Building Envelope and Structure (Part 9 of the NBC)
Building Envelope and Structure (Part 9 of the NBC) - Transcription
Slide 1
Hello. My name is Barry Craig. I'm a technical advisor at Codes Canada at the National Research Council. I would like to give you an overview of some changes to Part 9 in the 2015 National Building Code (NBC).
The changes here are good news stories. Many are relaxations of requirements, and some provide acceptable solutions.
You will find more detailed information about all the changes in your handbook.
Slide 2
This presentation is part of a series of 13 presentations on the 2015 editions of Codes Canada.
Before I begin with the technical content of this presentation, I will speak briefly about the code development system.
It is important to note that the model Codes, which are developed by the Canadian Commission on Building and Fire Codes, must be adopted by provincial/territorial authorities to become law.
This may mean that Code requirements enacted by legislation within your province or territory might differ from what is presented here. Please check with your local authority.
It is also important to point out that the National Codes are not a federal regulation.
This means it is not NRC or Codes Canada that decides what goes into the Codes but you!
Slide 3
Codes Canada facilitates an open, transparent, consensus-based process to come up with improvements.
Over 400 committee members volunteer their time to decide on changes to the next Codes.
All committees are balanced between regulators, industry and public interest so that no single category can outvote the other two.
This process is shown on the slide:
- It typically starts with someone requesting a Code change.
- It continues with technical committees developing proposed changes.
- It involves a public review and the final approval by the Canadian Commission on Building and Fire Codes.
It's a simple process and it depends on your input.
Please go to the Codes Canada website and find out how you can:
- submit code change requests,
- participate in committees, or
- comment on proposed changes during our public reviews.
Slide 4
And before we start, here are some clarifications on the presentations themselves:
The presentations cover only the changes from 2010/2011 to 2015 Codes and not how to use or interpret the Codes in general.
The presentations contain only the significant changes - the details are in the handbook. Each presentation contains a reference to the relevant pages in the handbook.
The presentations stay strictly within the scope of the National Codes and do not cover provincial or territorial variations.
Slide 5
You should know about theses changes in Part 9, which regulates the design and construction of housing and small buildings.
The changes include:
- lateral loads
- continuous insulation
- limited water doors
- new snow load values, and
- protection above cooktops.
Handbook pages 52-61.
Slide 6
New data was used to update the risk of earthquakes. The map shows seismic hazard values across Canada. Dark grey means high risk and light grey means low risk.
The risk decreased for most areas shown in blue.
The risk at 110 locations shown in red has increased; the size of the triangle is proportional to the percentage change.
We should be concerned where higher risks were found (red triangle) in areas where the risk was already high (dark grey).
Problem: Some regions, such as Vancouver Island, now have an increased seismic risk. These regions would have been outside the limits of the prescriptive solutions in Part 9, which would require designs to be according to Part 4, except to avoid this … (next slide)
Slides 7-11
Solution: The 2015 NBC provides ways to avoid designing to Part 4.
It provides new, more stringent prescriptive solutions for lateral loads by adding features for braced wall panels to resist seismic forces:
- increased sheathing thickness,
- horizontal blocking between studs,
- increased nailing of splices in top plates, and
- decreased spacing of anchor bolts.
Outcome: Housing and small buildings across Canada can still be designed to Part 9 (even higher hazard areas).
Slides 12-15
The 2015 NBC relaxes some requirements for exterior continuous insulation materials, such as rigid insulation, as shown in this wall section.
The NBC aims to minimize the occurrence of condensation in the assembly.
Assemblies with low permeance materials are at risk of creating condensation inside assemblies.
The NBC requires that:
- panel or sheet-type materials with an air leakage rate less than 0.1 L/(s•m²), and
- a water vapour permeance less than 60 ng/(Pa•s•m²) must comply with Table 9.25.5.2., which sets a minimum ratio of outboard to inboard thermal resistance values for all climate zones.
Why?
Keeping this plane (red line) warmer reduces the likelihood of condensation occurring here and being trapped in the assembly.
Problem:
This created an uneven playing field for some insulation manufacturers because:
- a material with a water vapour permeance greater than 60 ng does not have to comply with Table 9.25.5.2., but
- a material with a vapour permeance less than 60 ng requires a higher insulation value, at additional cost, to comply.
It was not clear what risk was associated with this 60 ng trigger.
Slides 16-17
This graph shows different materials with their air leakage (X axis) and range of water vapour permeances (Y axis).
The question was whether insulating sheathing with less than 60 ng water vapour permeance would have more risk of creating condensation than one with more than 60 ng.
NRC modelling of several wall configurations in different climate zones predicted the amount of condensation within the assembly. In general, all insulating sheathing materials performed well.
Solution:
As a result, the 2015 NBC relaxes the requirements for some exterior continuous insulation materials. Compliance with Table 9.25.5.2. is not necessary if the material:
- has a water vapour permeance between 30 and 60 ng,
- has a thermal resistance of at least an R4, and
- is in a location that has less than 6000 heating degree days.
Now, most exterior insulating sheathing materials need not comply with the Table.
Slide 18
To show this geographically, the relaxation applies to the areas below the yellow zone, which have less than 6000 heating-degree days (HDD).
This applies to most cities in Canada
Slide 19
Now let's look at limited water doors.
Doors protected from precipitation are tested with no pressure difference across the door, and have a “limited water” (LW) rating on the label.
Doors not protected from precipitation must be tested with a pressure difference across the door.
Problem: Some LW doors are being used in exposed locations that are not tested for use in these locations.
Solution:
This change:
- clarifies that LW doors may be used where they are protected from precipitation, and
- also clarifies requirements for air infiltration and resistance to forced entry.
Slide 20
The snow loading values for locations across Canada have been updated in the 2015 NBC. Snow load values:
- decreased in 39 locations (in green), and
- increased in 72 locations (in red).
Good news: There is no change to the design calculations in Part 9 because there is no evidence of roof failures due to snow loads on housing and small buildings that were built according to Code.
Slides 21-24
There was confusion about clearances above cooktops in the previous edition of the Code.
The 2010 NBC required:
- 750 mm minimum vertical clearance above a cooktop for framing, finishes and cabinets, or
- 600 mm minimum vertical clearance when framing, finishes and cabinets are non-combustible, or
- when protected by a metal hood projecting at least 125 mm.
Problem:
It wasn't clear whether the requirements for clearances also applied to microwaves.
The NBC 2015 explanatory Notes clarify that the clearances do not apply to microwave ovens and range hoods. They are deemed to provide protection for the cabinets and are regulated to address fire safety.
Slide 25
Before we finish, I will mention a few other changes that may be of interest to you.
They include:
a new exterior wall assembly in the Fire and Sound Resistance Tables called EW2 that has glass fiber insulation.
Previously, there was only one exterior fire-rated wall assembly in the Code and it did not have glass fiber.
The Tables were also moved from the Appendix to Part 9, which means:
you can choose an exterior wall assembly with glass fiber insulation that is considered acceptable, and assemblies in the Tables are now enforceable.
Slide 26
The Code references the new edition of CSA A23.1 standard which raises requirements for residential concrete.
Problem: There was little evidence of concrete failures attributed to the 15 MPa strength.
Solution: The Code references the new standard with qualifiers:
- 15 MPa strength for residential concrete walls is less than required in the new CSA standard,
- 20 MPa strength for residential concrete floors is less than required in the new CSA standard, and
- water cement ratios stay the same as in the 2010 NBC (though CSA reduced the water content).
Slide 27
The 2015 NBC now refers to two standards for the structural design of glass.
ASTM E 1300 is a more current standard and provides more options for compliance.
Slide 28
The 2010 NBC referenced a 1974 CSA standard that was written before power-driven fasteners were in common use.
In the 2015 NBC, there is a new reference to an ASTM standard that applies to fasteners driven by hand tools, power tools or mechanical devices.
Slide 29
There was confusion about whether mineral boards could be used on roofs because, the reference was in another Canadian standard that was removed in an update.
Solution: There is a new reference to a standard for mineral wool insulation board for roofing.
It is now clear that mineral wool roof insulation board can be used as an acceptable solution.
Slide 30
In conclusion, the Part 9 changes you should be aware of are:
- New prescriptive requirements for lateral loads (seismic).
- A relaxation for insulating sheathing materials > 30 ng < 60 ng with R4 insulation permitted in zones less than 6000 HDD
- Limited water doors permitted where weather protected.
- Microwaves and stove hoods over cooktops are exempt from clearances.
- The calculation method for snow loads hasn't changed, but check the data for your area.
- Several standards have been updated or added.
Slide 31
I have covered a lot of information in today's presentation. The handbook is a useful resource if you want to review the topics from this presentation in more detail.
It covers the majority of technical changes that were implemented in the 2015 National Building Code, National Fire Code, National Plumbing Code and National Energy Code for Buildings.
The handbook can be purchased on NRC's virtual store as a downloadable PDF or as a hard copy.
Slide 32
Contact Information
| Autre titre | Building Envelope and Structure (Part 9 of the National Building Code of Canada: 2015) |
|---|---|
| Téléchargement | |
| DOI | Trouver le DOI : https://doi.org/10.4224/40002094 |
| Auteur | Rechercher : 1; Rechercher : 1 |
| Orateur | Rechercher : Craig, Barry1 |
| Affiliation |
|
| Format | Vidéo, Object d'apprentissage |
| Sujet | Codes et guides; construction; bâtiment; NRCCode |
| Date de publication | 2015 |
| Maison d’édition | National Research Council of Canada |
| Publication connexe | |
| Langue | anglais |
| Exporter la notice | Exporter en format RIS |
| Signaler une correction | Signaler une correction (s'ouvre dans un nouvel onglet) |
| Identificateur de l’enregistrement | a032ca97-0cb7-4d1f-93ec-5fbc91b41c6b |
| Enregistrement créé | 2021-05-04 |
| Enregistrement modifié | 2022-06-21 |
- Date de modification :