMA for written proof of their claims. The consequences of this lack of challenge is best seen in the hardboard siding fiasco. The manufacturers got away with murder until one individual, at great personal financial risk, single handedly took them on and won. What are we waiting for? GeneL. In addition to the Rose paper, read Joe Lstiburek's article, " Unventing Attics in Cold Climates," publisahed in the November/December 1999 issue of HOME ENERGY. You are in for some interesting reading.
* James,
Joseph Fusco View Image "The price of apathy towards public affairs is to be ruled by evil men." -- Plato
* Gene,
Joseph Fusco View Image "The price of apathy towards public affairs is to be ruled by evil men." -- Plato
*Dear Mr. Fusco,Thank you for your comments and questions, having to do with venting and shingle service life. In my research, I measure the temperature of various roof system components under various conditions. I know of at least one researcher in the roofing industry who is working on describing and modeling the links between shingle temperature and shingle service life. The most current working model asserts that the hydrocarbon chains will be more or less volatile depending on their length and chemistry, and that the rate of diffusion of the short-chain molecules is temperature dependent (using the Arrhenius equation), and that the rate of embrittlement of the asphalt correlates with the loss of the short-chain molecules, and the shingles go bad as they become more brittle. This model makes sense to me, though we should be open to others.If the world were a world of pure research, we could then look at temperature profiles and assign a shingle service life to different temperature profiles. Assuming we could control some of the wild variables (such as the soup that is asphalt), we could say that temperature profile A will lead to a service life of, say, 10 years, and temperature profile B will lead to a service life of, say, 20 years. Then we could begin to assign a dollar value to the temperature reduction associated with the cooling effect of venting.I don't expect that will happen, for reasons of commerce. If we rank the factors that affect shingle temperature, color may be at the top, framing type (truss-framed v. cathedral) is very high, geographic location is very high, and venting is relatively low. If we say that temperature control is the key to shingle service life, then the industry and consumers alike must begin to contend with the consumer options that are the strongest determinants. You also deduce from reading the Issues article that the net effect is pro-venting. To some extent I agree. Venting certainly cools shingles, though not as strongly as does choice of color. Venting can dilute moisture that enters the cavity, though the aerodynamics of complex roofs can be counterproductive in terms of moisture. I hope no one presumes from reading the recent work on venting that we should go around and close up vents. There are many cases where venting is undesirable, inadvisable or impossible. I hope our research can help lift such constructions out of the limbo they presently occupy.Instead, through ASHRAE, we are working on a method to do improved moisture design of building envelope assemblies. To design a floor system to resist gravity loads, for example, we have a method that is not too complex: 1) determine the occupancy load, say 40 psf, 2) analyze the design using formulas or span tables, and 3) check the result against some criteria such as L/360 deflection. In this ASHRAE effort we are asking 1) what moisture loads should be used (interior humidity, weather conditions, and accidental wetting), 2) what analytic tools and tables derived from those tools should be used, and 3) what distinguishes acceptable from unacceptable building envelope assemblies (Preliminary answer: mold growth). From this point of view, we should be able to analyze the performance of any assembly for any load and climate and determine whether or not it is acceptable. This is likely to provide a new view on which assemblies are acceptable and which are not, though you can be sure that field experience will continue to serve as a validator. I believe that many of the builders and others who build and advocate assemblies that make others uncomfortable, are proceeding from such a perspective.
* Dear Mr. Rose,
Joseph Fusco View Image
*Joe H.Anytime I have mentioned my extensive experience with roofing and shingle warranties, Fred accuses me of "puffing my resume" and aj calls me a worry-wort. That in itself doesn't bother me, I just don't much enjoy arguing side issues. I think that only a few people here are very interested in this topic, but many enjoy the flaming.....but then I could be wrong.All my comments on this in past discussions are based on personal experience, not speculation or second hand information.If anyone is interested in this maybe we could start a seperate thread. John
*Mr. Rose,Thanks for your reponse to Joe Fusco's letter(thanks Joe for presenting the letter here at Breaktime!) I especially liked your comment "...you can be sure that field experience will continue to serve as a validator." It's nice to know that someone in research accepts the fact that contractor's experiences mean something in this discussion.John
*.......Gene, FredL, Joe, et al.....and a special thanks and a tip of the hat to Mr.Rose.....Gene....I think your novel approach to building envelope design is commendable and would/does especially lend itself to some systems mfr. of housing ...benefits, low energy use, low cost assemblies.. etc..yada, yada.. it's limitation is that it is not useable in all circumstances or designs , and has extremely limited use in my world of remodeling and additions....and I've read a lot of Lstiburek's stuff....me thinks he overreaches.... and the first thing he does is tell everyone who holds a different opinion what a jerk they are....so spare me the "Building Science" and other oxymorons.....FredL....your sometimes intelligent applications tend to be overshadowed by your tendency to brook no exceptions when it is perfectly obvious to me that the building world is mostly composed of exceptions and compromises,,,,, and "best solutions"...sometimes your "no-vent " pack- it- in solution works and sometimes it is inappropriate ... ...you generally seem to come across as having no respect for tradesmen and mechanics who also take pride in their work......Joe....I think you are espousing a real building world solution to most of these queries.....but you gotta work on your retoric... you know, more flies (or a better class of flies, anyways) with honey than shit...b but hey, whatta I know, just another frog in a little pond...Kermit
*Joe. You are of course correct that shinges are only one element in a system of elements comprising the roof. But in all the posts and writings the major emphaisi seems to be on shingles with little on the shearhing or the roofs structural members.I have always understood you to be concerned with the seeming lack--if not actual lack- of "fail-safe" features in unvented roofs. If I argue for attic ventilation--and egro, seem to contradict myself while argiung for unvented attics--it is because I have seen millions of dollars of roof damage. The damage is not a result of little or no attic ventilation but due to the failure to thoroughly seal the openings in the basement ceiling and the ceiling below the attic, and exacerbated by little or no attic ventilation. Here the attic ventilation devices--most of which don't work as claimed--are asked to do things they were never designed to do.Mike Smith. Thank you for your kind remarks. You are correct that my techniques do not all work in every situation especially remodeling. But the philosophy behind the techniques are IMHO universally applicable.I've known Joe Lstiburek for twenty years. Our personalities are such that I though we might conflict. But we became good friends in spite of his often being opinionated and lacking proof for some of his arguments. He single handedly--ignorin g the legal and financial risks involved-- backed-down the hardboard siding manufacturers. We owe him our thanks for this. Again, thank you. GeneL.
*Jeez, I promised myself I'd do this since rereading my earlier post aand those of others. This is gonna' hurt, but, as I keep telling myself, I'll feel better for it.Joe, I must apologize for my earlier comments. I was half-cocked and shot off my mouth anyway. I read Mr. Rose's lengthy article but didn't read your comments. My excuse is that Joe is Joe and he must be flaming someone. What an ass I was. Again, my apologies.
*Rich,
Joseph FuscoView Image"Whenever, therefore, people are deceived and form opinions wide of the truth, it is clear that the error has slid into their minds through the medium of certain resemblance's to that truth." Socrates