Sources and References

Primary texts — Straube, J. F. and Burnett, E. F. P., Building Science for Building Enclosures; Hutcheon, N. B. and Handegord, G. O. P., Building Science for a Cold Climate.

Supplementary texts — Hagentoft, C.-E., Introduction to Building Physics; Kumaran, M. K., Heat, Air and Moisture Transfer in Insulated Envelope Parts; ASHRAE, Handbook — Fundamentals.

Online resources — National Research Council of Canada, Canadian Centre for Housing Technology and Institute for Research in Construction open reports; Building Science Corporation (buildingscience.com) technical papers; ASHRAE Standards 62.1, 90.1 public summaries; NIST fire research publications.

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Chapter 1: The Building Process

A building is an assembly of systems: structure, enclosure, mechanical, electrical, and interior. Building science studies how these systems interact with each other and with the environment over the building’s life.

1.1 Project Delivery

The building process progresses from programming through schematic design, design development, construction documents, construction, commissioning, and operation. Project delivery methods — design-bid-build, design-build, construction management — affect how risk, innovation, and coordination flow between owner, designer, and constructor. Integrated project delivery and Building Information Modelling increasingly compress the boundary between design and construction.

1.2 Roles and Standards

National and provincial building codes specify minimum performance. In Canada the National Building Code and National Energy Code for Buildings establish requirements that provincial codes adopt and modify. Designers reference standards from CSA, ASHRAE, ASTM, and ISO for materials, testing, and performance metrics.

Chapter 2: Loadings on the Enclosure

The enclosure separates interior from exterior and must resist a multivariate set of loadings.

2.1 Gravity and Structural Loads

The enclosure carries its self-weight and transfers wind and seismic loads to the primary structure. Cladding attachments must accommodate movement — thermal, moisture, and structural — to avoid cracking and sealant failure.

2.2 Wind

Wind generates fluctuating positive and negative pressures on walls and roofs. Pressure at a point is

\[ p = q\, C_p\, C_g \]

with \(q = \tfrac{1}{2}\rho V^2\) the velocity pressure. Corners and parapet zones experience higher suction than centre-of-wall zones, requiring denser fastener spacing.

2.3 Thermal Loads

The enclosure sees interior and exterior temperature differentials that vary daily and seasonally. Expansion and contraction impose strains. A component of length \(L\) and coefficient of thermal expansion \(\alpha\) changes length by

\[ \Delta L = L\,\alpha\,\Delta T \]

The resulting stresses — if restrained — can exceed material capacity. Differential thermal movement between a dark metal cladding and a supporting steel frame is a routine source of cracked joints.

2.4 Moisture Loads

Rain, snow, groundwater, and water vapour all drive moisture into enclosures. Water vapour diffusion through a material of permeance \(\mu\) under a vapour pressure difference \(\Delta p_v\) is \(\dot m = \mu\,\Delta p_v\). Air leakage carries orders of magnitude more moisture than diffusion when interior humidity is high, which is why air barriers are central to cold-climate design.

2.5 Fire

Fire loads are characterized by the heat release rate and duration of a design fire. Codes require fire resistance ratings on structural and separating elements; these are based on ASTM E119 or CAN/ULC-S101 furnace tests. Protection strategies integrate compartmentation, active suppression (sprinklers), smoke control, and egress.

Chapter 3: Heat, Air, and Moisture Transfer

3.1 Heat Transfer

Steady-state one-dimensional conduction through a layered wall gives

\[ U = \frac{1}{R_{\text{total}}},\qquad R_{\text{total}} = R_{si} + \sum_i \frac{t_i}{k_i} + R_{so} \]

Thermal bridging through studs, fasteners, and slab edges reduces effective \(R\)-value; effective thermal resistance calculations (parallel-path or two-dimensional finite-element) are required for code compliance.

3.2 Air Leakage

Air flow through a crack of pressure drop \(\Delta p\) follows a power law \(\dot Q = C(\Delta p)^n\) with \(n\) typically \(0.6\text{–}0.7\). A whole-building air leakage of \(2.0\ \text{L/s·m}^2\) at \(75\ \text{Pa}\) is a common enclosure target. Leaks convey humid interior air into cold assemblies, producing condensation.

3.3 Moisture Transfer

Moisture moves through an assembly by vapour diffusion (Fick), air convection, capillary action, and gravity. Glaser analysis plots vapour pressure and saturation pressure across a wall section to identify potential condensation planes. Modern analyses use transient hygrothermal models (WUFI, Delphin) that couple heat and moisture with storage.

Chapter 4: Enclosure Design

4.1 Walls

A modern wall assembly implements the four control layers in order from exterior to interior: rain, air, vapour, and thermal. Rainscreen walls separate the cladding from a drainage plane, allowing incidental water to drain. The perfect wall concept places all control layers exterior to the structure, protecting the structure from thermal cycling and condensation.

4.2 Windows

Window performance is characterized by the U-factor, solar heat gain coefficient (SHGC), visible transmittance, and air leakage. Thermally improved frames, low-emissivity coatings, warm-edge spacers, and gas fills (argon, krypton) reduce U-factor to \(1.0\ \text{W/m}^2\cdot\text{K}\) or better. Window selection must balance winter heat loss, summer heat gain, daylighting, and glare.

4.3 Roofs

Low-slope roofs are either conventional (membrane above insulation, vapour retarder below) or protected membrane (insulation above the membrane). Steep-slope roofs rely on lapped shingles and ventilated attics. Roof failures cluster at penetrations, parapets, and drains; designers provide minimum 2% slopes to drains and overflow scuppers.

Chapter 5: Subgrade Construction

5.1 Foundations and Waterproofing

Below-grade walls must resist lateral earth pressures, hydrostatic pressure, and water intrusion. Dampproofing suffices where water tables are low and positive drainage is maintained; true waterproofing (self-adhered membranes, bentonite, fluid-applied systems) is required below the water table. Insulation is typically placed on the exterior to keep the concrete warm and dry.

5.2 Drainage and Radon

A perimeter drainage system of aggregate and perforated pipe at the footing conducts water to a sump or daylight. In many regions radon control — a sub-slab gravel layer, a sealed sheet, and a stub for future active extraction — is required.

5.3 Frost Protection

Foundations must extend below the frost depth or be protected with frost-protected shallow foundations that use horizontal insulation to redirect ground heat. The frost depth depends on climate and soil type; typical Canadian values are \(1.2\text{–}2.4\ \text{m}\).

Chapter 6: Energy and Operation

6.1 Energy Balance

Building energy demand is

\[ Q_{\text{heating}} = (UA + C_{\text{air}}\dot m_{\text{inf}})\,\Delta T - Q_{\text{solar}} - Q_{\text{internal}} \]

A superinsulated enclosure reduces the transmission and infiltration terms, allowing a small active system and opening the passive-house performance regime (annual heating demand below \(15\ \text{kWh/m}^2\)).

6.2 HVAC and Indoor Environment

Mechanical ventilation with heat recovery (HRV/ERV) supplies fresh air while recovering sensible and latent energy. ASHRAE 62.1 sets minimum outdoor-air rates. Indoor air quality depends not only on ventilation but on source control — low-emitting materials, moisture control, and pollutant isolation.

6.3 Durability and Maintenance

A building’s service life depends on detailing, materials, and maintenance. Flashing continuity at penetrations, the integrity of sealants, and the protection of water-sensitive materials dominate long-term performance. Whole-life carbon — operational plus embodied — is increasingly part of the brief, motivating mass timber, low-carbon concrete, and reuse of existing structures.

The engineer who masters building science combines a quantitative command of heat, air, and moisture with a sensitivity to climate, construction practice, and occupant behaviour. The goal is not merely code compliance but the design of enclosures that are durable, efficient, healthy, and resilient to a changing climate.