Important Changes to the NBC 2020: Penetrations and Continuity of Fire Separations
Julia Dalphy, Technical Advisor, Codes Canada
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Video transcript
Introduction
Hi, my name is Julia Dalphy and I am a Technical Advisor supporting the Canadian Board for Harmonized Construction Codes – also referred to as the CBHCC.
This committee is the federal-provincial-territorial body responsible for developing and maintaining the National Model Codes in Canada.
I am a member of the Codes Canada team at the National Research Council of Canada.
Codes Canada acts as the secretariat to the CBHCC, providing administrative, technical and policy support, including publishing the National Model Codes.
To learn more about code changes and provisions in the National Model Codes, or about Canada’s national model code development system, please visit CBHCC’s website.
This presentation is part of a video series led by the CBHCC on the key technical changes incorporated in the 2020 editions of the National Model Codes.
This presentation will focus on important changes related to penetrations and continuity of fire separations in the National Building Code of Canada 2020.
Topics
Here is an outline of how we’ll navigate through the topic.
We will start with an overview of fire separations and penetrations. Then, we will move into highlighting the important changes. These cover areas such as piping transitions; stack effect and the 50 Pa pressure differential; horizontal fire separations; outlet boxes; service equipment penetrations; and the Part 9 perspective. Lastly, we’ll cover continuity of fire separations.
What are “penetrations”?
Let’s start with a brief review of what constitutes a penetration. To do this, we also need to understand fire separations.
Fire separations and penetrations
“Fire separation” is a defined term in the NBC that is quite familiar. It is generally understood that the term “fire” refers to all products of combustion, including heat and smoke. Ideally, if the integrity of a fire separation is maintained, fire or smoke will not spread from one side to the other through the penetrations.
Fire separations can be penetrated by various objects in practice, such as building services and structural elements. The latter were added in the NBC 2020 to clarify that structural elements passing into or through the assembly should also be identified as penetrations.
You will notice two types of penetrations in the Code: membrane penetrations and through-penetrations. The term “membrane penetration” usually designates an opening made through one side of an assembly (for example, the wall, floor or ceiling membrane), whereas the term “through-penetration” designates an opening that passes through an entire assembly.
Firestop and cast in place
Given that the integrity of fire separations can be compromised by so many penetrating objects, the question becomes how to mitigate the risk of fire and smoke spread at the penetrations.
Penetrations can be sealed by a firestop that is tested to CAN/ULC-S115 and has an F rating not less than the required fire-resistance rating of the fire separation (shown in red in the photo).
In previous editions, the NBC requirement was “not less than the fire-protection rating required for closures in the fire separation.” Typically, the fire-protection rating for closures is less than the fire-resistance rating of the fire separation, which means the firestop may fail before the penetrated assembly does. For decades, the installation practice throughout Canada was to select and install firestops with a rating equal to the assembly's fire-resistance rating. Therefore, to ensure an equivalent level of performance and to align with industry practice, this requirement was changed to the fire-resistance rating of the fire separation in place of the fire protection rating for closures.
You may also have noticed that “firestop” is one word in the NBC 2020 instead of two; this editorial change was made to align the Code with industry practice.
The F rating is determined by the fire test where the firestop, for the rating period, does not permit the passage of flame through openings or the occurrence of flaming on any element of the unexposed side of the firestop.
Additionally, the T rating means that the transmission of heat through the firestop during the rating period should not raise the temperature of any thermocouple on the unexposed surface of the firestop more than 181°C above its initial temperature.
Another option to firestop is cast-in-place penetration.
The NBC 2015 was silent on the material of the penetrating item, which meant materials could be used that might melt in fire (e.g., foamed plastic insulation, as shown in the photo, which is not permitted), creating a gap for fire or smoke to pass through. As such, the NBC 2020 limits the cast-in-place penetrations to the five materials listed on this slide.
Important changes
There are various changes regarding penetrations by service equipment, pipes, outlet boxes, wires and cables in the NBC 2020, which have been consolidated in several Articles for easier reference and consultation by application.
The following highlights some important changes in the NBC 2020.
Transitions between combustible and noncombustible piping
The NBC 2015 permitted transitions between combustible and noncombustible drain, waste and vent pipes on one side of a vertical fire separation (typically a wall) provided they were not located in a vertical service space. But the previous edition did not address transitions between combustible and noncombustible pipes on one side of a horizontal fire separation (such as a floor or ceiling). This caused inconsistent interpretations in the field for decades.
Now, the NBC 2020 permits transitions between vertical noncombustible drain, waste and vent piping and combustible branches on either side of a fire separation (horizontal or vertical), provided that they are not located in a vertical service space. The integrity of the fire separation is maintained through the use of a firestop where vertical stack piping penetrates the fire separation.
If the penetration of a fire separation incorporates transitions between combustible and noncombustible piping, fire could possibly spread within the assembly. This would cause the structural failure and collapse of the assemblies.
To address this risk, a firestop is required at the penetration having an F rating when tested to CAN/ULC-S115, with a pressure differential of 50 Pa between the exposed and unexposed sides with the higher pressure set on the exposed side.
50 Pa pressure differential
During a fire, stack effect is often responsible for the propagation of smoke through a building. Stack effect varies in multi-storey buildings: its magnitude will depend on how large the interior-exterior temperature difference is and on the height of the building.
A 1960s research project showed a pressure differential of about 50 Pa in a 20-storey building using computer modeling. It also pointed out that the pressure differential would be proportional to the height of the building. However, the research was misapplied when developing requirements in NBC Parts 3 and 9, where a 50 Pa pressure differential for testing firestopped combustible piping was required, regardless of the height of the building and the temperature difference. This unnecessarily increased the cost and complexity of construction.
After reviewing the historical research data, the overly onerous requirement for Part 9 has been removed because such significant pressure differences are unlikely in adjacent floor areas within small buildings. The requirement in Part 3 is now only applicable to buildings that are more than three storeys in building height.
Horizontal fire separations
The T rating means that the transmission of heat through the firestop should not raise the temperature on the unexposed surface of the firestop more than 181°C above its initial temperature during the rating period.
The NBC 2015 required firestops for penetrations of a fire separation for horizontal service space to have an FT rating. However, at the service equipment penetrations, there is little possibility of ignition of combustibles on the unexposed side of the assembly due to heat transfer through the penetrating item. In addition, the location of the penetration is shielded from direct radiant and/or convective heat transfer from a fire compartment by an assembly with a Code-mandated fire-resistance rating. This means a rapid and excessive temperature rise is unlikely.
Based on this rationale, exemptions have been introduced in the NBC 2020 to waive the T-rating requirement for service equipment penetrations of horizontal fire separations under certain conditions.
Outlet boxes
The NBC 2015 specifically permitted combustible outlet boxes in an assembly required to have a fire-resistance rating, without them being incorporated in the assembly at the time of testing, as long as the opening through the membrane into the box was not more than 0.016 m2. The provision did not require the combustible outlet boxes to be firestopped.
However, another general requirement for all (both combustible and noncombustible) outlet boxes stated that the penetrations at the membrane should be firestopped with an FT rating. These conflicting requirements for combustible outlet boxes may have caused confusion for Code users. The requirements also made it difficult to ensure that the same level of performance was achieved for combustible and noncombustible outlet boxes.
Now, the NBC 2020 requires penetrations of a membrane of an assembly by combustible outlet boxes to be firestopped with an FT rating not less than the fire-resistance rating for the fire separation.
There were two options for the protection of outlet boxes on opposite sides of a fire-resistance-rated wall, either separated horizontally by:
- at least 600 mm, or
- a fire block.
But, in practice, outlet boxes on opposite sides of a wall are commonly located within 600 mm horizontally (as shown in the photo); and fire blocking is not desirable because it may be impractical or not economical.
A new option has been introduced to solve this issue: firestops (such as intumescent putty pads), which for decades have been considered by fire test laboratories a proven way to prevent fire and smoke spread from an outlet box into the wall space. Given that outlet boxes are membrane penetrations, a greater likelihood exists of someone placing combustible materials, even furniture or bedding, directly in contact with the unpenetrated membrane on the opposite side of the wall.
As such, both F and T ratings are required for the outlet boxes in order for their overall rating to be directly equivalent to the fire-resistance rating of the penetrated assembly. It should also be noted that this requirement applies to both combustible and noncombustible outlet boxes.
Service equipment penetrations
Some permissions for service equipment penetrations have been deleted from the NBC 2020 due to the risk of fire or smoke spreading around the gap at the penetration holes.
Totally enclosed non-metallic raceways; optical fibre cables; electrical wires and cables with combustible insulation, jackets or sheathes were permitted to penetrate a fire separation as long as the overall diameter was not more than 25 mm. However, firstly, the combustible insulation, jacket or sheathes may melt in a fire. Secondly, although the maximum diameter is 25 mm, the requirement does not specify how big the opening could be. Therefore, the risk of fire and smoke spreading through those types of penetrations existed.
Single conductor metal-sheathed cables with combustible jacketing more than 25 mm in overall diameter were permitted as long as they were not grouped and spaced more than 300 mm apart. However, they are problematic because there is no upper limit for the penetrating hole, which could be much larger than 25 mm in diameter. A series of large holes spaced at 300 mm would still present a significant risk.
The NBC 2020 deletes those permissions and still permits a variety of service equipment penetrations, as long as they are protected with a firestop having an F rating.
Other important changes in Part 9
Here are various changes in Part 9 of the NBC 2020 regarding penetrations, mostly to harmonize Part 9 with the changes introduced in Part 3. The following slides highlight some important changes to Part 9.
NBC Part 9 has general requirements for penetrations to be tightly fitted or sealed with a generic firestop in order to maintain the integrity of the fire separation. Examples of generic firestop materials (such as mineral wool (shown in the photo), gypsum plaster or Portland cement mortar) were provided in an existing Part 9 explanatory Note.
The NBC 2020 added two other options:
- cast-in-place penetration of the same materials permitted in Part 3 and
- firestop with a tested product
The explanatory Note has been revised to clarify the requirement. Both tightly fitted and cast-in-place solutions intend that no gap should exist between the penetrating item and the penetrated membrane or assembly.
The three Articles following the general requirements in Part 9 have been revised to address three types of penetrations. These changes reinforce the requirement that all penetrations are to be firestopped, sealed, tightly fitted or cast in place, with limited exceptions. The provisions either offer relief or reinforce the requirement for one or more of the protection options.
For example,
- Piping for water distribution, drain, waste, vent and central vacuum systems that penetrate a fire separation are required to be noncombustible, or sealed with a firestop tested to CAN/ULC-S115, “Fire Tests of Firestop Systems.” The requirement for noncombustiblity is similar to that in the NBC 2015, except that the new requirement allows combustible piping if the penetration is sealed with a firestop tested to the standard.
- A separate Article was revised to collect all penetration requirements for outlet boxes and related service equipment. All combustible or noncombustible outlet boxes are required to be sealed with a firestop tested to CAN/ULC-S115, except some small outlet boxes meeting certain criteria (such as having limited annular space).
- The next Article collects the requirements for penetrations by raceways, sprinklers and fire dampers. These requirements are largely the same as the previous provisions with the exception that totally enclosed raceways must be sealed with a firestop tested to CAN/ULC-S115.
Continuity of fire separations
In addition to protecting the penetrations, it is also necessary to ensure a continuous fire separation or barrier. Two Articles in Part 3 and Part 9 are revised.
To ensure the continuity of fire separations, where a fire separation abuts another fire separation, a floor, a ceiling or a roof, the joint must be firestopped with an FT rating when tested to CAN/ULC-S115, “Standard Method of Fire Tests of Firestop Systems".
Further, joints between a floor and exterior wall must be sealed by a firestop with an F rating when tested to ASTM E2307, “Standard Test Method for Determining Fire Resistance of Perimeter Fire Barriers Using Intermediate-Scale, Multi-storey Test Apparatus.”
An exemption is provided in both Parts 3 and 9 for joints between ceilings and walls, between floors and walls, and between walls at corners if such joints consist of gypsum board that is attached to the framing members and arranged to restrict the passage of flame and smoke through the joints.
These joints are protected by overlapping framing and should not contribute significantly to the spread of fire or smoke. Fire spread through gypsum board joints that are backed by framing members is not a problem. Adding a requirement for firestops in these locations would not be cost-effective.
Conclusion
This concludes the presentation about important changes related to penetrations and continuity of fire separations in the NBC 2020.
How to get involved
To participate in the code development process, visit the CBHCC’s website to find information about upcoming events and meetings, to submit a code change request, to comment on proposed changes during an open public review, or to volunteer to participate on a code development committee.
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The National Model Codes are published by the National Research Council of Canada.
Visit Codes Canada publications web page on the NRC’s website to purchase a paper copy of the Codes or to access them in free electronic format.
Thank you.