Windows, overview of issues

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Windows, overview of issues at a glance

Here is the reference data an Intern Architect needs before opening the paper.

Full titleWindows: overview of issues
AuthorM. Z. Rousseau, National Research Council of Canada, Institute for Research in Construction
PublisherNational Research Council of Canada (NRC). Published in the proceedings of Building Science Insight '88: Window Performance and New Technology.
YearAugust 1988
Length15 pages (pp. 1-15)
NRC numberNRCC 29348(1)
LanguagesEnglish. The NRC Publications Archive holds both English and French versions of many Building Science Insight papers; check the archive record to confirm availability in French.
Primary audienceArchitects, building scientists, and building envelope practitioners working with window selection, specification, and detailing in Canadian climates.
ExAC relevanceSupplementary reference on Examitect's ExAC study plan. Supports building science, fenestration, and environmental separation categories in Section 2 and Section 3.
Where to accessFree PDF through the NRC Publications Archive (nrc-publications.canada.ca). Use DOI 10.4224/40001236 or search for the NRC number NRCC 29348(1).

Why Windows, overview of issues matters for the ExAC

Windows are the most performance-critical component in a typical Canadian building envelope. A wall can be detailed around many failures; a poorly specified or installed window drags the thermal, air, moisture, acoustic, and fire performance of the entire assembly with it. The Examination for Architects in Canada (ExAC) tests whether you understand those interactions.

The paper is commonly cited on Examitect's ExAC study plan as a supplementary reference for the building science and assemblies categories in Section 3, and for the environmental separation categories in Section 2. The primary references for those categories are NBC 2020, CHING, and CHOP, but the vocabulary in the Rousseau paper is what makes the primary references readable when they address fenestration. Terms like air leakage class, rain penetration resistance, vapour flow, sound transmission class (STC), and fire-rated glazing all appear in NBC 2020 and in CHING, and Rousseau is where those terms are defined in plain language for practitioners.

You do not need this paper to answer every window question on the ExAC. You do need the performance framework it describes. One focused read, early in your study plan, will pay back many times over when those terms appear in scenario questions.

ExAC sections this reference supports

Section 1
Section 2
Section 3
Section 4

What Windows, overview of issues is

The paper's stated purpose is to examine window requirements from multiple perspectives and to describe the array of window types and components on the market at the time of writing. Rousseau organizes the paper around three frames of reference: windows as a system of elements, windows as part of the building envelope, and windows as part of the indoor environment.

The system frame treats the window as an assembly of frame, glazing, spacer, sealants, weatherstripping, and hardware that must perform as a unit. The envelope frame addresses what windows do as part of the larger wall assembly: controlling heat, air, vapour, water, sound, and fire. The indoor environment frame looks at how windows affect light, glare, view, condensation on interior surfaces, and acoustic comfort inside the building.

The paper is not a design guide and not a code. It is a performance framework that names the issues an architect needs to manage when specifying windows for a Canadian building. Because those issues have not changed since 1988, the paper remains a useful vocabulary primer for ExAC candidates even though the specific products it describes have evolved considerably.

Inside the paper: the four topic areas

The paper is organized around four main topics. Each maps to a recognizable category in Examitect's ExAC study plan.

Topic areaWhat it coversWhere it lands on the ExAC
Windows as a system of elements Frame materials, glazing types, spacers, sealants, weatherstripping, hardware, and how each component contributes to the unit's overall performance. Introduces the idea that a window fails as a system, not as a single part. Section 3 assemblies and detailing. Relevant when a question asks which component is responsible for a particular performance failure.
Windows as part of the building envelope The seven performance categories: moisture performance, air leakage, vapour flow, rain penetration, sound propagation, fire spread through glazings, and thermal performance. Frames each category in terms of the consequences of failure and the design parameters that control it. Section 2 environmental separation and Section 3 building science. Directly maps to NBC 2020 Part 5 control functions.
Windows as part of the indoor environment Interior condensation on glass and frames, daylight and glare, view to the exterior, and acoustic comfort. Treats windows as the interface between the interior programme and the exterior climate. Section 1 design and analysis, schematic design, and Section 3 building science. Interior condensation in particular is testable alongside NBC Part 5.
Current window market offerings and components A 1988 survey of available window types, frame materials, glazing options, and component combinations. Dated in product specifics but useful as a classification framework. Background only. The classification framework is useful; the specific product details are not examined.

The most exam-relevant topic area is the second: windows as part of the building envelope. If you are short on time, focus there and treat the rest as useful context.

Key window terms every ExAC candidate should know

These terms come from the paper's performance framework and from the related NBC 2020 and CHING content. Learn them before the exam.

TermWhat it means for the ExAC
FenestrationWindows, skylights, glazed doors, and other glazed openings in a building envelope. Subject to thermal, moisture, air, vapour, sound, and fire requirements under NBC 2020 Part 5.
GlazingThe glass or transparent infill panel in a window unit. Single, double, and triple glazing differ in U-value, solar heat gain coefficient, and condensation risk on interior surfaces.
Air leakage (windows)Uncontrolled air flow through and around the window unit, including frame joints, sash weatherstripping, and the perimeter seal at the rough opening. Carries energy and moisture in both directions.
Rain penetration resistanceThe ability of the window unit and its perimeter installation to prevent water from entering the building. Most rain penetration failures occur at the perimeter installation detail, not the glazing unit itself.
Vapour flowDiffusion of water vapour through window frames, spacers, and glazing edge seals. Poor vapour control leads to fogging inside a sealed glazing unit (seal failure) or condensation on the interior frame surface.
Sound transmission class (STC)A single-number rating of a window's ability to reduce airborne sound. Higher STC values indicate better sound isolation. Relevant for mixed-use buildings, suites near noise sources, and windows facing busy streets.
Fire-rated glazingGlazing assemblies tested and listed to limit fire and smoke spread for a rated duration. Required by NBC 2020 where spatial separation limits unprotected openings or where fire compartments are maintained at glazed partitions.
Fenestration U-valueThe thermal transmittance of a window assembly in W/m2K, measured for the whole unit including frame and edge effects. The NECB 2020 sets maximum U-values for fenestration by climate zone. Lower U-value means better thermal resistance.
Environmental separation (fenestration)The window assembly's function under NBC 2020 Part 5 to separate conditioned interior space from exterior conditions, controlling heat, air, vapour, water, and structural loads at the glazed opening.
Window systemThe complete assembly of frame, sash, glazing, spacer, sealants, weatherstripping, hardware, and perimeter installation, treated as a single performance unit.
Condensation resistanceThe ability of a window frame and glazing edge to keep interior surface temperatures above the dew point, preventing visible condensation that signals heat loss and potential mould risk.
Perimeter installation detailThe junction between the window frame and the surrounding wall assembly, including the air seal, flashing, sill pan, and drainage plane. Most window performance failures happen here, not in the glazing unit.

How Windows compares to other ExAC references

The paper sits in a cluster of envelope and fenestration references on Examitect's ExAC study plan. Use this table to decide which reference to open for which kind of question.

ReferenceWhat it's forHow Windows relates
Windows, overview of issuesPerformance vocabulary and framework for window systems in Canadian climates.The vocabulary primer that makes the other references readable when they discuss fenestration.
NBC 2020, Part 5Mandatory requirements for environmental separation: heat, air, vapour, water, sound, and fire at the building envelope.NBC Part 5 is the regulatory framework. The paper defines the performance categories that Part 5 regulates.
CHING (Building Construction Illustrated)Building science and assemblies with detailed illustrations. Chapters on walls and environmental control cover fenestration assembly and detailing.CHING is the primary reference for fenestration assembly; the paper is the vocabulary context behind it.
CHOP, Chapters 2.5 and 5.4The architect's responsibilities around construction principles, assemblies, and construction documents.CHOP frames the architect's role in fenestration selection and specification. The paper explains the performance criteria that inform those decisions.
NECB 2020Energy performance requirements for buildings, including maximum fenestration U-values by climate zone.The NECB sets the U-value targets. The paper explains why fenestration U-values matter in the context of the full window system.
Building Envelope Thermal Bridging GuideMethodology and catalogue for thermal bridging in opaque envelope assemblies and interface details.The Thermal Bridging Guide covers opaque assemblies; the paper covers glazed ones. Together they address the full envelope thermal performance picture.
Designing Exterior Walls According to the Rainscreen PrincipleRainscreen wall design and the pressure-equalized drainage plane that protects against rain penetration.The rainscreen principle applies to the wall cavity; the paper's rain penetration section covers the window unit and its perimeter installation. Read them as complements.

How to study Windows, overview of issues for the ExAC

  • Read it in one sitting. The paper is 15 pages. Block forty-five minutes early in your study plan and read it straight through. You are building a performance vocabulary, not memorizing facts.
  • Map the seven performance categories to NBC 2020 Part 5. After you read the paper, write the seven categories (moisture, air, vapour, rain, sound, fire, thermal) beside the corresponding Part 5 control functions. This mapping is the core testable skill.
  • Focus on moisture, air, and rain penetration. These three categories appear most often in ExAC scenario questions about window assemblies and are the failure modes that NBC Part 5 is most directly designed to prevent.
  • Learn the vocabulary, not the products. The 1988 product survey is dated. What carries forward is the vocabulary: air leakage class, vapour flow resistance, rain penetration resistance, STC, fire-rated glazing, U-value. These terms appear in current ExAC questions.
  • Connect glazing thermal performance to the NECB. The paper addresses window thermal resistance in the context of the full unit. Connect this to fenestration U-value requirements in the NECB 2020 and to the thermal bridging that occurs at window frames and perimeter seals, which the Building Envelope Thermal Bridging Guide covers in more depth.
  • Pair the paper with CHING's chapters on walls and environmental control. CHING provides the visual assembly context that the paper's text describes. Reading them together builds the mental model you need for both assembly and scenario questions.

ExAC sections Windows, overview of issues supports

Examitect's ExAC study plan lists primary and supplementary resources for each category. Here is where the paper shows up, based on its subject matter and the performance categories it addresses.

ExAC sectionHow Windows shows up on Examitect's study plan
Section 1
Design and analysis		Background reference for schematic design and design development categories where fenestration selection, window-to-wall ratio, and daylight strategy are part of the programme. The indoor environment section of the paper (condensation, glare, view) is relevant here.
Section 2
Codes		Supplementary reference for environmental separation objectives under NBC 2020 Part 5. The paper's seven-category performance framework maps directly to the heat, air, vapour, water, sound, and fire control functions that Part 5 regulates at glazed openings. Primary references for these objectives are NBC 2020 Part 5 and Section 9.7.
Section 3
Sustainability and final project		Supplementary reference for building science and systems objectives and for assemblies and detailing objectives. The paper's system-level view of window components and the envelope performance framework support both the conceptual and the detail-level questions in this section. Primary references are CHING and CHOP.
Section 4
Construction and practice		Not typically listed as a direct reference. Section 4 is covered primarily by CHOP, the RAIC documents, and the CCDC contracts. Window specification and shop drawing review are addressed in CHOP rather than in this paper.

Tips for Intern Architects reading Windows, overview of issues

The paper is written for building science practitioners at a 1988 conference, not for exam candidates in 2025. Here is how to read it efficiently for the ExAC.

Tip 1, read it as a vocabulary primer, not a textbook. The paper's lasting value is its performance framework: seven categories, three frames of reference, and the idea that a window is a system. Read it once with that framing in mind and you'll retain what matters for the exam.

Tip 2, prioritize the envelope section. The topic area covering windows as part of the building envelope is the most exam-relevant. It maps directly to NBC 2020 Part 5 environmental separation categories. Spend most of your reading time here and treat the indoor environment section as useful context.

Tip 3, the perimeter installation is where failures happen. Rousseau's framework makes clear that most window performance failures, whether air, water, vapour, or acoustic, occur at the perimeter installation detail rather than in the glazing unit itself. When a scenario question describes a window problem, look at the perimeter first.

Tip 4, windows bridge multiple control layers. NBC 2020 Part 5 requires control of heat, air, vapour, water, sound, and fire at the envelope. A window is the only component that must address all six simultaneously. The paper's multi-category framework is built around this fact. Internalize it and multi-variable scenario questions become easier to parse.

Tip 5, skip the 1988 product details. The market survey section describes specific frame materials, glazing types, and hardware from thirty-five-plus years ago. Skim it to understand the classification approach, then move on. The specific products are not examined and many no longer reflect current practice.

Tip 6, connect condensation to both thermal and moisture control. The paper treats interior window condensation as an indoor environment issue, but it is simultaneously a thermal bridging issue (frame runs cold) and a vapour issue (humid interior air meets cold surface). NBC Part 5 reads it the same way. When you see a condensation question, expect the answer to require both a thermal and a moisture control lens.

Tip 7, do not over-invest. The paper is a supplementary reference on Examitect's ExAC study plan. One focused read is the right investment. Spend the bulk of your fenestration study time on NBC Part 5, CHING, and CHOP, and use the Rousseau paper as the vocabulary bridge that makes those primary references click into place.

Common ExAC scenarios where Windows, overview of issues is the answer

These question types appear in Section 2 environmental separation categories and Section 3 building science and assemblies categories. The performance framework from Rousseau's paper is what you need to parse them.

  • A residential project in a cold climate shows aluminum-frame windows without a thermal break. The energy consultant flags a concern. Which performance categories from the window system framework are at risk, and what change to the specification addresses the problem?
  • Rain is infiltrating through a newly installed window on a mid-rise building, but the window unit passed the factory test. The site review reveals no sill pan flashing at the rough opening. Which part of the window system has failed, and what does the performance framework say about where rain penetration failures typically occur?
  • A mixed-use building has residential suites above a retail music venue. The architect must specify windows for the suites that limit sound transmission from below. Which performance category applies, and what window characteristic should the specification address?
  • A curtain wall elevation on a commercial project includes a section adjacent to a required fire separation. The design uses standard clear float glazing throughout. Which performance category flags a compliance issue, and what does the window system framework recommend?
  • An energy modeller reports that the building passes the NECB 2020 compliance path when using the fenestration's centre-of-glass U-value, but fails when whole-unit U-values are used. What does the window system framework say about the difference, and what design moves can close the gap?
  • A post-occupancy review finds visible condensation on the interior surface of window frames in a high-humidity occupancy (indoor pool facility). The glazing unit itself is not fogged. Which performance categories are at play, and what would a corrective specification address?
  • A heritage restoration project must replace single-glazed windows with assemblies that match the original profiles while improving thermal and moisture performance. Which performance categories must be balanced, and what does the paper's system frame say about the tradeoffs between frame, glazing, and perimeter detailing choices?

Each scenario tests whether you can assign the right performance category and then identify the design move that addresses it. The paper's framework is the tool that makes that assignment fast and accurate under exam pressure.

How Examitect reinforces Windows, overview of issues

Reading the Rousseau paper once gives you the performance vocabulary. Examitect's question bank puts that vocabulary to work in the scenario format the ExAC uses. Section 2 environmental separation questions and Section 3 building science and assemblies questions both draw on the fenestration performance framework, and each answer explanation points back to the specific category the question is testing. You learn which category, not just which answer.

You also get full-length mock exams that match ExAC pacing and free study notes for every section. Try a few sample questions to calibrate where you stand, then review pricing when you want the full bank.

Windows, overview of issues and ExAC FAQ

Windows, overview of issues is a 15-page conference paper by M. Z. Rousseau, published by the National Research Council of Canada's Institute for Research in Construction in August 1988 as part of the Building Science Insight '88 proceedings. It examines window performance from three angles: windows as a system of components, windows as part of the building envelope, and windows as part of the indoor environment. It also surveys the range of window types and components available at the time of writing.

The paper was written by M. Z. Rousseau and published in August 1988 by the NRC Institute for Research in Construction. It appeared in the proceedings of Building Science Insight '88, a conference focused on window performance and new technology. The NRC number is NRCC 29348(1) and the DOI is 10.4224/40001236. It is freely available through the NRC Publications Archive.

The paper is commonly cited as a supplementary reference for Section 3 objectives covering building science, systems, and assemblies, where fenestration is treated as an envelope component. It is also relevant to Section 2 objectives for environmental separation under NBC 2020 Part 5, around the moisture, air, and vapour control functions of window assemblies. Primary references for those objectives are NBC 2020, CHING, and CHOP.

Yes, for vocabulary and principles. The paper defines the performance categories that still frame how architects specify windows: moisture performance, air leakage, vapour flow, rain penetration, sound propagation, fire spread through glazings, and thermal resistance. These categories appear in NBC 2020 Part 5 and CHING today. Specific product details from 1988 have evolved, but the performance framework the paper establishes is the same framework the ExAC tests.

Seven categories: moisture performance (including condensation), air leakage and air tightness, vapour flow and vapour diffusion, rain penetration and drainage, sound propagation and sound transmission, fire spread through glazings, and thermal performance. The paper frames each from both an envelope standpoint and an indoor environment standpoint, which matches how NBC 2020 Part 5 organizes environmental separation requirements.

No. The product survey reflects 1988 market offerings and is dated. What you need is the performance vocabulary: air leakage class, vapour flow resistance, rain penetration resistance, sound transmission class (STC), fire-rated glazing, and fenestration U-value. Those terms appear in current ExAC questions regardless of which specific window products are on the market today.

Read it once as a fenestration vocabulary primer. It is 15 pages and a fast read. Then use CHING for the visual assembly context, NBC 2020 Part 5 for the regulatory requirements, and the Building Envelope Thermal Bridging Guide for thermal performance numbers at the window-to-wall interface. CHOP Chapters 2.5 and 5.4 cover the architect's responsibilities around assemblies and construction documents, which is where fenestration selection and specification show up in practice.

The paper is freely available through the NRC Publications Archive at nrc-publications.canada.ca. Search for NRCC 29348(1) or the author name Rousseau, or use the DOI 10.4224/40001236 to go directly to the record. Check the archive record for the French-language version if you are studying in French.

Keep exploring

Other ExAC reference books.

Windows, overview of issues is one of several envelope and building science references on Examitect's ExAC study plan. Continue with the rest.

NBC 2020

National Building Code of Canada. Part 5 (environmental separation) is the primary code reference for the performance categories the paper defines.

CHING

Building Construction Illustrated. Primary reference for fenestration assembly and detailing in Section 3, with illustrations that pair directly with the paper's vocabulary.

CHOP

Canadian Handbook of Practice. Chapters 2.5 and 5.4 cover the architect's responsibilities around assemblies, construction documents, and fenestration specification.

Building Envelope Thermal Bridging Guide

Covers thermal bridging in opaque assemblies and interface details, including the window-to-wall junction where much of the fenestration heat loss occurs.

Rainscreen Exterior Wall Design

The rainscreen principle governs the wall cavity where the window perimeter installation must integrate. Read alongside the paper's rain penetration section.

Supporting references

The extended reading list of supplementary references that appear across Examitect's ExAC study plan.