Pööningu soojustamine - aurutõkke vajadus?

T25
Ehitusguru
Ehitusguru
Postitusi: 913
Liitunud: 14 Mai 2007, 13:15
On tänanud: 5 korda
On tänatud: 9 korda

Re: Pööningu soojustamine - aurutõkke vajadus?

Lugemata postitus Postitas T25 »

noojah, las ta jääb :( Soovitan foorumite asemel lugeda esmalt mõnd alusteadmist andvat teksti nagu varem viidatud raamat või isegi netis on miskit olemas:
Ühes teises teemas ma juba mainisin, et usaldan välismaiseid foorumeid rohkem, kuna muu maiilm on meite maast oma 30 aastat ees. Ameerikamaal hakati maju soojustama juba 100 aastat tagasi. See selleks. Peno soovitasin sellepärast, et lugesin samast foorumist, et katuslae võid põhimõtteliselt soojustada sedamoodi, et peno võib tuugalt aluskatte külge kinni vahutada ja kui seestpoolt on ka peno tuugalt vahuga igalt poolt kinni pandud, siis selline lahendus töötab. Erinevalt villast, kus kondents jookseks. See kõik on välismaal juba ammu läbikäidud teema. Lihtsalt näiteks, et ei ole vaja isegi tuulutusvahet peno puhul, vill aga seda ei andesta. Üldiselt on seal foorumis ka mainitud, et vill vajab väga korralikku paigaldust ja seda on keeruline saavutada, tuuletõke jms. Peno on aga ise juba tuuletõke. Kõik see on praktika, erinevalt ehitusõpiku teoreetilistest klantspiltidest.
T25
Ehitusguru
Ehitusguru
Postitusi: 913
Liitunud: 14 Mai 2007, 13:15
On tänanud: 5 korda
On tänatud: 9 korda

Re: Pööningu soojustamine - aurutõkke vajadus?

Lugemata postitus Postitas T25 »

https://www.greenbuildingadvisor.com/ar ... al-ceiling
A brief history of cathedral ceilings
Insulated cathedral ceilings are a relatively recent phenomenon. The craze for insulated cathedral ceilings (and great rooms) really took off in the 1970s and 1980s, when examples began popping up like mushrooms after a warm rain. In those days, most builders stuffed cathedral ceiling rafter bays with fiberglass batts. Sometimes they included flimsy Proper-Vents between the fiberglass and the roof sheathing, but often they just specified thin batts to ensure that there would be an air space above the batts for ventilation.The cathedral ceilings of the 1970s and 1980s were thermal disasters. In most cases, these ceilings leaked air, leaked heat, created monumental ice dams, and encouraged condensation and rot. In many cases, roofers tried to solve these problems by improving ventilation openings in the soffits and at the ridge; these “improvements” often made every symptom worse.
Fortunately, most builders have learned a few lessons from these disasters.

Nagu näha, siis teinekord nö tuulutamise parandamine teeb asja hoopis halvemaks!!!
Does a cathedral ceiling need to be vented?
Until recently, building codes required that insulated sloped roofs include ventilation channels directly under the roof sheathing. Many builders still follow this time-tested technique.

As building scientist Bill Rose has shown, code requirements for roof venting were never based on research or scientific principles. In a well documented JLC article on roof venting (“Roof Ventilation Update”), Rose explained, “For the most part, the focus of codes, researchers, designers, and builders on roof ventilation is misplaced. Instead, the focus should be on building an airtight ceiling, which is far more important than roof ventilation in all climates and all seasons. … Once this is accomplished, roof ventilation becomes pretty much a nonissue.”
Roof ventilation cannot be used to lower indoor humidity levels.

Builders should not encourage the migration of water vapor through a cathedral ceiling.

During the summer, roof ventilation does not significantly lower the temperature of asphalt shingles or other types of roofing.

While roof ventilation can lower the risk of ice damming, it’s essential for builders to limit the flow of heat into roof ventilation channels by including one or more ceiling air barriers and by installing thick insulation, so that as little heat as possible escapes from the home.

While roof ventilation can help dry out damp roof sheathing, it’s essential to limit the flow of water vapor escaping from the home so that the roof sheathing never gets damp in the first place.

In the absence of an airtight ceiling, roof ventilation can do more harm than good, since air movement in rafter bays can encourage indoor air to leak through ceiling cracks.
Ülalolevast järelduks justkui, et tõepoolest, kile paigaldamine oleks kasulik villa puhul. Tegelikult piisab aga õhutõkkest. Ma ise olen villa vastane ja üldiselt villa teemasse väga ei süübi ka mitte.

Lugesin seda artiklit veel, see jutt, mis ma enne ajasin, et peno võib vastu aluskatet panna ja vahuga kinni lasta, tegelikult ei kehti. See kehtib ikka pritsvahu kohta. Penotükkidest tehtud ja vahutatud( inglise keeles cut n coble) tahab ka ikkagi tuulutust saada.

Tuulutuse kohta:

https://www.greenbuildingadvisor.com/ar ... ic-venting

Most homeowners and builders believe that attics should be vented. If you walk down to your local lumberyard and lean on the counter, the employees and nearby customers will offer a variety of opinions about why attics need to be vented. Unfortunately, it’s highly unlikely that the statements you hear will be true.

Here are the four most common reasons people suggest to explain the practice of venting attics:

To reduce the chance of moisture build-up in the attic or condensation on the underside of the roof sheathing.
To make roofing shingles last longer.
To lower cooling bills during the summer.
To reduce the chance of ice dams.
Although attic ventilation is sometimes able to contribute in a very small way to addressing the problems on this list, there are much better solutions to all four problems than ventilation.
R
educing moisture buildup in the attic
William Rose is a research architect at the Building Research Council at the University of Illinois. Rose has delved more deeply into the history of attic ventilation requirements than any other building scientist or historian. According to Rose, the stated aim for the first code requirements for attic venting was to reduce moisture buildup in the attic. Unfortunately, the code requirements were not based on science or research. Rose reports, “The attic ventilation ratio ‘1/300’ is an arbitrary number selected by the writers of FHA (1942) with no citations or references.”

High attic humidity usually shows up as dampness or frost on the underside of the roof sheathing. Another sign is mold (usually on the underside of the sheathing or the sides of the rafters). In almost all cases, these symptoms are due to two construction defects: a ceiling with air leaks, and a damp basement or crawl space. The way to solve this problem is to seal the air leaks and correct the moisture problems in the basement.

Rose advises, “Don’t rely on ventilation alone to take care of moisture in the attic. The best protection against condensation and mildew in the attic is a dry basement or crawlspace. Also important is an airtight ceiling.”
One of Rose’s colleagues at the Building Research Council is Jeff Gordon, who gave a presentation on attic ventilation at the 2011 Affordable Comfort conference. According to Gordon, “The three parameters for attic condensation in cold climates [are] interior house humidity, ceiling airtightness and pressures, [and] attic ventilation. Attic ventilation will have a slight positive influence, but it is third in the list.”
As often happens, the code gets it backwards
For years, building codes have required cold-climate builders to include interior vapor barriers, while almost totally ignoring air leakage. Yet vapor diffusion causes very few problems, while air leakage is a huge problem. For all these years, the building code was focusing on the wrong issue.
See artikkel võtab kokku, miks ma villa vastane olen ( kuigi ka minu maja soojustati villaga):

https://www.greenbuildingadvisor.com/ar ... ass-right

Mõned nopped:
Of all of the commonly used types of insulation — including cellulose, rigid foam, and spray polyurethane foam — fiberglass batts perform the worst. As typically installed, fiberglass batts do little to reduce airflow through a wall or ceiling assembly; rarely fill the entire cavity in which they are installed; and sometimes permit the development of convective loops that degrade insulation performance.

Knowing this, why would any builder choose to install fiberglass batts? The answer is simple: because fiberglass batts cost less than any other type of insulation.

Before we totally dismiss all fiberglass batt installations, however, it’s important to note that there is a big difference between the typical fiberglass batt installation and a best-practice installation. If a conscientious builder installs fiberglass batts carefully, it’s possible — although not easy — to get the best of both worlds: adequate thermal performance at a relatively low price.

In article in the April 2005 issue of Energy Design Update, “Fiberglass-Insulated Homes Are the Leakiest,” discussed the findings of Bruce Harley, the Conservation Services Group’s technical director for residential energy services. “Harley assembled airtightness data on Energy Star homes (including single-family and multifamily homes) completed in 2004 in Massachusetts and Rhode Island. All of the homes were blower-door tested after completion,” EDU reported. “Harley found that houses with walls insulated with spray polyurethane foam were significantly tighter than those houses with walls insulated with cellulose, and that houses with walls insulated with cellulose were significantly tighter than those insulated with fiberglass.”


It’s hard to do it right
Although the steps required to install fiberglass batts well are easy to describe, they are fairly difficult to achieve. It is the nature of a fiberglass batt to want to be installed sloppily. Unlike cellulose or spray polyurethane foam, a fiberglass batt doesn’t volunteer to fill a cavity completely; on the contrary, it tends to fight an installer’s attempt to make it fit snugly.
Minu poolt kõik selles teemas, teemaalgatajale on antud vajalik info edasi, et ise edasi uurida.
Viimati muutis T25, 25 Juul 2019, 02:57, muudetud 1 kord kokku.
T25
Ehitusguru
Ehitusguru
Postitusi: 913
Liitunud: 14 Mai 2007, 13:15
On tänanud: 5 korda
On tänatud: 9 korda

Re: Pööningu soojustamine - aurutõkke vajadus?

Lugemata postitus Postitas T25 »

Aurutõkkest siiski veel, sest sellest kogu see teema ju algaski:

https://www.greenbuildingadvisor.com/ar ... -air-leaks

I guess I need to make a presentation slide that says in big bold letters: Capillary materials do not exhibit condensation at the dewpoint. Take a can of beer from the fridge on a muggy day. Condensation. Liquid water. Take a block of 2x4 from the same fridge and set it next to the can of beer. Same temperature, same surrounding vapor pressure. No condensation. No liquid water. Something happens to the 2x4 but it isn’t condensation. Sorption happens. Sorption also happens at vapor pressures above and below the dewpoint. Get picky? Below freezing materials are far less sorptive, but they exhibit frosting, not condensation. Fully saturated materials may exhibit condensation (liquid water) but they’re no longer capillary materials. So I’ll repeat: Capillary materials do not exhibit condensation at the dewpoint.
I read your post here in Westford, Mass., where I just heard Bill Rose give a presentation on a variety of building science topics. He held up a mirror and asked the audience, "Can you get condensation on a mirror?" and he answered his own question: "Of course you can get condensation on a mirror."

Then he held up a sponge. "Can you get condensation on a sponge?" And he answered his own question, "Well, yes -- you can get condensation on a sponge -- if you use the sponge to wipe the mirror."

Then he told a story. "On a hot humid day, I take a beer out of the refrigerator. I put the cold beer on the table. Do I get condensation on the beer can? Of course. Now I go back to the refrigerator and I take a chunk of 2x4 that I keep in the fridge and I take that out and put it on the table. Do I get condensation on the 2x4?"

Finally, he said, "So I got a call from someone who said, "I've got a problem, Bill. I'm getting condensation in the inside of my wall cavities." Bill answered, "You've got condensation in your walls? Why are you building your wall out of beer cans?"

He advised the audience that the word "condensation" is often misused to talk about sorption.
"One of the problems in the building industry is that we have a spreading "cult-like" mentality that worships at the "church of polyethylene". This cult views the answer to all moisture problems as the installation of a polyethylene vapor barrier condom on the inside of buildings. This cult is responsible for many more building failures than building successes. It's time that the cult deprogramming started." -Joe Lstiburek, Ph.D., P.Eng.,
Ironically for Canadians, the first technical reference I can find of inward vapor drives trapped by poly causing rotting walls in cold climates, is from the Division of Build Research, dating to the early 1960's. At the University of Waterloo we were measuring and photographing test wall rotting starting in the early 1990s (I attach the photo of a brick veneer wall in Waterloo Canada: brick, Tyvek, fiberglass poly). At about this time the Swedes were also publishing results of rotting walls and mold due to warm weather condensation in their cold climate.
A major change in the last 20 years is the proliferation of air conditioning in cold climates. This is almost a prerequsite for moisture problems to occur due to poly. And AC is common in Minneapolis, Buffalo, Toronto, Ottawa, etc.
https://www.greenbuildingadvisor.com/ar ... into-walls

Because of inward solar vapor drive, vapor diffusion from the outside inward is often more worrisome than vapor diffusion from the inside outward — so you need a good vapor barrier strategy

Builders have worried about wintertime vapor diffusion ever since 1938, when Tyler Stewart Rogers published an influential article on condensation in the Architectural Record. Rogers’ article, “Preventing Condensation in Insulated Structures,” included this advice: “A vapor barrier undoubtedly should be employed on the warm side of any insulation as the first step in minimizing condensation.”

Rogers’ recommendation, which was eventually incorporated into most model building codes, was established dogma for over 40 years. Eventually, though, building scientists discovered that interior vapor barriers were causing more problems than they were solving.

Interior vapor barriers are rarely necessary, since wintertime vapor diffusion rarely leads to problems in walls or ceilings. A different phenomenon — summertime vapor diffusion — turns out to be a far more serious matter.
D
uring the 1990s, summertime vapor diffusion began to wreak havoc with hundreds of North American homes. This epidemic in rotting walls was brought on by two changes in building practice: The first was the widespread adoption of air conditioning, while the second was one unleashed by Rogers himself: the use of interior polyethylene vapor barriers.
Rogers conceived of interior vapor barriers as a defense against the diffusion of water vapor from the interior of a home into cold wall cavities. Rogers failed to foresee that these vapor barriers would eventually be cooled by air conditioningthereby turning into condensing surfaces that began dripping water into walls during the summer.
One early victim of this type of diffusion was Cincinnati builder Zaring Homes. In the mid-1990s, Zaring Homes was a thriving mid-size builder that completed over 1,500 new homes a year. But the company’s expansion plans came to a screeching halt in 1999 when dozens of its new homes developed mold and extensive rot.

The first signs of the disaster surfaced in July 1999, when homeowners at Zaring’s Parkside development in Mason, Ohio, first began complaining of wet carpets. These moisture problems emerged only ten weeks after the first residents moved in to the new neighborhood. When inspection holes were cut into the drywall, workers discovered 1/4 inch of standing water in the bottom of the stud cavities.We were able to wring water out of the fiberglass insulation,” said Stephen Vamosi, a consulting architect at Intertech Design in Cincinnati.
Consultants concluded that water vapor was being driven inward from the damp brick veneer through permeable fiberboard wall sheathing (Celotex). During the summer months, when the homes at Parkside were all air conditioned, moisture was condensing on the back of the polyethylene sheeting installed behind the drywall.
“Zaring Homes went out of business because they had a $20 to $50 million liability,” said building scientist Joseph Lstiburek. “Hundreds of homes were potentially involved. To fix the problems would probably cost $60,000 to $70,000 per home. It was a spectacular failure, and they are out of business.” (For more on Listiburek’s view of inward solar vapor drive, see Solar-Driven Moisture in Brick Veneer.)
I
nward solar vapor drive problems require four elements
The phenomenon that destroyed Zaring’s walls came to be known as inward solar vapor drive. The classic disaster requires four elements:

A “reservoir” cladding — that is, siding that can hold significant amounts of water;
Permeable wall sheathing like Celotex or Homosote (that is, fiberboard);
A polyethylene vapor barrier on the interior of the wall; and
An air-conditioned interior.
Problems with inward solar vapor drive show up first on elevations that get the most sun exposure; north walls are usually immune to the problem.

Whenever a wall separates environments at different temperatures and moisture conditions, the direction of the vapor drive is from the hot, moist side toward the cool, dry side. After a soaking rainstorm, the sun eventually comes out to bake the damp siding. When it comes to driving vapor, the sun is a powerful motor.

The heat of the sun easily drives the moisture in damp siding through housewrap and permeable wall sheathing. The first cold surface that the vapor encounters is usually the polyethylene behind the drywall. That’s where the moisture condenses; it runs down the poly and pools at the bottom of the wall cavity. It doesn’t take long before mold begins to grow and the walls begin to rot.

Once the phenomenon of inward solar vapor drive was well understood, it was identified as one of the main mechanisms causing a cluster of wall-rot problems in EIFS-clad homes in North Carolina. Inward solar vapor drive is also blamed for many of the “leaky condo” problems in stucco-clad multifamily buildings in Vancouver, British Columbia.
Data from a 2003-2004 wall-drying study by building scientists John Straube, Eric Burnett, and Randy Van Straaten confirmed the phenomenon of inward solar vapor drive.

Inward vapor drive resdistributes moisture quite dramatically,” said Straube. “Some people have said, ‘Summer condensation on the interior does not occur.’ But summer condensation does happen, even in Ottawa.”

For decades, builders have worried about vapor diffusion into walls from the indoors during the winter. But if a home has air conditioning, vapor diffusion into walls from the outdoors is a much bigger problem.

According to Straube, “Solar-driven vapor is much more important” than winter diffusion from the interior. He continued, “The moisture is coming from the other side of the assembly.”
After only 10 weeks of occupancy, some of the Zaring homes were so wet that most of the brick veneer, sheathing, insulation, and drywall had to be removed and demolished.
Never include interior polyethylene or vinyl wallpaper in an air-conditioned home. If your building inspector insists on a vapor retarder that comes in a roll, choose a smart retarder like MemBrain.
John Straube: “The whole reason we’re talking about vapor barriers is not because vapor diffusion control is so important, but because people believe it is so important. The question comes up, have we seen diffusion-related building failures? And the answer is, very few — maybe in rooms with a swimming pool. Assuming that the vapor came from the inside, you would have to have a very high load before you would see a problem. I think that solar-driven vapor is much more important. The moisture is coming from the other side of the assembly.”
Everyone wants good performance. No problem there. Prescriptive requirements are intended as shortcuts to good performance, and they facilitate commerce. They should be allowed to remain in effect only if: 1) their subject is critically important, 2) they are necessary, 3) they are sufficient, and 4) if the link between the prescription and the performance outcome is continually policed. In my opinion, all four are open to question. That said, we might imagine a future in which the building code sections that address the vapor barrier would all go blank. I bet most readers would be able to design excellent buildings that perform well and are quite durable, without using the word “vapor barrier” at any point in the process.
val
Ehitusveteran
Ehitusveteran
Postitusi: 1162
Liitunud: 28 Dets 2010, 13:32
On tänanud: 14 korda
On tänatud: 20 korda

Re: Pööningu soojustamine - aurutõkke vajadus?

Lugemata postitus Postitas val »

Viidatud tekstide lugemisel pead arvestama mis kliimatsooni (USAs 6 tsooni) ja mis konstruktsioonist või konkreetse juhtumi kontekstis räägitakse. Ma ei tea palju teadus vahepeal on edasi arenenud selle teemaga, aga kui 2011.a neid J.F. Straube tekste vaatasin (viewtopic.php?f=11&t=28287&p=163722&hil ... id#p163722), siis ei olnud USA teadlastel 3-5 tsooni aurutõkke teemal täit konsensust:
Kui konstruktsioon juba aurutõket vajab, siis lollikindlam on tõesti panna nn tark aurutõke .... eriti meie viimast kaht suve arvestades :) Samas ma ei ole kuulnud Eestis massilisi mädanema läinud majasid, seega projekteerijad vast teavad mis teevad.
Vasta