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BUILDING ENVELOPE DESIGN & CONSTRUCTION

REQUIREMENTS

NEW RESIDENTIAL WARRANTY PROGRAM

Prepared by:RDH Building Engineering Limited

- 1 -Document: 570303:03June 14, 1999 BUILDING ENVELOPE

DESIGN AND CONSTRUCTION REQUIREMENTS



Contents

1 OVERVIEW................................................................................................................1.1 THE ROLE OF THE ARCHITECT.............................................................................................1.2 THE ROLE OF THE BUILDING ENVELOPE PROFESSIONAL................................................1.3 THE ROLE OF THE WARRANTY PROVIDER.........................................................................1.4 BUILDING ENVELOPE DESIGN FUNDAMENTALS.................................................................

2 DESIGN REQUIREMENTS.......................................................................................2.1 EXPOSURE AND ENVIRONMENTAL DESIGN CRITERIA.......................................................2.2 SELECTION AND DOCUMENTATION OF ASSEMBLIES........................................................2.3 DETAILS..................................................................................................................................2.4 COMPONENTS AND MATERIALS...........................................................................................

3 CONSTRUCTION......................................................................................................3.1 MOCK-UPS AND TESTING......................................................................................................3.2 FIELD REVIEW........................................................................................................................

4 POST CONSTRUCTION...........................................................................................



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1 OverviewThe risk management process for the design and construction of the building envelope will involve the Architect, Building Envelope Professional (BEP), various contractors (general and trade contractors), and with the new warranty program in place, the warranty provider. Other consultants (structural and mechanical most notably) play lessor roles in determining the performance of the envelope assemblies but we believe that the key parties listed above can influence and control their impact.

This document provides requirements with respect to the role of the Architect, Building Envelope Professional (BEP) and the warranty provider in the building envelope risk management process. Please see the flow chart (Figure 1.1) at the end of this chapter for a summary of the involvement of each in managing the building envelope risk throughout the design and construction process.

1.1 The Role of the Architect

The Architect’s role must follow the basic agreement for services outlined in the National Practice Program for the Profession of Architecture in Canada – Document 6 and the Architectural Institute of British Columbia (AIBC). The Architect will have responsibility for the design of the envelope. They must follow these requirements, in addition to building codes and standards, other reference material and good practice to arrive at a design.

In addition to the Architect's basic scope of services the Architect is required to prepare a building envelope maintenance and renewals manual. The Architect may rely upon the BEP for the completion of this and other design tasks.

1.2 The Role of the Building Envelope Professional

The BEP provides additional expertise to the Architect to assist the Architect in his or her design and field review services with respect to building envelope assembly, component and material performance issues. The BEP's service does not replace any of the Architect's basic services or responsibilities. The BEP provides specialist consulting to the Architect and builder with respect of Part 5 Building Code issues, good practice and these requirements. The BEP provides the following services to the project:

Ongoing consultation with the design team during the schematic or conceptual stages regarding envelope assemblies

Review of the completed schematic design and preparation of a design report (sample format provided in Appendix B)



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Ongoing consultation with the design team during design development and construction document stages of the project regarding envelope performance and detailing issues

Review of the construction documents and preparation of a construction document review report (sample provided in Appendix B)

Supplementary field review and field testing of the envelope construction as is appropriate for the project and in accordance with municipal requirements in this regard

Review of the building envelope maintenance and renewals manual.

1.3 The Role of the Warranty Provider

The warranty provider is not part of the design team. However, since the warranty provider is providing the warranty there is a need to assure itself that appropriate design and construction decisions are being made so that it is not exposed to unnecessary risk. In this context it will be conducting independent reviews or checks on the quality assurance measures being taken by the design and construction team. It will rely on the reports prepared by the Architect and the BEP throughout the design and construction process and may on occasion conduct its own review of the design, construction documents and completed construction.

The warranty provider will maintain and make available a list of approved Architects, BEPs, general and trade contractors, and approved materials. The builder must select an approved contractor from this list. If the warranty provider has not provided the lists, the builder must obtain written approval to the contractor of its choice. Failure to do so may void the warranty.

The warranty provider's review does not relieve the Architect or the BEP from their obligation to meet their statutory and other obligations as well as the minimum design standards outlined in these requirements.

1.4 Building Envelope Design Fundamentals

Fundamental performance expectations and design principles for building envelopes are described in numerous documents including a variety of NRC-IRC, CSA and CMHC publications. Perhaps the most locally relevant document of this type is the recently published Best Practice Guide - Wood Frame Envelopes in the Coastal Climate of British Columbia (BPG) and it is therefore referenced throughout these requirements.

These requirements addresse moisture management issues as required by the warranty and therefore are closely linked to Part 5 of the building code. They do not address many of the other functions and performance criteria which the envelope must meet, such as acoustics, fire protection and structural issues. The design



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team must address these issues and integrate these design provisions with the moisture related warranty provisions outlined in these requirements.

The approach taken in the BPG and the one which is believed to be most appropriate for the Coastal Climate areas of BC is to focus on managing exterior moisture sources. Other moisture sources must also be managed, but the dominant influence in design decisions is rain penetration control.

The BPG can be used for other non coastal climate zones of the province, however the emphasis must be shifted more to cold climate issues such as air leakage control.

The BPG is directed at 3 and 4 storey wood frame buildings and therefore its details are not directly applicable to high rise construction. However, building science does not change from low rise to high rise construction and therefore most of the principles described in the BPG are also applicable to high rise construction. Key differences include the larger impact of stack effect in taller buildings, the fact that exposure to wind and exterior moisture sources is expected to be high on taller buildings, and the fact that much more exterior moisture can collect on wall surfaces as it runs down the building from floor to floor. The evaluation of exposure is therefore focussed more on how high rather than a decision between low, medium and high. Other materials are used for the structural components (steel and concrete instead of wood) and for envelope assemblies (window-wall, curtainwall, metal panels etc.).

The basic approach therefore starts with the consideration of the building form, location and orientation and the evaluation of exposure conditions. The guidance provided in Chapter 5 of the BPG is appropriate for this purpose. Once an exposure category has been determined for the building, or various parts of the building, then the selection of assemblies can proceed. Essentially Rainscreen assemblies are required for medium and high exposure conditions and face sealed or concealed barrier assemblies, if permitted by code or other regulations, can be considered for use in low or no exposure situations.

Once basic assemblies have been selected, details can be developed and decisions with respect to component and material selection can be made in anticipation of specification preparation.

These requirements refer to and incorporate design guidance from other sources. While the requirements attempt to consolidate design guidance into one fairly comprehensive yet concise package, it is not possible to prescribe requirements which adequately cover all issues and all design situations. It is for this reason that the warranty provider and the BEP are reviewing specific building designs to assess risk and for the builder and the architect to ensure the specific building designs comply with these requirements.

The following sections of these requirements outline requirements for selection of assemblies, components and materials. In addition to the general requirements



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regarding selection and development of the building envelope assemblies there are some prescriptive do's and don'ts which are referred to as rules.



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Figure 1.1BUILDING ENVELOPE RISK MANAGEMENT PROCESS

DESIGNPROCESS

CONCEPTUAL DESIGN

DESIGN DEVELOPMENT

CONSTRUCTION DOCUMENTS TENDER CONSTRUCTION

POST CONSTRUCTION

ARCHITECT(based on NPPDocument 6)

Program of Requirements

Review Construction Budget

Design Approaches

Review Regulations and Code

Prepare Schematic Design

Prepare Design Development Drawings and Other Documents

Prepare or Review Construction Cost Estimate

Review Applicable Codes, etc.

Prepare Construction Documents Including Drawings and Specifications

Review Construction Cost Estimates

Review Permit Requirements

Assist in Obtaining Bids, Awarding and Preparing Contracts for Construction

Review of the Work

Payment Certifier

Interrpet the Contract Documents

Review Contractor Submittals

Issue Instructions Regarding Adjustments to the Work

Undertake Warranty Inspections

Prepare or Assist in Development of Maintenance and Renewals Plan

BUILDING ENVELOPE PROFESSIONAL

Ongoing Consultation

Review of Schematic Design

Ongoing Consultation Review of Construction Documents

Consultation as Required

Supplementary Field Review and Testing

Preparation or Review of Maintenance and Renewals Manual

WARRANTY PROGRAM REVIEW

Approval of Architect and BEP

Review of Schematic Design

Consultation as Required

Review of Construction Documents

Confirmation of Trade Contractors, Suppliers and Materials

Monthly Review of Field Review Reports and Change Orders

On-site Review as Required

Review of Maintenance and Renewals Plan

Post Construction Examination of Envelope Performance Throughout Warranty Period

Document: 570303: 01 BUILDING ENVELOPEJune 14, 1999 DESIGN AND CONSTRUCTION REQUIREMENTS

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2 Design RequirementsThe design requirements set out in this section shall be considered minimum requirements. The builder can modifiy these design requirements by an alternative approach only upon submission to and acceptance by the warranty provider of a request for an alternative approach. The intent of any such requests must be to outline how the intended performance objectives are being met by other means.

2.1 Exposure and Environmental Design Criteria

This section describes environmental factors to be used in the selection of assemblies. This includes exterior climatic design data, interior conditions and exposure.

The builder must prepare a sheet which describes how the exposure category was rationalized for each wall and glazed assembly, as well as all exterior and interior design criteria.

Part 5 RequirementsPart 5 of the BC Building Code does not provide specific design solutions for envelope design. Rather it specifies design process and criteria and relies upon the designer to make appropriate design decisions to meet the performance objectives. The 1998 Code is intended to be a move towards objective based requirements. In general, this type of code places more onus on the designer to employ technology to match performance requirements.

A list of abbreviated part 5 clauses, design criteria that the builder must consider, and the design decisions for building envelope assemblies associated with them are listed in Table 2.1 below. The use of the word minimize occurs frequently in Part 5. The Appendix to the Code indicates that 'minimize' means reduce to a level that prevents long term damage to materials.

It is critical that the design consider all potential moisture sources identified in Part 5 of the Code.

Table 2.1: Summary of Part 5 Code RequirementsSection Design Criteria Design Tasks

5.1 Environmental Separation

All environmental loads and effects of loads that can be reasonably expected, compatibility of materials, mechanisms of deterioration

Components and assemblies to have sufficient capacity to resist environmental loads, materials to be compatible, resistant to deterioration, and designed in accordance with good practice such as CSA S478

5.2 Loads and Procedures

Climatic loads

Below ground environmental loads

Interior environmental loads

Heat, air, moisture transfer calculations

Wind load calculations

5.3 Heat Transfer Intended temperature differential

Required resistance to heat transfer

Minimize surface condensation

Minimize condensation in assembly


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Section Design Criteria Design TasksMeet interior design conditions

Minimize condensation at cold bridges

Prevent convective air flow in insulation

5.4 Air Leakage Air leakage limit for Windows and doors and air barrier assemblies specified wind load and safety factors

Wind load transfer to structure and deflection of the air barrier system

5.5 Vapour Diffusion

Temperature differential

Vapour pressure gradient

Minimize moisture transfer by diffusion into assemblies to

5.6 Precipitation Wind uplift loads Sealing, Drainage, Accumulation, and Disposal

Snow

Formation of ice

Minimize ingress into assemblies

Prevent ingress into interior space

Design cladding to shed precipitation

Minimize likely hood of snow and ice accumulation hazard

5.7 Surface Water Accumulation of water Prevent entry into building

Prevent damage to materials

5.8 Moisture in the Ground

Soil moisture and continuous hydrostatic pressure

Prevent moisture transfer into interior space

DurabilityThe 1998 BC Building code makes specific reference to the durability of materials in the building envelope assembly in section 5.1.4. It requires that the materials be 'compatible' with adjoining materials, and 'resistant' to any mechanisms of decay that can reasonably be expected given the use of the material. The code further references CSA S478 which provides guidelines on service life and materials use. These requirements more clearly establish the obligation for durable designs, although it does fall short in articulating specific durability performance expectations.

Mandating design for durability requires a service life for building envelope components. Achieving appropriate specifications for building envelope components therefore involves all of the usual Part 5 requirements for performance in service with the additional requirement that the function be preserved for a specific term. The design team must be able to identify design service lives of materials components and assemblies. It is also necessary to do so in order to develop a maintenance and renewals plan for the building envelope.

Suggested normal periods for the design service lives for residential buildings and most major components are summarized in the table below:


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Table 2.2: Design Service LivesBuilding or Component Normal design life

Residential building 50 to 99 years

Primary and most secondary structure Same as the building

Cladding, Window Frame More than 25 years

Window Insulated Glass Unit More than 10 years

Roofing More that 15 years

Interior finishes More that 5 years

These design lives are not specified in CSA S478 but in the absence of specific performance criteria set out by authorities having jurisdiction they would be considered reasonable by most owners of homes in BC. They must therefore be used as the starting point for the establishment of service life criteria for elements of the envelope. Specific building materials or components can be expected to last shorter or longer periods of time depending on where they occur within the assemblies (easily replaced) and how maintainable they are. For example, brick ties in a masonry veneer wall is a component that has a high requirement for reliability in service, is difficult to inspect, maintain, or repair, and therefore requires a service life which is equal to or exceeds that of the masonry veneer cladding. The CSA A370 Masonry Connectors standard recognizes this through a requirement for stainless steel ties.

ExposureIn order to assess and design wall and window assemblies for control of rain penetration there is a need to know the intensity and duration of wetting. The assessment and exposure of walls and windows to wetting is not dealt with explicitly in the code or its appendices, and therefore warrants the following specific guidelines:

The determination of exposure is a process that involves the consideration of both design and environmental factors. Design factors range from building orientation to how the building and its elements deflect water. Environmental factors include duration and intensity of rainfall, and wind velocity and orientation during these rain events. Together these factors will determine how often, and for how long, the building walls will be wet. The process of evaluating exposure can be simplified by considering only the three most influential factors; climate, overhang and terrain.

Although the coastal climate zone contains various microclimate zones where rainfall intensity and wind directions vary, it is reasonable to establish the entire coastal climate zone as a severe wetting environment for the determination of exposure categories for all buildings. Similarly, areas of the province not in the coastal climate zone may be characterized generally as a relatively cold and dryer climate zone. The following two nomographs must be used for these two climate zones to determine exposure conditions. Locations which are not clearly in one zone or another must use the more conservative determination of exposure.

The consideration of exposure conditions can be simplified to an examination of overhang and terrain.


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Overhang is usually created by the roof but may also be created by other features of the building such as awnings or floor assemblies which are extended. An overhang ratio can be defined as:

Overhang Ratio = Overhang WidthWall Height

Where:

Wall Height is the height above the lowest moisture sensitive element (eg. wood framing but not concrete foundation wall height)Overhang is the horizontal distance between the outer surface of the cladding and the outer surface of the overhang

Terrain has a large influence on how much wind driven rain will impact on the walls of a building. For the purposes of this guide we have defined four categories which are described in the nomograph figures.

The nomographs can be used to deterime a general exposures category for different combinations of overhang ratios and terrain.

While the range of exposure categories are somewhat arbitrary and require an assessment by the designer they could be summarized as follows:

High - Wall is not wet under normal service conditions and is subject to significant exposure to wind

Medium - Wall is often wet under normal service conditions

Low - Wall is rarely wet under normal service conditions

None - Wall is not wet under normal service conditions

An example of a wall in exposure category None would be a recessed ground floor level wall effectively protected from wetting by large overhangs.


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Figure 2.1: Coastal Climate Zone Exposure Nomograph

Figure 2.2: Interior Climate Zone Exposure NomographRatio


Overhang Ratio

Exposure Category

Terrain

0

0.1

0.2

0.3

0.4

0.5

D - Building located within 1 km of direct waterfront exposure, or small or few surrounding obstructions, or located on a hill or cliff overlooking adjacent buildings

C - Rural areas, moderately treed, or buildings mostly fewer than 4 stories within 5 Building heights

B - Many large buildings within 2 building heights

A - Adjacent buildings of equal or greater height located within one building height in all directions

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The tables which follows identify acceptable exterior assembly moisture control strategies for walls and windows and various exposure levels. The BPG describes the intent of the various exterior moisture control strategy for commonly used wall and window assemblies.

Table 2.3: Wall Assembly Exterior Moisture Control Strategy

Exposure Level Face SealConcealed

Barrier Rainscreen

Pressure Moderated Rainscreen

High Not Acceptable Not Acceptable Not Acceptable Acceptable

Medium Not Acceptable Not Acceptable Acceptable Acceptable

Low Not Acceptable Acceptable Acceptable Acceptable

None Acceptable Acceptable Acceptable Acceptable


Overhang Ratio

Exposure Category

Terrain

0

0.1

0.2

0.3

0.4

0.5

D - Building located within 1 km of direct waterfront exposure, or small or few surrounding obstructions, or located on a hill or cliff overlooking adjacent buildings

C - Rural areas, moderately treed, or buildings mostly fewer than 4 stories within 5 Building heights

B - Many large buildings within 2 building heights

A - Adjacent buildings of equal or greater height located within one building height in all directions

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Table 2.4: Window Assembly Exterior Moisture Control Strategy

EXPOSURE LEVEL

WINDOW ASSEMBLIES None Low Medium High

AL-1: Aluminum – Face Seal

AL-2: Aluminum – Concealed Barrier

AL-3: Aluminum – Concealed Barrier (Improved)

AL-4: Aluminum – Rainscreen

VY-1: Vinyl – Concealed Barrier

VY-2: Vinyl – Rainscreen

Exterior Design Conditions

Exterior design conditions are referenced in Appendix B of the BC Building Code. For the purposes of calculating condensation potential it is acceptable to use temperatures higher than the 2.5% January design temperature. The intent is that no adverse effects shall occur as a result of condensation, and since many building materials have some capability to safely store moisture to be released at a later time, it is not a requirement that no condensation occur. It is therefore permissible to use temperatures which are 2ºC to 5ºC higher than the 2.5% January design temperature. The determination of the design temperature must be made based on the moisture storage capability and moisture sensitivity of each assembly. Thermal bridging (concentration of studs, non thermally broken window sub-sill flashings) can be more significant considerations than the preciseness of the design temperature.

Interior Design Conditions

Recent interior suite measurements of actual in service conditions in multi-unit residential buildings in BC have indicated that actual relative humidity levels may exceed those previously felt to be acceptable for design purposes. For the purpose of building enclosure assembly design the interior winter design conditions must therefore be at least 22°C and 60% RH. Higher levels must be used if the building use and occupancy or ventilation capability are expected to result in different conditions.

2.2 Selection and Documentation of Assemblies

The selection or development of assemblies based on an exposure category for wood frame buildings must proceed on the basis described in the BPG. If not using one of the assemblies specifically described in one the data sheets of the BPG then a work sheet (enclosed in Appendix A) must be prepared which documents the assembly materials and layers and describes how they manage all moisture sources. Sample sheets for two non combustible assemblies are enclosed for reference purposes in Appendix B.


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RULES:General

High humidity locations such as swimming pools, and hot tubs require special consideration with respect to ventilation and assembly design to accommodate large moisture sources.

Wall Assemblies All combustible and non-combustible rainscreen wall assemblies in a medium

and high exposure categories must be compartmentalized at building corners and at each floor level

All combustible and non-combustible rainscreen wall assemblies in high exposure categories must utilize a continuous exterior bituminous membrane as the air barrier.

Rainscreen wall drainage cavities to be unobstructed for 70% minimum of wall perimeter, with unobstructed drainage paths at all details and penetrations.

Medium and high exposure walls may utilize mass wall assemblies which have adequate storage capacity to retain water without damage to wall assembly materials until the following drying period. Mass walls must contain water stopped control joints caulked on the exterior, and fully grouted tie holes.

Prefabricated EIFS panel systems must not be used unless they are exterior to a continuous water shedding surface. EIFS assemblies are not permitted in high exposure categories. In medium exposure categories EIFS assemblies must be mechanically fastened and placed over a sheet waterproof membrane

Wall claddings must only be used in vertical applications; all sloped surfaces greater than 15º from the vertical must be treated as roofs.

Wall claddings must be sufficiently durable to withstand damage from intended access equipment such as ladders, swingstages and boatswains chairs.

Windows, Doors & Other Glazed Assemblies Windows and curtain wall assemblies must be used only in vertical

applications.

Secondary sloped sub-sill drainage must be used for all glazed assemblies and doors in medium and high exposure conditions

Roofs, Decks, Balcony & Walkway Assemblies Waterproof membrane roof assemblies must be designed so that the

waterproof membrane and the air-barrier are the same component. Pitched water shedding roofs which are vented to the exterior must have different air barrier and moisture barrier components within the assemblies.


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All roof, deck, balcony & walkway assemblies must be designed with positive slope to drain (minimum 2%) after permanent long term building movements have occurred (shrinkage, creep).

Unprotected membranes must not be used on decks located over living spaces (can't act as both a waterproof membrane and wearing surface)

Membranes must not be buried under concrete or asphalt unless membrane life expectancy is greater than 20 years. Drainage mat must be used above membrane and all landscape elements must be able to be relocated on site for membrane replacement. All toppings (pavers, wood wearing surface etc.) over other types of membrane must be removable by hand for servicing of membrane.

All roof or waterproofing assemblies for pools or water features over occupied spaces must be a double waterproofing system which eliminates hydrostatic head on the lower membrane surface. All penetrations through the membranes must be located to minimize hydrostatic pressure at the penetration.

2.3 Details

Design detailing and construction of the interfaces between the envelope assemblies is critical in ensuring performance of the assemblies themselves. The design details must therefore incorporate the following:

The details must show all of the typical interfaces between assemblies and sufficiently illustrate the intent.

The details must show the intent for difficult or atypical details.

The details must be drawn at a scale that allows the design intent to be clearly illustrated and individual components, layers & connections to be identified.

The details must be drawn in 3-D or as isometrics if it is necessary to show the intent of the completed assembly.

Details must indicate the intended location, materials and components comprising the air barrier, moisture barrier and vapour barrier on the drawings (in a similar manner to that shown in the BPG)

In addition to these general detailing principles the following rules must apply to the development of details.

RULES: Positive drainage path must be incorporated at the moisture barrier.

Sub-sill drainage path must be provided under all windows and doors and must be sloped to the exterior.


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Cross cavity flashing must be provided as a minimum at every second floor level for medium and low exposure conditions, every floor level for high exposure conditions.

All cap flashing must have a minimum 1:6 slope.

All other drip flashing and cross cavity flashing must have a minimum 1:4 slope.

End dams must be utilized on all cross cavity flashing

Sealant must not be relied upon as a part of the primary moisture barrier in medium or high exposure situations in a location which is exposed to direct exterior moisture, UV rays or cyclic temperature movements greater than 20°C.

All doors must be protected by an overhang with an overhang ratio of 0.33 relative to the threshold.

All roofs, decks, balconies and walkways must be designed and constructed to slope both the wearing surface and the waterproof membrane away from door thresholds and towards drainage points

Scuppers must not be used as primary drainage mechanisms except with PVC coated metal and heat weldable PVC surface membranes.

Clamped membrane floor drains or direct runoff from drip edge must be the primary drainage mechanisms for balconies and walkways

Drain locations must be clearly marked on concrete pavers and in planters and be easily accessible for maintenance.

Protect traffic paths on roofs with additional wearing surface.

Metal flashing must not be used as the moisture barrier except in low exposure situations. Metal flashing must shed the majority of the water and protect a waterproof membrane below.

The type of waterproof membrane to be used on a roof must be selected depending on the complexity of the roof configuration. For example, a multi-ply reinforced liquid applied membrane may be the best selection for a complex roof configuration with many details and irregular shapes.

Vent hoods must be designed so that water drips away from the building. Vent hoods must be designed so that screens can be maintained. Vent systems must be designed so that they can be tied into the building air-barrier system.

Cladding must be designed to accommodate daily and seasonal thermal movements without permanent deformation or cracking.

Sandwich slab systems must not be used without concrete perimeter curb and membrane which extends 100mm above upper slab surface.


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Window-wall assemblies must create a rainscreen cavity in spandrel areas which directs all water in the cavity to the exterior over a waterproof moisture barrier. The barrier must terminate on a vertical surface, to the exterior of, and lapped over the moisture barrier for the element below

2.4 Components and Materials

The selection of materials and components for a project is a complicated process involving consideration of exposure conditions, maintainability, compatibility with adjacent materials, aesthetics, and costs. There is a great deal of guidance with respect to the selection of building envelope components and materials for wood frame construction provided in the BPG. As a guideline it is not prescriptive by nature and thus is open to interpretation. The generic specification for a material is often not enough to ensure that good quality products end up being used on the project. For example, various manufacturers of self adhesive membrane have different performance characteristics as well as different application requirements. Similarly, some window manufacturers use their own forces for installation and others contract this work out. Even if the proper materials are specified and used, the application may be full of deficiencies resulting in failure of the detail. As a result, specific products and trades will need to be reviewed by the warranty provider on a project by project basis to ascertain that acceptable materials, suppliers and installers are being used. The form for use in indicating proposed trade contractors and materials is enclosed in Appendix A.

The following general rules must be followed in the development of specifications.

RULES: The builder must develop appropriate mock-up and testing requirements for

inclusion in the project specifications

Specification of wood products must follow the Wood Product Selection Guide in the BPG

Sheathing Membranes - Breather Type in medium exposure conditions must only be used with an air cavity greater than 12mm located to the exterior of the membrane. Only non-breather type to be used in high exposure conditions.

The use of waterproof sheathing membranes on wood frame structures creates a situation where water vapour can not readily migrate to either the interior or exterior. The wood products must therefore be at or below 19% moisture content at the time the wall is enclosed

The builder must follow CSA A370-94 requirements for corrosion resistance on metal connectors in masonry

Minimum level of zinc coating required for corrosion protection on inaccessible sheet steel products located outside the moisture barrier is G200. This may require the use of thicker sheet steel than is required for structural purposes.


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Windows and doors are required to meet CSA A440.1-M98 User Selection Guide performance criteria with respect to air leakage, water leakage and wind load resistance. Minimum condensation resistance for windows must be TF48 and for doors D1 as described in CSA A440-M98

Only factory glazed unit skylights, pressure cap drained skylights, and pressure cap pressure equalized rainscreen skylights (as defined in the BPG) are to be used in assemblies which separate indoors from outdoors

Exposed polyurethane membranes must not be used on wood surfaced deck and balcony sheathing

Metal fasteners must have sufficient corrosion resistance for the exposure conditions (corrosion potential), and reflect the location within the assembly the fastener is located (ability to replace and maintain). Fasteners hidden behind the cladding but exposed to wetting within the drainage cavity must have at least as much corrosion resistance capacity as the life expectancy for the cladding.

3 ConstructionThe specific quality assurance process for the building envelope will vary from building to building, however, in many ways the risk management process described within this documents forms a fundamental part of the projects overall quality assurance plan. The guide follows the normal design process and incorporates a series of checks by both the BEP and the warranty provider. Specific ways in which the process outlined in this guide can be incorporated into the overall quality assurance plan with contractor activities include the following:

The builder must submit a qualifications statement for the site superintendent and all other office and site personnel involved in the construction of the envelope.

The contractor must have a project specific quality control plan developed and presented to the warranty provider in writing.

The Architect and BEP must review the contractors quality control plan.

A building envelope start-up meeting must be held on site with all of the envelope trades, the builder, architect and BEP. The purpose of the meeting is to review the design intent, answer questions related to the construction of the envelope and to review the quality control plan and responsibilities.

The contractor must ensure that moisture content of wood products are at or below 19% moisture content at the time the assembly is closed in.

The BEP together with the contractor is to undertake on site window water penetration field testing as described in the BPG.

The BEP together with the contractor must flood test all roofs for a minimum of 24 hours.


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The warranty provider must be provided with copies of all field review reports conducted by the Architect, BEP, material supplier or manufacturer as well as any site instructions and change orders relevant to the building envelope.

3.1 Mock-ups and Testing

Mock-ups have become an accepted and even desirable part of the construction process supported by both the designers and contractors. Mock-ups are full size construction of important or difficult assemblies and details that are intended to form part of the construction for the building in question. They can be done separately from the actual building (mock-up) or they can be built to be incorporated into the final construction (field demonstration).

The purpose of the mock-up is to confirm and convey the design intent for typical and difficult interfaces. They are usually done prior to construction or at the start of the work for typical details, and during the construction for atypical details.

The key to successful use of mock-ups is to identify the scope, size and location of mock-ups as much as possible at the design stage, and to include a mechanism for requesting additional mock-ups should a difficult detailing situation arise during construction. Furthermore the construction of mock-ups must be undertaken by the actual trade contractors who will be performing the construction of the building, and upon completion the mock-ups must be available as a reference standard expected for the balance of the envelope construction.

Testing has also become an accepted part of the construction process. Aside the from the results of component testing which can be requested prior to construction, on most projects there will be a need to test the installed assemblies to confirm performance of not just the assemblies but the interfaces between the assemblies. Wording must be included in the specification documents to define the extent and nature of this testing on a building specific basis.

Depending on the size and nature of the mock-ups, performance testing can be undertaken on them. Alternately, testing can be undertaken in the field on selected elements of the construction. Decisions with respect to number, location and timing of tests needs to be made on a individual project basis.

Testing must be done by the builder or trade contractor as part of their quality control procedures. In addition, testing can be undertaken by the developer, architect, BEP or warranty provider as part of the quality assurance process. This testing essentially acts as a check on the builder or contractor's quality control procedures.

3.2 Field Review

Field review of the envelope construction is part of the quality assurance process and must be undertaken by both the project Architect and the BEP. The architect has the primary responsibility for field review but may rely upon the supplementary review undertaken by the BEP. The warranty provider's reviews are not part of the project and must not be relied upon by the architect as supplementary reviews.


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The field review effort must be coordinated between the architect, BEP, builder and trade contractors. A specific plan must be developed for this work which deals with the following:

How are issues identified as discrepancies by the BEP to be resolved

How are issues not dealt with in the construction documents to be resolved

How is the resolution of discrepancies tracked and who takes responsibility for completion of each item

What is the schedule for field review activities

Who is to receive copies of field review reports

How is information regarding discrepancies relayed to the trade contractors

4 Post ConstructionMaintenance and Renewals PlansA key to managing risk in the post construction period is the development of a maintenance and renewals plan for each building. These are now becoming more commonplace with new developments, and the preparation of this plan is part of the warranty providers requirements of the design team.

The maintenance and renewal plans must be reasonable in terms of scope and costs, however the provision and implementation of the plan must ensure that the building does achieve the desired performance throughout the warranty period. If followed, it must provide a reasonable opportunity for the building envelope to achieve it's design life.

An outline describing the typical contents of a maintenance and renewals plan is enclosed in Appendix A.

The warranty provider will review these documents.

Post Construction Performance AssessmentThroughout the warranty period there will be a need to review the performance of the envelope. The purpose of these reviews is be twofold; to ensure that maintenance and renewals work is being undertaken, and to identify small warranty issues before they become bigger issues.

These reviews for the purpose of the building envelope warranty must be undertaken after the first year and just prior to the expiry of the envelope warranty period. These reviews will be conducted by the Architect, BEP and the warranty provider and will normally consist of a visual examination only. A report must be produced for each assessment.


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APPENDIX A

FORMS AND REPORT FORMATS


Page 21 of 20

APPENDIX B

SAMPLE REPORTS


Date post:	12-Apr-2018
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