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Recently our home was rebuilt. It seems the contractors did not quite know what they were doing. Exterior walls in our new bathroom seem to be ducts for cold air flow. We have a cathedral ceiling with a ridge vent on the top of the roof. How does this system properly work? I have been on the roof and it seems the ridge vent is allowing room temperature air out. There are no vents in the sofit. Is this right?
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Replies
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I'm looking for a way to provide a clear airflow channel to vent the individual bays of a cathedral ceiling from the soffit vents to the ridge vent. We will pack the 2x8 rafter bays with F/g insulation, and want to keep a 1.5 in. clear air space to allow ventilation. Does anyone make a product that mounts on the underside of the sheathing to do this? Thanks.
Larry
*Larry the home depots and other building supply stores carry a styrofoam form that fits inside most cavities that you describe and has a bend in it to channel air between the insulation and the roof layer so that the flow from the soffit to the ridge is clear.
*Thanks Gabe I'll check with them. Have you (or anyone else) used a product called "Raft-R-Mate" from Owens Corning? It appears to be designed for this application, but would be curious if it really works well and if its cost effective.Larry
*Larry. Who is going to install the fiberglass in the 2x8 raftyer bays? If professionals are coming inot to insulate the bays after the propervent --polystyrene air chute--is installed they could well crush the vent flat againt the roof sheathing underside.I'd think carefully before running those air chutes from soffit to ridge vent The underside of the roof sheathing is normally the coldest surface and is called the first condensing surface. When you install the air chutes the first condensing surface now become the air chute.Warm air eascaping through the fiberglass insulations condesnse on the surface of the air chute.The condesnsed moisture will eventually find its way to the ceilig below.er We've had lots of reports of this happening. reports of this happening. Remember that the air chute will reduce the depth of the 2x8 cavity by 1 or 2-inches leaving a vcavity of possibly 5-1/4 inches, giving you an R-21 fiberglass batt if you use high density batts. Isn't this a step backward? GeneL.
*Yes Larry, Raft-R-Mate works as well as any of the very similar products designed for that purpose.Make sure that styrofoam baffles are fitted neatly to the underside of the deck and the butts are tight.Install your insulation as neat as posible and cover the ceiling with poly before installing your drywall or wood ceiling material. If you use drywall, you should strap the ceiling with 1x3 at 16" intervals for a better installation.Not having proper ventilation would void your shingle warrantees.
*Gabe,If you insulate then strap for drywall, won't you be creating a space between the FG and the drywall? I've read over and over that for FG to work well it has to be in firm contact with the warm side of the cavity. Is this a misconception?Steve
*Steve, the strapping is running across your ceiling to help maintain the integrity of the roof joists and the drywall. If you ever looked carefully at a ceiling that has drywall attached directly to it without strapping, you will see a bowing between joists. The gentle weight of the insulation will push down on the drywall, giving this effect.The installation of strapping does not adversely effect the effectiveness of the insulation. Whatever little bit is not touching wouldn't amount to a fart in a hurricane.
*Gene,Critiques without solutions are more than useless....Would you post your methods and solutions...J
*Gabe,It's getting very hard to get any direction at all from these boards because there is so much contradictory information flying around. I've read over and over in other threads that successful installation of FG is highly dependent on the FG maintaing firm contact with the warm side of the cavity. What's a person to believe?I strap in retrofits on restoration work because the ceiling joists run so wildly different from joist to joist. In new construction I've never seen bowing from the weight of the FG. Not on 16" centers anyway.Steve
*Steve your right about all the different directions on this subject.The US department of Energy and the Energy Efficiency and Renewable Energy Network have good information, but some of it is tempered with a little industry hype.What I have found in 35 years of construction is that there is no one thing that will give you a perfect house. We build the best we can with the resources that we have available to us today.What I find most disturbing in reading some of the advice in these postings is the total lack of concern by some giving advise to people who may not be as experienced as others.These people will take one small piece of the puzzle and run with it. Not knowing that the one piece will do damage if not used in conjunction with another vital piece of information.With regards to proper insulation, my personal belief is that a combination of celulose and FG in flat ceilings with FG in the walls. The perimeter of the house should be properly vented into the attic and a proper ridge vent should also be continuous.The exterior walls should be sheated with 1/2 plywood and covered immediately with Tyvek, mostly for the protection of the sheating.The interior of the outside walls should properly insulated with FG friction fit, all wall recepticles should be poly wrapped from behind and with enough overlap to be taped effectively with the main poly on the walls. This goes a long way to ensure a reasonable envelope is maintained. Deletion of the poly layer on the inside of a house in our climate would be ridiculous. One of the biggest headaches in housing today is the proliferation of huge houses with incredibly complex intersecting roof lines. Most of which is wasted space and a nightmare to ventilate. They form pockets of dead air and cause more damage than people realize.Poor insulation will cost you to have a higher than acceptable heating bill, poor ventilation will cause your house structural damage and that cost more.
*Steve - there was an article in Home Energy last month that had the test information showing that the gaps created by the strapping will significantly reduce the insulations effectivness.
*Hi Bill,Thanks for the confirmation.Hi Gabe,Thanks for your insights. Yes, I do believe that a little information is a dangerous thing. I'm glad I've had quite a while to mine everybody here for information in bits and pieces over quite a long period of time to try and build a bigger picture of the various schools of thought that are out there.'So I take it you are not convinced that a dense-packed cellulose cavity with no vapor barrier is a a good solution to those complex rooflines. It seems to me that if the DensePack prescription performs as advertised, it is the perfect solution to complex, unventable dead-end roof framing. I can see where it might cause intallation headaches and inspection arguments, but I don't see any falacy in the actual performance of the system. It makes sense to me.Just because the industry has to date failed to adopt its use on a widespread basis doesn't mean it has no merit, does it? It seems to me that those who are using it are having good results.What do you think? Also, do you have anything to verify that the space between the ceiling and the FG won't effect the insulation's effectiveness?Steve
*Bill, did those same test reveal what happens to the roof's joists or rafters if they are not properly secured? Did they indicate that drywall is not sufficient in strength to secure anything but itself?Did they indicate what happens to a roof structure after a 2 foot snow fall?
*Steve I'm quiet willing to accept the fact that there's a tradeoff when you strap a ceiling.I don't strap a ceiling when I install planking instead of drywall.Do understand that the industry is relunctant to give "carte blanche" to any contraversial methods. It has had too much history of failed applications in the past.We all have to be on guard.If you read all of the claims made by product innovators, it will start to look like the snake oil double talk used by travelling salesmen of long ago.Everyone of them fails to address the big picture. It's very much like an argument between a dedicated general family practitioner and a brilliant specialist. One looks at the whole person and the other only focuses on the single organ.The operation was a success but the patient died.
*Gabe,I agree with you about the snake-oil vendors inherent in this business. It's so product driven I don't trust any manufacturer. I don't trust trusses, I don't trust engineered wood, I don't trust adhesives, and I don't trust plastic, among other things.I think folks like Fred and Gene do care very much about the big picture, as I'm sure you do. I don't think they are manufacturer's shills, just very much convinced that their understanding of the big picture is rational.What precisely about the DP Cells approach is it that gives you such pause? To me it just seems like another perfectly viable solution, and one that is simple and not prone to degradation at the hands of homeowner abuse down the line. When you build a house that is dependent on the thermal envelope never being punctured by later remodels, etc. it seems to me you are courting trouble. What happens when Uncle Vinny who is ever so handy with a sawzall says he'll be happy to come over and install some recessed lights in the bathroom ceiling for you? Or a ceiling fan in the bedroom.Steve
*Steve, right at the moment, it's the part about packing and not allowing proper ventilation in the ceiling joists. Do you know what happens inside an attic of a conventional house in the summertime? Do you beleive that an attic in Louisiana, or Alaska, or North Dakota, or Prince Edward Island, or Florida, or Arizona, all have the same temperature changes, seasonal changes,or humidity levels?What happens to the inside temperature when you replace black shingles with white shingles? Did you know that in our eastern provinces, they don't install white shingles because the sun can't heat them enough to seal them on their own without adding tar to every one.There is an incredible number of little things that greatly affect the temperature inside an enclosed space.It's not the product that I'm challenging, it's the cure all propaganda that is attached to it.In contruction there will always be tradeoffs. Good insulation practises MUST be tempered with good ventilation practises.
*Gene,The insulation contractor will be installing the F/g, I'm not sure who will be installing the venting subsystem, probably the GC?? In your scenario above, if warm air is leaking into the bays, won't I have a problem whether it condenses on the air chute or whether it condenses on the roof sheathing? Either way I have moisture in the bays, or am I misinterpreting what you are saying?I agree that with the channel I have to go with thinner batts, which will cut down on the R value. In our climate (SF Bay Area), I am more worried about venting to reduce heat buildup under the roof surface in the summer, our winters are mild. Am I looking at the issue correctly?Larry
*For what it's worth I'm with steve on this. If you insist on furring, then skip the poly and install foil faced rigid between the strapping and tape over the joints and the strapping to make a vapor barrier.Use resilient furring strips to help with sound.-Rob
*Gabe,It seems to me that one of the plusses of packing the cavity into a solid organic mass is that you've reduced the media across which the temperature differential must be handled to an impermeable solid as far as air is concerned. Isn't it the air moving through the cavity that causes all the moisture problems?A vaulted ceiling with the DP in the rafter bays seems to me to be a good solution in any climate.Turn your roof into a huge slab of dimensional lumber which just happens to have extremely large, low-density (3.5 lbs/cf) growth rings, and yields an acceptable r-value per inch. Even with conventional houses with moisture problems, the dimensional lumber isn't rotting from within. It rots from the outside in due to condensation on the surface of the members.If there are no surfaces within the wall or roof for moisture to condense on it seems to me you've solved most of the problem. Not all of it of course, but it's a good subset of the overall system.Consider the log house. It's an extremely dense-packed cellulose wall, no?. I don't think there is any condensation going on inside the logs of a log cabin in any climate (I'm guessing). If a DP cells wall or roof becomes a solid organic mass, then there is no place for condensation to occur. It seems to me it would take very continuous, very high humidity levels to bring the humidity within the DP wall or roof to a level where it would cause problems. If such conditions were to exist, they would also cause problems in a permeable, stratified cavity that no amount of ventilation would solve.I think I would still vent an attic that had the thermal envelope on the attic floor, in in the event that there were punctures or breaches of the envelope that allowed moist air into the attic space, but I wouldn't be worried about the actual dense-packed cavities themselves. They would be behaving like dimensional lumber as far as moisture migration through them is concerned. That's my perception of DP. Perhaps it's wrong. I would love data either supporting or denying that perception. I haven't heard any horror stories of people ripping open cellulose walls to find rampant rot, and I have heard such stories about conventional stratified cavity walls. I'm enjoying discussing this with you, and hope you are too.Steve
*Steve, Your point is well taken. Strapping or furring of ceilings is a common practice on east coast especially in New England.But not in the rest of the country.When was the last time you saw anyone shimming the strapping for a level ceiling? Gabe. How does the gentle weight of the fiberglass above the strapping push down on the gypsum board? You say," The installation of strapping does not adversely effect the effectiveness of the insulation. Whatever little bit is not touching wouldn't amount to a fart in a hurricane." Remember the little fly landing on the 45,000 pound aircraft carrier moves it. Au contraire. The strapping is usually installed Before the insulation is in. Are the framers coming back to install the strapping after the insulation is up? Not likely. There are exceptions of course. If the fiberglass batts(installed after the strapping is attached)are Kraft faced you have a disaster in the making, a fire hazard and a code violation (three model codes). Again,depressed insulation can and does have a considerable effect on the performance of fiberglass batts.One study reported in ASTM STP 789 showed a 34 percent reduction in R-value resulting from edge compression of the insulation. GeneL.
*Gene take your last sentence in paragraph 3 to answer your question in paragraph 2.Insulation is installed first, followed by the poly and then the strapping is installed last. Not every in North American has read you book so you have to appreciate that regional differences exist. My method is code in Canada and was developed with consultations between US and Canadian national housing authorities.We do not and I repeat, do not install strapping to level out or shim a ceiling, we do it for structural integrity.There was no mention of compressing the insulation, he already acknowledged that he was using a thinner insulation in the ceiling cavity.
*Steve in order to discuss the matter properly, ya gotta answer the questions before heading off into the wild blue yonder.Go back to my post and answer the questions as I put them so that I can go to the next level of explaining my thoughts to you.If we stay on track, we will come to some type of understanding.
*Gabe - I am a know nothing for sure, but I don't recall seeing your name here before. This topic was taken up this long road before. The result - Gene and Fred littered the place with facts, experience, studies, and pictures that to me at least has me convinced that fg and vents are not the way to go in the north. The fg people always stuck to generalizations and unsubstantiated theory and used absolutes alot like "always" and "never" which, to a scientist anyways, discredits the whole statement. I encourage you to continue but you will truly be one of the only people on your side. Except for maybe "him."I guess I have to believe Fred when he says he guarantees no venting with his own money, no one selling vents will do that. Paraphrased, but in my experience true so far.On Southern roofs:Wasn't it about two years ago that a study was release by ASHRAE or NAHB that said venting in the south is no longer a good idea.1 - roof temps didn't change much2 - Vents provided a continuous supply of hot, moist air to saturate the raftersI seem to recall that the moisture level in unvented southern attics was found to drop off dramatically after it's initial high value at the time of construction. Seems the demon heat dried it out! Of course I can't find the srticle and am thus reduced tobeing a talking head.I vote with Fred and Gene on this one. Good air barrier, no vapor barrier needed, no condensing surface.
*Hi Gabe,1) it gets hot (what is your definition of comventional?)2) no3) it decreases4) Now I doNow what?Steve
*Way to go Steve.So do we agree that there is an incredible difference between the energy requirements of housing throughout North America and what works in one part may not work in another?(source: US Dept. of Energy is conducting these housing energy efficiency trials in all zones because they recognize the variations.)
*Gabe,Re: the energy requirements, absolutely. As to prescriptions that can handle varying conditions with equal aplomb, I'ld have consider each on a case by case basis. Not a big fan of the universal building code idea. Not a big fan of codes at all. Flaming libertarian, truth be told.Steve
*Next phase Steve, In a cathedral ceiling, using the cellulose packing, stem to stern. Roofing, sheating, cellulose, drywall or whatever. Packed joist to joist, no air, right.Is this what we're examining?PS Did you get the picture that I emailed you?
*Throw in my undervalued vote to(o)!!!!No more fiberglass for this DP cowboy.J
*Get with the program Rob,Surely, if these experts of yours are so good then why do they need a flock of sheep to defend them? Is it because they figure the wolves will get the sheep first and forget about them?
*Dear FredIf your going to try to shoot this fish, try answering the questions in sequence first.1. What part of "We don't use strapping to shim and level, we use them to tie up and secure the ceiling joists" don't you understand?2. Explain where in the hell you got the data that by installing this 1x3 strapping, every 16" would reduce the thermal resistance of R32 FG by half down to R16 when less than 2% of the entire surface would be elevated off the drywall.3. Even without the insulation, something, I believe it's called gravity, will cause the drywall to sag between the joists. Most Joists are installed at 24" around here and if you were to paint the ceiling with high gloss paint and check it out at night with a halogen spot light, you will see something that resembles the hills of Vermont.If you don't look to see, you will never see when you look.See if you can address these questions and comments without your usual.....
*Dear Fred,Stop running away and answer the questions in my last response to you.
*Just trying to give some advice is all.I am with the program.These experts have given me (us) information, refernces, and sources of their beliefs. All any of the fiberglass proponents have ever said is you always need a vapor barrier and you always need vents. No fg proponent has ever listed studies and facts to prove their opinions. I wonder if it isn't a forest from the trees thing - you know. If the glass always needs a vent, then why would that equate to all others needing a vent? Perhaps it is required with the fg system ONLY. Three ideas came to mind on the drive home yesterday:The first "It's not better, just more popular" was a line from a friend Joe Rainville about the small block chevy engine. 60 million or so made to date, with some of the poorest design features of any engine (next to the ford windsor series). Because fg enjoys wide implementation is it better? What are the criteria. As an engineer my only concern is for performance.The second is that because something works does not mean it's right. I routinely fix the belt on the answering machine with an o-ring. the sound goofs a little but it works. Is the vent "right" or does it just work?The third - vents are fixing the symptom, not the problem. The symptom is the roof deck heating up, the problem is that hot air left the house to do it - period. Fg does not stop convection, it seems obvious to me. fg is not a solid mass - it's a loose group of fibers. dp packs into a solid cellular mass.I wonder if the cotton batt insulation made from old blue jeans works well - it seems like it should.Questioning from a philosophical, scientific, point of view.Was I a sheep at all here?-Rob
*Rob,I've got three expert running away from my questions as it is, I don't have time to waste having to start all over with another.
*Rob, I had no business making this assumption as to your intent and I wish to retract my comment.You state that you are an engineer so I will forward you, via E-mail a photo for you to review, and then I will discuss it with you on this format.
*My intent is discussion - free exchange of ideas, facts, etc.Okay, I looked your picture over. I have a few questions.What was the insulation?How were the planks sealed against each other?Where did all the moisrue come from, and where did it go? I ask this because the wood appears dry. You named the picture "dryrot" and that was my interpretation as well. My understanding of dryrot is that it is due to fibers breaking down from repeated swelling and shrinking from grodd FLUCTUATIONS in moisture level. I don't think this wall was "sealed."Regular rot is a result of continuous humidity and plenty of air to support biological activity. I wish I had pictures from my last job. It was an excavation next to a 18' high cast in place concrete foundation wall with the wood forms still in place. The pictures showed the top of the forms completely gonerotted down to about six feet below grade. The bottom of the forms were black and soaking wet, upon cutting a 2 x 4 apart the interior wood was still yellow. There was not enough air there to support rot. My point, I guess, is that I think the picture you have is a dryrot situation where the moisture fluctuated alot. From the picture I am guessing this was eye level. What were the conditions at the bottom of the wall? What are you hoping to prove to me?-Rob
*RobThe wall was sealed exterior and interior, my finger is pointing to poly layer that was cut back for photo. There was no insulation, it was solid wood. It was eye level. Damage was caused by trapped moisture inside the wood itself and the daily severe changes in temperature, during the summer, not winter, was the cause of the fluctuations.Point is, if you don't allow wood to breath with the changes in temperature experienced in some parts of the country, what you see in that photo, will be exactly what you will see in homes that are sealed off. The only difference will be that this time the damage will be in the structural parts of the house.A house is not a laboratory experiment. It's somebody's home. If you don't know the long term effects of what you do, you don't do it to other people's homes.Go back on your own experiences as an engineer, and tell me how many times did you find something that went terribly wrong (without logic), when you had done it a hundred times before and all was well.If that building that I photographed during a technical audit, had been rotated 10 degrees, there would not have been any damage, whatsoever.
*FredLet me guess, you swallowed a dictionary and it choked off the blood flow to your brain.Ya can fool the amateurs, but you can't fool the big boys, you're nuts.You couldn't run a project without at least 5 attempts on your life.You've never answered a straight question with a straight answer, because you can't. You don't actually know anything about real construction, do you?Your men aren't laughing because their having fun at your site, their laughing at you and your theories or should I say stories.
*Gabe,I haven't had a chance to chime in about the photo you sent me. It sounds like the same one you and Rob are discussing.This looks like it's a corner to me. Is it? What was the inside and outside surfaces of the wall? Was the poly part of the wall sandwich? Can you describe the construction of the wall, material by material, inside to outside? was is upstairs or downstairs? What was the cellar of the building? Dirt floor? Concrete? Dry or wet? What was the attic plane like? Sealed or full of holes? Any attic insulation, and what if any?Steve
*Steve,1 It's an outside corner. 2 From the outside in, steel siding, painted 1/2 plywood,(caulked and taped, 2x10, 2x10, (staggered joints) poly, 1/2 plywood caulked and painted.3 1st level4 no cellar5 crushed stone, 5 feet thick with a drain tile in the bottom, very dry.Last three questions not relevant to photo or audit.good luck
*Gabe,Yes. and Yes. See my post after your discussion with Rob about the picture.Steve
*Gabe,That's what I thought. What is different about the conditions for rotten wall on the left vs. the sound wall on the right? The last three questions are relevant to what may or may not be happening as far as moisture generation and the direction of the forces that are moving that moisture, therefore they are relevant to me.Steve
*Steve,Not relevant because there was no attic and no insulation, and no heat. Wall on right was identical to damaged wall, same material, same assembly, same age, 5 years. All assembled by same DIY.Your ball....
*Garbage in, garbage out.J
*I think it proved that metal is a damn good vapor barrier if nothing else.What were you trying to illustrate with this picture and how does it relate to venting a roof?I was thinking that if this wall was filled with cellulose it may have actually helped with the problem as you see it. Correct me if I am wrong but you belive that the moisture here was from initial moisture content of the framing? If that's the case then I supppose cellulose would have arguably had a desiccant effect in this cavity. If the cellulose is 6% moisture and the wood is 16% I would guess that the final moisture level would have been:Hypothetically 8' wall, 3 1/2" studs, 16" bays. 2# per stud. Based on 3.11 cubic feet of cels @ 3# per cubic foot that would be 9# of cellulose. So a weight averaged moisture level for the bay and two studs would be 9%. Is this low enough to prevent rot? I don't know, just an idea.What did the rest of the wall look like? My neighbors barn has a corner that looks just like this where an ell meets the main barn. The catch is that there is no poly, no interior sheathing, just exterior vertical T&G siding and -no- flashings. Lots of bulk water traverses that corner on rainy days.In conclusion I think you had a rot problem, and a conclusion, not necessarily related. I still don't know how this justifies fg and venting.I suspect if you keep up the personal attacks you'll be the lone voice left in this thread.-Rob
*As I understand it this wall had poly on both sides. If that's the case then this clearly illustrates the problem with two vapor barriers.The fact that the neighboring wall is ok with same techniques leads me to believe that this is an isolated problem, unrelated to the framing/sheathing system. How well flashed are these corners. I think the fact that the remaining framing is OK illustrates that this is anecdotal data for your conclusion at best. If your conclusion were water infiltration, then I think it would be dead on. How well are these corners flashed.-Rob
*Rob,I'll wait for Steve's comments before I give you "the rest of the story". To clear up any confusion, there was on room for insulation in this wall, as I indicated in my post, it was solid wood.
*Gabe,If you ask me this wall was a recipe for rot. It's a good example of why you should not trap the interior of the wall between layers of plastic and other moisture impermeable layers like steel and painted, taped and caulked plywood. However the moisture got in, (I would guess from some exterior leakage due to bad corner detailing, judging from the localized aspect of it) it had no chance to dry out, sandwiched as it is between all those impermeable layers. Seems to me to be a good example of why poly bagged construction practice is not good. When things do get wet, they need a chance to dry out. When's the last time you put a wet sponge in a plastic bag and had it dry out on you?Steve
*Dear Rob & Steve.You both recognize the dangers of encapsulation of materials that contain moisture. You both recognize that lumber contains moisture.You're both intelligent enough to know that we can both accelerate or retard the effects of any natural process by good or bad construction methods.The picture, showed accellerated and severe damage to solid wood, that was only 5 years old at the time. The actual building was 120 ft by 100 ft. in size at the time of the photo. The exterior wall surface was 5,280 sq. ft. The damaged area was 6 sq. ft. and was confined to the north west corner of the building.The west side was fully exposed to the sun and the north side was fully protected and shaded.During the summer months, the metal siding's temperature difference between the two faces wasin excess of 30 degrees C. (Not unlike temperature differences found in most homes when comparing inside temperature and outside temperatures.)The top and bottom of the corner had a breach in the integrity of the seal(which allowed the wood to breath) and served to prevent the damage from extending any further than it did.Now picture if you will, a typical wall assembly section, at the top of the wall and in a corner.You have a standard wall with double 2x whatever plates, double 2x whatever studs in the corner, gable end 2x whatever stacked on top.I think you would both agree that in very few instances do we have a such a mass of lumber in one location, all nailed together and if you caulk as per the new guidelines, cover with any of a large variety of sidings (metal or panels that are coated) line the inside with drywall and painted surfaces (with is accepted as an air barrier and with the wrong paint also becomes a vapour barrier) and then you stuff the remaining gaps with cellulose and if that doesn't enough, lets close all the vents in the attic.You have just recreated the exact same scenario, that this DIY did in his building.And just as for 99% of the building in question, all was well for a while, but then things started to sour. If the addition would not have been required, the corner of the building would have collapsed within the 20 year period.As you have indicated, you are both aware of the problems associated with inspections of this system and I think, that you both can envision the pitfalls associated with DIYer's trying this on their own without prior experiences.And that gentlemen is why I say that before you preach to others what they should do, know absolutely what the results will be.I don't mind the expressions of opinions, what I'm against is the pressure tactics to influence people who are new to the industry, to try something that they are not trained to understand or able to appreciate the inherent dangers associated with sealing.
*Steve,Save me time by signing me with your posts...You go boy!JGlad to have another "sponge in a bagger" amongst us.
*Larry. You are correct the moisture will condense on the coldest surface whether it be the roof shething or the propervent.Excuse my sloppy way of trying to tell you to stay away from the vent chute.Fred as usual gives good advice. Even power venting an atic will have little or no effect on the house's air conditioning. Yes it does reduce the attic temperature by 20 or 30 degrtees but the overall effect on the air conditioning load is minor. All the studies in real attics on this question show that insulation is more effective and less costly way to reduce heat moving from the attic to the spaces below.Jack. I don't use fiberglass insulation--only cellulose in attics. And even if I use ridge/soffit vents I don't use air chutes. I run the sheathing up between the rafters to within two inches of the underside of the roof sheathing.This "baffle" keeps wind away from insulation, keeps insul;ation out of soffit vents, and directs air flow upward.Gabe. My intent with the strapping issue was to show that strapping can raise particular hell with insulation's effectiveness. You'll note that in my rewponse I said the strapping is "usually" installed Before the insulation is installed. Obviously this is not always the case. Some years ago I asked the Truss Plate Institute why one couild not use the strapping, so common in New England, as bracing for the btoom chords, rather than the methods they required. They said they would go along with it if someone would furnish the E and Fb of 1x3 strapping.I don't believe that information exists, at least it is not in nay books on wood structural properties that I have. The codes until recently did not require floor bridging unitl one exceeded the 50 lbs/ft square LL+DL or the joist depth was 14 inches or more deep. Given the the way floors are constructed why does the Canadian Building code require strapping...if you know? GeneL.
*Gene what's this I read in your advise to Jack, you build a baffle out of plywood, as opposed to using a prefab baffle to do exactly the same thing AND VENTILATE BETWEEN THE LAYER OF INSULATION AND THE ROOF MEMBRANE??????This kind of reversal in advise will kill Fred and Jack.
*"And even if I use ridge/soffit vents I don't use air chutes." Didn't sound like a ringing endorsement to me. Most people I spoke to about metal roofing insisted on an airspace because metal has a perm rate of zero. I am installing 1/2" sleepers under the ply per their recommendation, based on insulation retrofits. They felt that exfiltration through the roof would be minimal at worst, but being that metal won't let it out they recommended minimum airspace.-Rob
*Rob, if he builds a clear passage for air, from the soffit to the ridge vent, out of plywood with a clearance to the underside of the roof, then my friend, that's called a chute.You all spent 1,000's of words, beating your chest and inventing new words, to end up suggesting, what I said in my FIRST POST, to the question asked..
*Gabe,Your understanding of the most up to date and best weatherization methods and systems is housewrap over wood sheathing/r-19 fiberglass/poly/drywall and eave/ridgevent?....This technology has been the norm since 19___???No other possibly newer ideas, systems since the date above??Set me straight,J
*Sorry Jack, if I told you I'd have to shoot you afterwards. This is out of your league or level of comprehension.
*Gabe,I'm sure most people that log on and read these threads would be interested in what your best systems are...Don't you too?I wasn't asking for a silly answer but...J
*I'll repeat, "And even if I use ridge/soffit vents I don't use air chutes." Didn't sound like a ringing endorsement to me.The foam air chutes found in stores are hardly airtight. I like gene's idea because he constructs a sealed channel for the vented ir to travel in, which prevents many of the problems caused by wind blown anything and washing air through the fg.-Rob
*Rob stop looking down and look up...Neither the "chute" or the "sealed chambers" are there for the insulation's benefit. They are there for the roof membrane's benefit and it's components.Can you imagine what the temperature would be between a tin roof membrane and the top of the insulation if no air was allowed to flow over it?Get out of the forest, you've loss sight of the trees.
*Not going to get into any arguments with you Jack. You already made your position crystal clear when you thought I was a fish in a barrel ready to be shot by your friend, FredL. Now that you found out I'm a shark, you find yourself painted into a corner and you're looking towards me to open the window for you to crawl out of.Whenever somebody comes up with what they believe to to be a better mousetrap, the onus is on them to prove it to the market. Not for the market to defend the mousetraps that have been working for generations and continue to do so. If you were a "free thinking" I would enter into a dialogue with you on the subject, but I fear, you're just one of those people that actually thinks Alex Trebek knows all of the answers on Jeopardy....
*>>You have just recreated the exact same scenario, that this DIY did in his building.<<I don't think so, Gabe. I would leave out the poly and the steel siding. The critical factor that led to the demise of this corner, in my estimation, is that it was sealed on both sides with moisture impermeable layers. Water got in, but couldn't dry out.Had the poly (and the steel) not been there, the wall probably would have been able to dry out.This example only strengthens the case against poly on either side of the cavity in any temperature/humidity scenario. Sure poly, perfectly applied can prevent moisture migration into the cavity...for a while. But what happens when the flashing fails, or thehomeowner pokes all kinds of holes in the poly, and the wall loads up with moisture. Then it's wet and wrapped in plastic. A good formula for rot.One argument made by cells advocates is that packing the bays with cellulose doesn't "encapsulate" the moisture. It diffuses it under time of high moisture load, and allows it to dry under times of reduced moisture load.Plus it is more effective at preventing the moisture from getting in in the first place, as 95 percent of moisture infiltration is airborne, rather than through diffusion.In any event, cells or FG and Poly, neither scenario is vented. The cavity is still a six-sided closed box. Best to leave it permeable to diffusion so the wall can dry, no? Especially since diffusion is not the driving factor as far as wetting is concerned.What thinks you?Steve
*Gabe,This is no reversal for Gene. He has always maintained the ventilation, properly engineered can be benificial under certain circumstances. He also maintains that you can properly build so that you don't need ventilation. Lighten up.Gene,Would you choose to build your home-grown chute in this instance? Or do you think PAcking the bays with cells would do the job? When might you want to use such a chute?Steve
*No - they didn't address those things. I didn't see much connection between whether or not there is an air space bwteen the back of the drywall and the insulation and those other issues you mention. Seems that any number of approaches can eliminate the gap while still being more than adequate to handle those other design isses. I haven't seen the "drywall is not sufficient in strength to secure anything but itself" documented. Crawling around in attics like I do on occasion and having stepped on drywall, I'm usually amazed how strong it is. I just don't understand why strapping and batts are necessary - but I can see that they would result in a lot of heat getting into the space above the batts.
*Gabe,If you're not willing to discuss...then whatever, but there isn't a huge need to suggest to me that I need any escape path....I love weatherization and the possiblities of new methods and improvement in systems...And my all time hero is Joe L. If you ever have a chance to talk to him or attend at one of his speaking engagements, I'm sure you would at least like the man and his style if not the message...Joe has more "energy" than any one I have ever met...And I'm not any easy sell and question anything that comes my way, including from Fred L, Joe L, and of course your ideas,Gabe.I'll talk building systems with you any time but would rather not have you acting like a "shark" as you self-proclaimed...There is a much better side of you "lurking" somewhere...You know it and so do I.Lets be much more freindly yet disagree as often as we each feel the need...Sound like a good plan to you???J
*Gabe - who in this thread says "he builds a clear passage for air, from the soffit to the ridge vent, out of plywood with a clearance to the underside of the roof"? If you mean Gene's baffle, thats just a dam at the eve to contain the cellulose.
*He's alive and kicking!!!!Gabe,We are all individuals here....I agree with some of the others in b someinstances.I don't think anyone of us is dependent on the other in any way that calls for you to think that we are....The one thing it seems you're having trouble with is the rest of us "get along with each other most of the time...I think you could likewise without having to agree, just state your case, argue your points and leave the less acrimonious yak a little farther from the keyboard...Though it is fun to duke it out once in awhile...as long as it is keptb playful in intent!!!Trying to be your friend that thinks differently...b More alive than ever,J
*Gabe - could you explain what the specific benefits are in your statement "Neither the "chute" or the "sealed chambers" are there for the insulation's benefit. They are there for the roof membrane's benefit and it's components." Even the composition roofing manufacturers seem to have admitted that even a slight difference in reflectance is a much bigger factor in the life of the material than all the fresh air in the world on the underside of the deck.
*Bill,Thanks for clearing that up....I noticed the misread also but have been busy with brush fires...J
*"Neither the "chute" or the "sealed chambers" are there for the insulation's benefit. They are there for the roof membrane's benefit and it's components."Agreed - But conventional chutes allow and perhaps encourage airflow through the batt. So, using the sealed channels "protects" the roof and keeps the outdoor air from washing in and blowing snow on the top of the ceiling. I consider these to be smart vents, as opposed to easy vents. How well is a 12" chute working in a 16" bay - active area of 75%. Then there are those ribs and bumps in the styrofoam, this can't help convection.I have always thought, and studies here are starting to prove it (help me here fred and gene) that the heat buildup argument was crap - no kidding, at age 12 I asked why all the free convection on the outside wouldn't also cool the roof? And wouldn't it work better because that is the hot side. At the time I didn't know what free convection was. It seems that on a windy or brrezy day quite literally tons of air blows over the roof on the outside, and only a small amount goes through the vents.No we can argue attic temperature. The attic gets hot how? Because the sun heats it up. OK - nothing new there. Now there are two cases to discuss, finished and unfinished attics.Finished - if that much heat is getting in isn't that merely a symptom. The problem being conductive and radiative heat gain. The insulation (the primary means of defense) should address these issues. Radiated heat gets transferred whether there is wind or complete vacuum. The reynolds number of a small amount of air through any chute HAS to be lower than that for the free air blowing accross the roof. My point? Wind will pull more heat off the top of the roof due to great boundary conditions (especially with shingles) and even free convection will pull heat off. Laminar, stratified flow through any chute probably wouldn't be a drop in the bucket. (again - help me fred and gene, I need some facts) Conductive heat gain is adressed by not letting air circulate through the insulation.Unfinished - who cares how hot it gets! If there is a complete air seal in the ceiling then the hotter air will convect to the peak of the attic, on the inside the colder air will convect towards the floor. It seems plain old stratification will address the comfort issue. Again, the insulation should seek to block convection and radiation here as well. What is the autoignition temperature of wood? This is now the only concern with temperature in the unfinished attic.If heat is the concern than why don't we worry about all of these other things left out in the sun?I can imagine how hot the roof would get no better than I can imagine how much venting cools it. This is where studies and facts come in - maybe others can help here. All I can say is pick light colored roofing materials.Here is some anectdotal data for you - This fall I re-roofed my barn. It is not particularly drafty. The roof is not vented, from 1940 to 1980 the loft was full of hay and straw. 9 square originally some kind of red green blue rainbow organic T-lock shingle. No shade in sight. The boxes from the shingles were stapled on the hips the date was 1939!! I have pictures of the place from the 60's that show the same shingles. Why didn't they start on fire, and how in the hell did they last 60 years? They were totally shot when I took them off, dried and cracked, admittedly well past their prime, but they didn't leak. If you said because organic shingles are better than fiberglass I would agree, but you seem to think without venting this roof would not have held up.I will take roof temps this summer to see what they are, now light-gray T-locks.How'd I manage to get thru that without name calling, or an insult or need to give directions of any kind?-Rob
*I think you both may be wrong. My inerpretation was the clear passage with blocking on the sides of the rafters and osb type stuff to fasten to the blocking strips and form a chute. I think he specifically mentioned the construction months ago on this same thread, or was it a previous thread on the smae subject? I think I'm having Deja-Vu. Help Me1 8-)-Rob
*Rob,I'll have to take you flying sometime with all the laminar flow yak...I agree with most of what you are saying.One idea though that I think was shot down is that air in convection moves like a big loop....The studies of doulbe envelope homes finally with enough probes showed that there are many eddy currents exchanging warmth from here to there and that even though the homes used very little energy to heat, that there was no big loop of air going round the built loop...Popular Science article ten or fifteen years ago??? And the same for eddies in fiberglass and other ultra low density materials...
*Rob, in your story about the barn, you didn't mention if the roof was insulated with cellulose and sealed off from any air as what has been discussed here over the past few days.The roof assembly that has been completely sealed off could best be compared to a boiling pot of water.If you leave the pot open, it will take a measured time to boil, if you cover it, the boil will be much faster.Why would the roof membrane, sealed off, with no way for the trapped air to escape or exchange, not cause the same reaction?
*Rob,I'll have to take you flying sometime with all the boundary layer flow yak...I agree with most of what you are saying.Except about laminar flow at convection rates of velocity...One idea that I think was shot down is that air in convection moves like a big loop....The studies of double envelope homes finally with enough probes showed that there are many eddy currents exchanging warmth from here to there and that even though the homes used very little energy to heat, that there was no big loop of air going "round the built loop"..."Popular Science" article ten or fifteen years ago??? And the same for eddies in fiberglass and other ultra low density materials...Energizing the Boundary layers,J
*Please excuse the quoting, but it makes it easier to follow the thread."Rob, in your story about the barn, you didn't mention if the roof was insulated with cellulose and sealed off from any air as what has been discussed here over the past few days."I was specifically addressing the heat issue - Arguably, any heat ain't leaving easily. Probably why the cat sleeps up in the collar ties."The roof assembly that has been completely sealed off could best be compared to a boiling pot of water. If you leave the pot open, it will take a measured time to boil, if you cover it, the boil will be much faster. Why would the roof membrane, sealed off, with no way for the trapped air to escape or exchange, not cause the same reaction?"The pot boils slower because heat escapes. Or more generically air and energy is exchanged with the outside surroundings. Are you suggesting it is a good idea to freely exchange interior and exterior air? Are you of the opinion that exchanging air and energy is good? I preferr to keep the lid on and control the inside environment. Unless it is night time, then I'll open the windows, let the cold air in, then close 'em in the morning.-Rob
*Rob, We have to separate the two main components of the house.What lies on one side of the insulation and what lies on the other side of insulation.On one side, the perfect scenerio would be an inverted styrofoam spere, no windows, no doors to the outside, entry would be through a tunnel with several air locks in between.On the other side, we would all have exterior shells that look like the Buckingham Palace or such, in order to define our place in the race against the Jone's.Reality is that the entire house is built on compromise.My focus in our discussion is that layer, immediately between the insulation (whether cellulose or FG) and the sheating layer (whether plywood or regurgitized wood chips)and it's covering, (whether wood shingles, organic or fibreglass shingles, steel, copper, aluminium)and it's ability to cope with the intense temperature changes that occur within and upon the layer in question. The inside temperature of the house is not part of this discussion at this time.Can we agree on this....
*So far so good
*Gabe, et al. I apologise if my writing wasn't clear. Here is what I said: "Jack. I don't use fiberglass insulation--only cellulose in attics. And even if I use ridge/soffit vents I don't use air chutes. I run the sheathing up between the rafters to within two inches of the underside of the roof sheathing.This "baffle" keeps wind away from insulation, keeps insul;ation out of soffit vents, and directs air flow upward. "The top course of exterior plywood/OSB is not termibated at the top plate. Instead the 4'x 8'sheet is notched 2-inches less deep than the distance from the top plate to the underside of the roof sheathing. The notches are spaced 24"oc., because the trusses are 24"oc. . This baffle is on the exterior, not in the interior, but beween the trusses and 2 inches below the roof sheathing. I hope the clears up the misunderstanding.Joe Lstiburek is a friend of some 17 years.I've attended many of his seminars and have just about everything he has published. I have been openly criticalof him when necessary. Neither he nor FredL nor I advocate the indiscriminate sealing(two so-called vapor barriers, with one on the "wrong "side) of walls.(Lstiburek warns constantly about not interfering with the wall's drying capacity.Search as you may you will find no evidence to the contrary. Having said that, here's a shocker. Builders in this country-and no doubt in Canada- have indiscriminately applied two vapor barriers [sic]to millions of houses: the interior polyethylene and the exterior plywood.According to the NAHB, there are no reported failures because of the added vapor barrier on the wrong side. I hope you will not see this as meaning GeneL advocates the indiscriminate sealing of walls.During the last 3 years time I have been on various building web sites I have argued that those advocating non-vented attics MUST know as much about correct attic ventilation as they do about not ventilating garrets. But what is correct attic ventilation? What is adequate ventilation? The codes are silent, unless one fooishly argues that the 1/150-1/300 ratios are adequate ventilation. Snow belt residents know they are not. Manufcturers' literature is conflicting and contradictory.How can we help questioners if we know only non-venting? But where obtain the correct information? From the experts almost all of whom say ridge/soffit vents are the answer? But this answer is unsatisfacrtory. What or whose ridge vent and what soffit vents? And why? My 20 page chapter on attic ventilation in my book attempts to deal with this confusing situation.The book offers no comfort to those who argue for gable-end louvered vents, roof vents, turbine vents, and nearly all ridge vents.Why should I not refer readers to it rather than atempt to write 20 pags on this web page? As a Code Enforcement Officer I have seen millions of dollars of attic structural damage, ice dam damage and interior ceiling damage caused by little or no attic ventilation. Right? Wrong. The damage is a result of a leaky attic floor, and exacerbated by little or no attic ventilation. The upshot of this was my *radical* announcement several years ago that the first line of defense against ice dams is not ventilation but sealing the basement ceiling. The second line of defense is in sealing the attic floor. The third line of defense is filling the attic with cellulose insulation if there is no useable space. If there is habitable space incorporate the attic into the thermal envelpes by insulating and tightly sealing the rafters.This of course obviates the need for ventilation.In new construction and this is SOP in a Leger MESH house, the best: most effective and least expensive way is to not have to seal the ceiling below the attic. In a MESH(Micro Energy System House) there is no wiring, plumbing, ductwork in the attic, or in exterior walls. Because the partitions are not erected until after the ceiling gypsum board is installed there are no penetrations in the air retarder except for the stack vent.This again obviates the need for a vapor diffusion retarder (VDR). The latex painted ceiling provides a VDR to handle any minor moisture diffusion.Over the last 22 years I have designed and built houses this way all over the country and some in Canada. The 1977 Leger house in Pepperell, Massachusetts still stands, has not suffered from ice dams(roof is equipped with Air Vent baffled ridge vent and double louvered soffit vents located next to the fascia board)nor structural rotting. It continue to perform as beautifuly today as it did 22 years ago. I received no complaints over these years from owners of house I designed and built for them. I personally supervised the construction of most of these houses. Preconstruction conferences--rare inb residential construction--we a must. Lead framers were taken to dinner where we could discuss what I wanted. Hope this helps abit. GeneL. I assure you that I share your concerns.I cocnur with Thomas Jefferson's caution not to lightly overturn long established customs--paraphrasing of course.We too often ignore ancient lore that has its place: slopped window sills and other water shedding techniques.But I am no slave to 11th commandment framing. Value analysis amd Ockam's Razor are my guides, and should be every architect's and builder's guides. .
*Rob,In the most basic of terms, if we have two roofs, side by side, constructed with asphalt shingles, felt paper, 9/16 plywood, 2x12s, 5/8 drywall and insulated with whatever, built on a 6/12 pitch. One has a ridge vent/soffit vent combination and the other has the roof sealed.With the warming of the sun, which roof will get hotter first and why?
*Gene, I'm not sure anymore if you said you have a full open vent from the soffit on up to the ridge in your last narrative.I think you recognize the need for venting in a lot of circumstance.I think FredL doesn't.And Jack, fellow pilot, fairs fair, I think we can dialogue.
*When I'm required to, I construct vent shutes between rafters, from soffitt to ridge, with strips of "Glasclad", a compressed f/g rigid board insulation(R4.5/") with a Tyvek type facer on one side, cut to fit tightly, laying up against 1x2 strapping. My thought has always been; if I have to provide a 'shute' it might as well have some insulating properties as well!!! I install the Glasclad with the paper side up, to protect the f/g from air currents and anyi possiblecondensation that might drip down from the underside of the metal roofing that I always instal on strapping (skip sheathing).Although my provincial code no longer requires venting in a completly 'packed' roof, any roof design that has a 'free air' area above it (typical attic or lateral venting area as a result of steel roof type strapping) is still required to have venting.
*Gabe,If you pack the bay with cells, there is no air that needs to be exchanged. And since most of the moisture is brought into this "pot" via air movement through the insulation, by packing the bays, you deny most of the moisture the chance to get in in the first place.And if you don't cover the packed bay with impermeable materials on both sides, whatever moisture does make its way in via diffusion will still be free to "boil" away. I will use my slab roof metaphor again. What if you built the roof out of a slab of pine, 12 inches thick and the size of the entire roof (that would be one hell of a tree!), then shingled over it. Would the slab of pine rot? Would the shingles melt?What happens in an SIP roof? There is no vent.How is packing the cavity with cells worse then packing it with foam? Both are better than FG because they both stop air migration through the cavity.Ventilation is probably needed in a poly/batt roof because the poly/batt assembly fails to do what is asked of it. And even then, ventilation in such a roof often fails to work properly, and often makes matters worse in other ways.Steve
*I'll offer an answer. If you build 4 - 2 dark and 2 light colored; one of each color with venting and one without - the dark ones will be much hotter. In fact, the difference in temperature between the dark ones vented and unvented will be much less than teh difference between either dark one and either light one.
*Steve,I'm signing my name to your post also.Thanks for well thought out discourse,J
*If there is no vent, then it can't "boil away".The thermal resistance of solid wood is much less than either FG or Cellulose. On commercial projects with inverted roof system, there is no venting between the membrane and the insulation is on top of it. However in the summer months, on standard applied roofing, with the membrane on top, the tar will boil on the roof. Is this what the average home owner wants his shingles to do? I don't think so...By the way, it's getting harder to keep track of who said what on this posting.
*Gabe,So with DP cells in a vaulted ceiling with no poly layer are we reduced to the concern that the shingles will melt? Or are you still of the opinion that moisture will be trapped in such an assembly? Any other concerns?Steve
*No Steve, I'm not concerned that the shingles will melt, however, I do know that with any increase in heat, the shingles won't last as long. And that is a fact.
*So, are you saying the reason to vent is to make the shingles last longer? How much longer will shingles on a vented roof last? And what about the tests that show lighter colored roof will last much longer than a darker colored roof, regardless of venting?
*Bill, apples to apples, oranges to oranges.As I indicated earlier, lighter shingles are cooler on a roof than darker ones.If you compare white shingles on an unvented roof versus white shingles on a vented roof, I don't think you will find anyone that will not agree that the shingles on the vented roof will not age as fast, all things being equal.If you check the US statistics on the life expectancy of 20 year shingles in the various zones, you will generally find that as you move south towards the hotter states, the expectancy drops down by several years. So heat is a major contributor to early deteriation.
*Gabe,Twenty year shingles don't last five years in my Northern neck of the woods....Never use them, vent or no vent.25 year minimum and astm passed with high marks...J
*For one who introduced framing and drywall into a thermal discussion above, it seems inconsistent to dismiss teh color of the roofing when discussing roofing degradation resulting from the sun's energy.Never-the-less, I'm not sure everyone would agree with "If you compare white shingles on an unvented roof versus white shingles on a vented roof, I don't think you will find anyone that will not agree that the shingles on the vented roof will not age as fast, all things being equal" unless you want to exclude the link between roof venting and increased moisture in the attic and mositures effect on roofing.But, if anyone would ever recommend or install venting based on increasing the life of the roofing - maybe a few percent at most - then that same person would never permit dark colored roofing - which would shorten the life by much more - like 20% or greater I suspect. Ultraviolet light is much more damaging to roofing materilas then heat underneath and I believe that moisture is even more likely to shorten the life of the roofing material than heat or ultraviolet radiation.
*Jack the reference to 20 year shingles was a reference point not an endorsement. I'll see your 25 and raise you 5.
*Bill you have to ask yourself one little question.Why would all the shingle manufacturers indicate that improper ventilation is a reason to void their warrantees, if it weren't important?
*Gabe,Maybe like most capitalist weasels out there, they don't want to have to stand behind what they sell (ba-da-boom).Seriously though, I know it voids the warranty, but every roofer I've ever met says that they have never been able to get the mfgrs. to honor a shingle warranty. They always find some minor deviation from the recommended installation proceedures to base voiding it on.For cripes sake, the computer manufactures void your warranty if you install extra RAM by yourself.Do you have any hard data about just how much the life expectancy of the shingles could be reduced in various climates? It would be good to know when evaluating the tradeoffs between what I perceive to be superior protection against moisture damage and ice dams that you get from DP cells vs. shortened shingle life.I seem to recall reading of studies that refuted the shortened lifespan of non-vented assemblies. Anyone out there that can verify that?StevePS: What are your feelings about the moisture issue?
*Maybe they know a little more than you do FredL.Bill with regards to the regional climatic effects on shingles, I have located the following:Average expected life of 20 asphalt shingles in Penn. 20.7, Chicago 19.7, Florida 14.1, and Arizona 12.6 years.Solar reflectance of asphalt shingles: Bright white 41%,white 28%, gold 17%, brown 15%, red 15%, green 9% and black 4%..Without exception, all endorse proper ventilation.
*Because they make big profits at selling the vent products.Now, ask yourself how often have you or anyone you know ever collected on a shingle warranty? They have been discussed here and the consensus seemed to be they were worthless. Like 20 years out on a 25 year shingle you get a 20% credit towards the replacement shingles - but no their installation - and only the shingles that have failed - not the whole roof. A bundle of shingles! What a deal!
*Patrick.It is my understanding that Glassclad is no longer manufactured in Canada? Gabe.There are no obstructions between the soffit vents and the ridge vents...but neither are there any air chutes. I' m struggling to answer your statement "I think you recognize the need for venting in a lot of circumstance." In new construction if everything is sealed correctly--the air retarders are free of penetrations-- and there is plenty of insulation in the attic, ventilation is unnecessary.But given the usual method of construction, leaky, ventilation is necessary....that is no attempt is made to seal the leaks. However, just adding any attic ventilation device will not do.Gable-end louvered vents with or without out soffit vents are useless, as are roof vents, turbine vents and most ridge vents. If what I'm saying is true, I think then you are being a bit hard on FredL.He thinks ventilation is iffy and he finds it unpredictable. Given that 40 years ago Hinrichs proved in a real house attic that 99 percent of all attic vnetilation devices do not work...any inhabitant of the snow belt know this..Fred is right to not trust attic ventilation devices. These devices are asked to do something they were not designed to do. Some of the more enlightened pushers of attic ventilation argue do not depend ONLY on attic ventilation to rid the space of moisture and heat.To examine why the codes and others call for attic ventilation, is to recognize that it is one, ONE answer albeit not a very good one. (By the bye Gabe, there are seven different schools of thought on attic ventilation}. Yes sealing--note that we call for thorough careful sealing, not just no venting-and not ventilating is another answer. Pressurizing the attic space is another answer, and in some instances the only practical answer. What to do? Use Value Analysis to arrive at the conclusion retard the leaks and obviate the need for ventilation. While we call for attic ventilation to rid the attic of summer heat--how do you flush radiant heat out of an attic?--the overseas inhabitants of hot dry/hunid regions of the globe do not ventilate attics, or high ceilings without attics. They depend on thermal and reflective insulations and light covered roofs, and done so for hundreds of years. But ever so slowly this is changing in the hot humid/hot dry regions of this country. The Florida Solar Energy Center, and other researchers are calling for the use of insulations rather than ventilation as a more effective and less costly method. By the bye. This goes for the northern part of the US and Canada in hot humid summers.By all means let us continue this discussion now that it seems to be a bit less abrasive. GeneL.
*Gabe. I have been trying for years to get ARMA (Asphalt Roofing Manufacturers Association) to provide documented evidence to suypport theor claims. All I get from them is, "If You Knew What WE Kow About Shingles You Would Know That We Are Right." Does the name General Hague ring a bell?You can quote all the real roof research by competent engineers that venting make no difference(one of these studies spans ten year of constant monitoring)until you are blue in the face. The answer is always IF You Knew...GeneL
*Bill and all,At least notice that I did post my warranty claim that covered labor too.J
*That's a tough one Bill, I've never had to replace a roof.Maybe it's that good venting that I use..........
*Recently our home was rebuilt. It seems the contractors did not quite know what they were doing. Exterior walls in our new bathroom seem to be ducts for cold air flow. We have a cathedral ceiling with a ridge vent on the top of the roof. How does this system properly work? I have been on the roof and it seems the ridge vent is allowing room temperature air out. There are no vents in the sofit. Is this right?
*Your ridge vent is doing what they all do...helping you heat the great outdoors...Read hear all the debate and check much of what Fred l has to say...Also check Building Science CorporationNear the stream,j
*Graham, was your contractor using Gene's book for guidance by any chance?I don't know if you have a soffit vent, I can't see it, so unlike some, I won't try to quess if you have one.With regards to your bathroom walls, is the cold localized or is the whole wall cold? Check the plugs in the wall and see if you can feel a draft coming from them. Take the cover off and let me know if the draft is sufficient to vibrate a tissue held in front of it.
*FredL,If you weren't so full of yourself, you would know that many homeowners do not know that the vinyl soffit material with the tiny perforation is the venting. Sometimes they expect the venting to only be with grills etc.So back off and spend more time off the air and looking for any missing bricks to your load.
*Graham: >>There are no vents in the sofit. Is this right?<<Gabe: >>I don't know if you have a soffit vent, I can't see it, so unlike some, I won't try to quess if you have one.<< Gabe, you took the first shot here. Don't fire and expect not to be shot back at. Better yet, how about you stick to the issues.Steve
*Steve,No one sticks to issues when they have not an issue to stick to...Joe and Gabe are pretty good at sand kicking though when they have to!Safety glasses and fireproof underwear inplace,JGabe, you're really a good sport and like the help in defining what is and aint in the world's of poly, and rebar...Moistfully yours,J
*Steve,You're wrong, it wasn't a first shot, only facts.There are no vents in the soffit. Is this right?Can you see them Steve? I can't. (fact)Have you never had a home owner ask you where the vents were when they were in full view? Sticking to issues is not a strong point demonstrated by yourself. The post was not directed at you.
*Gabe,I guess when the the poster states he has no soffit vents, I take it he knows what a soffit vent is.It's your arrogance that makes you assume the poster doesn't know what he's really saying.I know the post wasn't directed at me, but I grow weary of watching you boys piss on each other, and think you should know it. I'm sure I'm not alone.Steve
*Steve,Don't you think you should put your own bias aside and let the poster answer the question.Don't confuse standing up for what I know to be true with a pissing contest. Just because I choose not follow every little breeze that came along, doesn't mean that I'm wrong.
*After all this touting different flavors of snake oil I'm going back to the old Yukon style of sawdust walls and military surplus mattress ceilings.