7. Design Development

Design Development on the ExAC: the 1 sub-category you need to know

The official ExAC objectives place Design Development inside Section 1, alongside Programming, Site and Environmental Analysis, Coordinating Engineering Systems, Cost Management, and Schematic Design, with one sub-category: 7.1. Questions test your knowledge of DD tasks, deliverables, consultant coordination, and the documents produced before moving to construction documents. The sub-category draws from professional practice, and candidates with direct DD experience often find it more intuitive than code or cost management topics. The reference pairings in the table below are Examitect's own; the official objectives list carries no references.

What design development is, and what it produces

Design development is the phase of the project that follows schematic design and precedes construction documents. CHOP Chapter 6.3 draws the distinction clearly: schematic design answers "what" will be built; design development answers "how" it will be built and how it will operate. By the end of DD, every major building component is resolved and the consultant team has enough information to start drawing their full construction documents.

DD is often where planning approvals are obtained. In most Canadian jurisdictions, the development permit comes after schematic design or during DD, while the building permit requires sealed construction documents. Knowing this sequence matters for ExAC ordering questions.

What DD produces

• Coordinated architectural, structural, mechanical, electrical, civil, and landscape drawings
• An outline specification describing materials and systems in general terms (CSI/CSC UniFormat)
• An updated construction cost estimate, typically advancing from Class C (area-based) to Class B (elemental with quantities)
• An optional DD report documenting design decisions, risks, updated schedule, and project status
• Written client approval to proceed to construction documents

7.1 Understand aspects of design development

What sub-category 7.1 tests. Sub-category 7.1 of the official ExAC objectives is "Understand aspects of design development." The objectives list names no references, so the reading below is Examitect's mapping: CHING Chapters 2 to 12 and CHOP Chapter 6.3 as the primary references, with Heating, Cooling, Lighting 4th Edition Chapters 15 and 16, and The Architect's Studio Companion 6th Edition as supplementary.

Questions in this sub-category cover DD tasks, the information exchanged between the architect and each consultant, the deliverables produced, the cost estimate class, and the phase sequence. You will also see questions about envelope assembly selection and mechanical system types, which draw from the supplementary references.

The design development process

A typical DD phase follows this sequence:

1. Client provides written approval of the schematic design.
2. The architect briefs each consultant (structural, mechanical, electrical, civil, landscape) with the approved SD package and the additional information each discipline needs to begin their work.
3. Parallel design development begins across all disciplines. The architect leads coordination.
4. Coordination meetings at approximately 30 percent, 60 percent, and 90 percent DD confirm progress and resolve clashes.
5. The outline specification is drafted in parallel with the DD drawings.
6. The cost estimate is updated to a Class B elemental estimate.
7. Regulatory contacts are maintained; development permits are pursued.
8. The complete DD package is submitted to the client for written approval.
9. Upon approval, the project advances to construction documents.

BIM and the front-loaded design process

Building information modelling has shifted the balance of effort earlier in the design process. When a full BIM process is used, detailed decisions that once happened at construction documents are now made during DD or even SD. This is called "front-end loading." The result is higher fees at DD and lower production time at CDs, and a redistribution of effort that should be reflected in the project fee schedule. CHOP 6.3 notes this explicitly and flags that energy modelling, required by many energy codes, is now a common addition to the DD scope of services.

DD tasks: architectural and structural coordination

Architectural tasks during DD

The architect resolves the design of all major building components during DD. This includes confirming floor-to-floor heights, ceiling clearances, and vertical circulation core layout. It also includes developing details for typical conditions, applying building code compliance at a detailed level (not just classification, which was done at SD), and coordinating interior finish schedules. The architect also prepares presentation materials required by the client-architect agreement, such as computer renderings and colour boards.

What the architect provides to the structural engineer at the start of DD

CHOP 6.3 lists the specific information the structural engineer needs before structural design development can begin:

What the structural engineer resolves at DD

• Typical bay framing, including beam and column sizes
• Maximum member depths and all critical dimensions
• Size and location of openings through the structure for mechanical, electrical, and plumbing
• Minimum ceiling clearances to the underside of structure
• Floor-to-floor heights
• Fire ratings on structural elements
• Seismic and wind load considerations (including any local special requirements)
• Radon gas infiltration potential under the slab
• Provisions for special equipment: mechanical rooftop units, slab depressions, fall-arrest anchors

DD tasks: mechanical, electrical, civil, and landscape

What the architect provides to the mechanical engineer

Before the mechanical engineer can start DD work, CHOP 6.3 identifies the following as required:

• The approved schematic design and accompanying reports
• Type of glazing and window coverings, along with their energy characteristics
• Hours of occupancy for each space
• Allowable variation in room temperatures and humidity
• Areas requiring special treatment for air conditioning, fire protection, plumbing, or noise
• Preliminary code analysis including building classification and required fire separations
• Operating cost projections and energy benchmarks, if available

What the mechanical engineer resolves at DD

• HVAC system type (hot-water, hot-air, mixed-mode, variable air volume)
• Location, path, and rough dimensions of main vertical shafts and horizontal ducts for plumbing, fire protection, and HVAC
• Mechanical room sizes and locations
• High-level clash detection between mechanical and structural
• Energy modelling for operating cost projections
• Fire damper and fire protection system coordination

Electrical engineer tasks at DD

The architect provides the electrical engineer with space functions, finishes, and lighting levels; the size and power requirements of major mechanical equipment; and the delivery method and schedule. The electrical engineer resolves the anticipated electrical load, incoming service requirements, distribution voltages, and the locations of power rooms and electrical vaults.

Civil and landscape at DD

The civil engineer resolves below-grade services connecting to municipal infrastructure, site grading strategy, surface water management, and vehicular and pedestrian traffic patterns in collaboration with the architect and landscape architect. The landscape architect requires the approved SD drawings, a briefing on architectural design intent, site utilities locations, and programmatic requirements for outdoor elements such as bicycle racks, gathering spaces, and site lighting.

Thermal envelope at DD: insulation, heat bridges, and glazing

Heating, Cooling, Lighting Chapter 15 ("The Thermal Envelope") is a supplementary reference for DD because envelope assembly selection happens during design development. You choose the wall, roof, and foundation assemblies at DD; the details get drawn at CDs.

The three-tier approach

Lechner's Heating, Cooling, Lighting proposes a three-tier design approach to managing energy use in buildings:

1. Tier 1: Load avoidance through the basic design of the building. Orientation, form, insulation, air tightness, shading, exterior colour, thermal mass, and glazing all cut the heating and cooling load before any system is chosen. The thermal envelope side of Tier 1 is Chapter 15.
2. Tier 2: Passive systems. Passive solar heating, passive cooling (comfort ventilation and night-flush ventilation), and daylighting meet part of the remaining load without mechanical equipment.
3. Tier 3: Mechanical and electrical equipment. Size heating, cooling, and lighting equipment to the residual load left after Tiers 1 and 2. A well-insulated envelope means smaller, less expensive equipment. Addressed in Chapter 16.

The implication for DD: selecting a higher-performing envelope assembly at Tier 1 directly reduces the mechanical system size and cost at Tier 3. The ExAC tests this relationship through questions set in a project scenario.

Heat loss and heat bridges

Heat leaves a building through three paths: transmission (conduction through the envelope), infiltration (air leakage through joints and penetrations), and ventilation (controlled fresh air exchange). Transmission is the path most directly affected by assembly selection at DD.

Heat bridges reduce the actual thermal performance of an assembly below the nominal R-value of its insulation layer. The Building Envelope Thermal Bridging Guide splits the effect into three categories that matter for DD decisions:

• Clear field (area) transmittance: The heat flow through the assembly as a whole, already including the uniformly distributed bridges that are not practical to count one by one: structural studs, girts supporting cladding, and brick ties. Steel studs can reduce cavity insulation effectiveness by more than 50 percent, which is why they are captured here rather than counted as separate bridges.
• Linear bridges: Detail conditions that run as a line across the thermal plane, such as shelf angles, exposed slab edges, parapets, window and door transitions, and cantilevered concrete balconies.
• Point bridges: Discrete fasteners, anchor bolts, and connectors that penetrate insulation.

Addressing thermal bridging at DD typically means specifying continuous exterior insulation (ci) to break the path through the framing, which improves the clear field transmittance, and requiring thermal breaks at balcony and slab edge connections, which improves the linear transmittances.

Insulation selection at DD

Common insulation materials and their approximate RSI values per 100 mm (SI metric, Canada):

Window specification at DD

At DD you choose the window system type and write the performance criteria into the outline specification. Always specify both the R-value (total thermal resistance, including frames and edge spacers) and the SHGC (solar heat gain coefficient, the fraction of incident solar energy admitted as heat). Specifying only U-value without SHGC is incomplete and is a common ExAC trap.

• Cold climate, north windows: Maximize R-value; SHGC is less critical since there is little solar gain on a north facade.
• Cold climate, south windows: Maximize both R-value and SHGC to benefit from passive solar heating.
• Mixed or hot climates, east and west windows: Maximize R-value and minimize SHGC to reduce overheating.

Mechanical systems sizing at DD

Heating, Cooling, Lighting Chapter 16 ("Mechanical Equipment for Heating and Cooling") covers the HVAC system types you encounter at DD. You confirm system selection with the mechanical engineer during DD; you do not design the system, but you need to know which system type is appropriate for the building type and size so you can evaluate trade-offs and allocate space.

Heating systems

• Hot-water (hydronic) heating: A boiler heats water that is distributed to terminal units (baseboard convectors, fan coil units, or radiant floor panels). Efficient, quiet, and flexible. Requires a mechanical room with a boiler and pump set.
• Hot-air (forced-air) heating: A furnace heats air that is distributed through ducts and supply registers. Common in smaller buildings and residential. Combined heating and cooling is straightforward with this system type.
• Radiant panels (floor or ceiling): Water is circulated through tubing embedded in the floor or ceiling slab. Provides high thermal comfort through mean radiant temperature. Slow response to occupancy changes; not suitable for spaces with variable loads.
• Electric resistance heating: Simple but expensive to operate. Appropriate only where energy costs are low or as supplementary heating.

Cooling systems

• Direct expansion (DX): Refrigerant coils in an air handling unit absorb heat directly. Common for small buildings and residential air conditioning.
• Chilled water: A central chiller produces chilled water that is distributed to cooling coils in air handling units. Efficient at scale; requires a central plant and distribution piping.
• Heat pump (air-source): A reversible refrigerant system that provides both heating and cooling. Efficient in moderate climates; performance decreases in very cold weather.
• Geo-exchange (ground-source heat pump, GSHP): Uses the earth as a stable heat source and sink. Very high efficiency (COP of 3 to 5) but high first cost due to ground loop installation.

HVAC for small versus large buildings

Ventilation

Ventilation removes stale air and moisture and introduces fresh air. Note that the air-change figures below are airtightness benchmarks, not ventilation supply rates: they measure uncontrolled air leakage with the building pressurized to 50 pascals (ACH50). Key benchmarks from Heating, Cooling, Lighting Table 15.13 and ASHRAE that may appear in ExAC questions:

• Airtightness, ASHRAE residential: 0.1 to 2.0 air changes per hour at 50 pascals (ACH50)
• Airtightness, ASHRAE commercial: 0.5 to 2.0 ACH50
• Airtightness, Passivhaus standard: maximum 0.6 ACH50
• Energy recovery ventilation (ERV): recovers both heat and moisture from exhaust air; appropriate for humid climates
• Heat recovery ventilation (HRV): recovers heat only; appropriate for dry cold climates

Outline specifications and DD documents

What is an outline specification?

An outline specification is a description of proposed materials and construction systems written in general terms. It expresses the architect's intent about performance, appearance, texture, durability, and operating criteria for each major building component. It is not a fully edited project manual; that belongs to the construction documents phase.

Classification systems used in outline specifications

• CSI/CSC UniFormat: An element-based classification (e.g., A10 Foundations, B10 Superstructure, C20 Interior Finishes, D30 HVAC). UniFormat organizes the spec by building element rather than by trade, making it well-suited for DD and elemental cost estimating.
• CSI MasterFormat: A section-based classification organized by trade (e.g., Division 03 Concrete, Division 05 Metals, Division 09 Finishes). Used for the full project manual at construction documents.
• Alternatively, the framework from the BIM execution plan may be used if the project is delivered using BIM.

The outline spec includes contributions from the mechanical, electrical, IT, and other subconsultants, not just the architectural sections.

What DD drawings include

• Floor plans at 1:100 showing all major architectural, structural, mechanical, and electrical elements in coordinated form
• Elevations at 1:100 or 1:200
• Building sections at 1:100
• Plans for mechanical and electrical systems, typically shown diagrammatically rather than in full detail
• Details of significant design features and materials
• Special code compliance plans: exit travel distances, fire compartmentation, barrier-free paths
• Preliminary furniture and equipment layouts confirming that everything fits and is functional
• Presentation drawings: computer renderings, colour boards, interior and exterior views, as required by the contract

The DD report

On projects with identified risks (budget, schedule, constructability, hazardous material removals), a DD report is a valuable tool. It documents the design decisions made, confirms that identified risks have been addressed, and provides a work breakdown structure, updated schedule, and risk register. CHOP 6.3 recommends it for any project where significant design decisions need to be traceable by stakeholders who were not present throughout the process.

Client approval

The client must review and provide written approval of the DD package before the architect is authorized to begin construction documents. This is a defined milestone in RAIC Document Six. Proceeding to CDs without written approval is a contract risk and is the wrong answer on the ExAC.

Building cost analysis and regulatory approvals at DD

Updating the construction cost estimate

The cost estimate at design development advances from a Class C schematic estimate to a Class B elemental estimate. The Public Services and Procurement Canada (PSPC) classification system, referenced in CHOP, describes Class B as an estimate prepared from elemental quantities extracted from the DD drawings and outline specification. Typical accuracy is plus or minus 10 to 15 percent.

With more design information, the contingency allocation may decrease. CHOP 4.2 puts contingencies as high as 25 percent at the early stages of a project, falling to 2 to 5 percent as uncertainty is resolved, and stresses that the design contingency and the construction contingency are separate allowances. CHOP 6.3 notes that the decrease is not automatic: unexpected findings during DD can maintain or increase contingency.

The architect or a specialist cost consultant prepares the updated estimate. If the estimate shows that the project has drifted significantly from the budget established at SD, the architect must work with the client to adjust scope, quality, or budget before proceeding.

Regulatory reviews and planning approvals

The architect initiates contact with authorities having jurisdiction (AHJ) during schematic design and continues that contact throughout DD. Key milestones:

• Development permit: A planning or zoning approval from the municipality. It is typically applied for during or after schematic design and may be issued during DD. It does not require sealed construction documents.
• Building permit: A construction authorization that requires sealed and coordinated construction documents from all disciplines. Applied for upon completion of CDs, not at the end of DD.

Regular contact with the AHJ during DD confirms that the design approach is acceptable and promotes early resolution of any concerns. CHOP 6.3 notes that municipalities vary significantly in their requirements and review timing, so the architect must stay current with the applicable jurisdiction.

How each reference fits the Design Development sub-categories

Each reference for sub-category 7.1 contributes a distinct body of knowledge. Knowing what each covers helps you track down the source when an ExAC question seems to come from a specific reference.

Key Design Development terms (glossary)

Design development (DD)

The project phase following schematic design. The architect and consultants determine how the building will be built: system types, material selections, and coordinated sizing. Produces coordinated drawings, an outline specification, and an updated cost estimate.

Outline specification

A description of proposed materials and systems in general terms, prepared during DD. Uses CSI/CSC UniFormat or CSC classification. Becomes the basis for the full project manual at construction documents.

Class B estimate

An elemental cost estimate based on quantities extracted from DD drawings and the outline specification. Typically accurate to plus or minus 10 to 15 percent. Follows the Class C (schematic) estimate.

Class C estimate

A schematic cost estimate based on gross floor area, volume, or other high-level metrics. Prepared at the end of schematic design. Typical accuracy is plus or minus 15 to 20 percent.

UniFormat

An element-based classification system for building components: A Substructure, B Shell, C Interiors, D Services, E Equipment, F Special Construction. Used for DD outline specifications and elemental cost estimates.

MasterFormat

A section-based classification system organized by construction trade (Division 03 Concrete, Division 05 Metals, etc.). Used for the full project manual at the construction documents stage, not at DD.

BIM (Building Information Modelling)

A digital 3D model that integrates geometry, materials, systems, and schedule data. BIM makes design "front-end loaded" by requiring more detailed decisions earlier in the design process.

Front-loaded design

The shift of detailed design decisions from construction documents to SD and DD phases, driven by BIM and integrated design processes. Higher fees at DD; lower production time at CDs.

Integrated Design Process (IDP)

A multi-disciplinary approach where all consultants contribute simultaneously throughout the design phases, rather than in sequence. The architect leads the integrated design team.

R-value (RSI)

Thermal resistance of a material or assembly. Higher is better for insulation. R-value is the I-P (imperial) unit; RSI is the SI (metric) unit used in Canada. RSI = R / 5.678.

SHGC (Solar Heat Gain Coefficient)

The fraction of incident solar energy that passes through a window assembly as heat gain. A lower SHGC blocks more solar gain. Always specify with R-value when selecting glazing at DD.

Heat bridge (thermal bridge)

A building component with higher thermal conductivity than the surrounding assembly, reducing the effective R-value of the assembly below the nominal value of its insulation. Categories: clear field (the assembly transmittance, which already includes uniformly distributed bridges such as structural studs, girts, and brick ties), linear (detail conditions such as shelf angles, slab edges, parapets, and window transitions), and point (fasteners, anchors, and isolated penetrations).

Thermal break

A low-conductivity material inserted at a structural connection to interrupt a heat bridge path. Used at balcony connections, curtain wall mullions, and window frames.

Authority Having Jurisdiction (AHJ)

The regulatory body that reviews and approves permit applications. Contact with the AHJ should begin at SD and continue through DD to confirm that the design approach is acceptable before construction documents are sealed.

Development permit

A planning or zoning approval from the municipality. Typically applied for during or after SD and issued during DD. Does not require sealed construction documents.

Building permit

A construction authorization from the AHJ. Requires sealed and coordinated construction documents. Applied for upon completion of CDs, not at the end of DD.

DD report

A document prepared at the end of DD that summarizes major design decisions, confirms risks have been addressed, and provides an updated work breakdown structure, schedule, and risk register.

Geo-exchange (GSHP)

A ground-source heat pump system that uses the earth as a stable heat source and sink. Very high coefficient of performance (COP of 3 to 5); high first cost due to ground loop installation.

Variable air volume (VAV)

An HVAC distribution system that varies the volume of conditioned air delivered to each thermal zone based on load, rather than varying the temperature. Standard for large multi-storey commercial buildings.

Contingency

A cost allowance for unknown or unforeseen work in the estimate. CHOP 4.2 says it may be as high as 25 percent at the early stages of a project and falls to 2 to 5 percent as uncertainty is resolved. Design contingency and construction contingency are separate allowances.

Geotechnical (soils) report

A report by a geotechnical engineer identifying soil bearing capacity, groundwater levels, and seismic considerations. The structural engineer requires this before structural design development can begin.

Mechanical shaft

A vertical penetration through multiple floors reserved for ductwork, plumbing piping, or electrical conduit. Size and location are resolved at DD based on the mechanical engineer's system layout.

Dedicated Outdoor Air System (DOAS)

A ventilation system that provides 100 percent outdoor air to each zone from a separate air handling unit, decoupled from the heating and cooling system. Common in high-performance large buildings.

Energy recovery ventilation (ERV)

A ventilation system that transfers both heat and moisture from exhaust air to incoming fresh air. Appropriate for humid climates where controlling indoor humidity is important.

Heat recovery ventilation (HRV)

A ventilation system that transfers heat (but not moisture) from exhaust air to incoming fresh air. Appropriate for dry cold climates where moisture transfer is not needed or desired.

How Design Development questions are asked on the ExAC

The ExAC Framework Document names five question types: multiple choice, pairing or matching of components, ordering of elements, completion of sentences or fill in the blank, and short answer. Section 1 uses all five. Ordering questions are especially common for sub-category 7.1 because DD is fundamentally about sequencing decisions correctly and knowing which phase owns each task, and project scenarios are the usual way multiple choice items are set up.

Common ExAC traps in Design Development questions

1. Deferring resolution to construction documents. The ExAC tests whether you know that coordination conflicts, system sizing decisions, and assembly selections belong at DD. If a distractor says "resolve this at CDs," it is almost always wrong.
2. Confusing outline specification with project manual. The outline spec (DD) uses UniFormat. The full project manual (CDs) uses MasterFormat. Questions may ask which classification system is appropriate for each phase.
3. Confusing Class B and Class C estimates. Class C is area-based and belongs at SD. Class B is elemental with quantities and belongs at DD. Mixing these up is the most common DD cost estimating trap.
4. Confusing development permit with building permit. Development permits come during or after SD and may be issued during DD. Building permits require sealed CDs. The ExAC tests this sequencing directly.
5. Specifying glazing with only one performance parameter. Any window selection that names only U-value (or R-value) without SHGC is incomplete at the DD stage. Both values are required for a performance-based specification.

Tips for Intern Architects studying Design Development

• Read CHOP Chapter 6.3 end to end. It is the single most testable source for DD process questions. Pay particular attention to the lists of information the architect provides to each consultant and the deliverables checklist.
• Know the five consultant briefs. Structural, mechanical, electrical, civil, and landscape all receive distinct information from the architect at the start of DD. The structural brief (especially the eight items from CHOP 6.3) is directly testable.
• Know CHING chapter by chapter. You do not need to memorize every detail. Know which chapter covers which system so you can cross-reference when a question involves a specific building component: Ch 3 is foundation systems, Ch 4 is floor systems, Ch 5 is wall systems, Ch 6 is roof systems, Ch 7 is moisture and thermal protection, Ch 8 is doors and windows, Ch 9 is special construction, Ch 10 is finish work, Ch 11 is mechanical and electrical systems, and Ch 12 is notes on materials.
• Link HCL Chapter 15 to the assembly selection moment. When you choose a wall assembly at DD, you are making a Tier 1 decision. HCL Chapter 15 gives you the framework to evaluate it: R-value, heat bridges, SHGC, moisture control.
• Know system types by name. For HCL Chapter 16: hot-water (hydronic), hot-air, radiant, DX, chilled water, heat pump, geo-exchange. Know which is appropriate for small versus large buildings and for different climates.
• Always ask "which phase?" For any ExAC question that describes a design decision, confirm it belongs at DD before selecting the answer. If it involves system sizing, assembly selection, or the outline spec, the answer is DD.

How to study Design Development in 12 to 15 hours

1. Hours 1 to 3: Read CHOP Chapter 6.3 in full. Take notes on the task list, the information each consultant needs, the deliverables, and the client approval requirement. Pay attention to the regulatory review sequencing.
2. Hours 4 to 6: Skim CHING Chapters 2 to 12. Focus on identifying which chapter covers which structural or building system. Note the typical details and assembly options shown in each chapter rather than memorizing exact dimensions.
3. Hours 7 to 9: Read Heating, Cooling, Lighting Chapter 15 (Thermal Envelope) and Chapter 16 (Mechanical Equipment). Build a mental model of the three-tier approach, the insulation types and RSI values, the heat bridge categories, and the HVAC system options.
4. Hours 10 to 11: Work through Examitect's practice questions on Design Development. Identify which traps you fall into and review the corresponding source material for each one.
5. Hours 12 to 13: Review the glossary and the deliverables tables. Quiz yourself on the differences between outline spec and project manual, Class B and Class C, development permit and building permit, R-value and SHGC.
6. Hours 14 to 15 (if needed): Re-read CHOP 6.3 sections on consultant coordination and complete a second set of practice questions to confirm retention.