Moisture Management Fundamentals with Joe Lstiburek

good afternoon everyone we're going to get started here in just a moment so sit tight and we will be right back okay hello again everyone our guest today is Joe Seabrook whom many of you probably know or at least it heard of but you might not know today is Joe's birthday so we're all going to sing happy birthday to him no now I'm just kidding you're all on mute but go ahead and sing like no one's listening anyway a large majority of construction litigation involves moisture intrusion but it doesn't have to be that way by properly managing moisture and design and construction of your projects you can help your home buyers avoid costly and exasperating problems at the same time reduce your callback risk now Joe Steve Burke is the founding principle of building science corporation dr. Steve Rick's work ranges from providing expert witness testimony to overseeing research and development projects to writing for the ASHRAE journal and building science comm dr. Steve Brooks commitment to advancing the building industry has had a lasting impact on building codes and practices throughout the world particularly in the areas of air barriers vapor barriers invented and unvented roof assemblies dr. Steve Burke is an acclaimed educator and author and he holds a Bachelor of Applied Science in mechanical engineering a master of engineering and civil engineering and a Doctor of Philosophy and building science today's webinar is made possible by fortify per Florida fiber produces a highly flexible system of products that prevent moisture intrusion as well as the mold and rot problems that can result from leaks the product line includes weather resistive barriers flashings and sealants that when used together are covered by an industry-leading 15 year labor plus materials warranty the extensive product line is based on science and it's proven in the field versatile components ensure protection in every North American climate while also providing options that support regional building practices with its more than 75 year history fortify bur has become a trusted partner to builders architects and local building code officials now during today's presentation you can submit questions for our guests simply use the questions box on the right side of your screen I'll review those questions and pose them to Joe during the Q&A time set aside after his presentation concludes Joe I humbly step out of your way well good afternoon everybody let's get rolling here why am i unable to there we go building is considered an environmental separator and from our perspective it keeps the outside out in the inside in every now and then the outside gets into the thing that separates the inside from the outside and we have to decide whether to kick it back or let it through and sometimes the inside goes into the thing that separates the inside from the outside we have to decide whether to kick it back or let it through now the thing that we most worry about happens to be moisture both coming from the outside in and the inside out a material scientist looks at life a little differently than most normal people material scientist looks at the world in terms of damage functions and there are three principal damage functions water heat and ultraviolet light and basically these are the three things that make things go bad for a building material or any material and of the three water is way more significant than heat an ultraviolet light so if you want a durable structure you have to address damage functions and other the principal damage functions water is the worst in fact when I was going through the ranks way back when people had taught me said that the three biggest problems in buildings are water water and water of the various phases of water rain is the biggest single thing to to worry about more problems occur because of rain than than any other single issue in construction and and the best you know the approach is you do the best you can on on rain control but you have to assume that things are going to get wet no matter how good you are so you have to design the assembly for dry so we try to keep the rain out we do everything possible to keep the rain out but no matter how good we are some water some moisture is going again so we have to design the building to dry so first strategy is keep stuff out second strategy is assume that you're not going to be successful and let things dry the approach for building a wall or designing a wall is to have four things after we've handled the structure we need a water control layer and air control layer of April control layer and a thermal control layer and they're listed in order of importance the water control layer is way more important in the out control layer and both are more important than the vapor control layer and all three are more important than the thermal control layer I've been doing this for a long time I'm not going to tell you how old I am today but a long time and I've never gotten a call at 3:00 in the morning saying my building is leaking air so water control is way more important than air control of these four things that are listed the only one that we can calculate and measure with a reasonable degree of precision and accuracy is the thermal control layer so if it's not particularly important and you can calculate the building code obsesses over it you value this I'll tell you that the most important one is the water control layer and pretty much the only thing that you can find is to be good and good luck well we have to be good but we can't rely on luck I'm demonstrating here a water the water holdout capacity or capability of brick using a an old-fashioned garden hose clearly this person's being the test is a Canadian he's a he's a hoser okay bad joke the water passes through the brick in approximately 20 seconds and so the point of this is to say that claddings leak brick leak stucco leaks everything leaks and a good assumption is that about 1% of the water that's incident on your wall is going to pass through the clouding system and we have to figure out a way to deal with it historically one of the most successful ways of dealing with that is to put a water control layer behind the cladding system so that the 1% of the water that passes through the clouding system basically hits the water control layer and this drain downward using gravity to a way of expelling it the water from the base of the walled assembly typically with a flashing so what we want is we want drainage to occur behind a cladding system and for drainage to occur along a water control layer the typical brick wall historically has had a 1-inch airspace between it and the water control layer which is in this particular case building paper the 1-inch airspace is as a historic artifact it's not piston on physics it's based on tradition Masons knuckles and fingers are typically one-inch and that's where that believe it or not comes from you know need an inch you need you can go as low as 1/32 or 16th of an inch to get drainage if the space is continuous so Blair now we're asking for an inch behind brick in order to get a continuous thirty-second to sixteenth to quarter inch gap to provide that drainage your water control if we didn't have to worry about mortar dropping sir of course life would be easy the issue is that the mortar droppings clog up the drainage and sometimes we use a more sophisticated approach by basically putting a drainage mat against the water control layer and so that the drainage map provides that continuous space to provide drainage there are many different forms of this water control layer it evolved traditionally from the asphalt impregnated cells some type D covered papers to plastic materials spray applied materials fully adhered materials they all have a place in the assembly and we have similar materials both residential and commercial construction more recently the water control layer has become integrated onto the sheathing itself and so here we have a structural sheathing with an integral water control layer note that the joints have to be sealed to provide continuity of this water control layer you can do a similar thing with an insulating sheeting in this case it's an extruded polystyrene again the point is is that the water control layer can be many forms from the film it can be sheets it can be a combination of things this is a fully adhered peel-and-stick membrane acting as the water control later this is also of course acting as a very effective air control layer and a vapor control layer and over this would would go the thermal control layer we're also seeing spray applied water control layers that also can act as air control layer ISM and bakery control layers here's a hybrid where we're taking we're treating the joints of gypsum board which is a fire control and sheathing and provides some structural support covering it with the joints with a mesh tape and then a a paint applied water control and air control layer at the end of the day that principals are all all the same we basically have to expel the water at the bottom of the assembly with a flashing system and we integrate the flashing system with some kind of a water control layer traditionally we did again with with building paper with the joints overlap this gravity deal is pretty fundamental gravity requires no no maintenance it haven't figured out how to tax it yet so it's a it's a pretty Universal method of dealing with with incident water 1% of the water passes through the cladding it's the water control layer would rely on on gravity and drainage to manage that water that penetrates and gets kicked out at the bottom of the wall this approach of drainage is this fundamental to not just the wall but the roofs the foundations the site the various components you drain everything you drain drain the material during the component drain the opening drain everything for those of you who are American high school graduates have never seen this before this is a map of North America and I point out that where it rains more you need more rain control you can do pretty silly things in Las Vegas and in California because it doesn't rain very much apparently what happens in Vegas stays in Vegas you don't have the same luxury one year in Seattle or in Halifax Nova Scotia or on ascend or swamp in the middle of the Gulf of Mexico like say the state of Florida the emphasis on water control is directly related to the amount of rainfall that occurs annually once you get above 20 inches of rain a year you have to be serious about drainage as well as having continuity of your of your water control later buildings don't get wet uniformly most water entry occurs at where rooms meet walls at upper corners and where the building needs the ground where the building needs the ground of course the round is wet but also the rain hits the ground and splashes upwards so we have there ring-around-the-collar basically at the base of the building let's flashback and then the output parts of the building windows are their own special nightmare when rainwater hits a window or glass the glass of course doesn't absorb the water so although the surface area of the window is non absorption so the water runs down that surface and is concentrated at the corners we call the damage must ashen and so basically buildings leak at the bottom of windows the bottom of doors where the building touches the ground and at the edges of the building especially a brick just the building and where the walls need the roofs another factor that has become very significant lately because of historical changes to building materials and the energy flow across an assembly is inward Drive of moisture out of a reservoir cladding in a classic reservoir cladding would be it would be brick it rains on brick the brick gets wet you have to think of the brick as a as a moisture capacitor that is charged during a rain event when the Sun when the Sun hits the moisture capacitor is it discharges both to the outside and the inside so brick gets wet stores water the Sun heats the water increases it's vapor pressure and the moisture is driven both outward and inward one is driven inward if the assembly is too paper open you will drive that moisture to the inside and it will pass through your shadings and your water controllers through your cavity insulation if you have a vapor barrier on the inside such as polyethylene our vinyl wall coverings or epoxy paint you're going to end up with a serious problem and so the general rule now is do not install a vapor barrier on the inside of the building that is air conditioned so if you have air conditioning don't have a vapor barrier on the inside a vapor barrier is different than a vapor retarder or a vapor deeper throttle gypsum board with latex paint not a problem gypsum board with alkyd or epoxy paint you're going to have a problem and this is exacerbated with a reservoir clouding such as brick or stucco excuse me historically we could get away a lot with a lot of inward drive when we had plywood but now we have OSB and this is a side by side comparison of plywood nos B being exposed to the same temperature humidity in the OSB goes bad very very very quickly Moisture that used to be able to be stored and plywood or passed through plywood is no longer stored and absorbed effectively in OSB and so we have to provide a drying mechanism for the OSP that we did not have to provide for plywood and this is especially of an issue with a highly insulated wall so when we've got went from two-by-four construction with plywood to 2x6 construction with our OS B we have to change the way we handle our rainwater management so for example with respect to stucco we would put stucco traditionally over two layers of building paper over plywood and not have an issue when we went to two by sixes with OSB we actually have to have a drainage gap space between the two layers of building paper typically 1/4 inch to allow the OSB to dry into that space because it can no longer distribute the moisture as effectively as plywood used to so what we're finding is that anywhere that it rains more than 20 inches of rainfall annually and you have stucco and you have an OSP wall you're going to require a quarter-inch drainage gap to facilitate not just drainage but to provide a space for dry we used the term hydric redistribution a big word that means that the OSB is able to redistribute moisture in that airspace because it's not able to redistribute the moisture within the OSP flakes themselves very different than plywood we know this is a case where you know this would have not had happened had we had plywood the wall assembly could have dried to the interior this is an example of a little bit of water entry but a lot of vapor dripping in through a reservoir cladding called stucco had we had vinyl siding not a reservoir not a problem so back to the fundamental principle we actually want not just drainage but some air flow to provide a space for some drying to occur and that air flow needs to be behind the cladding system we can use to have this requirement but again as the materials that we construct with their more moisture sensitive and when we have significantly less energy available to us to evaporate water that air gap becomes critical to the durability of the assembly what would be a good method of with a brick veneer well you don't want a vapor barrier on the inside you could have gypsum choosing plywood OSB you want some kind of a water resistant barrier WRB 10 to 20 perms is the sweet spot greater than 20 you'll have too much in revive less than 10 and you don't have enough drying capacity I wanted that vented air space that means you need an air and Inlet at the bottom and an air inlet at and the air outlet at the top and you want a clear space this is a fabulous way to do a brick veneer in the lower 48 states only start getting into for example places like Canada we're going to require a more resistant vapor layer on the interior to reduce the amount of wetting from the interior going to the exterior because apparently winters are longer in Canada than they are in say st. Louis with with a stone cladding system it's very very difficult to keep some order out of a an airspace so we provide a mechanism to create a clear airspace typically a 3/4 inch drainage mat with a filter fabric so in essence take in the previous assembly and get rid of the brick but keep everything else the same add your drainage mat with the filter fabric now you can add your stone and what's nice about this is you're able to continue to provide obviously drainage but you're also providing some airflow and you're providing an air gap that the wall assembly can dry into from the interior to the exterior this is both of these are in essence flow through assemblies now they can dry out and they can dry yeah only go to stucco in essence we take exactly the same approach that we have with the stone except the gap doesn't have to be as great why well we don't get as much water through stucco as we do through stone but we do need some kind of a gap I prefer a quarter of an inch to 3/8 of an inch and I still want my water control my water resistant barrier my water control layer to be in the 10 to 20 perm range and I don't have an issue with gypsum gorge as an extra sheathing plywood OSB or a great deal of insulation in the wall with the understanding that I do not have an interior vapor barrier I'm able to have this assembly dry both to the inside and to the outside when the rainfall annual rainfall exceeds 20 inches of rain per year you need that training mat or the drainage gap when you're less than that say California two layers of building paper are still okay you're in Salt Lake City you're in Edmonton two layers of building paper are just fine you don't have the rain load that is necessary that requires the quarter inch to three inch drainage mat behind stucco this drainage gap is all about controlling hydrostatic pressure if you have pre gate free drainage occurring the water doesn't build up that means that you don't really care about staple holes you don't care about fasteners or cladding attachments penetrations through the water control later because hydrostatic pressure is not allowed to build up one of the ways to demonstrate this is you need to get a hockey puck in the easiest place to get a hockey puck is you can find them most often in the net behind the Toronto Maple Leafs goalie but if you take a hockey puck and you put it against your water control layer it's one inch thick you've got at hockey puck represents a hunk of mortar that's suspended on the wall so if the water passes through the brick runs down the water control layer hits our C Racal mortar the drains to either side and we don't we don't particularly care I have two hockey pucks I still have drainage I don't care if I have three configured this way the water begins to build up the weight of that water is what we call hydrostatic pressure and that water exerts a tremendous force against the wall this is certainly a pretty bad mortar dropping brick linear assembly but but you get that you get the point the secret to rainwater control is to basically not have a place for hydrostatic pressure to build up that pressure once you get to for example a half an inch of water and height that's equivalent to a 35 mile an hour wind you can basically get hurricane-force loads on a wall in the absence of a hurricane simply if it rains and water leaks in behind the cladding and begins to build up hydrostatic pressure you are really stressing that wall if you have a clear drainage space you don't have the hydrostatic pressure you can even call it you can tolerate nail holes and staple holes through the double the water resistant barrier and not have an issue so now I want to leave you with one aha thing is the secret to rainwater control is to control the hydrostatic pressure and you don't need much of a gap to do this as long as it's continuous here's a plot of wind speed versus Pascal's and Pascal's can be converted into inches by dividing by 250 so you know 150 Pascal's is about 1/2 an inch of water and that's 35 miles per hour this idea of providing at a gap for hydrostatic pressure is important especially important at corners here's how you do it with with with trim you basically nail the trim to each ship it to itself in essence creating this l-shaped piece and then you hang it on the wall over a spacer strip the spacer strip could be a very thin strip of foam I've used fill gasket material very effectively as the gasket is a quarter-inch the thinnest layers of foam you can find which were underlayment for the old aluminum siding is about 3/8 of an inch but you get you get the idea this is the same works if we have a continuous sheathing such as a so extruded polystyrene you want that small gap to occur and it's especially critical at corners especially behind trim we didn't care much about this in the old days because we had the ability for these assemblies to dry and there was energy available for the drying to occur and we had plywood and we had board sheathing with water sensitive materials like engineered wood and lots of thermal resistance this back venting and draining is is very important for rain control this is a this is a drainage mat over this could be installed a paper back laugh or cedar shakes or cedar shingles and you've got a continuous and it continues air space these drainages mats are available in quarter inch to 3/8 inch and you can go up to three quarters of an inch and remember three quarters of an inch is what I recommend when we got a stone stone cladding system but you need some kind of a filter medium to keep the drainage mat from clogging up with mortars with ours you have to make sure that the mid-range Matt doesn't get clocked this is suppose cedar shingles in yeah a classic approach is two layers of building paper the outer layer is a bond break that prevents the martyr from the stucco itself by rendering from adhering to the principle water control layer which is the one directly against the shiva so less than twenty inches of rainfall a year California OSB one layer of building paper another layer Reina shmatte are your wire laughs you're good to go Miami not going to work you're going to need a quarter inch gap or mesh between the two layers of building paper to handle the increased rain mode here we have a WRB a plastic film apply WRB and we've got a 3/8 inch drainage mat with filter fabric attached to it over this you see at the bottom corner is you've got a building felt is going to be installed with a wire laughs so we're going to end up with stucco your filter fabric your water control layer and your LSD it was actually a 2 by 6 assembly with an R 20 wall a little bit of physics here if I have a cup horizontal and it rains into the cup Cup is configured to provide drainage and it's pretty obvious how this works if I have it windy and the wind blows into the cup the cup becomes pressurized if there's no holes in the back of the cup the wind can't get out the back of the cup if wind can't get out the back of the cup more wind can't enter so I'm addressing wind driven rain I'm excluding in driven rain from entering the cup because I pressurized the cup mounting it does leak and I can still drain it to the exterior if I put a baffle over this but leave a part of the cup exposed at the bottom when we'll enter at the bottom of the the cop onto the bottom part of the baffle and still pressurize the cup because the baffle is leaky there isn't much of a pressure drop across the baffle the pressure is taken across the back of the cup if I have water on the surface of the baffle I'm not going to basically suck the water across because of a pressure difference to do you know basically win so we call this concept pressure equalization or pressure relief where we take the pressure across the inside of the cup not across the baffle now why this is a big deal is this is the principle behind a typical glazing system we have an inner seal in an outer seal and we have an extrusion and which is more or less a gutter system and we suspend the or elevate the the glass so it doesn't sit in the bottom of the gutter so you want to keep that bottom seal dry if anything leaks we want to drain it out the bottom and not let the bottom seal put that hole at the bottom that allows water to get out sure to get in serves a very important function in that it allows air to get in to pressurize that entire chamber and so when we pressurize the chamber the pressure is taken across the inner seal not the outer seal now the outer seal doesn't have to be very good that it's going to age because it's exposed to water heat and ultraviolet light and as of the ages we don't care because there isn't a pressure drop across that seal the pressure is taken across the inner seal and one of the things that we've learned historically is that for this pressurization to occur we need a ratio of 10 to 1 and tightness between the inner seal and the outer seal well we make the outer seal 10 times leak third in the inner seal by making sure that the holes are big enough on the outside to pressurize that space so if I have large enough holes and that's the right word is large enough holes you don't want the holes to be too small you want to be able to have the outer side of this assembly ten times weaker than the inner side if they both start out with the same material the outer seal is going to age faster than the inner seal because it's exposed to the outside so the ratio always stays ten to one or greater as of ages so we don't care about the failure of the outer seal if the inner seal is ten times tighter than the outer seal and we're able to pressurize that space believe it or not this was figured out in the late 1950s and it's been the fundamental way of doing commercial and residential windows for over a half a century pretty impressive now what we want to do is apply exactly the same approach to the window to wall interface what we want is a tight inner seal that's where that red blob is you want a four-sided airtight inner seal but we want to allow air to get into that space at the bottom of the window to pressurize the space so we want in essence rain shedding at the top and the sides of the window on the outside a four-sided air seal at the bottom of the window we want the opening to be like a gutter so we want to in essence a flashing system at the bottom so that when the wind of the wall interface leaks or when the window itself leaks it leaks into this gutter and is trained to the exterior so here's here's how would you done we assume that some water is going to be running behind the building paper house wrap at the intercept between the sheathing and the building paper and that's what's represented by these dashed lines but we don't care about that if we allow that water to drain out we do that by cutting a flap and the building paper or WRB at the head and sealing the flange of a window with a flashing typical flashing membrane directly to the sheathing when we fold that flap down the water that's running behind the building paper hits that red horizontal flashing tape and is kicked to the exterior so we don't direct water in at the head we kick it to the outside at the jams we fold the building paper WRV into the opening and then we provide a heavy bead of sealant behind the flange and when we screw the flange in place that acts as a gasket to prevent the water from running in at the size of the window and then we apply a flashing tape so here's here's the sequence it's nice to have a sloping sill we cut the water resistant barrier in the shape of an upside-down martini we fold the bottom and the sides in and the top up we put in a flashing system so we've got side dams we've got some stove at the back we install our window and we provide a sealant only on three sides we want the water to be able to drain out at the bottom they apply the fashion tape at the jambs flashing at the head hold it down we do not tape across the top of the window at the head because I mean water we want the water to be able to drain out we're still not done we need a four side of your seal on the inside and that's how you do a window installation to provide drainage and pressure relief or pressure equalization at the window to wall interface pretty fundamental but I can't tell you how many people get it wrong by not appreciating how important that four-sided air seal is on the interior I like to I have to be very careful with that air seal on the inside a lot of people are using spray foam but that stray foam can clog the drainage gap so whenever we use spray foam we shove a sealant backer rod in so that the sealant backer rod acts as a backstop so that the spray foam doesn't completely go to the back of the flange so you speaking technically you smoosh your sealing backer rod in to about a half an inch away from the flange and then you can then spray that you can then inject spray foam into that space and you know that you're going to have a clear drainage space and air space between the sealant backer on in the flange these flashing membranes to be effective have to be have to be rolled I can't tell you what a big deal rolling these flashing tape splashing tapes is this is a slick way of doing things there's our rainwater management and we've got a system of furring strips to basically create that drainage gap you don't necessarily have to install your WRB before you install your windows you can alter the sequence and install the window first and then the WRB but the general principles of sealing at the head are the same and again don't forget to roll the flashing membrane of the flashing tape to the WRB then your quality control typically in commercial buildings as we test 10% of the windows that are installed with a water leakage test in essence we simulate wind driven rain by building a pressure chamber on the inside using a modified vacuum cleaner to create suction and spraying water on the outside you don't need a very sophisticated technology to do fish you can you can spray this with Anniston put a blower door in your building to create the pressure difference in see you could do a very low-tech version of a water leakage test as a very quick quality control uh not just your window but your lender to wall interface why are we focusing on windows well there are only two kinds of windows in the world windows that leak in windows that will leak so what do we know about windows they're going to leak especially as they get older so we do everything we can at the window the wall in your face still accept the fact that someone's going to get in and design the assembly to dry to both the inside and the outside there's our waters test in action with the spray rack on the outside we have other penetrations and this is obviously a drier event I hate this because there's not enough of a flange on the accessory to be able to integrate the WRB tube this is just a real bad situation but the approach to get is pretty straightforward you can purchase accessories that have flanges this is a flange for commercial installation this is my colleague who's taking the roof jack that has a big plan John it to provide basically water management of where the refrigerant line enters the entries of the building so it works on your roof is probably going to work on your wall some of you might recognize that as a young professor Straub when he had hair of course don't do stupid things and one of the stupidest things is to install vinyl wall coverings on the inside that they prevent the wall assembly from from from from in essence being able to dry to the inside or a plastic vapor barrier there are two sides to a wall and it is desirable to have the assembly to be able to dry on both of those you want the wall to dry inward during air conditioning you want the wall to dry outward during the heating season for outward drying to occur you're going to need an an air gap between your cladding and your water control layer especially where they have basically lots of rainfall so let me let me sort of summarize summarize all of this of all of the mechanisms we have to worry about moisture and water is the most significant the biggest leading mechanism from a water perspective is rainwater and where it rains more as you need more rain control the water control layer on the outside to handle rainwater is likely going to need a drainage gap between it and you're clouding systems to control hydrostatic pressure especially where it rains more than 20 inches of rain a year when we have more than 20 inches of rain a year and we couple it with engineered wood that doesn't have the same drying characteristics or durability characteristics as plywood and bore achieving that drainage gap also becomes an air gap to provide drying capability so we want the wall assemblies to be able to dry into that gap when we have high levels of insulation and moisture sensitive materials and then avoid the vapor barriers on the inside in places where you where you air-conditioned and with that I'll turn you back over to to Mike Thank You Joan appreciate it much for those of you who have questions please don't hesitate to enter those into the questions box and send those in and we'll be getting to those momentarily I wanted to address the question that we get all the time which is are there going to be any handouts or these slides going to be available so I'll repeat this later on but I'll go ahead and get to it first the slides are going to be available tomorrow on building science comm you just need to go to the building science comm website click on recent presentations will be a PDF there and as always green building media records these webinars and post those on the green building media YouTube channel so I'll repeat that again later but for those who are asking or wondering alright Joe the first question we've got is from Tyler he wants to know if you've got a continuous drainage mat such as sure cavity and it's used behind brick or stone does the depth of the cavity matter with respect to moisture control yes and no terrible answer but you don't need a one inch gap between the brick you can treat the brick if you put a quarter inch or 3/8 inch drainage mat over building paper and put another layer of building paper over that you could smoosh the brick directly against that in other words a 1/4 inch to 3/8 inch continuous gap behind brick veneer will work just fine the brick can drain and dry into that space the wall assembly can do can do the same here's a warning however brick Masons like the 1-inch because it allows them to also straighten out the wall it's very difficult to have a brick veneer installed over less than say a half an inch airspace because it doesn't give the Masons enough room to be able to straighten things out inline things out believe it or not so even though from a building physics perspective you could pretty much get away we're not get away it will work with 1/4 inch to 3/8 inch gap experience has told me that I think if they want a half an inch to 3/4 of an inch in order for me to be able to give enough enough space for the mason to line things up but the gap isn't just critical that one knows I wanted share space again was a historic artifact it wasn't based on on measurements and physics we could go down to the quarter to three eighths of an inch but remember the installation becomes more we get to become fastidious when you do it gotcha Tom had a question for stucco on a sip wall in the Virginia Maryland area what type of drainage matter system would you recommend well have a water resistant barrier WRB of between 10 and 20 perms and I put a I would put a 3/8 inch drainage mat over that with a filter fabric and then I put a laugh-in stucco so I end up with stucco a building paper filter fab or filter fabric 3/8 inch drainage mat my WRB between 10 and 20 perms and my sip panel and I'd be I'd be in bliss it would work just fine all right Elisha wanted to know you know there's some breathable bears on the market as high as 84 perms and they claim that the higher the perms the better the ability to cavity to dry can you speak a little about that well that that is true if you don't have a reservoir cladding if you've got vinyl siding aluminum siding you got a metal panel or a fiberglass panel the higher the permeance of that layer not an issue but once you the moment you have a reservoir cladding like stucco or brick or wood or fiber cement and that reservoir cladding is going to get wet the Sun will drive out moisture in and it will blow through that very very high permeance layer and it's going to get yourself into trouble so for example I would never use anything greater than 20 perms over gypsum board shaving so let's say that I have a brick veneer and I'm installing it over I'm building a platform bill in apartment building and three four story building with gypsum board sheeting on the outside that gypsum board is very vey droven it's around 30 perms 30 to 40 perms if I have a 50 perm or an 80 perm WRB that water vapor is going to be blown through that WRB and that gypsum board into the wall cavity and caused me problems on the other hand if I have my gypsum board sheeting which is three 20 to 30 to 40 perms and I've got a 10 to 20 perm vapor throttle the inward drive isn't as great and I'm able to dissipate that moisture and the air space between the cladding system and the face of that vapor throttle when I get to oh s D vos B itself becomes the vapor throttle but I don't want that to be to get too wet either so I still want a vapor throttle over my vapor throttle so I'm going to want something between 10 and 20 perms over my over my OS B as well so the OSB prevents the water from getting into the wall cavity but I want to prevent the water from getting into the surface of the OSB from the outside as well but I don't want to stop it completely because I want that OSB to be able to try back to the outside and OSB in itself isn't a perfect vapor barrier it runs between one and three perms I still have a little bit of trying to the outside as well and so I want the stuff that goes from the cavity into the USB to get out of the OSD into that airspace so you know the sweet spot is between 10 and 20 perms with a reservoir clouding again when I go to a purple panel or aluminum siding or vinyl siding or whatever something is a non reservoir we don't have an issue with the high perm layers okay we're going to take you south now Joe Fernando wants to know how you would address a core insulated concrete panel so this is kind of a reverse ICF you've got an inch and a half concrete layer on the exterior and interior sides and a 4-inch EPS core that's a fabulous wall I'm the big issue are the joints and say you would do two stage joints basically an inner seal and outer seal at the joint then you drain the space between these two joints this is a common method of precast panel assemblies and it's phenomenal if I was to want to paint the concrete I would use a high perm paint greater than ten perms why do we know it has to be greater than ten perms if it's less than ten perms of bubbles and blisters so they're unpainted concrete or if you do paint the outside surface it's got to be greater than ten perms and you want a two-stage joint between the the inner and outer layers and you're good to go the window to wall interface we would typically want line the opening with a fully insured membrane we call that raccoon e as in raccoon eyes and then again do the two stage joint a four-sided inner seal and it's recited seal to the exterior that's a proven southern technology that came to the south from the north so there you go all right Dan's question references a slide you had earlier the stone veneer that you discussed is that a thin stone system or is it a laid up veneer like brick it doesn't matter there's the image I'm like oh sure we don't care I don't care passionately or deeply I just want that gap so it could be a manufactured stone veneer which I call lumpy stucco it could be a dry stack it could be you know stone with mortar all of them are going to be handled in essence the same way a drainage mat with a filter fabric so why am I looking to 3/4 of an inch if I've got say a manufactured stone veneer which is lumpy stucco well because lumpy stalker leaks more than regular stucco that's that's that's the reason okay we got a question from David and David's an architect he's going to know if you can discuss your feelings on dew point I think you should go to our website and read it read the building science inside called confusion about diffusion there's absolutely no reason to do dewpoint calculation the dew point is always going to be on the backside of the sheathing and so I'll show you an image here condensation is always going to occur at the insulation sheathing interface and the reason for that is is that when you have a change in phase the enormous amount of energy occurs is released and fiberglass and cellulose cavity insulation doesn't have enough thermal mass to handle this change in phase energy so for condensation occur you need a surface below the dew point temperature with sufficient thermal mass to handle the changing phase and that's the back side of the sheathing so you always are going to have the dew point location be the back of the sheathing so the calculation is is pointless okay a question from Douglas and believe Douglas is an energy consultant he said he came across a house had Tyvek installed under the exterior sheathing and he had the homeowner to open the drywall to inspect the wall cavity based on that do you recommend any further action to identify any other damage that may be occurring to the shell of the house there's a lot of information missing in what she gave me I'm assuming that the reason that the wall was opened up was because perhaps something smelled or sustained or whatever if the question is is opening up the wall to have a look a good idea absolutely I think it's way more reliable than moisture meters it's way more reliable than an infrared camera and to me it's the it's the best investigation technology around the person becomes how many walls how many holes be put into your building and the answer to that is going to be depends on what you find I would tend to want to look under my windows and under my doors because those are where I probably have got my biggest risk and probably going to also want to look where I have decks attached to a building or balconies I'm going to want to look at where rooms meet walls and so I look at probably quote a hole in the inside of the outside or both sides to look at things at the highest risk locations but besides opening things up I don't think you need to do anything else and that's going to tell you from my experience everything that almost everything is you're going to want to know all right we're going to ask you to play long distance consultant one more time Joe we're in the Denver climate we've got cement fiber board siding is one layer so Denver is where they have a semi professional football team now I think ouch is is one layer Bob's want to know is one layer of Tyvek WRB okay and there's no vent space or mat and it's OSB sheathing the answer is yes Denver gets less than 20 inches of rain a year Tyvek or any one of those water resistant barriers are good enough OSD is the vapor throttle with the fiber cement I prefer to paint the backside of it to reduces water control the water absorption and would be nice to use the commercial Tyvek the commercial high back is twenty firms the residential one is fifty five so ten to twenty perm WRB OSD in Denver you know fiber cement beautiful job beautiful recommend that all the time Lisa was going back in referencing a slide you had earlier you had the building type wall sections she knows that the stucco and the stone versions did not show a low air intake or high air outlet for the drainage and drying gap can we assume that those are needed for all cladding types the answer is yes and I hate it when I'm caught deliberately not putting information in because it's complicated on how to put that in and I tend to vent a wall at the top behind some kind of a band board at the bottom I need some kind of a trim assembly but yes I want a continuous gap at the top and a continuous gap at the bottom I just didn't want to get into a lot of details and how to show it I leave that up to all y'all to sort out okay we're here at the top of the hour and Joe has agreed to stay on a little extra to address any further questions so I'm putting out right now the last call for questions if you've got any Joe you know I had one for you are you seeing any better air sealing on the inside since the energy code started making significant gains in efficiency I'm talking like the past five years or so because it took a while for the own I'd actually get into the marketplace and people start adopting it and using it so have you seen any better air sealing the past five years yeah it's been quite noticeable quite significant ever since EPA's energy you know if mo by cuffs checklist was more or less written into the code and colder climates were typically seeing three to four below three year changes per hour at 50 Pascal's and in the South were regularly seeing four to five year change crowd at 50 Pascal's that's a that's a huge improvement in air leakage across the building the reason for the difference between the north and the south is in places up north we have basements and that's where we put mechanical systems in ductwork in the south we don't have basements we put our duct work in vented attics and that accounts for the higher air leakage if we were to have conditioned attics the air tightness of the buildings between the North and the South would be very similar and they'd be in the 3-yard changes per hour 50 Pascal's range that's a huge huge change we were typically in the five to seven range and now we're consistently in the cold climates at the less than three range that's a remarkable achievement okay thank you sir Brian's an architect and he has a question he wants to know yeah it has regretted similar to sips what is your recommendation on exterior and interior because he's been advocating seal taping all the seams on the interior and exterior before installing drywall on the interior typ and dr on the interior and WRB on the exterior I'm sorry what I don't I didn't understand that the question I I like to I like to air seal on the exterior and the interior like a double seal and I find that the gypsum board is a reasonable air control layer on the inside with all of the drafts topping and then they continues the exterior sheathing is a very very good air seal and air seal on the exterior as well so I like to see I like to see both help me out with a question Mike yeah yeah so he's saying in in lieu of wood or metal framing building using sips instead so using sips what's your recommendation on exterior and interior well it's critical that we have an air seal at the inner side inner layer of the ship in for roofing applications in terms of walls it's not so critical because we're always going to see some kind of a ventilated cladding system so I want both an into inner seal and outer seal wherever possible but the inner seal becomes critical in roofing applications because normally we put shingles on those on those zip ribs and if the inner seal isn't perfect we're going to get moisture accumulation at at that outer at that outer layer that's been such a serious problem with with tsipras that we we recommend putting it we recommend put it we recommend putting a vented / roof over the SIP panels on the roof so we would put down our sip panel we put down roofing paper we put down you know two by twos and then we put another layer of plywood OSB on the top of that and our roofing cervesa khalipa ting a vented over roof over the top of the over the top of the sub panels this is a concern walls not so much Maria's got a question and we're going to take you back north to Wisconsin when you were talking about Tyvek with cement board she's seen an increased use of LP smartside so do you require a drainage gap or is OSB and Tyvek sufficient now I like to see a I like to see a gap got more than 20 inches of rainfall a year I think you want to I think you want a gap between your your cladding system and your OSD in places like Wisconsin I just wrote a column on our website it's the most recent posted building science inside DSi it's called stress relief and it deals with how to install siding and trim and to provide that gap so the short answer is in Wisconsin I'd like to see a gap between my clouding systems and my my WRB and I have no problem with alt smart side both the siding and the trim work phenomenally well when you have a gap okay the last question goes to Michael he he's referencing the current IRC and he says it asks for a vapor retarder on the inside of the wall with a class 1 rating any thoughts on that well it it doesn't require a class 1 rating anywhere I know that because I wrote that section of the code there's no requirement for a class 1 only it's a class 1 or class 2 in all of the climate zones there's also an exception where you can go to a class 3 if you have sufficient thermal resistance of your continuous insulation on the outside so class 1 is point 1 perms or less class 2 is between 1 between point 1 and 1 and class 3 is between 1 and 10 perms so you could easily install a class 2 and a place like Minnesota Wisconsin it does not require a class 1 vapor retarder Wow now thanks for the awesome well there are some building officials that interpret things their own way and the practice in Minnesota is to wrap the building with plastic vapor barrier the code the IRC doesn't require that but the local Minnesota Code and the building officials interpretations of it differ from the actual language of the IRC and by the way the IDC gotcha alright I think we exhaust all the questions Joe so I want to thank you for sharing your time your wit and your knowledge with us today and as I mentioned before if you'd like a copy of his slides tomorrow you can go to building science comm click on recent presentations and you can download the PDF there I want to thank our audience for attending and asking the wonderful questions that they did and to fortify bur for their generous sponsorship of this webinar now we'll be right back here again two weeks from today so make sure you all set your calendars come on back two weeks from now invite your friends and your family we're going to be here Wednesday May 17th 2 p.m. Eastern Time Joe is going to be with us and he's going to be talking about building beyond Net Zero and enabling us to design and build homes that are net positive energy producers so you're not gonna want to miss that so come on back until next time stay dry take care

Channel: Fortifiber Building Systems Group

Views: 65,309

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Id: rem5WhFiiwU

Length: 68min 19sec (4099 seconds)

Published: Thu Jun 01 2017