Persist

[conarb]

There have been building scientists pushing an exterior cladding system developed in Canada called "PERSIST", it is being used in the Eastern portions of the United States apparently without objection by the local building departments. Here is a good simple explanation or PERSIST on the Green Building Adviser.I see many problems, not the least of which is that it violates the codes, I haven't bought the CBC version of the iRC (due to take effect January 1st), our current IBC based CBC states: (I would appreciated it if one of you people familiar with the IRC would post the relevant IRC section):

1404.2 Water-resistive barrier.

A minimum of one layer of No.15 asphalt felt, complying with ASTM D 226 for Type 1 felt or other approved materials, shall be attached to the studs or sheathing, with flashing as described in Section 1405.3, in such a manner as to provide a continuous water-resistive barrierbehind the exterior wall veneer.

Here is the abstract from ASTM D 226:

Abstract

This specification covers asphalt-saturated organic felt used in roofing and waterproofing. Two types of asphalt-saturated felts are presented: type I - commonly called No. 15 asphalt felt, and type II - commonly called No. 30 asphalt felt. In the process of manufacture a single thickness of dry felt shall be saturated with an asphaltic saturant. The methods for the determination of openness of the perforations in saturated felts are presented in detail.

Note that our former UBC also stated "or an approved Kraft paper", that has been deleted in the iBC based code. But also note that the code goes on to say in reference to stucco:

2510.6 Water-resistive barriers.

Water-resistive barriers shall be installed as required in Section 1404.2 and, where applied over wood-based sheathing, shall include a water-resistive vapor-permeable barrier with a performance at least equivalent to two layers of Grade D paper.

Exception:


Where the water-resistive barrier that is appliedover wood-based sheathing has a water resistance equal toor greater than that of 60-minute Grade D paper and is separatedfrom the stucco by an intervening, substantiallynonwater-absorbing layer or drainage space.

Other problems as I see:

1. Non-permeable walls can create dryrot problems if moisture enters the wall assembly from the exterior due to a flaw or breach in the covering.
2. Non-permeable walls can create dryrot problems if moisture enters the wall assembly from the interior, I've heard that each occupant produces somewhere between 3 and 6 gallons of water per day that escapes through the walls (I know that it seems unbelievable but I've seen it in building science articles several times).
3. The exterior insulation in PRESIST structures is one form or another of styrofoam, if H.R. 5820, the Toxic Chemicals Safety Act of 2010, passes the House, the Senate, and is signed into law, the following chemicals will be made illegal, it's my position that installing them in structures now is tantamount to painting with lead paint when we knew lead paint was going to be made illegal, or wrapping ductwork with asbestos when we knew the health problems with asbestos. We here also know the problems our firefighter brethren have with toxic foams, to say nothing of the large portions of this nation subject to insect infestation in all foam products.

‘‘(1) ESTABLISHMENT OF LIST.— ‘‘(A) As of the date of enactment of the Toxic Chemicals Safety Act of 2010, there shall be established a list of chemical substances for which safety standard determinations under this section shall first be made, which shall consist of the following chemical substances: ‘‘(i) Bisphenol A. ‘‘(ii) Formaldehyde. ‘‘(iii) N–Hexane. ‘‘(iv) Hexavalent chromium. ‘‘(v) Methylene chloride.‘‘(vi) Trichloroethylene. ‘‘(vii) Vinyl chloride. ‘‘(viii) The following phthalates:


‘‘(I) Benzylbutyl phthalate. ‘‘(II) Dibutyl phthalate. ‘‘(III) Diethylhexyl phthalate. ‘‘(IV) Di-isodecyl phthalate. ‘‘(V) Di-isononyl phthalate. ‘‘(VI) Di-n-hexyl phthalate. ‘‘(VII) Di-n-octyl phthalate.


‘‘(ix) Perchlorate. ‘‘(x) Tetrachloroethylene. ‘‘(xi) Tris (1,3-dichloro-2-propyl) phosphate. ‘‘(xii) Tris (2-chloroethyl) phosphate. ‘‘(xiii) Tris (2,3-dibromopropyl) phosphate.¹

The code goes on to say:

2603.8 Protection against termites.

In areas where the probability of termite infestation is very heavy in accordance with Figure 2603.8, extruded and expanded polystyrene, polyisocyanurate and other foam plastics shall not be installed on the exterior face or under interior or exterior foundation walls or slab foundations located below grade. The clearance between foam plastics installed above grade and exposed earth shall be at least 6 inches (152 mm).

Exceptions:


1. Buildings where the structural members of walls, floors, ceilings and roofs are entirely of noncombustible materials or preservative-treated wood.2. An approved method of protecting the foam plastic and structure from subterranean termite damage is provided.3. On the interior side of basement walls.

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As one can easily see most of the United States is subject to termite infestation, and even areas not subject to termites can be subject to other "critter" infestation. So my question to inspectors is, why is this system being allowed? Particularly in the New England area, and unbelievably I am even seeing it going in in the hot humid climate of Texas, several installations in Austin. Are inspectors in these areas placing energy efficiency ahead of the code? BTW just so your know, the stock answer coming from the energy efficiency fanatics is Lstiburek;s mantra: "Build it tight and ventilate it right", they are running fan systems, (fans, ERVs, HRVs) 24/7 to continually replace the toxic air they have just sealed in with the toxic substances.

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¹ http://energycommerce.house.gov/documents/20100722/HR5820.pdf

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[Uncle Bob]

Conarb,

I've glaced at some Green nut"s web sites, that are calling for "PERSIST"; but, have not found any specification on the method; or how it will be consistant with the existing code requirements. However, I feel that there is nothing we can do about these people; who have total control of the federal and state government agencies; and, have total disregard for structural stability, and/or inhabitant's health.

In fact they are using "double speak" to give the impression that this is good for the built environment, energy efficiency, and healthy living.

We will not win this fight; and as for me; all I can do as an inspector is try to make sure that construction meets all the requirements.

They will soon have homes that are sealed as tight as commercial refrigeration boxes.

I haven't seen any of this so far,

Uncle Bob

 

[RJJ]

As Always CA you provide to much info in one post. How about breaking it down alittle. In the roofing area I see products that are somewhat normal. A fast scan of the site leaves my little mind spinning. The basement fit out I see problems with. Next I need to look at the foundation drainage issues. Well I need a break! Interesting stuff. Wrap it up tight and run fans to save energy. Remove toxins or die and if you want fresh air go out side.

 

[conarb]

Okay guys, for simplicity's sake, let's say you go out to make an inspection, you find that they have covered the walls of the building with Grace's Vycor or Ice & Water Shield creating a non-permeable WRB sealing up the walls, what do you do? I've listed the IBC sections above, and would appreciate the comparable IRC sections as well.

This is not a rhetorical question, this is being done in New England and parts of Texas, I am being attacked for telling them that it violates code.

 

[RJJ]

CA: I believe Ice and water shield exceeds the code requirement.

 

[conarb]

RJJ:

You are answering my question as to how they are getting away with it, inspectors don't understand, you say "exceeds the code requirement", Ice & Water Shield has a permeance of less than 1, meaning that it is waterproof, if you install a waterproof WRB the wall can't "breathe" and "dry-out", California requires a minimum permeance of 5 for conventional building paper and 10 for plastic wraps:

5.0 Summary of ResultsKey findings regarding the Title 24 SLA reduction credit are summarized below.

• This research effort was not able to identify any peer-reviewed field data or other technical studies that support or refute a specific perm limit in walls with stucco cladding in California homes. The current limit in Title 24 reflects consensus engineering judgment and risk management decisions in the absence of authoritative technical data.

• The 10 perm minimum requirement for the SLA credit was established by consensus to address potential moisture concerns associated with building tighter homes. In the absence of field data relating housewrap permeance to installed performance, the justification for the specific value was based on the Committee’s interest in maintaining drying capability equivalent to 5 perm building paper without taped seams. No peer-reviewed field evidence to date in California homes on causes of building failures has identified any linkage between WRB perm rating and widespread moisture problems.¹

In the mid 1970s, after the first oil shortage, the asphalt paper manufacturers removed lots of asphalt from their paper, 15# felt meant it weighed 15 pounds per hundred square feet. after reducing the asphalt content to about half they renamed their product #15 felt, in a slight of hand 15 pound felt became Number 15 felt, taking advantage of the fact that the "#" sign was used both for "pound" and "number". I had three large homes under construction in two AHJs both leaking before completion (much of this had to do with the approval of staples as opposed to asphalt impregnated button nails, something that worked going through 15# felt, but not #15 felt). I had two more large homes in for permit in another AHJ, I went in to see the plan checker (a structural engineer) proposing that I use an asphalt membrane on the walls that I was using under slabs, it looked and felt like flashing material, black asphalt paper with crossed threads to keep it from tearing. This is what I use under slabs today, note that it comes in .02, .03, and .07 perms, California minimums for walls are 5.0 for asphalt products, and 10.0 for plastic wraps (Tyvek had a perm rating of 50.0 the last I looked). The plan checker yelled at me that I was an idiot, that I was proposing sealing my houses up so they couldn't breathe, I was young and dumb then, but he taught me a valuable lesson. WRBs are a delicate balance of waterproofing the wall and allowing air to permeate the wall for drying. If inspectors don't understand these basic building science concepts, these green nuts are going to be building buildings that rot out and defeat all of our structural efforts, to say nothing of making people sick from mold and other chemical products.

¹ http://media.godashboard.com/gti/1ResearchCap/1_3EnergyUtil/MoldResearch/Task5_1FinalTitle24AirLeakageRept.pdf

 

[Uncle Bob]

Conarb,

The only place we allow those "Greengos" is Austin; the liberal colony of Texas. You should move to Texas before we close the border to Californians.

Uncle bob

 

[conarb]

Uncle Bob:

How's that movement coming in Texas to secede?

 

[RJJ]

OK CA I will take the bait! If the wall is made water proof and exceeds the level required by code other then the lack of ability to breath whats the big deal? This is the way of green!

 

[Yankee]

I don't hear anyone yelling about using non-perm material as a vapor barrier on the (assume inside) warm side. Same issue. The issue is, if the assembly is designed to allow for drying whether it be from the outside of the assembly or from the inside of the assembly, it is fine. I prefer both but I am really happy if I see one.

 

[conarb]

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Yankee:Joe Lstiburek's Building Science corporation says that interior vapor barriers should only be installed in the Very Cold and Arctic/Subarctic hygro-thermal zones on the North American continent, that appears to be about 1% of the lower 48 states.​

Vapor barriers are also a cold climate artifact that have diffused into other climates more from ignorance than need. The history of cold climate vapor barriers itself is a story based more on personalities than physics. Rose (1997) regales readers of this history. It is frightening indeed that construction practices can be so dramatically influenced by so little research and reassuring indeed that the inherent robustness of most building assemblies has been able to tolerate such foolishness. So What is The Problem?Incorrect use of vapor barriers is leading to an increase in moisture related problems. Vapor barriers were originally intended to prevent assemblies from getting wet. However, they often prevent assemblies from drying. Vapor barriers installed on the interior of assemblies prevent assemblies from drying inward. This can be a problem in any air-conditioned enclosure. This can be a problem in any below grade space. This can be a problem when there is also a vapor barrier on the exterior. This can be a problem where brick is installed over building paper and vapor permeable sheathing.¹

Quite simply stated, code mandated WRBs are required to be permeable, and for good reason, sealing wall cavities on the inside or outside can cause massive problems including dryrot and health problems, especially with the use of today's toxic building products, there solution to the health problems is expansive ERV or HRV air-exchange units. ¹ http://www.buildingscience.com/documents/digests/bsd-106-understanding-vapor-barriers/?searchterm=hygro-thermal%20regions

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[Uncle Bob]

We didn't have any moisture (or mold) problems; when we wrapped the house with felt and allowed the house to breath.

Saving energy is another way for the utililty companies to get more money for supplying less energy.

Your energy bill is not going down; only your intelligence; if you buy into this crap.

You get these houses any tighter; and you won't be able to close the front door without opening a window.

Uncle Bob

 

[Yankee]

Vapor barriers are not required to be permeable per code, unfortunately

SECTION R318 MOISTURE VAPOR RETARDERS

R318.1 Moisture control.

In all framed walls, floors and roof/ceilings comprising elements of the building thermal envelope, a vapor retarder shall be installed on the warm- in-winter side of the insulation.

Exceptions:

1. In construction where moisture or freezing will not damage the materials.

2. Where the framed cavity or space is ventilated to allow moisture to escape.

3. In counties identified as in climate zones 1 through 4 in Table N1101.2.

 

[conarb]

Yankee:

A "vapor retarder" by definition is not a "vapor barrier", some more words from the energy efficiency mavens' God Lstiburek:

The recommendations are based on the following principles:

• Avoidance of using vapor barriers where vapor retarders will provide satisfactory performance
  
• Avoidance of using vapor retarders where vapor permeable materials will provide satisfactory performance. Thereby encouraging drying mechanisms over wetting prevention mechanisms.
  
• Avoidance of the installation of vapor barriers on both sides of assemblies – i.e. “double vapor barriers” in order to facilitate assembly drying in at least one direction.
  
• Avoidance of the installation of vapor barriers such as polyethylene vapor barriers, foil faced batt insulation and reflective radiant barrier foil insulation on the interior of air-conditioned assemblies – a practice that has been linked with moldy buildings (Lstiburek, 2002).
  
• Avoidance of the installation of vinyl wall coverings on the inside of air-conditioned assemblies – a practice that has been linked with moldy buildings (Lstiburek, 1993).
  
• Enclosures are ventilated meeting ASHRAE Standard 62.2 or 62.1.¹

You put a vapor barrier under a slab and on a roof, you put a vapor retarder on your walls, if your walls can't breathe your building cannot dry-in or dry-out, your building can rot-out, and you trap toxics in the building making people sick, or worse causing cancer and birth defects.

¹ http://www.buildingscience.com/documents/digests/bsd-106-understanding-vapor-barriers/?searchterm=hygro-thermal%20regions

 

[Yankee]

I am well aware of the theory Conarb. You are preaching to the choir. I think the conversation is about what the code requires (or allows). A "vapor retarder" under the IRC has a perm of 1 or less, no bottom minimum.

 

[conarb]

Here are examples of Fortifiber's vapor retarders for installation in wall construction:

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Here are examples of Fortifiber's vapor barriers for installation under concrete slabs.​

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Note the permeability differences, these are ASTM requirements, inspectors are going to be seeing this and they better get up on the code and ASTM requirements or they are going to be approving rotting buildings housing sick people. Uncle Bob and other Texans, do you guys know any Austin inspectors who you can ask why they are allowing this? Similarly Yankee and other New England inspectors, why are ASTM violations being allowed?​

A "vapor retarder" under the IRC has a perm of 1 or less, no bottom minimum.

No, a "vapor retarder has a minimum perm of 5 or 10, a "vapor barrier" has a perm of 1 or less. I know this can get confusing but we better be prepared.

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[Mule]

Is this what you are looking for?

R703.2 Water-resistive barrier. One layer of No. 15 asphalt

felt, free from holes and breaks, complying with ASTM D 226

for Type 1 felt or other approvedwater-resistive barrier shall be

applied over studs or sheathing of all exteriorwalls. Such felt or

material shall be applied horizontally, with the upper layer

lapped over the lower layer not less than 2 inches (51 mm).

Where joints occur, felt shall be lapped not less than 6 inches

(152 mm). The felt or other approved material shall be continuous

to the top ofwalls and terminated at penetrations and building

appendages in a manner to meet the requirements of the

exterior wall envelope as described in Section R703.1.

Exception: Omission of the water-resistive barrier is permitted

in the following situations:

1. In detached accessory buildings.

2. Under exterior wall finish materials as permitted in

Table R703.4.

3. Under paperbacked stucco lath when the paper backing

is an approved weather-resistive sheathing paper.

 

[conarb]

Thanks Mule, one of these days I'm going to have to buy our new CBC that has IRC based sections, then we will all be on the same numbering, be interesting how Housing and Community Development has amended these sections.

Does anyone have the complete ASTM D 226 and not just the abstract?

 

[Yankee]

IRC 2006

SECTION R202 DEFINITIONS

VAPOR PERMEABLE MEMBRANE. A material or covering having a permeance rating of 5 perms (2.9 × 10-10 kg/Pa× s × m2) or greater, when tested in accordance with the desiccant method using Procedure A of ASTM E 96. A vapor permeable material permits the passage of moisture vapor.

VAPOR RETARDER. A vapor resistant material, membrane or covering such as foil, plastic sheeting, or insulation facing having a permeance rating of 1 perm (5.7 × 10-11 kg/Pa × s × m2) or less, when tested in accordance with the dessicant method using Procedure A of ASTM E 96. Vapor retarders limit the amount of moisture vapor that passes through a material or wall assembly.

SECTION R318 MOISTURE VAPOR RETARDERS

R318.1 Moisture control.

In all framed walls, floors and roof/ceilings comprising elements of the building thermal envelope, a vapor retarder shall be installed on the warm- in-winter side of the insulation.

Exceptions:

1. In construction where moisture or freezing will not damage the materials.

2. Where the framed cavity or space is ventilated to allow moisture to escape.

3. In counties identified as in climate zones 1 through 4 in Table N1101.2.

 

[conarb]

Yankee:

Thanks for that, the IRC defines a "vapor retarder" differently than California, it will be interesting to see how California's version of the IRC handles it.

My question is that if the IRC defines a "vapor retarder" as 1 perm or less, that's the classic definition of a "vapor barrier", how does R202 define a "vapor barrier"? The next question is then, what do you IRC guys enforce for a WRB? All asphalt felts, Kraft papers, and plastic wraps are anywhere from 3 to 50 perms, so you are not installing "vapor retarders" as WRBs.

 

[TJacobs]

IRC 2006 Definitions:

WATER-RESISTIVE BARRIER. A material behind an exterior wall covering that is intended to resist liquid water that has penetrated behind the exterior covering from further intruding into the exterior wall assembly.

Yankee:Thanks for that, the IRC defines a "vapor retarder" differently than California, it will be interesting to see how California's version of the IRC handles it.

My question is that if the IRC defines a "vapor retarder" as 1 perm or less, that's the classic definition of a "vapor barrier", how does R202 define a "vapor barrier"? The next question is then, what do you IRC guys enforce for a WRB? All asphalt felts, Kraft papers, and plastic wraps are anywhere from 3 to 50 perms, so you are not installing "vapor retarders" as WRBs.

 

[Yankee]

Yankee: All asphalt felts, Kraft papers, and plastic wraps are anywhere from 3 to 50 perms, so you are not installing "vapor retarders" as WRBs.

That's true, in new england we wouldn't want the vapor retarder as a WRB because the vapor retarder goes on the warm in winter side (inside) and the WRB goes on the (wet) outside. If they are both non-perm, as you say, it is Trouble.

 

[RJJ]

Mule: If you don't put holes in the felt hows it stay on the building.

I see this as a situation that is basically a failure to communicate. It seems that a small handful of code people are not embracing the Green movement.

 

[conarb]

There is confusion in terminology here, to go back to Lstiburek:

What is required is to define vapor control measures on a more regional climatic basis and to define the vapor control measures more precisely. Part of the problem is that we struggle with names and terms. We have vapor retarders, we have vapor barriers, we have vapor permeable we have vapor impermeable, etc. What do these terms mean? It depends on whom you ask and whether they are selling something or arguing with a building official. In an attempt to clear up some of the confusion the following definitions are proposed: Vapor Retarder*: The element that is designed and installed in an assembly to retard the movement of water by vapor diffusion. * taken somewhat from ASHRAE Fundamentals 2001, Chapter 23. The unit of measurement typically used in characterizing the water vapor permeance of materials is the “perm.” It is further proposed here that there should be several classes of vapor retarders (this is nothing new – it is an extension and modification of the Canadian General Standards Board approach that specifies Type I and Type II vapor retarders – the numbers here are a little different however): Class I Vapor Retarder: 0.1 perm or less Class II Vapor Retarder: 1.0 perm or less and greater than 0.1 perm Class III Vapor Retarder 10 perm or less and greater than 1.0 perm Test Procedure for vapor retarders: ASTM E-96 Test Method A (the desiccant method or dry cup method) Finally, a vapor barrier is defined as: Vapor Barrier: A Class I vapor retarder. The current International Building Code (and its derivative codes) defines a vapor retarder as 1.0 perm or less (using the same test procedure). In other words the current code definition of a vapor retarder is equivalent to the definition of a Class II Vapor Retarder proposed by the author. Continuing in the spirit of finally defining terms that are tossed around in the enclosure business. It is also proposed that materials be separated into four general classes based on their permeance (again nothing new, this is an extension of the discussion in ASHRAE Journal, February 02 – Moisture Control for Buildings): Vapor impermeable 0.1 perm or less Vapor semi-impermeable 1.0 perm or less and greater than 0.1 perm Vapor semi-permeable: 10 perms or less and greater than 1.0 perm Vapor permeable: greater than 10 perms¹

The code mandated WRB states:

R703.2 Water-resistive barrier. One layer of No. 15 asphalt felt, free from holes and breaks, complying with ASTM D 226 for Type 1 felt or other approved water-resistive barrier shall be applied over studs or sheathing of all exterior walls. Such felt or material shall be applied horizontally, with the upper layer lapped over the lower layer not less than 2 inches (51 mm). etc.

The PERSIST system requires an impermeable membrane, no impermeable membrane complies with ASTM D 226, as to other "approved water-resistive barrier(s)" they use a peel and stick, the largest manufacturer is W.R. Grace with their Vycor peel and stick flashing and their Ice and Water Shield roofing membrane, neither Vycor nor Ice and Water Shield is approved as a WRB. Unless someone can show you an approval for a peel and stick as a WRB you have to disapprove it, note that Lstiburek says "or arguing with a building official. " he seems to like that, so have at it if anyone attempts it in your jurisdiction.

Here is a W.R. Grace picture showing where their products can be used.

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¹​

http://www.buildingscience.com/documents/digests/bsd-106-understanding-vapor-barriers/?searchterm=hygro-thermal%20regions
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