*
Mauri,
In the last 60 years, many studies have been set up to show that in a side-by-side comparison of venting and not venting, venting looks good. Many in the roofing industry who see vented and unvented roofs are also led to the conclusion that venting looks good. Many people conclude from this that not-venting is bad. Other people, including myself, challenge the logic of that conclusion. There are many instances of fine roof systems that don’t use venting.
Codes generally require venting. Many experts will advise you to vent. If you want to look at alternatives to venting, do your homework. Here’s an article on some of the issues.
www.fpl.fs.fed.us/documnts/pdf1999/tenwo99a.pdf.
Good luck.
Replies
*
I think a lot of this vent/novent issue is climate as much as anything else. Non venting may be applicable in a climate with 7 months of winter, however, I myself live in a mixed cooling/heating climate zone and anybody with good sense can figure out that attic temperatures of 150 degrees f + are not a good thing.
One of the premises of a non vented roof is that the living space ceiling be
i perfectly
sealed from the attic, which, in practice is not feasible. The only way around this is to build like Gene Ledger has suggested in the past where you hang and finish the sheetrock lid before installing any interior partitions (truss roof construction only). No ceiling penetrations are allowed (overhead lights, exhaust fans, wires, pipes). Wires can be installed in surface mounted conduit - read uuugleee!! And still attic access is required by fire code.
Generally,
b re non-vented roofs - I'm not buying it and I'm not
b building it!!
,although a northern location 10 x 10 vestibule type room with a hip roof, which wouldn't fit much of any ridge vent anyway, would be a good an application as any.
As far as the pi$$ing match, I think we all know who presents facts, experience, and information with some opinion mixed in, and who attempts to present their opinion as fact and then backs it up with a slanted bit of information, all of which was authored by the same. Save the "because I said so" attitude and stick figures for your kids. The best way to win adults over to your way of thinking is to leave emotion, sarcasm, and attitude in general out of the communication process.
As to the pi$$ers: If your going to have an "authoritative" web site out there, you ought to at least make it somewhat complete (no names mentioned). Recently was the first time I had looked at the "expert" web page in about 2 years and it is still about 35% complete. Further, I don't think anybody should dignify an attack here with a response soiled with emotion. Rather, respond with polite information and opinion pertinent to the topic only - or don't respond at all. If you all want to sling "waste material" use e-mail. The entire smelly environment degrades this great Breaktime resource!
Remember: Do as I say, not as I do!! :)
J
*
Joe,
I think Fred puts forth more then just stuffing cells and sealing vents.
I've found the whole issue of improving the building envelope to be quite enlightening. From stopping moisture infiltration through basements and crawlspaces, to eliminating, or at least sealing attic floor perforations, to the advantages/disadvantages of cells and fiberglass.
You're correct in that Fred didn't "invent" these things. He is, however, the loudest proponent of them that I know of. As such, he is placed on a pedestal by those that support him, and is villified by those that oppose him.
Do I read his posts and change my practices immediately? No. Do I read your posts, discount Freds ideas as lunacy, and continue with the status quo? No.
There are flaws with fiberglass. There are flaws with the currently accepted methods of contructing the average envelope. There are limitations to cells.
To me, venting was designed as a solution to a problem. Eliminate that problem and you don't need the solution anymore. That, however, is too black and white for me. There are other considerations that need to be addressed, and that's where the debate comes in. Building envelopes are indeed complex, and once an envelope is constructed, it's neither easy nor inexpensive to alter it.
It's an issue that still has legs. I'm reading. I'm cutting and pasting. I'm (hopefully) learning. I do think, though, that in the end, if we can properly seal the bottom of the envelope, if we can effectively deal with the moisture generators and the depressurization that comes from evacuating the moisture from the living space, then we can go ahead and seal the top of he envelope.
Regards, Mongo
*My, what an interesting exchange, better than professional wrestling, at least less sweaty. I enjoy the debate over reading comprehension because that's a big part of what lawyers do and a favorite task of mine. Clerking for a court in Chicago, I found that many lawyers would emphasize certain passages or even individual words in precedent to support their case while missing the opinion's point. We liked to think these errors were inadvertant. There was even a guy who left out a critical "not" in his quote. Whoops.There is evidence of this sort of reading incomprehension here, quite unintentional. Anyway, continuing or commenting on the ad hominem, or on whether you're a convert, is vain. Everything that can be said has been, don't consume the board striving desperately for the last word.Mauri, disregard all the "venting" in this thread. No issue is more bitterly contested on B'time. You innocently trod upon a land mine.I'll modestly note my earlier contribution in this area: I actually contacted Elk on this issue. They will warrant applications over specifically tested brands of SIPs -- they conduct the tests themselves. Because of deck movement concerns, they are hesitant to warrant applications over field-constructed nonvented assemblies because they have no way of knowing whether the work was done properly.Shingle temperature is unimportant -- as my contact put it, the same shingles work in Arizona as New England. Heat does modestly shorten shingle life, so one may want to choose a lighter color.True, an airtight ceiling is very difficult to achieve for the same reasons an airtight wall. Because walls can't be vented, and leakage into them is extremely harmful, it is matter of course now to seal them as well as possible. Why not extend the exact same approach to the roof? Why depend on more holes to compensate for unnecessary holes in the ceiling? Cellulose's nature makes it well-suited to ensuring airtightness, as it tends to suffocate air movement rather than, with fiberglass, merely filter it.There can be no doubt that a nonvented attic requires a more sophisticated approach. It requires attention to many, many details, including the method of framing, the closure of joist and stud bays, the caulking of sill plates, sealing of pipe chases, etc. But greater sophistication is reaching nearly aspect of building with energy concerns, the use of engineered lumber, etc. -- you can't just put it together like your grandfather did.Also see: Rich Beckman "Shingle Recomendations" 10/24/99 8:10pm
*Matt, I wasn't criticizing anyone selectively. I haven't done more than skim the article, but can say some of the microanalysis is futile. Venting is a "supplemental" measure, but one with cost. In mysituation, I have 2x6 rafters and little opportunity to fur out the ceiling. If I do fur it out, I want every inch to go towards insulation. Also, vents can fail and let in water or critters. But the hybrid approach that the authors suggest in the summary is perfectly sensible. The one method they doubt is attic pressurization, not airtightness.Mongo -- do you have a cut-and-paste digest of these discussions? Could I look at it? I could also post it on the internet, with a link here -- a Mongo-FAQ, if you will.
*JRS. CertainTeed now gives a 10 year warranty for their shingles installed on an unvented attic.Have you noticed that no shingle manufacturer has provided or provides written documentation for their claims of non-vented attics degrading the performance of their shingles? No matter what documentation ones provides to them,their answer is always, "If you knew what we know about shingles you would know that we are right." GeneL.
*Mongo,
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
*Gene, So, when I bid a $3,000.00 roof job, I can save the customer $150.00 in vents and offer a warranty that has 60% LESS life than with the vents. You tell me how many customers would go for that. That is how the real world works.Customers don't ask me for documentation to prove why manufacturers require venting in their warranties. Manufacturers make the shingles, and they write the warranties. And all of them have almost identicle requirements. Why doesn't even one mfr. break out and offer a full life ventless warranty? Seems as though they would have a great sales advantage over the others.John
*JRS,Wow do you like to worry!!!!....My Grandmother worried like you.....Too, too much for me laddy!!!!....My experience with all the roofs that I have done is that the longer life shingles are the only ones worth half their rated life spans and that ice and water shield along with removal of heavy snows takes is the generally accepted conservative approach employed around here...Twenty year fiberglass shingles have proved to be worthless locally and also paying subcontractors as little as possible...well, you get what you pay for unless you luckily hire someone who really loves his work more than money.As for Fred...glad he's explaining the ventless/cellulose ideas....and as for Joe's barbecues...the flames sure are entertaining!!!!near the stream, going ventless if possible,ajPS...attics can be accessed from an outside hatch as I plan to do to my own home so as to seal my ceiling as tight as possible...Take a risk...see possibilities where little appears at first...and don't worry so much...be happy!!!!
*JRS - based on your 30 years could you give some insight as to how much the warranties are worth? Like how many houses a year you do typically and how many ever get warranty work or something to show that the warranty is worth anything? Thanks in advance.
*aj,Are outside attic hatches generally code?Jerry
*Great Thread!I am, however, still trying to find legitimate info that deals with real world venting problems, in real world climates. All I see when I look at articles and books is "Northern" applications, methods, and techniques. I do not have anything whatsoever against "northern", except the fact that I live in the "southern" portion of the U.S. that gets hotter than hell.I need some real, scientific evidence and findings for tests conducted over long periods of time in my type of climate. I live in Southeast Texas, right on the Gulf of Mexico. We have 8 months of extreme summer (most of it +100 degrees) 3 months of spring, and one month of a really mild winter (warmer than most fall temps elsewhere). We have no ice dams, snow, ice, or other cold weather problems. We have heat. Lots and lots of heat. We also have humidity. Lots and lots of humidity. The relative humidity here (on average) stays above the 80% mark for almost the entire year. Where exactly can I find accurate info on THESE kinds of conditions, and how to keep the home's attic dry and cool?Do not tell me that humidity problems, temp problems, and so forth are the same all over, and that the methods are the same. It just ain't so. I do a lot of roof and attic repairs, and one thing I find most often when damage is severe is serious lack of proper ventilation. Heat buildup and moisture buildup in attics here causes a tremendous amount of damage to framing and sheathing. I know that there are many causes for the moisture to buildup in the attic, but the problems I face here, and the corrective actions to be taken are not being accurately covered by any of the so called "venting experts". They all seem to concentrate on colder climates, and ignore us. I see a mention every once in a while about "mixed" climates, but no real meat to the content. After reading the articles and books, it is quite obvious that the info was gathered, and the techniques used in a cold climate. I read an article once by a so called expert and he clearly stated that in Southern climates, the vapor barrier (paper face) of the wall insulation should face OUTWARD. Do that here, and someone will be hiring me to come and fix the mess. I have actually seen this done, and the mold and mildew, not to mention the soaking wet sole plates, were a site to behold. There was no exterior water pentration (leak) to cause this, just moisture vapor coming from the inside of the house, passing through the walls (because of lack of vapor barrier on interior side), and collecting on the back side of the insulation paper, and the felt paper used as an exterior moisture barrier. I understnad the need for vapor barriers, but what type of barrier to use, and when and where to use them needs to be researched far more for the southern portion of the U.S. Also needed is accurate research findings for attic ventilation advantages/disadvantages for the same region.Anybody know of accurate info that covers my area's high heat/moisture problems?James DuHamel
*Fred I will have to agree with Joe on this one. This is a hot topic and both of you gave an opinion. He didnt start with you so you should let it drop.Rick Tuk
*Gentlemen,Yes this is a hotly debated topic. I do not believe there is one answer to this question. The Question of location and climate has a lot to do with it. I live in a hot wet climate. For the past 15 years or so many people have been advocating sealing a house more and more tightly. we are starting to see more and more disasterous results from this.A missing shingle causing a small leak that gets in a sealed area and rots out walls before it is noticed. I do not believe it is possible to seal out all water for all time from a house. Time and nature will not allow it. Putting controlled venting in a house is my way of doing it.In a different climate I may do it differently. The wood you put in your walls has moisture in it. if they cant breath it can never dry out. Things I have seen after storms make me believe non venting is not practical in the real world (at least in this area). Dealing with older houses i see a lot of the effects of time and different building practices on a structure. These are the conclusions I have drawn. I have no scientific data or studies to back me up, only my experience in this area of the country. I am always glad to hear different opinions, it makes me rethink my own. But nothing said here has changed my opinion on this.Rick Tuk
* Fred,
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
*Rick - how can you say that? Read posts 1 and 2 in this thread. Fred answers the question with explanations of his position in post 1. In post 2 Joe attacks Fred ("resident expert on gas") and offers no answer or rational except to search the site.I can't believe you sucked me into this - I hadn't read one of Joe's posts in over a year until I read your post and knew the part about Fred starting it couldn't be true.
*I'm amused James doesn't think of the North as a "real world climate."Yes, most of the vent debate centers on cold climates where the problem faced is moisture escaping -- theses are Yankees arguing with each other, from NY and NH (which has recently shown notably good taste in Republicans). In the south the problem is reversed, and placing the vapor barrier on the OUTSIDE is the sensible thing to do -- for exactly the same reason, so that warm, moist air doesn't encounter a cold surface inside the wall and condense. You would then have an inward-drying wall -- certainly you can't expect much drying to the outside with 80% humidity (yuck, i spent a summer working outside in that stuff).In fact, I'm certain the CABO req. for a vapor retarder has a qualifier for your climate, requiring that it go on the outside. To put it on the inside would invite the same kind of problems you probably see in crawlspaces. This sort of problem is a side-effect of tight, central A/C homes.
*Wow, even the sages Bill and Mongo have been sucked into the vortex!Hey Bill, long time no see.
*Obviously the whole problem is not in the venting, but using that infernal insulation. Why not just skip that? In winter, just throw a couple extra logs on the fire. In summer, turn the AC way way down. No vapor barriers and no vents. But here, if you want vents, no problem.Again, I don't have any science to back this up, no solid research yet either, only personal observation!*****
*No profanity, OK? It is a self-policing aspect of the board, better than big brother or some idiot bot looking over our shoulders.
*andrew,
Joseph FuscoView Image© 1999"It is better to be feared. . . Then loved!" Machiavelli
*Conner's,
Joseph FuscoView Image© 1999"It is better to be feared. . . Then loved!" Machiavelli
*Golly! That hurt my feelings! You sure dish out the zingers! Hope you take 'em too.P.S. You lose on both counts with Machiavelli. Also, is English your second language? "Then"? "Resemblance's"? You're kidding around, right?
*
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
*
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
*>I always find it very interesting how any topic like this one and involving these players always losses it focus.Practice what you preach! Are you nuts or a contented hypocrite? Really, which one, I'm sincerely interested.In the SECOND post, which you have conveniently forgotten, you started this nonsense. True, Fred shouldn't have taken the bait, but most unreasonable is that you expect to dish out cheap shots AND criticize your victims for firing back! You can't have it both ways. Do you think you make yourself look smarter by sniping? "Before you go and take the recommendation of resident expert on gas..." Now, I doubt this was meant to suggest Fred is a pipefitter, chemist, physicist, or Gas-X distributor. I salute your audacity. Or density.You really are a remarkable and amusing piece of work. Prove you believe your words above by sticking to the substantive yourself, be a leader. I know you won't be able to. On a serious note, a free timesaving tip: you can't hit me, you don't have what it takes. Not that I care ... but I do encourage you to do so by e-mail. I'm posting this note because there seems to be some confusion over who's playing the bully.Don't you have some work to do? I have to go attend to mine.
*Actually Andrew, No I don't think of the north as a real world climate as far as MY NEED FOR INFO!I live in the south, remember? Repeat after me...SOUTH... Got it? Now maybe you could offer some intelligent information for me, backed by facts. The info on northern climates, and northern procedures and techniques doesn't help me. It is all good info, and very practical for people who live, and build there. But I ain't there. I'm here. You said this:"In fact, I'm certain the CABO req. for a vapor retarder has a qualifier for your climate, requiring that it go on the outside. To put it on the inside would invite the same kind of problems you probably see in crawlspaces. This sort of problem is a side-effect of tight, central A/C homes."The vapor barrier has been facing the "heated" living spaces for as long as there has been a vapor barrier. Every insulation manufacturer, and every inspector require this. I have seen first hand the results if you do NOT install it this way. As far as crawl spaces, most are open, and the wind and air circulation that flows through them keeps them nice and dry. Once in a while I find people who board them up tight, or put in small vents to let them "brathe". The crawl spaces that are open are dry, the crawl spaces that are cloded up stay damp, or wet. The moisture has to go somewhere, so it usually goes right on up into the house, or collects on the bottom side of the floor decking/sheathing.Instead of useless info , why not be helpful and give me some information I can use, or at least a source for some info I could use. If you do not have any useful, accurate, scientifically backed information, then why are you answering my post? Just curious... I asked for this type of info, and you mention my view of the northern climates, and somethign about good taste in Republicans. How about leaving the useless info at home, and passing on some USEFUL info for a change, fellas?The exchange of ideas is USEFUL info, but the exchange of one sided info with nothing to back it up is worthless. Like Joe said, and I agree with him, lets get some info posted, with sources to back them up, THEN lets discuss the info.Just a thought...James DuHamel
*James....so you and Joe like to barbecue!!!!Here's some of my thoughts on how to build in your Southern warm and humid climate....Concrete slabs, walls and all....clay tile roofing...the Spaniards figured it out a long time ago!!!! I built cedar log home in Curacao a few years back for a group that wanted to start selling somthing different on the island to break into the building market...Well, from what I saw down there, they were waisting their time!!! There were so many concrete structures there that were pleasing to look at and seemed to function so well that it was obvious to me that they were just trying to force an un-natural use of materials into a profitable business...Why are any of your local builders building the crap that you say you are working on??...If you don't want rotted structures of wood...don't build that way!!!Tell me James...What do you think.Near the stream,aj
*Maybe everyone should put their penis rulers away and harken back to what started this thread in the first place. I doubt Mauri is even still around in the event something helpful to his situation inadvertently comes up.Imagine walking into a lumberyard to buy nails. The guy behind the counter asks what kind? Before you can answer, someone else comes running out of the front office screaming at the clerk, he doesn't want nails he needs screws you dipshit. At about this time the sawman rushes in from the yard with a scrap of oak 1 x 2 and starts to pummel the two of them and yelling, not screws, glue.Anyone feel like sticking around to find out what happens? Mauri probably didn't either. In fact, he's probably given up the idea of an addition altogether.We've got a lot of credible craftsmen and builders here. Unfortunately, if one stopped at this post first, there wouldn't be much incentive to investigate further.EB
*I wasn't trying to bait or anger you, honest. You did ask for info about real world climates, not simply your climate, and I thought it was kind of funny. I respect you, even if I don't always show it...Re vapor retarder orientation (I'll do the good lawyer thing and even provide links):Certainteed fg specs: >5. INSTALLATION For most areas, vapor retarders should be installed on the warm-in-winter side of the insulation (toward the interior). For some warm and humid areas, the vapor retarder should be installed facing the exterior. Check local practice and/or building codes.OWENS-CORNING vapor-barrier fg wrapper (in front of me):>... Install isulation ... with vapor barrier toward the living area. However, this application may not be recommended in the Gulf Coast area and Florida ... check your local building codes, as they may call for the vapor barrier to be installed toward the outside in exterior walls and floors.1995 CABO § 321.1 Retarder required.>... [A]n approved vapor retarder ... shall be used on the warm-in-winter side of the thermal insulation.>Exceptions.>...>2. In hot and humid climate areas where either of the conditions occur: 67°F (19°C) or higher wet-bulb temperature [a measure of relative humidity] for 3,000 or more hours during the warmest six consecutive months of the year, or 73°F (23°C) or higher wet-bulb temperature for 1,500 or more hours during the warmest six consecutive months of the year.The CABO exception #2 may be read to allow omitting the vapor barrier or as requiring the barrier, but on the outside. I think the first interpretation is what was meant; whether it is the best building practice I don't know. I also don't know whether your climate meets these criteria -- probably not -- and the data should be readily obtained.On crawl spaces, you do not mention whether the soil surface and house floor were sealed off, as they should be. If not, then yes you are going to have plenty of moisture to remove.OK, I've wasted 40 minutes verifying what I already knew (while my baby slept on my lap, so not a complete waste). I hope the citations are useful, and to hear a concession that while you or your inspectors may have never heard of these mfr instructions and code provisions, that they have nonetheless existed all along.
*andrew,
Joseph FuscoView Image© 1999"He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich W. Nietzsche
*View ImageUh, I don't care if you vent me or not, whatever works for you!
*I was just sufferin' some thermal breakdown.
*Hey Jack,All I can say is "Job Security". As long as builders (of which I am not) build the way they have been, ignoring the proper venting/non-venting procedures, then I am sure to get a call sooner or later to fix the damage. But... while I am fixing the damage, I really want to know what caused the problem in the first place, and why. All I ask is for someone with scientifically backed, or heck man, even real world experience backed information. What is NOT helpful is opinions, or theories. Everybody has them, but few people have the info that is most helpful.Eric Borgman sent me some info, and I thank you Eric. Not only is it helpful, but it is backed by real, scientific data that is collected on a constant basis. The houses refered to in the info are monitored daily by computer. Now that's helpful info! Here is a climate map that I found useful in determining just where we all fit in as far as climates and temps go. Maybe this will shed some light on why some of the info for northern, cold climates does not help those of us in the hot, humid climates. Not bad info, mind you, just wrong info for the application. Climate MapNow as far as blasting Andrew, I really didn't mean any disrespect, nor did I mean to banter him. I apologize Andrew for my harsh statement. My nerves are shot, and I am in a bad mood. I should not have taken it out on you.Now back to business...James DuHamel
*Ever been in a thick-walled adobe house? Very nice.
*I suspect that in the long run the whole vapor barier concept will come crashing down. What we need (IMHO) are thermal envelopes that stop air movement and hence greatly retard the resultant moisture loading of framing cavities, but that don't impede the ability of the envelope to dry out or at least reach equalibrium accross the barrier between the conditions inside and the conditions outside (w/respect to moisture).For now, I see dense packed cells or foam as the only two solutions that do that. Anything employing plastic, particularly in mixed climates is asking for trouble.I hope there is some real research going on in this arena.I for one don't take the word of Joe or Fred or anyone as gospel.When I first encountered Fred online several years ago, I was taken aback by his in-your-face approach, but didn't let it stop me from listening to his experiences. Now I know Fred personally, having worked with him for the last two months, and find him good humored, fun, inquisative, and bright. We disagree on lots of things, not the least of which is our politcal world view, but remain friends. I would hope Joe is better company in person than on-line. He must be, or he would be out of business pretty darn quick.Steve
*I agree -- the one thing Gene Leger said that really struck me was that moisture travels by convection AND diffusion; and that a little convection dwarfs a wall full of diffusion. Analogously, noise travels through a wall by vibration and direct air transmission, but direct transmission makes such a disproportonate contribution that very small holes may negate extensive soundproofing features of the wall construction.Poly over fg supposedly blocks both diffusion and convection, and leads us to conflate the two. This system does a poor job of stopping convection, as all of us who have removed filthy fg from wall cavities know, and so really falls short.One note: most foams do not allow significant diffusion. Only Icynene allows some, to my knowlege. One person I spoke with suggested foams might interfere with the drying of green lumber ... no comment from me. I am concerned that rigid foam (polyurethane spray) would pop free from the framing as the house sinks, settles, and creaks, compromising the critical air seal. I saw this happen when I attempted using it as a sole plate sealer (gonna use caulk). Cellulose and Icynene can cope with movement -- cellulose woill even be drawn towards and clog a lea -- and so are more appealing despite their lower R-value. Re cellulose, I am convinced if dense-packed it is the hands-down best for retrofit of intact old cavities. I tried blowing it behind a piece of plexiglas installed over a stud bay and observed how it swrled, packed and settled -- very interesting and yielding an impressive, airtight mass.
*Andrew - thank you for the notice. I've been checking in regularily - but long gone are the days when I read all the posts - hard enough to read the weatherization threads.
*Or else!
*Like not mentioning "Voldemort". (Apologies to readers without kids - its a Harry Potter thing!)
*.........so, here's the consensus , as I see it....1) moisture always moves from wet to dry2) warm air carries more moisture than cool air3) vapor barriers are helpful4) air movement retarders are helpful5) reducing the temperature in the attic will lower the cooling load6) insulation is a good thing7) more insulation is a better thing8) homeowners don't want to live in caves, they like windows and doors9) in some locations, vapor barriers are MUCH more important than air retarders. Slabs on grade Crawl space floors Basement walls Basement floor slabs10) when you take care of one of these parameters, or problems, the other problems become MORE significant, but hopefully the sum of the problems becomes less.11) regional climate has a VERY significant effect on the total strategy for solving these building envelope problems....... ......and don't underrate the tremendous significance of MICRO CLIMATES, in other words one community near a river or ocean will have significant differences from another just 10 miles away... .......micro climates are significant depending on the site conditions and the orientation of the house and EVEN which side of the house we are developing a strategy for.12) given the right budget, the strategy for the home should include: heating, cooling, humidity, air cleaning, combustion products, insulation, vapor barriers, venting, infiltration, crack loss (one of America's greatest trajedies), testing, workmanship, maintenance (ease of, durability, budget for).And all of these should be designed with the KISS code.The average homeowner is not going to know or care about any of this until it is too late.b but, Hey, what do I know ?....Kermit
*Mike:I'm with ya on it all, except the "crack loss"?? Waz that? When the refrigerator repairman stands up after peering under the fridge and pulls up his pants? Which reminds me... How i do those kids with the baggy cloths keep their pants from falling off?Seriously though, you say "testing". Can't say I know much about that either; I know Fred knows a lot about this. Maybe I'll start a thread in the Energy: Heating, Insulating, & Venting a House area.
*.....mattG... good point, I keep meaning to ask FredL to repeat some of his field testing techniques......I've even been thinking of buying a blower door set up..what would that cost FredL? since Solar went south with the Reagan Administratin, I've misplaced all my test tools except for my sling psychrometer...as to "edge crack".....when you're calculating heat loss one of the factors is edge crack.....every door, and most architectural features have a crack, so you have to figure how many BTUs are lost to that (air infiltration)...heat loss is figured for average worst case, so like around here , I figure the outside design temp. is 0 deg. and the wind is blowing 50 mph, the ground at grade is 0 deg. and under my basement is 45 deg. The edge crack for an 8' sliding door would be (8+7+7+8) or 30 lf.........ASHRAE publishes data for calculating heat loss, and you modify some of that based on your own experience....kind of like how no two contractors figure a job the same way..Cooling loads are even more fun.....
*Mike,I don't know about the stuff on your list. But if you are looking for consensus, I think it exists on:Completely air sealing the attic floorA complete vapor barrier (or is that retarder?) on the crawlspace floorAir sealing the crawlspace ceiling (but not necessarily the basement sealing).Rich Beckman
*Fred, could you explain a little better about the part where "The condensation process is a case where water leaves a relatively dry place and accumulates into a wetter place."Thanks, Ralph
*I'm with Ralph, I'd like to know a little more too.Where I come from, we call that "drainage"Just a thought...James DuHamel
* Fred,
Joseph Fusco View Image "The price of apathy towards public affairs is to be ruled by evil men." -- Plato
*.........well FredL..we could do it for fun..but it might be fun and educational if we try to acheive a goal of arriving at consensus instead of winning...I mean if all you want to do is confuse the issue, then why bother.....I think you're a pretty smart guy and I could learn a lot from you .......but not if you start out by right out of the box mixing up a statement about (diffusion) and substituting a statement about convection....so, this is not the most important thing I got to do today..and I'm not going to check all my references...so if you'll excuse the occasional lapse of maybe the incorrect choice os a word or two...then , yea !, we can go thru the listI hope everyone is taking notes...cause there is going to be a quiz...and FredL is going to present Certificates of excellence to all of us at Petefest2K.
*Mike Smith. Re #5. A lot of research in real attics on real houses shows that even power venting an attic has little or no effect on reducing the house's air conditioning load. Insulation is more effective and less costly than ventilation, common sense notwithstanding.#9. There are 3 schools of thought on VDR's under slabs- on- ground: 1) They are necessary; 2) they are unnecessary; 3) the end use of the slab determines the need for a vapor diffusion retarder. GeneL.
*Fred,So when did you start caring about the fun zone when responding to those YOU disagree with?John
*Fred,
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
*FredL:It may just be me, but your comparisons are messin' with my mind. So please be patient as I respond.Whether you have a single drop of liquid water, a balloon full, or a whole ocean of liquid water it is the same medium and neither is wetter than the other just because the volume is different. The force of gravity has nothing to do with the equation other than to bring the two or three volumes together thereby increasing the physical size of a single volume. This is not the same as condensation, just a simple physical mixing, not even qualifying as diffusion. My original post just asked you to explain your definition of condensation a little better.The relative humidity factor says that a parcel of air will hold a percentage of water vapor at a specific temperature, which is to say that if you lowered the heat output of your wood stove and thusly the temperature of the house you would then find that the RH would increase, if all other factors remain the same. You could then lower the temperature further until a point of saturation was reached. The point at which saturation is reached is called the dew-point temperature and can be determined with Mike's sling psychrometer. Any further drop in temperature will cause condensation to occur.An additional definition: diffusion is the physical process of distributing water vapor, a gas, throughout a parcel of air (a room, a house) and physical air movement (mixing) will further that process.Taking it a step further. The statement, Nature abhors a vacumn, applies to the law of partial pressure. Each gas, in a mixture of gases, exerts a pressure proportional to its percentage in the mixture. And, if another mixture of gases (say, the other side of a wall, or attic) contains water vapor at a lower partial pressure then the pressure gradient (difference) will cause the higher amount to migrate until equilibrium is reached. Vapor partial pressure is usually higher within a house because of people, heating combustion, toilets and even inadequate vapor retarders below, to name a few.As this parcel of air migrates toward your external surface, the roof deck, for instance, one of two things will usually happen. 1. The temperature of that surface will be above the dew point and the water vapor will not condense or, 2. the temperature of that surface will be below the dewpoint and the parcel of air at that contact point will supersaturate and precipitate as condensation.And, here, if I read it correctly, is the point of all this discussion: Do you isolate the condensation prone points or surfaces as completely as possible with vapor barriers/retarders and/or insulation to keep the vapor pressure from doing its thing or do you attempt to dilute - by ventilation - the water vapor content. Or, is there a way to ensure that the dew point temperature is lower than the temperature of the contact surface and condensation cannot occur.Am I close, guys? Ralph
* Ralph,
Joseph Fusco View Image "The price of apathy towards public affairs is to be ruled by evil men." -- Plato
*....FredL.....I deal with lots of people on a daily basis and part of my personality displays itself a lot like yours...I try to overcome and eliminate sarcasm which most people don't get, misinterpret, and get defensive about....if you read contempt....you MISREAD it (not that I haven't shown that for you in other posts)........I do think we can lower the retoric and have fun... and I would assume that those of who turn out to be good students of this thread would deserve an "atta boy" from you at Petefest2k...no sarcasm intended.......Ralph...thanks for expressing the scientific explanation of my basic strategy in handling moisture levels in a structure.....I think we're making a good start...I've got an email list I made up of BT and I'll try and edit it so I can send out a printable list of numbered points to those who want to jump in...kind of like a menu in a chinese restaurant (#5!......#10....#7..cause I get confused about which one we're talking about..when I try to print off the screen , it wants to print the whole thread....Ok point #1 is tougher than I thought so I'm going to rephrase it and we can pull it apart...b I'll be baaaaaak.....
*sorry for jumping around, but I thot we could have amore meaningful discussion if we split the thread off...hope you guys won't mind making a fresh start..so, FredL.... MattG. BillR. ....Joe Fusco, ....Scott,...Rick Tuk,...Andrew d,...JRS,....MONGO,....Norm Kerr,...Steve Zerby,....Jonathan Stonely,...James DuHamel ,... AJ,....Mad Dog,....Eric M. Borgman,... Ralph, .... Gene L,... Rich Beckman,... and everyone else i've insulted and belittled by not listing you....PLEASE come on over.....its a great day, isn't it Jim ?
*I took a year of inorganic chem, not that I remember much ... but the discussion of partial pressure and RH is basically right. If RH exceeds 100%, either because of cooling or increasing the % by volume of H2O vapor, the situation is ripe for condensation -- the phase change of water from its vapor state to its liquid state. Not something you want happening inside a wall.That partial pressures of various gases will average out over time if given a permeable membrane is just the natural result of random movement. Water vapor is diffusing across the membrane -- the house wall -- in both directions, but on average there are a lot more molecules on the inside trying to get out and the system will tend towards equilibrium. A latex helium balloon will soon sink not just because helium has escaped, but also because air is diffusing in and decreasing its purity.However, a house is not a closed system because when occupied we keep pumping moisture into it, so the net movement of vapor will be outwards. If vapor is moving faster than the outside air can absorb it (saturation), condensation is risked. So a vapor retarder/barrier is essential unless we contrive a way of constantly drying the wall interior by venting it (the old house strategy that worked OK except at places like the corners, vulnerable to "dry rot").Incidentally, an RH of 100%+ does not necessarily lead to formation of liquid water or rain. Air can become "supersaturated" and not condense until it encounters a contaminant or surface -- such as dust or an airplane wing. That's why we "seed" clouds. Water can also be supercooled, not freezing until disturbed. This accounts for the phenomenon of freezing rain.Anyway, is roof venting needed? Yeah, if you're going to allow moisture to escape by diffusion and mass air movement (which may or may not be driven by thermal convection), you need venting. But a lot of venting schemes don't work reliably and cause other problems, like snow and rain getting in. Freddy's preference in the New England climate is to seal the house, and skip the vents.
*Andrew - you toch on some key issues and it raises some questions.Are you suggesting that "mass air movement" is (a) desirable or (b) unavoidable or (c) what?I believe that the amount of moisture moved by diffusion through solid materials is insignificant compared to the moisture moved by convection or "mass air movement" as you call it - do you agree?Can I infer from your statement that the opposite is true - if you are not going to allow moisture to escape then roof venting isn't needed?Can you quantify amounts when "we keep pumping moisture into it"? Fred has mentioned research suggesting 40 pounds or more of water per day from a basement or crawlspace and but that showers and cooking is measured in ounces.Always looking for thoughtful answers and opinions from other than he who shall not be named. Thanks.
*Fred, you were making sense to me here, but you stopped. Where was the moisture coming from? What would you propose to solve the problem?MD
*Mass air movement (which generally is driven by convection, but also the wind, exhaust fans, etc.) is bad if uncontrolled because it may deliver moisture where you're unprepared for it. By comparison, you seal and slope the exhaust duct while the wall interior just can't deal with injected liquid. Vents are an effort to get the warm damp air out before it condenses -- tough to do without lots of extra warmth coming from inside to keep the moisture moving.I could quantify if I knew where my p-chem book was -- I think the saturation vapor pressure of H2O in air vs. temp. was charted in there. Difficult to quantify the amount anyway. Passive humidity sources include the wet earth, unducted clothes dryers ... cooking and showers relatively trivial, intermittant contributors. As for "pumping" moisture, I was thinking of the humidifiers everyone seems to have -- they can produce many gallons of water vapor every 24 hours, as one can see in the portable tank-loaded ones. (A gallon weighs 8.33 pounds, and that's all the numbers I'm doing for today...)I'm speaking from a p-chem point of view, not a builder's. I did get an A- though. :)
*Andrew - Thank you. I think you avoided answering all of my questions.
*So here are some related thoughts/questions for anyone who might know such things:Say you densepack at the rafters.Can you stop the air-borne movement of moisture accross the thermal boundry via dense-pack cells, or just retard it? If indeed you do stop it, and reduce th transfer of moisture from in to out to just the diffusion component, what level of indoor RH can the denspacked "membrane" tolerate before it becomes dangerously saturated? If it's say 10% RH outside and the house is at 60% inside for a long stable period of time, what would the equilibrium RH of the membrane be? Is time a factor? How much of one? What level of RH can the DP cells get too before they are a hazard?Steve
*Fred, Thanks for finishing the story. I know it goes against your method, but if this person had better ventilation, would it have released enough heat/moisture to solve the ice-damming? In other words, is that a possibility, even if you'd consider it wrong, basically
*I did? Maybe I had to put them in architect-speak.
*Fred, others as well... A few posts back I was fishing for ideas on rafter packing for a finished attic. What I'm required to do by my inspector is to not violate the soffit-to-ridge airspace beneath the roof sheathing. So, for cells/RFBI combos, do you see advantages or disadvantages, and an overall preference for either of the following (or do you have other recommendations?:From living space to shingles:1)gypsum board, strapping/furring strips, RFBI, DP cells, vent chute ("perforated" chute, not air-tight).2)gypsum board, strapping/furring (or build-down)to hold gyp from rafters, dp cells, RFBI friction fit between rafters, held off sheathing to form chutes.Option #1 would result in the RFBI acting as an air barrier in front of the DP cells. While this would prevent the cells from picking up moisture coming through the gypboard, it would also limit the cells diffusing moisture (terminology?) back into the living space, if req'd. Though, with this setup, theoretically (bad, bad word) the only moisture entering the cells would be that coming from the soffit-ridge vent channel. Once again, the chute would be strong enough so the cells could be DP. Also, with the bottom of the roof sheathing being "hot", it should be encourage cells drying, with them giving up moisture into the vent...Yea? Nay?In the second option, some moisture could certainly pass through the painted gyp board and enter the DP cells. With the air-tight foam board acting as the chute, it would not be able to pass through the cells and exit via the vent chute. Based on the holding capacity of cells, it seems that the cells should be able to hold the moisture until drier times, when it would send the moisture back through the drywall and into the living space. Having a thick and dense enough layer of cells should ensure that the moisture does not approach condensation within the cells.Any preference for foam types and thicknesses of foam layers?Steve mentioned difficulty in rocking over foam. Have you found that to be a factor as well?Climate-wise, I'm in CT.With regards to barriers used with cells...I've read many posts where several have mentioned not to use poly between gypsum and cells, yet have recommended elsewhere using foam board between the gyp and the cells. Do you object to an air barrier, or is that because the integrity of the poly is easily compromised and thus fails as an air barrier, allowing moisture-laden air into the cells via convective air currents, but restricting cells drying by limiting diffusion (or was it adsorption, I think Steve wrote?) back through the gypsum and into the living space?thanks to all...
*So Fred -- if the cellar is the root of all evil (ha-ha, get it?), does that mean I won't have to weatherize my kid's new tree house? (He's almost 4 now, we figure it's time for him to start sleeping outside.)P.S. I'm working on a friend's townhouse basement and offhandedly solved their heat pump problem. The upstairs has 3 br's with registers, plus a central return in the hall. Doors not undercut. At night, with the kids' doors shut and the grown-ups door open, the kids freeze and the parents roast. Worse, the thermostat is downstairs.I suggested they leave all the doors open. Now they think -I'm- smart. Don't worry, I referred them to your site for proper credit. I now propose they try the high-low return duct through the BR stud bays, which I think was your idea too. Oh, and their air is terribly dry, despite the humidifier... There's this loose attic hatch, you see... And I had earlier mentioned to them all the cold air squirting into the basement at every crack and penetration gave me a sense of foreboding... plus the dirty fg chunks stuck uselessly against the band joist...Thanks for help with connect-the-dots. Wish cel blowers were more affordable or accessible.
*Fred, I realize that these repeated discussions can get tedious at times, so I truly appreciate you taking time to respond to my specific Q's.Thanks much, Mongo
*P.S. My comments were brought mind reading your response, not by the topic of conversation. I doubt you get enough thanks for your efforts here, pounding on our thick skulls. I am fascinated with thinking of the house as a a system, as opposed to the blindered view of "that roof problem" or "that dry air" or "that darn dry rot."And thanks for putting up with Mongo, too. ;-)
*MongoI've installed d/wall over RFBI often, and don't find it unpleasant at all!! On slope ceilings I use a combo of adhesive and screws. (Some may recall my post last winter looking for 3.5" d/wall screws . . . turns out they were readily available to me.) While it's easier with a crew, I've installed up to 4'x9' sheets of 1/2" d/wall directly over 2" RFBI on a 6/12 slope by myself. .. starting at the bottom and using a few judiciously placed swivelling cleats (and no I'm not Hercules). The end result is a very smooth looking d/wall job. I also caulk the ship-lapped RFBI joints with acoustical caulking. Because of availabilty I use Dow Styrofoam (blue) R5/". They keep changing the name, from i Styrofoam SMto i Styrospan,to whatever this week. Owens-Corning are now promoting a competitve product in designer Pink.I always find it handy to make a quick framing map of each wall/ceiling for future reference for both me and the customer. Especially if there is any oddball framing as is usually the case in older buildings.-pm
*Donkey shane, Paddy.
*I finally took the time to read thru this entire thread.Having a few resident experts on board, I thought I would expand my horizons.I was taught and followed the Pro-Vent school of thought.Luckily for me, I have a background in H.S. and college Physical Science, Physics and a degree in Flight Technology which covered meteorlogy and flight physics.All of these covered in depth the studies of air/moisture movement.I want to thank Ralph Wickland for saving me the trouble of a longer post to explain scientifically and factually what our resident "Non-Vent" experts were unable to explain. I don't claim to be an expert with years of experience to go on, but I'm still gonna vent.Soffit and Ridge.On a hip, you can drill holes and use a roll type.On a ridge, I prefer an interlocking type w/baffles.Does this make me right?Not necessarily so, but no more wrong that someone that thinks a drop of water into the ocean is the same as moisture movement in a enclosed structure.Why not talk about surface tension while you're at it? But the way, I do remodeling and work mostly on older(35 to 100yrs old) homes.What should I do with the built up moisture in the attics if I don't vent at the top.And am I to believe that a system of soffit vents, ridge vent, and properly installed insulation with baffles and non-compressed fiberglass insulation will suck exhaust fumes thru the house.If the gas appliances or flue is back drafting, fix that ventalation problem! Next time a plumbing vent is tied to the main stack improperly, I'll throw a tarp over the ridge vent...in theory that will help.Jeff
*>>What should I do with the built up moisture in the attics if I don't vent at the top.<<Jeff,For starters you might want to reduce the supply of moisture to the attic. Then vent to your heart's content. I'm not anti-vent. But realize it treats a symptom (and not very effectively), not a cause. As Joe just said elswhere, you should try to fix the underlying structure above all.Steve
*Steve, thanks for the reply.As one who is on the outskirts of the pro/con vent debate, a direct answer to a direct question is what I was looking for.Not a round-a-bout answer that states opinion over fact.My problem is that the roofing I do is on a limited basis, either tying into an existing structure or a reroof for a previous client.I'm always looking for the latest info on all methods of construction, but if the whole house is leaking moisture into the attic I have to deal with it.The roofing jobs I've run into haven't been large enough to warrent the customer tearing off the whloe thing and starting from scratch.Jeff
*Jeff, you may have missed the no-vent thrust -- it is not against vents themselves, but against using vents as a way to deal with moisture problems. It does not say "skip the vents and turn a blind eye to the moisture problem."It is argued that vents often won't do the job, that they introduce their own problems, and anyway that air-sealing the attic will provide benefits beyond moisture control -- energy efficiency, interior humidity, occupant comfort, even heating of the dwelling, etc. Tearing off the roof and starting from scratch just wouldn't seem necessary -- it's the attic floor and NOT the roof that's doing the job in most cases.I'm not sure how you can accept the no-vent arguments and then rely on vents anyway. The bang for the buck from air-sealing is considerably higher than from vents, and if you do a proper job the vents are unnecessary. It does take a leap of faith to leave vents out when everyone else has them, true!
*So how exactly do you completely seal the attic floor.I'm going on the assumption that it can't be done effectively.(Note to everyone else, we're not in third grade so the term "assumption" stays!)If I add an addition to the back of a house that is aprox. 1/2 to 2/3 of the size of the back wall(existing), I still have 1/2 to 1/3 of the original wall and ceiling space feeding into the attic.That's what I meant about tearing off the whole thing.I can't propose to tear down all the existing ceilings to poly and foam it off.And that just takes care of the back of the house.What about the entire front half(assume gable) that is to be undisturbed? All that ceiling space is still connected to 75year old house that leaks.Now, w/o venting, what to do? I thought venting was to help keep the fiberglass from getting soaked and dissapating some heat.It also helps dry the sheathing.In the soffit and out the ridge.The theory works for me.Easier than trying to sell tearing down all the ceilings and seal the top.Is that basically the no-vent approach?Given that choice , I root for vents. I've also seen roofs fail...framing/sheathing/shingles...where on a cool day I cut into and pulled back the shingles/felt and had steam and heat comming off the moldy rotted sheathing.No vents. In those cases( one over an enclosed room and one over a porch w/finished ceiling) a nice stream of fresh air under the sheathing would have cured it.I'm still open minded...to facts/not conjecture...help me see the no-vent light. Keep in mind, S.W Penna(which is N.E.)and no total new const. Thanks, Jeff
*Hi Jeff,Sounds to me like your type of work is very similar to mine. I don't want to have to rip everything open if I don't have to either, because I'm intensely committed to the restoration and preservation of old houses, and I like to keep as much of the original fabric of the house as is practical. Reading your reply to Andrew has prompted me to talk with you some more.You want to know how to go about choking off the flow of moisture to the attic without ripping open all the walls and ceilings. How you proceed in an old balloon-framed house just depends on what you have access to. A recent house I did was pretty straightforward. It was a thirty-by-thirty square house with unoccupied attic space that was supposedly outside the thermal envelope. But there were all kinds of big holes into the attic through which heat and moisture travelled. The biggest offenders were the balloon-framed exterior walls with top plates that were above the level of the attic floor. I started by pulling up all the old fiberglass, stuffing it into plastic bags and plugging the tops of each exterior wall bay with one of those plastic bags. This was not possible on two of the four walls, as the ceiling joists on those two walls blocked acess to the tops of the bays, which were dumping into the soffit. I foamed the crack between the ceiling joist and the top plate to keep the heat and moisture out of the attic at least, and left those bays alone for now. They are still leaking major heat to the out-of-doors, but not to the attic. I'll get them this summer by removing a row of clapboards at the top of the wall and stuffing them from the outside, then replacing the clapboards. Then I plugged the interior partitions that had no top plates on them. Then I foamed all the cracks around any partitions with top plates, foamed all electrical penetrations, and foamed any other hole I could see. Then I made a metal gasket around a chimney to seal an interior chimney chase that was about 8 square feet. Then I blew in about 18 inches of cellulose. I could have densepacked the walls too, but they already had FG in them and that makes it harder, and has less payback. Just corking the tops of the walls goes a long way in terms of both heat and moisture migration. This attic is still vented. I see no need to plug the vents, as they are doing no harm and may being doing some good.That is the hard way. It's easier to densepack everything, and it gives a more foolproof seal. If the attic is inside the thermal envolope, I would drill 4" holes in each rafter framing bay and densepack cellulose to about 3.5-4 lbs per cubic foot. This completely seals the roof. No air movement through it, no moisture problem. No vent needed. No need to tear up the whole house. Same can be done for walls, but the payback is much higher for the roof plane.If the attic is outside the thermal envelope but they want to be able to use it for storage, etc., I would build a floor structure and blow dense-packed cells into the attic floor.You cannot do this unless the production of moisture within the house is under control. That means no wet basements and no dirt floors, not even dry ones, in cellars or crawlspaces unless you cover them with a vapor barrier. If you seal up a house that is pumping gallons of water a day into itself, you are asking for trouble.Hope this helps. Steve
*
I plan to add a mud-room to my house. It will be about 10'by 10'with a hip roof (4.5 to 12 slope)and 2" by 6" rafters and joists. I want to fill the attic space with insulation from ceiling to roof and use no venting. My question is....what precautions should I take? Is this called a hot roof?
*Mauri,
Joseph FuscoView Image© 1999"The first step towards vice is to shroud innocent actions in mystery, and whoever likes to conceal something sooner or later has reason to conceal it." Aristotle
*Does anyone know if Fine Homebuilding has ever covered this topic?....if so, in which issue?
*Mauri:There is a magazine index/search available from the main Fine Homebuilding page.As Joe said use the Breaktime search function to read 100s of posts relating to roof venting. Yours is a FAQ.
*Dear Mauri,You’ll content on this topic in FHb issues #105, #113, #125, and others. It’s state-of-the-art stuff.Regards, FredView Image
*Mauri,
Joseph FuscoView Image© 1999"The first step towards vice is to shroud innocent actions in mystery, and whoever likes to conceal something sooner or later has reason to conceal it." Aristotle
*
Joseph FuscoView Image© 1999"The first step towards vice is to shroud innocent actions in mystery, and whoever likes to conceal something sooner or later has reason to conceal it." Aristotle
*
Joseph FuscoView Image© 1999"It is better to be feared. . . Then loved!" Machiavelli
*Mauri,In the last 60 years, many studies have been set up to show that in a side-by-side comparison of venting and not venting, venting looks good. Many in the roofing industry who see vented and unvented roofs are also led to the conclusion that venting looks good. Many people conclude from this that not-venting is bad. Other people, including myself, challenge the logic of that conclusion. There are many instances of fine roof systems that don't use venting. Codes generally require venting. Many experts will advise you to vent. If you want to look at alternatives to venting, do your homework. Here's an article on some of the issues.www.fpl.fs.fed.us/documnts/pdf1999/tenwo99a.pdf.Good luck.
*Fred and Joe,Slam each other on your own time. The board is slow enough as it is.
*Mauri, et al. See Joe Lstiburek's article, "Unventing Attics in Cold Climates" published in the Nove/Dec 1999 issue of _Home_Energy_. Also check out the link suggested by BillR. GeneL.
*Wow Bill, that link is some food for thought.
*Wow, this movement is "heating up" in the trade press. Now all I need is a literate building inspector ... hmm.As for the thread netiquette, well, when an irresistable force meets an immovable object, head for the fallout shelter.
* Scott,
Joseph Fusco View Image "The price of apathy towards public affairs is to be ruled by evil men." -- Plato
* et al,
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
*Mauri,I agree with Fred on one point. It's probably dumb to make a federal case out of a 10x10 addition. But there are some things you should be aware of. Fred routinely and in an offhand manner suggests ignoring code requirements and mfrs. warranty requirements. Even to the point of deceit by installing fake vents to fool inspectors.You may convince your local inspecter to allow non- ventilation, but I have yet to see any mfr. lift this requirement. (some folks who post here say they have, but I haven't seen it first hand-there is even a clause in all the warranties that I have checked that states"NO PERSON IS AUTHORIZED TO ALTER THIS LIMITED WARRANTY EITHER ORALLY OR IN WRITING")So, if you have your eyes open, and understand the responsibility that you are assuming, and are convinced that you can seal off your attic space to perfection, then go for it. I have been in this business for 30 yrs. and have first hand experience to vouch for the effectivness of roof ventilation. I think that cartoon stick figures meant to insult speak to the character of the artist, and add nothing to the discussion. But I will defend the right for anyone to make an ass of themself on this board.John
*Andrew:I guess I read it a bit differently than you did, although I will admit I only read carefully the summary at the end. What I got out of it was that non vent is appropriate is some situations (cold wet coastal, or hot humid climates) and that in any case (vent/novent) other precautions such as preventing air leakage through the "lid" and indoor humidity control was as much if not more important than attic ventilation.Further I read that attic ventilation was recommend to augment the above "other precautions" in other than than damp climates. It was nice to read a credible document on the topic that appears to be based on research rather than just opinion.I printed it and will read it in full later.
*Hey, FredL and Joe Fusco have got me rolling on the floor laughing. I really enjoy listening to their dialogue, they sound like good friends who know each other's foibles and a stranger overhearing them in a bar might duck for fear of a fight breaking out...Of course, I could be wrong. But they both do raise points and they both do keep the talk lively, so I say, 'Let 'em at it'.
*
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
*Dear John,Would you care to put a present value price on a warranty for 5 bundles of shingles? You make such a big deal out of "NO PERSON IS AUTHORIZED...", I'd like to bring to light just what those threating words are worth to our Mauri.Look, he asked questions and I answered them in a direct, honest way. READ his questions. Just exact what did YOU add to the discussion other than to puff yourself up and put me down? Also on a personal note, when you say again and again "I've been in this business for 30 years...", it sounds a lot like "I've got nothin' left to learn in this business". You see, doing time doesn't equal knowing everything. You've missed a big opportunity to learn something very important to your business and it's too bad that my personality has been a problem there.Sorry you think I'm an ass, Fred
*Fred,
Joseph FuscoView Image© 1999"It is better to be feared. . . Then loved!" Machiavelli
*Fred,I stated that a 10x10 addition shouldn't be made into a federal case. But I'm sure its important to mauri. As for the "big deal" I simply quoted directly from the Elk shingle warranty. The caps are theirs not mine. Maybe you should ask Elk why it's a "big deal". Part of my business is doing warranty work (there I go puffing myself up again- apparently you want exclusive rights to that privilege). It sounds like you get involved in some pretty large roof projects. How do you handle the warranty issue? Do you have your customer sign a release freeing you of warranty responsibility? Or do you have enough clout to get the mfr. to give you special dispensation? Or are you sticking your own neck out if something goes wrong with the shingles? Don't tell me nothing goes wrong because your system is infallible. The potential for failure always exists, and someone is exposed to risk whether they want to hide their head in the sand or not. Manufacturer, contractor, or customer, when something goes wrong one of them will pay.You imply I didn't respond in a direct, honest way to the post. I believe in following code and warranty requirements. What is indirect or dishonest about that? You believe that mauri shouldn't be fully informed, I guess.You think I have a closed mind. Nothing could be further from the truth. If and when the codes and warranties change I won't oppose it. No vents makes my job easier. Just don't expect me to jump on your band wagon against vents. I don't think the answers are that black and white.By the way, I still learn something new every day. John
*That's a well-written post which, to me, presents your perspective quite nicely...Code has never, ever really been innovative in terms of changing building methods or practices. It does tend to lag a bit to changes in building methods that occur in the field. Innovators in construction practices are the ones that change code. Code changes then force the laggards to adopt the newer, supposedly better, methods.Changes in building envelopes (residential, at least) are on the way. As moisture control becomes something taken care of during the design stage of a house, instead of something addressed after problems arise within a few years of habitation, code changes or options, especially for new construction, will most likely follow.This is one area of construction, both in practice and in theory, that is, to me, "on the edge". It'll be interesting to see how it all pans out. I enjoy the debate (not the bickering, but the debate...actually, the bickering is humorous), and the exchange of ideas that is involved.Keep the exchange of ideas coming...
* Fred,
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
* Mongo,
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
*Joe,>>However, if there are strong reasons why effective attic vents are undesirable, unvented attics can perform well in cold and mixed climates if measures are taken to control indoor humidity, to minimize heat sources in the attic, and to minimize air leakage into the attic from below, or vice versa."<<This is the operative clause in Fred's (and my) point of view.Some reasons why vents may be undesirable could be:heat lossdepressurizationbackdraftingice damscondensationIf you completely disconnect the vented area from the rest of the house with a perfect air seal, then some of these problems become minimized. The ASHRE paper recognizes the difficulty in attaining a perfect air seal, particularly if there is a substantial pressure differential accross the ceiling plane (which the attic vents contribute to). Since attaining a good air seal, minimizing excessive household humidity, and minimizing heat leakage into the attic are all good building practice anyway, and if addressed, pretty much eliminate moisture and ice-dam problems, the sole rationale left becomes the issue of shingle life, which is a marginal issue at best.Anyway, Fred doesn't advocate a monolithic approach. He advocates a system-wide evaluation of the entire house, something that is sorely lacking in most tradesmen's approach.Personalities aside, you are foolish to dismiss what he has to say.Maybe you should come and build in the north country for a while and find out just how ineffective Poly-batt-venting can be. Northern New Jersey is not a demanding test of that marginal system. It works for you where you are largely because it is not very heavily taxed in New Jersey's mild winter months. As you so aptly point out, a monolithic approach is for people with limited capabilities.Maybe you should broaden your perspective a bit. Or don't.I don't care. But you should.Steve
* Steve,
Joseph Fusco View Image "The price of apathy towards public affairs is to be ruled by evil men." -- Plato
When looking for info concerning placement of vaporbarriers in a hot moist southern climate and the judicious use of the word 'always' I came across this thread.
Not having been a Breaktimer at that time, I pretty much missed the bulk of the monumentous vent wars lore. I take it this thread was a part of that era.
After seeing various present time venting comments here and there and then this old thread, it got me to wondering if during the last 5 years a common basis of understanding has developed to the point where there is an agreement among all parties over any certain facts concerning the correct application of venting or not?
not meaning to be-come a troll
Rez-
Venting is a load of dog poop in most circumstances. Just yesterday I had 2250 sq ft of roof deck sprayed unvented. Had to jump through hoops to get the officials to sign off, but they did and it's done (inspection tomorrow).
As it turns out I had to get an engineer to design the roof assembly and write a signed letter. Basically he designed a system that "dries to the inside". Since I have asphault shingles, apparently vapor is driven into the shingles so I used a vapor permeable foam that allows that moisture to escape to the inside.
My foamer told me that Elk roofing has discovered that their shingles actually last longer on unvented foamed roofs. Apparently the thermal mass of the foam keeps the shingles from rapidly expanding/contracting during fast weather changes (100 degrees, sunny to being rained on in 15 minutes....etc.). Don't know if it's true or not.
At any rate, it's just another one of those things that building industry can't give up because it defies "what daddy taught me". To answer your question though, I don't think any common approach has surfaced.
MERC.
Seems like a lot of varibles involved as in depending on if new construction or style and shape of building in a renovation.
You going to put your location in yer profile? bwaa!
be a pain