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2021 IBC and IRC Adopt Improved Vapor Retarder Requirements Part I

2021 IBC and IRC Adopt Improved Vapor Retarder Requirements Part I

Originally published by the following source: SBC Magazine — July 29, 2020
by Jay H. Crandell, P.E., ARES/ABTG

This article addresses advancements to the water vapor retarder provisions of the 2021 IBC and IRC.  It is also related to properly coordinating the use of cavity and continuous insulation materials to comply with the energy code, and also water vapor retarders to comply with the building code, as addressed in a separate article on the newly updated wall calculators.

To start, the new 2021 IRC code language for vapor retarders is shown in Figure 1 (as based on ICC code change proposal RB223-19(link is external)). The 2021 IBC code language will be similar (except as noted in Figure 1). This may appear to be a lot to digest, but it is actually pretty straight-forward and effective. To help, a brief explanation of the most significant aspects of this code change follows.

R702.7 Vapor Retarders. Vapor retarder materials shall be classified in accordance with Table R702.7(1). A vapor retarder shall be provided on the interior side of frame walls of the class indicated in Table R702.7(2), including compliance with Table R702.7(3) or Table R702.7(4) where applicable. An approved design using accepted engineering practice for hygrothermal analysis shall be an alternative. The climate zone shall be determined in accordance with Section N1101.7 (R301.1) [ See Figure 1].

Exceptions:

  1. Basement walls.
  2. Below-grade portion of any wall.
  3. Construction where accumulation, condensation or freezing of moisture will not damage the materials.
  4. A vapor retarder shall not be required in Climate Zones 1, 2, and 3. [This exception is not in 2021 IBC]

R702.7.1 Spray foam plastic insulation for moisture control with Class II and III vapor retarders. For purposes of compliance with Tables R702.7(3) and R702.7(4), spray foam with a maximum permeance of 1.5 perms at the installed thickness applied to the interior side of wood structural panels, fiberboard, insulating sheathing or gypsum shall be deemed to meet the continuous insulation moisture control requirement in accordance with one of the following conditions:

  1. The spray foam R-value is equal to or greater than the specified continuous insulation R-value.
  2. The combined R-value of the spray foam and continuous insulation is equal to or greater than the specified continuous insulation R-value.

 

TABLE R702.7(1)
VAPOR RETARDER MATERIALS AND CLASSES
CLASS ACCEPTABLE MATERIALS
I Sheet polyethylene, nonperforated aluminum foil, or other approved materials with a perm rating of less than or equal to 0.1.
II Kraft-faced fiberglass batts, vapor retarder paint, or other approved materials applied in accordance with the manufacturer’s installation instructions for a perm rating greater than 0.1 and less than or equal to 1.0.
III Latex pain, enamel paint, or other approved materials applied in accordance with the manufacturer’s installation instructions for a perm rating of grater than 1.0 and less than or equal to 10.0.

 

TABLE R702.7(2)
VAPOR RETARDER OPTIONS
CLIMATE ZONE VAPOR RETARDER CLASS
CLASS Ia CLASS IIa CLASS III
1, 2 Not Permitted Not Permitted Permitted
3, 4 (except Marine 4) Not Permitted Permittedc Permitted
Marine 4, 5, 6, 7, 8 Permittedb Permittedc See Table R702.7(3)

 

  1. Class I and II vapor retarders with vapor permeance greater than 1 perm when measured by ASTM E96 water method (Procedure B) shall be allowed on the interior side of any frame wall in all climate zones.
  2. Use of a Class I interior vapor retarder in frame walls with a Class I vapor retarder on the exterior side shall require an approved design.
  3. Where a Class II vapor retarder is used in combination with foam plastic insulating sheathing installed as continuous insulation on the exterior side of frame walls, the continuous insulation shall comply with Table R702.7(4) and the Class II vapor retarder shall have a vapor permeance of greater than 1 perm when measured by ASTM E96 water method (Procedure B).

 

TABLE R702.7(3)
CLASS III VAPOR RETARDERS
CLIMATE ZONE CLASS III VAPOR RETARDERS PERMITTED FOR:a,b
Marine 4

[or all of 4 for 2021 IBC]		 Vented cladding over wood structural panels.
Vented cladding over fiberboard.
Vented cladding over gypsum.
Continuous insulation with R-value ≥ 2.5 over 2 x 4 wall.
Continuous insulation with R-value ≥ 3.75 over 2 x 6 wall.
5 Vented cladding over wood structural panels.
Vented cladding over fiberboard.
Vented cladding over gypsum.
Continuous insulation with R-value ≥ 5 over 2 x 4 wall.
Continuous insulation with R-value ≥ 7.5 over 2 x 6 wall.
6 Vented cladding over fiberboard.
Vented cladding over gypsum.
Continuous insulation with R-value ≥ 7.5 over 2 x 4 wall.
Continuous insulation with R-value ≥ 11.25 over 2 x 6 wall.
7 Continuous insulation with R-value ≥ 10 over 2 x 4 wall.
Continuous insulation with R-value ≥ 15 over 2 x 6 wall.
8 Continuous insulation with R-value ≥ 12.5 over 2 x 4 wall.
Continuous insulation with R-value ≥ 20 over 2 x 6 wall.

 

  1.  Vented cladding shall include vinyl, polypropylene, or horizontal aluminum siding, or brick veneer with a clear airspace as specified in Table R703.8.4(1), or other approved vented claddings.
  2. The requirements of this table apply only to insulation used to control moisture in order to permit the use of Class III vapor retarders. The insulation materials used to satisfy this option also contribute to but do not supersede the thermal envelope requirements of Chapter 11.

TABLE R702.7(4)
CONTINUOUS INSULATION WITH CLASS II VAPOR RETARDER
CLIMATE ZONE CLASS II VAPOR RETARDERS PERMITTED FOR:a
3 Continuous insulation with R-value ≥ 2.
4, 5, and 6 Continuous insulation with R-value ≥ 3 over 2 x 4 wall.
Continuous insulation with R-value ≥ 5 over 2 x 6 wall.
7 Continuous insulation with R-value ≥ 5 over 2 x 4 wall.
Continuous insulation with R-value ≥ 7.5 over 2 x 6 wall.
8 Continuous insulation with R-value ≥ 7.5 over 2 x 4 wall.
Continuous insulation with R-value ≥ 10 over 2 x 6 wall.

 

a.  The requirements of this table apply only to insulation used to control moisture in order to permit the use of Class II vapor retarders. The insulation materials used to satisfy this option also contribute to but do not supersede the thermal envelope requirements of Chapter 11.

FIGURE 1. New Vapor Retarder Provisions for the 2021 I-Codes (IRC shown)The requirements of this table apply only to insulation used to control moisture in order to permit the use of Class II vapor retarders. The insulation materials used to satisfy this option also contribute to but do not supersede the thermal envelope requirements of Chapter 11.

NOTE: For more options and an automated means of compliance, refer to http://www.appliedbuildingtech.com/rr/1701-01(link is external) and the wall calculators found at www.continuousinsulation.org(link is external).

Come back Tuesday for Part II, the conclusion of this article.

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Ever Wonder What a Post Frame Engineer Does? Part I

I have been pooh-poohed on occasion for my insistence every post frame building (or barndominium) should have an engineer involved. Very few potential building owners understand what it is an engineer does or how they are adding value to a particular project. 

To follow, in its entirety, is an article by Jess Lohse, originally published in SBC Magazine, June 10, 2019. Once read, you should (like me) go away wondering how it is engineers work as reasonably as they do.

Structural engineers, often referred to as an Engineer of Record (EOR), are positioned early in the construction design process ensure the structural viability of buildings designed by Architects or Building Designers. Certain buildings are exempted from the legal requirements for the use of an Architect or Engineer. Generally these buildings are designated as 1 and 2 family residential structures designed within the prescriptive code. Buildings designed under the IBC, exceeding certain provisions of the IRC or exceeding legal exemption requirements will employ the use of an EOR. Structural engineers are typically brought into a project by the architect/building designer and work on behalf of the project owner and remain engaged throughout the construction of a structure to review and accept deferred submittals and RFIs (request for information) for conformance with the structural plans and specifications, monitor construction and perform special inspections as defined on the permit or as contracted to undertake. Once engaged on a project an EOR will typically work through the following processes:

  1. Conceptual Design
  2. System Design
  3. Element Engineering
  4. Iterative Design & Drafting
  5. Construction Administration

Conceptual Design

  • Review Arch drawings
    • Unit types
    • Bearing walls stack?
  • Location requirements
    • Soil report
    • Exposure Category
    • Wind Load
    • Seismic Load
  • Initial design of building elements
    • Roof, wall & floor layout per Arch drawings
    • Footings & Slabs
    • Bearing walls, Beams & Columns
    • Review MEP conflicts

Conceptual Design

An initial step a structural engineer will take is to review the drawings produced by the architect/building designer. The engineer will look at the various types of units on a larger multifamily project or the variety of room uses in a larger single family home or commercial structure to have an idea of the various uses of a structure. Consideration will be given to potential bearing walls, obviously inclusive of the exterior walls, but potentially to utilize interior walls should the need arise to distribute loads through the interior of the structure.  If the structure has multiple levels, the engineer will note if interior walls fall on top of each other, commonly referred to as ‘stacking’, to efficiently transfer loads between levels.  This information will be referred back to the architect to make any necessary adjustments.

The EOR will determine site specific requirements for the structure that are dependent on its location. This will include a soil report to determine potential footings, which exposure category to design to, applicable wind loads as well as seismic considerations. Once the environmental factors have been determined, the engineer will perform an initial design of building elements such as roof, wall and floor layouts per the architectural drawings, footings and/or slabs, bearing walls including beams and columns, and identify potential mechanical, electrical, and plumbing conflicts. 

Come back tomorrow for a continuation of what an EOR, Engineer of Record, adds to the design and scope of a post frame building.

This entry was posted in Pole Barn Design, Building Department, Pole Barn Planning, Pole Barn Structure, Professional Engineer, Pole Barn Homes, Barndominium and tagged , , , , , , , on by .

Tornadoes Reek Havoc

Tornadoes Reek Havoc, Don’t Let Them Wreck You
Excerpts in italics below are from an article first appearing in SBC Magazine June 3, 2019:
“In the past few weeks, weather systems throughout Texas, Oklahoma, Missouri, Indiana and Ohio have had a significant impact on the built environment. As is well known, tornadoes cause severe stress on buildings where the high localized wind loading conditions find the weak point of the structure quickly. This usually is at the location of a wood nail, wood connector or anchor bolt connection, or in our testing experience, a knot or slope of grain deviation in a lumber tension member. An interesting point is that most studs in wall systems are meant to see compression forces not tension, where studs in tension may also be a structural weak point.

As the pictures herein attest, finding the key building material weak point that caused the structural performance to be a debris field is challenging, if not impossible, to do.

Tornado damage in Jefferson City, Mo. as seen on Thursday, May 23, 2019. Photo by David Carson, St. Louis Post-Dispatch.

Questions that need to be sincerely addressed follow, which include but are certainly not limited to:
What were the as-built conditions?
Was the building built to code?
Which aspects of the structure were built to code?
Which aspects of the structure were not built to code?
What is the cause/effect analysis for each code compliant and each non-code compliant condition?

It is obvious that proper construction implementation is key to satisfactory building material performance. Paying close attention to all connecting systems that make up the load path is essential.

The most important outcomes of poor building performance in a high wind or seismic event are that no one gets hurt; the construction industry continues to learn and evolve; and design and installation best practices improve.

The entire construction industry can greatly benefit by staying focused on providing framer-friendly details that are easy to understand and implement. It’s critical that we come together with the goal of fostering innovation, using accepted engineering practice, creating installation best practices, working closely with professional framers and assisting building departments to focus inspections on key load path elements. We all are educators. By working together, we will significantly improve the built environment.”

 

Mike the Pole Barn Guru adds:
Readers will note, these failures are in stick frame construction. Certainly there were also pole barns failing in tornado areas as well, however it is my opinion post frame buildings, engineered to withstand appropriate wind speeds, and assembled according to engineering documents would survive these storms – preventing both loss of property and life.

Code requirements are merely minimum design standards and often do not address severity of real life events. My recommendation is when in doubt, design to higher loads than minimum, in most cases these higher design loads involve a nominal investment and your family and expensive possessions deserve this type of protection.

Talk with your Hansen Pole Buildings’ Designer today at 1(866)200-9657 to find out what a lifetime of protection will involve.

This entry was posted in Building Department, Pole Barn Planning, Pole Barn Structure, Building Contractor, Pole Barn Design and tagged , , , , , , on by .

What is a Building Official?

What is a Building Official, and what is their Scope of Work?

The average potential new post frame owner (as well as most building contractors) has little or no idea of what a Building Official’s scope of work truly is. Sean Shields and Kirk Grundahl, P.E. (Professional Engineer) recently published an article in SBC Magazine in regards to this very subject. At the end of this article, I will tell you why this is so important.

I will include here only excerpts from the authors’ summary:

“The following simply summarizes what the model code states, as it is adopted into law:

A building official’s role is to administer and enforce the adopted building code, nothing more and nothing less.

The building official shall examine all aspects of the construction project for compliance with the specific charging language and scope of the section of the code being evaluated.

If anything about the construction project does not conform to the requirements of pertinent laws, the building official shall, if there are any non-conforming issues, reject in writing, stating the reasons therefor.

Implied here is that the written rejection shall provide:

  1. Specific evidence of non-conformance, and
  2. Enough information for the owner of the building to be able to cure the non-conformance based on the evidence provided, and
  3. A clear and easy to understand pathway to cure the deficiency.

Building PermitThe building official is also authorized and directed to enforce the provisions of this code. The building official shall have the authority to render interpretations of this code and to adopt policies and procedures in order to clarify the application of its provisions. Such interpretations, policies and procedures shall comply with the intent and purpose of this code.

Implied here is the fact that not everything needed to enforce the code is going to be written in the code. Hence, interpretations will need to be made with respect to what meets the intent of the code. This is generally and easily undertaken as follows:

  1. A registered design professional (RDP) or approved source provide an accepted engineering analysis or research report and signs and certifies their belief that the issue being dealt with conforms to the code.
  2. A research report is provided by an approved source.
  3. A research report also known as a technical evaluation or accepted engineering analysis is provided by an ANSI ISO/IEC 17065 Accredited Product Certification Body
  1. Obviously, the best-case scenario for building official authorized interpretations is to have them based by an RDP that signs, certifies and seals conformance with the building code provisions. Why?
  • This says that the given RDP takes responsibility for their engineering evaluation scope of work.
  • The work of the RDP is under the authority of a legal entity generally called a Licensing Board and by law has to work in their area of expertise or be subject to fines and loss of their license.
  • The work of the RDP is also generally insured through professional liability insurance.

As a final analogy, a building official is identical to a police officer, where all of us desire that the police officer follow the rule of laws as written. In other words, we would not want a police officer to do the following:

  1. A police officer picks me up for driving under the influence.
  2. My hair was just dyed scarlet and gray because I am an Ohio State fan.
  3. The police officer thinks this is weird and says you must be intoxicated.
  4. The police officer handcuffs me, takes me down to the station, and puts me in jail.

Preferably, the police officer would do a definitive science-based test to ensure I was indeed intoxicated before putting me in jail.

Thankfully, all professional building officials we know base their decisions:

  1. On following the rule of law, and
  2. Using accepted engineering as the basis of interpretations when needed, and
  3. Provide evidence of non-conformances to the law, and
  4. When non-conformances exist, provide an easy to understand pathway to cure it.”

I told you I would tell you why this is important – because a building official cannot merely say something is wrong. He or she is required to put any non-conforming issue in writing and why. And, most importantly, provide an easy to understand method to solve the issue.  

 

 

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