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I stopped to talk to a builder who instead of using a house wrap uses a wide tape on all the seams between the pieces of sheathing, and the sheathing and rim joists. He claims it is more airtight since air can leak around the top and bottom and seams of the housewrap anyway. I assume the plywood or foamboard sheathing is impervious to air infiltration in itself and it’s the seams you have to worry about anyway. Has anyone else heard of this method?
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Here's something to think about:
How long is the tape going to stay in place? Of course, housewrap tape has the same issue, but housewrap has a few less seams to leak once the tape dries up and falls apart.
*You could, arguably, use mastic on those joints for a long-lived seal. Though I am starting to think caulking the sheathing before its fastening would be better.I would at least use tar paper to shed water that might get behind the siding.-Rob
*I think Tyvek's greatest function is as a drainage membrane. Asphalt felt paper is fine too. What matters most IMHO is proper lapping of whatever you use for wrap. I've seen some really laughable installations of housewrap. Scraps thrown up every which way, reverse laps, etc.You could argue that asphalt is better for air sealing, particular with a rigid siding that will press the tar paper hard to the sheathing. That should effectively seal it pretty well. Ever tried to peel old tar paper off that's been pinched to the building? It don't come real easy.Steve
*... and the felt is cheap! Tyvek is $$$, and you're right people install it in the most bizarre ways imaginable. I've heard Tyvek's water repellancy can be defeated if you backprime with latex.
*Tyvek is the fastest thing the framers do in my neighborhood.
*MattG. The longevity of the tape is the big unknown.Is Tyvek or other housewraps the answer? But for Tyvek to work it too must be sealed...with tape. What if we took a roll of polyethylene sill sealer and cut in into 1-1/2-inch wide strips and attached these strips--gaskets-- to the exterior of the studs at the joints between the RFBI, corners and around openings.Now install the RFBI. Do we now have a reasonably air-tight connection thast makes housewrap unnecessary? GeneL.
*This is very similar to the "Air Tight Drywall" approach using gaskets at all of the plates and windows. The idea is gasket all of the joints and then to eliminate the vapor barrier since it rarely gets installed correctly.
*GeneWhy not just use i shiplapRFBI, assemble with tight joints and caulk the laps with acoustical sealant?? At outside corners a right angled butt joint could also be caulked.-Patrick
*Dear Rd,If you think the VB rarely gets installed correctly, what makes you think those same people can be trusted to install gaskets properly?
*Hi Mark,The main question is "what is expected of tyvek"?I only use tyvek as a rain screen, as do all builders. Tyvek is not intended to be an air barrier, sealing it to be one would be impossible.Your contractor friend is only wasting his time in taping the sheating. It accomplishes nothing.Gabe
*Gabe,I disagree with both of your statements...Tyvek is advertised to reduce air infiltrion and water but allow water vapor to pass...And yes it is well known that a long term rated tape applied to sheathing seams will reduce air flow through the structure. I know no one other than you that would disagree with what I just said...If so please post here and explain to me enough to chang my mind on this as I am always open to learning.Love, peace and groovieness, near the stream,J
*Hi Jack,Oops I forgot, we're both pilots and we're not supposed to say that.You disagreed and then you agreed.What We both sayed was that the Tyvek was not an air barrier.Whether tape is long term rated or whatever, it is time rated and as caulking will fail so will it.So where do we disagree, Jack?
*Gabe,you're saying Tyvek is not for stopping air...I am saying that is it's main selling point. We are not agreeing unless you are digging very deep into the semantics of all.And I wuold think a long term tape is do-able. Still I am not fond of most residential caulks...Some of the expensive comercial urathanes seem to be made to stand more tiime but residential construction uses it not as far as I ever notice.Near the stream, and gonna be flyin off the lake soon again,J
*Jack,If it wasn't for the quick protection it gives to the house during construction, I probably still would be using felt paper. Tyvek will let air through and deflect water away, because it's meant to. Tyvek is neither an air barrier nor a vapour barrier.I still believe a house has to breath on the outside, both are good at diverting water away from the house, and with the use of a good poly vapour barrier on the inside under the drywall, what should stay inside does and what should breath does.Caulking be damned, don't use it unless I hafta.Gabe
*>>Caulking be damned, don't use it unless I hafta.<<Gabe,Doesn't R2000 interior air-sealing rely heavily on caulk in conjunction with the poly?Steve
*Steve,That's one of the times when I hafta.Try again.Gabe
*Gabe,When you hafta, what kind do you use?Only when I hafta too........Ron
*OK Gabe,>>it is time rated and as caulking will fail so will it<<Why build a house with an air-sealing system that is destined to fail? You don't hafta. There are alternatives.Steve
*Hi again Steve,First of all, what is used is an acoustical sealant on the poly joints, secondly, once the rest of the components are in place, the drywall against the studs and insulation sandwich the poly with the 2 foot overlaps and the accoustical sealants in between so if one would fail in 100 years or so the rest of the assembly would hold quiet well for the next 100 yrs.Therefore nothing is designed to fail, nor will it.Still waiting for credentials, fellas.Gabe
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You guys agree then that Tyvek is not really a barrier to air infiltration. But that's exactly what the manufacturer is trying to have the public believe. I can see where it is good as a moisture barrier.
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Actually Mark, it is not a good moisture barrier but it is a fair water (LIQUID water) barrier.
*I recently did a simple test in which water passed through Typar faster from the written on side than from the blank side. As I install Typar, and a breeze gets behind it, it sure wants to "hold" that air - like a sail would. I wonder how the heck I can get any impartial straight talk about this stuff. Guess I'll just keep reading these posts and hope something rings true. - yb
*Typar and Tyvek are differently made products...I'm sur you're water test will come show differences as well. Both are advertised to reduce air movement through a wall without causing a build up of moisture...That is they both are made to allow water vapor to pass much more readily than standard poly sheating would...Near the stream and knowing a lobster trap when I see one and also know what's wrong with capillary and double trouble barrier construction.Near the pressure plane, the hang glider and the ultralights, and yes even the heavy iron (aluminum) Cessna stuff.J
*Mark,Try to blow through a piece of Tyvek...It is a great reducer of air flow...But it has other drawbcks that you are missing such as wood siding attached tight to it having more problems in some climates than the venerable felt paper causes...There are other issues that have been raised in earlier threads such as how long will the stuff last in real use...Ten years isn't long enough for me but a hundred would be great.Near the stream, and not totally sold on any benefit over felt.J
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As a relative newcomer to the trade I've noticed the great attention always paid to preventing air infiltration into wall cavities. However, ventilation is always mandatory in attics and roof designs to eliminate moisture buildup from potential condensation in cold climates. But the insulation in these areas is always installed totally exposed to air movement. Although this insulation may be installed carefully to eliminate gaps between ceiling joists and penetrations, any wind blowing through the gable and eve vents, it seems to me, would prevent it from performing to its full R value no matter how thick, and you'd end up with the same situation as with air movement in your walls. I'm just curious as to why this is never addressed. Case in point, while drywalling a cathedral ceiling recently during a wind storm I watched the vapor retarder bulge out with every gust. What good, I wondered at the time, does it make to have airtight walls when there's obvious air penetration into 12" of ceiling insulation?
Learning to do it right in AK
Bob
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Hi Bob,
The basic difference between the roof and walls is what we expect of it and it's function in keeping occupants comfortable.
The wall composition from the occupants outward is basically, drywall, poly to prevent moisture from entering the wall cavity, insulation to keep everyone toasty warm or cool, sheating and housewrap to protect as a rainscreen and still allow vapour to escape or breathe.
The roof composition from the occupants outward is similar except that the roofing material is specifically designed to keep rain or water out 100%. It is also the area where most heat loss occurs. Therefore, instead of sheating and housewrap, we allow space for ventilation between the insulation and roofing systems. The ventilation will reduce the heat buidup both on and under the roofing and thereby extend the life of the roofing. There will be a loss in R factor but the resulting benefits will more than compensate for this.
Gabe
*Lobsters in and out of the pot everywhere...Lets have a beach party!Near the stream, thinkin what's up is stinkin,JOh no, I'm flamin!!!
*GabeI find the concept of> "housewrap . . . to allow vapour to escape or breathe." rather strange when the wrap is coupled with sheathing. How much "vapour" do you think passes to the outside through plywood, aspenite,or OSB???-pm
*I don't understand why the the "wisest" frequent posters here are clueless even with millions of marketing dollars spent a year as to the function of housewraps...I guess I better capture the company literature and post it here.It stops air from blowing through the leaky sheathed walls, reducing air changes on windy days considerably...My problem with it is damage it may cause wood sidings applied tight to it and also will it last a hundred years.Near the stream scratchin my head,J
*Morning Patrick,Come on Patrick, put on your thinking cap. Are you going to make me believe that plywood doesn't absorb water and afterwards can't dry out?That's called beathing.Try to change your focus from attacking to thinking, will you?Gabe
*HiJack,You can capture all the literature you want, Jack, what it won't say is that it does 100% of anything. It reduces up to 90% but is not guaranteed to absolutely stop anything. Not air, not vapour and not water.Buddy, you've got to start bringing bottled oxygen with you on those flights.Gabe
*Gabe,It drastically reduces air movement which if you read all your posts you just dance around that idea..The reason it is made to allow vapor movement is because if you used poly over wood sheathing you would have another of my famous "lobster traps!!!"Near the stream and lovin the oxygen...Ain't life grand!!!!J
*HiJack,COngratulations, you've finally figured out that housewrap is meant to BREATH!!!!!!!!!Who said you can't teach an old dog new tricks?Still in shock,Gabe
*Afternoon GabeGot any black flies up there??Get a brace for that knee jerk of yours. . . re-read my post and try to think in terms of legitimate query as opposed to attack.While I am sure I could neveri make you believe anything, consider the fact that exterior "manufactured" sheathing is supposed to be b waterproofhaving been laminated/pressed with waterproof glue. . . in the case of osb type productsb a sh*t loadof waterproof glue!!!!!If this sheathing gets wet due to condensation via convection from the interior do you really believe it CAN dry to the exterior?? I think NOT!!! Or at best not much!!!By all means support your hypothesis. . .. but don't feel compelled to start yet another fight!!!gratiously (for now)-pm
*JackThe assumption of "the leaky sheathed walls" has always confounded me. With horizontally applied sheathing,b carefully installed,starting at 1/2"(?) below the mud sill, a single story house would have several horizontal joints, but need only haveb onehorizontal joint around the building that wouldi need to be sealed.A two story would have two such joints.I'd rather seal up those joints with thin backers, or rely upon tarpaper, than wrap the whole bloody place with pseudo paper/plastic that is supposed to be waterproof, wind resistant,i andmoisture permeable.Just a young dinosaur I guess-pm.
*Rd. You are right. It is similar to Joe Lstiburek's ADA. The difference is that the gaskets are installed on the exterior.Patrick. Even with the shiplap joint you won't ghet as air tight a seal as is possible with the combination I suggest. and we both agree that caulking is the last resort. by the bye. Have you ever read any of Simplex Industries literature on their Thermoply? GeneL.
*Afternoon Patrick,No, we don't get black flies in the land of milk and honey. Besides the weather has been unreal lately and there hasn't been any rain. So that means the mosquitoes are drier than a fart right now and no eggs.I don't have a knee jerk, I have an ankle that acts up once in a while. The result of a fall off a wall while installing trusses.Don't use osb except for roofs and only use plywood sheating for my walls. The glue may be waterproof, but the layers of wood sure aren't. I never caulk the plywood joints and always use a gasket under my wall plates.With the layer of poly that I install on the inside, I don't believe that it's possible for any moisture to get inside the walls. Only that moisture that comes in with the wood.Once commented that if I had my drudders, I'd only use felt over the outside layer and I still stand by that.Besides the weather is super today, from what I hear, you've got the same,So your absolutely right, today is a day to be gracious.Gabe
*Gabe,Sorry to see you in shock but hope it lasts for a long long time. I think post and read posts and then mix up who's the author of what...My lobsters are gonna get you some day,J (Gabe, you didn't post this message)
*Patrick,Framing shrinks incredibly...This leaves a gap that allows air flow between and past sheathing and building components...Windy days will send a wash of cold air through fiberglass but maybe not throuogh DP cells as well...And maybe not so bad with housewrap or tarpaper applied...I have listed my main two reservations with housewrap use...Longevity and woodsiding possible problems...Near the stream and happy to use felt to(o),J
*Gabe,You sure are one of a kind compared to my neck of the woods...I have never used OSB on a roof or a floor and always use it one walls...Strange reversal but I'm sure you can flame me straight...Near the stream and never hiring Gabe to design a home for me,J
*HiJackThanks Jack for the kind complements.By the way, I don't use OSB on floors either. The roof material I use is super roof OSB, probably a little too heavy for you guys to lift onto a roof.Before I forget Jack, you can't afford me anyways, I don't use vinyl siding.Gabe
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I stopped to talk to a builder who instead of using a house wrap uses a wide tape on all the seams between the pieces of sheathing, and the sheathing and rim joists. He claims it is more airtight since air can leak around the top and bottom and seams of the housewrap anyway. I assume the plywood or foamboard sheathing is impervious to air infiltration in itself and it's the seams you have to worry about anyway. Has anyone else heard of this method?