National Energy Code (NECB) 2020

NECB 2020 on the ExAC: the sub-category you need to know

Examitect's ExAC study plan places NECB 2020 in one sub-category. Sub-category 5.25 appears in Section 2 (Codes and Regulations) and tests your ability to apply the code in project scenarios, not just recite its structure. Section 2 consists of approximately 75 multiple-choice questions, many of them scenario-based or calculation-style.

The NECB is a model code, adopted provincially with or without amendments. It applies to new buildings and additions, covering envelope, lighting, HVAC, service water heating, electrical power systems, and motors. It does not apply to farm buildings. Always check the authority having jurisdiction for the locally adopted version.

What the NECB is, and what it governs

The National Energy Code of Canada for Buildings 2020 is the fifth edition (following 2017) of Canada's model energy code. The Canadian Commission on Building and Fire Codes developed it under the governance of the National Research Council of Canada, with support from Natural Resources Canada. Since 2022, the Canadian Board for Harmonized Construction Codes (CBHCC) is responsible for maintaining and updating the National Model Codes.

The NECB is not a design guideline. It is a minimum performance code. It tells you the lowest level of energy efficiency a building must achieve, expressed as limits on heat transfer, air leakage, lighting power, and equipment efficiency. Designing a genuinely energy-efficient building requires going beyond the NECB minimum.

NECB code structure: three divisions and eight technical parts

The NECB uses the same three-division objective-based format as the NBC, NFC, and NPC. Division A defines the scope, objectives, and functional statements. Division B contains the technical requirements (the "acceptable solutions"). Division C contains administrative provisions. You work almost entirely in Division B on an exam question.

Division A: objectives and functional statements

The NECB has one principal objective: OE (Environment). Under OE sits one second-level objective, OE1 (Resources), which addresses OE1.1 (Excessive Use of Energy). Every NECB requirement links back to OE1.1. The functional statements (F90 through F100) describe the building functions the code aims to protect: limiting air leakage (F90, F91), limiting thermal transfer (F92, F93), limiting unnecessary lighting energy (F94), limiting unnecessary HVAC energy (F95), limiting service water energy (F96), limiting electrical equipment energy (F97), limiting equipment inefficiency (F98), limiting system inefficiency (F99), and limiting rejection of reusable waste energy (F100).

Division B parts

5.25 Apply the principles of the National Energy Code of Canada for Buildings (NECB)

What sub-category 5.25 tests. Sub-category 5.25 of Examitect's ExAC study plan is "Apply the principles of the National Energy Code of Canada for Buildings (NECB)." The primary reference is NECB 2020. The supplementary references are the BC Energy Step Code Builder Guide and the BC Energy Step Code Design Guide. Questions here ask you to apply the code to a project scenario, not just describe it.

Expect multiple choice questions on climate zone determination, U-value compliance, compliance path selection, air leakage specifications, lighting power density, and HVAC efficiency. Calculation questions may ask you to verify whether a proposed wall assembly meets the U-value limit for a given zone, or whether a glazing area exceeds the maximum FDWR.

The three compliance paths

Division B Article 1.1.2.1 requires every building to comply with one of three paths. You need to know when each path is appropriate and what it requires.

1. Prescriptive path (Parts 3 to 7). You meet each specific limit stated in the relevant Part. This is the simplest path: look up the required U-value in Table 3.2.2.2 for your climate zone, specify a wall assembly that meets it, verify the FDWR, and confirm your air barrier specification. No energy modelling required. Each Part is largely independent: you can meet Part 3 prescriptively while using the performance path for Part 5.
2. Trade-off path. Within a given Part, you exceed one limit while compensating elsewhere. For envelope (Part 3), you can use larger windows than the FDWR allows if you reduce the U-value of the opaque walls enough to keep total heat loss equivalent. The trade-off path is limited to within-Part adjustments; you cannot trade off lighting for envelope.
3. Performance path (Part 8). You model the proposed building's annual energy consumption and compare it to a reference building that meets all prescriptive requirements. If the proposed building uses no more energy than the reference building, it complies. This path allows the most design freedom but requires a full energy model. Part 10 adds a tiered version with four performance tiers above the NECB baseline.

NECB climate zones: six zones from HDD data

The NECB divides Canada into six climate zones defined by heating degree-days at 18 degrees Celsius (HDD18). The zone number drives the required thermal performance for every envelope component. Higher zone numbers indicate colder climates and require lower U-values (more insulation). Climate data for specific locations is in Table C-1 (Appendix C) of the NECB.

Applying climate data on the ExAC

On the exam, you will either be told the city, given the HDD directly, or asked to use Table C-1 to look up values. Know the approximate HDD for major Canadian cities so you can quickly place a project in the correct zone without needing to do arithmetic. The contour map in Note A-1.1.4.1.(1) shows approximately 3,000 to 7,000 HDD contours across the country.

NECB Part 3: building envelope requirements

Part 3 is the most heavily tested section of NECB on the ExAC. It governs thermal transmittance, air leakage, fenestration area, and vestibules. The prescriptive path requires each component to meet the U-value listed in the relevant table for the building's climate zone.

Above-ground opaque assembly U-values (Table 3.2.2.2)

The table sets maximum overall thermal transmittance (U-value) in W/(m2 K) for walls, roofs, and floors. These are effective U-values that include all thermal bridging from framing, fasteners, shelf angles, and structural elements.

Fenestration and door U-values

Vertical fenestration (windows) must meet Table 3.2.2.3 limits. In zones 4 and 5 the maximum is 1.90 W/(m2 K); Zone 6 and 7A at 1.73; Zones 7B and 8 at 1.44. Skylights have slightly higher limits (2.69 in zones 4 and 5, stepping down to 2.01 in zones 7B and 8). Doors must meet Table 3.2.2.4 limits, generally ranging from 2.12 in Zone 4 down to 1.44 in Zone 8. Doors under 2 percent of gross wall area with a U-value not exceeding 4.4 W/(m2 K) are exempt.

Fenestration and door area ratio (FDWR)

Article 3.2.1.4 limits total vertical fenestration and door area as a fraction of gross wall area. The formula ties the maximum FDWR to HDD: as the climate gets colder, the allowed window-to-wall ratio drops. Skylight area must be less than 2 percent of gross roof area regardless of zone. Under the trade-off path you can exceed the FDWR if compensating reductions in opaque U-values keep total envelope heat loss equal or less than the prescriptive-compliant version.

Thermal bridging

Article 3.1.1.7 requires you to include thermal bridging in all U-value calculations. You must account for closely spaced repetitive structural members (studs, joists), major structural elements that penetrate the envelope, junctions between components (parapets, corners, roof-to-wall), and secondary structural members. Fasteners and pipes through walls are exempt. In practice, use ASHRAE Handbook Fundamentals procedures, ISO 14683, or 2D/3D thermal modelling. The Building Envelope Thermal Bridging Guide (BC Hydro, 2014) is cited in the NECB as a reference for complex bridging calculations.

Air leakage requirements under NECB Part 3

Article 3.2.4 requires every building to have a continuous air barrier system. The air barrier is the most critical and most tested Part 3 topic after U-values. You need to know the two compliance routes and the component limits.

Two routes to air barrier compliance

1. Whole-building fan pressurization test (Article 3.2.4.2). Test the assembled building to ASTM E3158 at 75 Pa. The maximum allowable air leakage rate is 1.50 L/(s per m2) of building envelope area, averaged between pressurized and depressurized tests.
2. Air barrier assembly specification (Article 3.2.4.3). Specify an assembly meeting CAN/ULC-S742 at 0.20 L/(s per m2) at 75 Pa, OR design a custom assembly using CAN/ULC-S741 materials with a design wind pressure of 1-in-50. No field testing is required, but the assembly must be shown to be continuous.

Component air leakage limits

NECB Part 4: lighting power density and controls

Part 4 governs interior and exterior lighting. The two main requirements you need to know for the ExAC are lighting power density limits and control requirements. Daylighting credits are also testable for larger commercial projects.

Lighting power density (LPD)

LPD is the installed lighting power in watts divided by the floor area served, expressed in W/m2. NECB Table 4.2.1.6 lists maximum LPD values by occupancy type (offices, schools, retail, hospitals, etc.). You verify compliance by calculating the total installed wattage for a space and dividing by the gross lighted area. If the result is at or below the table value, the space complies prescriptively.

Lighting controls

NECB Part 4 requires automatic shutoff controls for most interior spaces (occupancy sensors or scheduled controls). Daylight areas near windows or under skylights require additional dimming or switching controls when the calculated mean daylight factor exceeds 2 percent. Article 4.3.2.9 provides the daylight supply factor calculation for toplighting (skylights), and Article 4.3.2.10 provides occupancy and personal control factors used in energy calculations for the performance path.

Exterior lighting

NECB Part 4 also sets limits on exterior lighting power for parking areas, building facades, entrances, and signage. Exterior lighting must have automatic shutoff controls based on daylight levels or time schedules.

NECB Part 5: HVAC efficiency and duct requirements

Part 5 is the most technically detailed Part in the NECB. For ExAC purposes, focus on equipment efficiency minimums, duct sealing, vestibule requirements, and energy recovery requirements. You will not need to reproduce the full Table 5.2.12.1 equipment tables from memory, but you need to know what they govern and how to find compliance.

Equipment efficiency

NECB Table 5.2.12.1 sets minimum efficiency for dozens of HVAC equipment types. The key metrics are COP (coefficient of performance) for heat pumps and chillers, EER and IEER (energy efficiency ratio, integrated EER) for cooling equipment, AFUE (annual fuel utilization efficiency) for furnaces and boilers, and SCOP (seasonal COP) for newer heat pump products. The minimum values increase with climate zone severity for some equipment categories. Equipment must also meet the federal Energy Efficiency Regulations (NRCan SOR/2016-311).

Duct sealing (Articles 5.2.2.3 and 5.2.2.4)

HVAC ductwork must be sealed to limit air leakage. Duct construction standards follow SMACNA 006; duct leakage testing follows SMACNA 016. The tightness class required depends on duct static pressure. Fibreglass ductwork must follow SMACNA standards for fibrous glass.

Vestibules (Article 3.2.2.1 in Part 3, applied with HVAC context)

Exterior doors separating conditioned space from the outside generally require an enclosed vestibule with self-closing doors. Exceptions apply to revolving doors, doors used primarily for vehicles, service or emergency exit doors, seasonal doors, doors directly from dwelling units, and doors in buildings under 5 storeys in areas with fewer than 3,500 HDD.

Energy recovery ventilation (Article 5.2.10)

Many ventilation systems serving spaces with high exhaust rates require heat or energy recovery ventilators (HRV/ERV). The NECB specifies minimum sensible effectiveness for the heat exchanger based on the climate zone and the ventilation airflow rate. This is a growing area of ExAC questions as energy recovery becomes more standard in practice.

How each reference fits NECB sub-category 5.25

Sub-category 5.25 has one primary reference and two supplementary references. Each covers a different slice of the topic.

Key NECB terms (glossary)

Addition

Any conditioned space added to an existing building that increases floor surface area by more than 10 m2. Additions must comply with NECB.

Air barrier assembly

The combination of materials and accessories within the environmental separator that form a continuous barrier to air movement through the building envelope.

Annual energy consumption

The annual sum of lighting, service water heating, and space-conditioning energy for the proposed building, calculated using Part 8 procedures for performance path compliance.

Building energy target

The annual energy consumption of a hypothetical reference building identical to the proposed building except that it meets all prescriptive requirements. Used as the performance path compliance benchmark in Part 8.

Building envelope

All components that separate conditioned space from unconditioned space, exterior air, or the ground, or that separate spaces conditioned to temperatures differing by more than 10 degrees Celsius.

Conditioned space

Any space within a building whose temperature is controlled by heating or cooling to limit variation in response to outdoor temperature over substantial portions of the year.

COP (coefficient of performance)

For a heat pump in heating mode: the ratio of net heat output to total energy input. For cooling equipment: the ratio of heat removed to energy input. Higher COP means higher efficiency.

EER (energy efficiency ratio)

For cooling equipment: net cooling capacity in Btu/h divided by total electric input in watts under rated conditions. The integrated version (IEER) accounts for part-load operation.

FDWR (fenestration and door to wall area ratio)

Total vertical fenestration and door area divided by gross wall area. Article 3.2.1.4 sets the maximum FDWR as a function of HDD, with a separate 2 percent limit for skylights relative to gross roof area.

Fenestration

All building envelope assemblies that transmit visible light: windows, clerestories, skylights, translucent panels, glass block, transoms, sidelights, and glazed door inserts.

Gross lighted area

Total area served by interior lighting, including partitions but excluding exterior enclosing assemblies and elevator and service shafts. Used to calculate lighting power density compliance.

HDD (heating degree-days)

The cumulative sum of degrees by which the daily mean temperature falls below 18 degrees Celsius over one year. Used to determine NECB climate zone. Table C-1 provides HDD18 for hundreds of Canadian locations.

Overall thermal transmittance (U-value)

The rate of heat transfer through a building assembly per unit area per degree of temperature difference, in W/(m2 K). The inverse of effective RSI. Accounts for thermal bridging; it is not a nominal insulation value.

Prescriptive path

The compliance route in which each building system meets the specific limits in NECB Parts 3 to 7. No energy modelling is required, but every table limit must be satisfied individually.

RSI

Metric thermal resistance (m2 K/W). To convert to imperial R-value: multiply by 5.678. RSI is used for insulation; U-value is used for assemblies. U-value = 1 / effective RSI.

Thermal block

A space or group of spaces treated as one homogeneous zone for energy modelling. Thermal blocks must share a secondary system, be operated the same way, and have similar envelope and use characteristics.

Thermal bridging

Heat transfer through a conductive element that bypasses the insulation plane, such as steel studs, concrete slab edges, shelf angles, and cladding anchors. Article 3.1.1.7 requires all bridging to be included in U-value calculations.

Trade-off path

A compliance option within one NECB Part that allows exceeding one limit if another is tightened enough to keep total performance equivalent. It cannot cross Parts (for example, no trading envelope for lighting).

Vestibule

An enclosed entry buffer zone required by Article 3.2.2.1 between conditioned space and exterior doors, fitted with self-closing devices on both interior and exterior doors to limit infiltration losses.

How NECB questions are asked on the ExAC

Sub-category 5.25 appears across several question formats. The table below shows the most common formats and what they look like for NECB.

Common ExAC traps in NECB questions

These are the patterns that reliably catch candidates who have studied the code but not practised applying it to scenarios.

1. Nominal vs. effective R-value. The most common NECB trap. A wall assembly with RSI-3.5 batt insulation between steel studs does not have an effective RSI of 3.5. Steel studs create significant thermal bridging. You must calculate the effective U-value including all bridging. Questions often give you a nominal value and ask whether the wall complies: if the effective value is not given, assume bridging losses and choose the answer that reflects a lower effective RSI than the stated nominal.
2. Wrong climate zone. Questions state the city name, not the zone number. Know approximate HDD values for major cities. Ottawa and Edmonton sit in Zone 6 (4,000 to 4,999 HDD); Toronto sits in Zone 5 (3,000 to 3,999); Vancouver sits in Zone 4. Getting the zone wrong gets the U-value table row wrong and leads to the wrong compliance answer.
3. NECB vs. NBC 9.36. NECB governs large buildings; NBC Section 9.36 governs houses and small buildings. If the question describes a single-family house or a small building under Part 9, 9.36 applies by default. NECB can be used as an acceptable solution for 9.36, but it is not the default path. Questions that mix building types rely on this confusion.
4. Trade-off path scope. The trade-off path only works within one Part. You cannot trade excess wall glazing against high-efficiency lighting to achieve overall compliance. Envelope trade-offs stay within Part 3; HVAC trade-offs stay within Part 5. A common wrong answer offers an across-Part trade-off that NECB does not permit.
5. Air barrier vs. vapour barrier. NECB addresses air leakage. Vapour control requirements come from NBC Part 5. Questions that ask about moisture control in the building envelope may test whether you know which code governs which function.
6. Performance path conditions. The performance path requires the proposed building to have annual energy consumption no greater than the reference building. The reference building uses the same geometry, occupancy, and climate data as the proposed building but complies with all prescriptive requirements. It is not a standard "typical" building; it is a virtual replica of the actual project set to prescriptive compliance. Wrong answers often describe the reference building as a generic standard building.

Tips for Intern Architects studying NECB

• Build a zone quick-reference card. Write down the six zones, their HDD ranges, and two representative cities each. You will use this for every NECB envelope question. Forty minutes of memorization saves time on every question.
• Practise the U-value tables. Open Table 3.2.2.2 and run through the wall, roof, and floor values for each zone until you can recall the Zone 6 limits without looking. Ottawa and Montreal questions are common because Zone 6 is a middle zone, easy to test.
• Know the air barrier numbers cold. 1.50 L/(s m2) for whole-building test, 0.20 for assembly compliance, 0.20 for fixed windows, 0.50 for operable windows. These come up in multiple-select questions and the distractors use nearby numbers.
• Understand the performance path conceptually. You do not need to run an energy model on the exam, but you need to know what the performance path requires, what the reference building is, and when the path is useful. Scenario questions about glazing-heavy buildings often end in "use the performance path."
• Connect Part 3 to the Building Envelope Thermal Bridging Guide. The NECB cites this guide in its notes. Questions about how to calculate effective U-values for complex assemblies may reference it. Know that it addresses linear thermal transmittance (psi values) at junctions.
• Practise reading the FDWR formula. Article 3.2.1.4 states the formula. You may not need to derive it from scratch, but you do need to verify whether a given window-to-wall ratio complies for a given HDD value.

How to study NECB in 15 to 20 hours

1. Hours 1 to 2: Read Division A of NECB (Compliance, Objectives, Functional Statements). Understand the three-part structure, the OE1.1 objective, and the three compliance paths in Part 1 of Division B. Draw the compliance flowchart from Figure A-1.1.2.1.
2. Hours 3 to 5: Work through Division B Part 3 (Building Envelope). Memorize Tables 3.2.2.2, 3.2.2.3, and 3.2.2.4 for Zones 5, 6, and 7A. Practise the FDWR formula. Understand Articles 3.2.4.2 and 3.2.4.3 (air leakage compliance routes) and the component limits in 3.2.4.3.
3. Hours 6 to 8: Read Division B Part 4 (Lighting). Review the LPD table by occupancy, understand control requirements, and read the daylighting articles (4.3.2.9, 4.3.2.10) at a high level.
4. Hours 9 to 11: Read Division B Part 5 (HVAC) at a high level. Focus on equipment efficiency table structure (what COP, EER, IEER, AFUE measure and which equipment types each applies to), duct sealing, and energy recovery requirements.
5. Hours 12 to 13: Skim Parts 6 and 7 (service water, electrical). Know the 250 kVA threshold for electrical monitoring, voltage drop limits (2 percent feeders, 3 percent branch circuits), and motor efficiency standard CSA C390.
6. Hours 14 to 15: Read the BC Energy Step Code Design Guide summary to understand the tiered above-code framework. Note how the Step Code connects to NECB Part 10 tiered performance compliance.
7. Hours 16 to 20: Work through Examitect practice questions for sub-category 5.25. Review every wrong answer by locating the relevant NECB article. Track the six traps from the section above and note which ones caught you.