1. Design Requirements 19 Designing Cladding Systems Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

2. Primary Functions of Cladding Keeping water out –Prevent the entry or rain, snow and ice into the building –Water is driven inwards by many forces such as wind, air pressures and gravity –Water problems are more acute in tall buildings Preventing air leakage –Prevent unintended passage of air between indoors and outdoors –Smaller air leaks waste conditioned air, carry water through the wall and allow noise to penetrate –Large air leaks cause imbalance in air distribution within the building Design Requirements For Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved. Modern Day Glass and Metal Curtain Wall

3. Primary Functions of Cladding Controlling light –Control sunlight to balance between useful illumination and detrimental effects such as glare, fading of materials and damage to skin –Control can be provided by balance of amount of windows, exterior shading devices, types of glass, and interior blinds and curtains Controlling the radiation of heat –Interior surfaces can cause discomfort due to radiant heat transfer in summer and winter –Shading devices, thermal insulation, thermal breaks and appropriate glass can be used to control radiant heat Design Requirements For Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved. Windows and Spandrel Panels

4. Primary Functions of Cladding Controlling conduction of heat –Resist the conduction of heat into and out of the building –Requires insulation plus avoidance of thermal bridges –Thermal insulation requirements often dictated by codes Controlling sound –Isolate the inside of the building from noises outside and vice versa –Requirements will vary by type of building and their location Design Requirements For Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved. Insulation in a Masonry Cladding System

5. This cladding system uses glass with varying optical properties and external, hanging shades to control the passage of light and heat into and out of the building. Design Requirements For Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved. Primary Functions of Cladding

6. Secondary Functions of Cladding Resisting wind forces –Provide adequate strength and stiffness to sustain pressures and suctions due to wind. –Pressure and suction will vary by height and location of the cladding elements such as corners Controlling water vapor –Resist diffusion of water vapor to parts within wall with possibility of condensation –Such condensation can cause loss of insulating value, corrosion of metals, and decay of wood Design Requirements For Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved. Wind Forces on Building Face

7. Secondary Functions of Cladding Movement – thermal expansion and contraction –Accommodate movements due to changes in temperature –Differential thermal expansion and contraction of inside and outside of cladding –Differential thermal expansion and contraction of cladding relative to frame Movement - moisture expansion and contraction –Bricks, building stone, concrete and wood change dimension due to moisture content and can cause problems which need to be taken into account Design Requirements For Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

8. Secondary Functions of Cladding Movement - Structural –Adjust to structural movements in frame due to: –Building foundation settlement –Shortening of columns –Wind and earthquake forces can cause racking effect –Long term creep of concrete –Wall systems can result in –Broken glass –Buckled cladding –Sealant failures –Broken cladding attachments –Failure of whole wall Design Requirements For Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

9. Secondary Functions of Cladding Resisting Fire –The exterior wall of a building can interact in several ways with building fires –There are a number of building code provisions relating to the construction of building exterior walls systems with respect to fire safety Weathering gracefully –Cladding must weather gracefully –Dirt and grime should not detract from the aesthetics –Cladding must resist oxidation, UV degradation, breakdown of organic materials, corrosion of metallic components, chemical attack and freeze thaw damage Design Requirements For Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

10. Installation Requirements for Cladding Secure places for installers Tolerance for inaccuracies Dimensional clearances for installation of components Levels of redundancy –Air barriers and drainage channels to get rid of moisture from faulty joints –Generous edge clearance for glass to prevent contact with hard surfaces Design Requirements For Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

11. Conceptual Approaches to Watertightness in Cladding 19 Designing Cladding Systems Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

12. Conditions for Water Penetration Water –Water can be kept away from the wall in some situations by overhangs but otherwise it is difficult to keep it away from the wall Opening –Openings can be eliminated by carefully sealing every seam with membranes, sealants or gaskets. Practically it is very difficult to eliminate openings –Internal drainage can be provided to move the penetrated water to the outside –Force –Forces are always present. Forces can be neutralized at a plane which is on the outside of the weather barrier Conceptual Approaches to Watertightness in Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

13. Forces - Gravity Gravity –It is a factor in pulling water through a wall only if the wall contains an an inclined plane that slopes inwards. –Designing inclined planes to drain away from the interior is an effective approach to deal with water flow through gravity Conceptual Approaches to Watertightness in Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

14. Forces - Momentum Momentum –The momentum of falling raindrops can drive water through a wall only if there is a suitably oriented hole that goes completely through the wall –Providing a cover to each joint or designing a joint as a labyrinth can neutralize water driven by momentum Conceptual Approaches to Watertightness in Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

15. Forces – Surface Tension Surface tension –The surface tension of water which causes it to adhere to the cladding component in defiance of gravity can allow water to be drawn into the building –Provision of a simple drip on any underside surface to which water might adhere helps with this force Conceptual Approaches to Watertightness in Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

16. Forces – Capillary Action Capillary action –Capillary action is the surface tension effect that pulls water through any opening that can be bridged by a water drop –This force can be dealt with by making openings in walls wider than a water drop or by providing capillary breaks or by providing coating of silicone based water repellant Conceptual Approaches to Watertightness in Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

17. Forces – Air Pressure Difference Air pressure difference –It is caused by wind currents which result in a higher pressure on the outside then the inside that drives air and along with it rain into the wall –It is the most difficult to deal with in designing the watertightness of the wall. –It can be neutralized by employing pressure- equalized wall design Conceptual Approaches to Watertightness in Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

18. Rainscreen Cladding and Pressure Equalized Wall Design Pressure-equalized wall design –Allow wind pressure differences to neutralize –Involves creation of an air-barrier plane of airtightness –Air barrier is protected by rainscreen which is unsealed, labyrinth-jointed layer –Pressure equalization chamber (PEC) is between the rainscreen and the air-barrier –PEC must be divided into compartments to prevent cross currents –Rainscreen cladding is used to describe systems that have internal drainage regardless of the level of compartmentalization and degree or pressure equalization Conceptual Approaches to Watertightness in Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

19. Rainscreen Cladding and Pressure Equalized Wall Design Pressure equalized wall design –No surface joint sealants or gaskets are used –The metal rainscreen panels do not touch each other –Gaps preclude capillary movement, provide installation tolerances and allow for expansion and contraction –Labyrinth joints are created –Sloping surfaces couteract surface tension and gravity –Installation is simple and forgiving –Space between the metal rainscreen and insulation provides drainage space –PEC is divided into narrow compartments by vertical and horizontal channels Conceptual Approaches to Watertightness in Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved. An Example of a Metal Panel Pressure Equalized Wall

20. Rainscreen Cladding and Pressure Equalized Wall Design Pressure equalization at a smaller scale –Weatherstrip acts as an air barrier –The open joint under the sash rail is provided with a capillary break and acts as a PEC –A wash or the slope on the sill acts to facilitate water drainage by gravity –The groove in the lower edge of sash acts as a drip to counteract surface tension –The L-shaped joint between the sash and the sill acts as a labyrinth Conceptual Approaches to Watertightness in Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

21. Sealant Joints in Cladding 19 Designing Cladding Systems Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

22. Sealant Materials - Gunnable Sealant materials - gunnable –Viscous, sticky liquids (mastic) that are injected into the sealant joints with sealant gun –Cure to rubberlike materials in the joint Three categories of material –Low-range called caulks with low range elongation used to fill minor cracks –Medium-range such as butyl rubber or acrylics used for sealing nonworking joints –High-range such as polysulfides, polyurethanes and silicones are highly resilient and durable for 20 years or more and used for working joints –Characteristics –Elongation, number of components, pourable, nonsag, traffic, and immersible Sealant Joints in Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved. Sealant Material Applied Using a Gun

23. Sealant Materials Solid Gaskets –Strips of cured elastomeric material –Compressed into joint or installed using lockstrip insert Preformed cellular tapes –Strip of polyurethane sponge material impregnated with mastic sealant –Strip is compressed and expands to fill joint after installation Preformed solid tape –Thick sticky ribbons of polybutene or polyisobutylene used in lap joints. They come with a release tape Sealant Joints in Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

24. Sealant Joint Design and Installation Tooling to ensure proper surface contact Width to control strain Depth to control stress Correct proportioning to control strain and stress Typical installation steps –Joint must be cleaned of oil, dirt, oxide, moisture or concrete form release compound –Apply primer if necessary –Backer rod or backup rod is inserted to limit the depth –Sealant is extruded into the joint and tooled Sealant Joints in Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

25. Sealant Joint Design – Proper Contact Sealant joint design – bond breaker –Sealant should only contact two sides of the joint. If it contacts the third side then the effective width of the sealant is reduced resulting in extra strain –A bond breaker material is used to prevent the sealant from coming in contact with more than two sides Sealant Joints in Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

26. Temperature And Joint Design Sealant joint design – temperature –For a joint between materials with high coefficients of expansion, the time of the year when the sealant is to be installed must be taken into account when specifying the size of the joint and the type of the sealant –Sealants installed in cold weather will have to stretch less but compress more and vice versa for sealant installed in hot weather Sealant Joints in Cladding Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

27. Basic Concepts Of Cladding Systems 19 Designing Cladding Systems Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

28. Load Bearing and Curtain Wall Load bearing –Until late in the 19 th century all large buildings were built with loadbearing walls –They were poor insulators, developed water leaks and heavy requiring large foundations –Modern day loadbearing walls have been brought up to date with higher strength masonry and concrete with components such as steel reinforcing, insulation, cavities, flashings, air barriers, vapor retarders. They are used in low and medium rise buildings Curtain Wall –The concept of curtain wall was introduced in late 19 th century with the advent of skyscrapers –It is an exterior wall supported at each story by a frame and derives from the idea that the wall is thin and hangs like a curtain on the structural frame –It bears no vertical load and can be thin and light in weight –Curtain walls may be constructed in place or prefabricated of masonry, concrete, metal and glass Basic Concepts of Cladding Systems Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

29. Testing And Codes 19 Designing Cladding Systems Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved.

30. Testing Cladding Systems Types of tests –Resistance to infiltration of air –Resistance to infiltration of water –Structural performance –Thermal Properties Scale –Typically full-scale tests often with two storey high specimen are conducted in laboratory Standards –Many standards such as AAMA, ASTM, and CSA Field Testing –Often field testing is conducted to ensure that performance of installed system is similar to designed system Testing and Codes Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved. Schematic Showing Water Leakage Testing of Exterior Wall in a Test Chamber

31. Cladding and the Building Codes Major impact of building codes on the design of exterior wall is in the following areas –Structural strength –Fire resistance –Energy efficiency Structural –Strength and stiffness of wall and adequacy of attachment Fire –Combustibility –Fire resistance rating –Firestopping Energy –Minimum thermal resistance –Maximum levels of air leakage –Performance requirements Testing and Codes Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright © 2009 John Wiley & Sons. All rights reserved. Installation of Firestopping using Safing