Designing Robust Details for Resilient Buildings

Transcription

1 Designing Robust Details for Resilient Buildings Andrea Wagner Dow Corning dowcorning.com/construction

2 WHERE BUILDING ENVELOPE DETAILS GO WRONG

3 So What happens when the different components of a building enclosure come together?

4 Many Substrates, One Corner Dow Corning INTERNAL

5 A Corner + a Window = Tight Tolerances

6 Why do these details happen!?! Inadequate Details Unrealistic Tolerances Poor Installation Difficult Substrates

7 How do we get to the RIGHT DETAILS

8 Window-to-Wall Transitions Variety of Substrates Movement Accountability Code requirements for continuous air and vapor barriers

9 Continuous Air Barriers Dow Corning INTERNAL

10 A new issue at window transitions Sealant Sealant Air barriers can have a lower bond strength between layers The primary seal is getting hidden deeper in the cavity which makes for harder replacement if there is an later failure.

11 How do you complete this detail? Dow Corning INTERNAL

12 RIGHT DETAILS, RIGHT PROCESS

13 5 steps to robust details 1. Consider the movement of the building and materials, 2. Refer to material requirements for durability, compatibility, adhesion and clearances, 3. Think through the order and process of installation of the detail, 4. Determine if the detail can be made simpler and the process leaner, and finally 5. Communicate the detail to the applicable construction team members for input on practicality

14 Movement Within a Wall System 14

15 Thermal movement 15

16 Live load deflections between columns 16

17 Seismic and wind sway 17

18 Elastic frame shortening and creep 18

19 The movement of materials Thermal Movements (Coefficients of Thermal Expansion) Aluminum = 12.9 x 10-6 Glass = 5.1 x 10-6 Concrete = 6.5 x 10-6

20 The Performance of Your Wall System Relies on Details 20

21 FOUNDATION DETAILS 21

22 WINDOW OPENING DETAILS 22

23 PARAPET DETAILS 23

24 PENETRATION DETAILS 24

25 Resilient Material Interfaces 25

26 Detailing and Installation No two buildings are exactly the same, and having a flexible system to create an airtight envelope is important. Photo courtesy of BIG 26

27 The Details Are Not Always Simple 27

28 What are the material requirements for durability compatibility, adhesion and clearances? Material exposure (such as UV, temperatures) Construction Tolerances Joint size required for sealant material Product Compatibility

29 UV Stability Relies on Chemistry Ultraviolet (UV) light will degrade the carbon-carbon or carbon-oxygen bond of an organic material There is not enough energy in UV light to degrade the Si-O bond of a silicone material Therefore, an organic sealant will degrade in sunlight, while a silicone sealant will be virtually unaffected 29

30 Sealant Chemistries There are two broad categories of sealant chemistries available: Organic which consist of a carbon based polymer (-C-C-O-C-C-) Single and multi-component polyurethane Polysulfide Acrylic Modified Silicone Inorganic which consist of a non-carbon-based polymer (-Si-O-Si-O-Si-) Silicone 30

31 Sealant Joint Design Dow Corning INTERNAL Maintain a minimum ¼ contact to each joint surface Minimum ¼ sealant thickness 2-to-1 width-to-depth ratio minimum Avoid 3-sided adhesion 31

32 Flashing Window Perimeters Place for frequent premature failures Fragile substrates Sheet-applied membranes require complex cutting and layering to wrap a window perimeter. 32

33 Liquid-Applied Flashing Easily tooled around corners and into openings Seamlessly seal around complex shapes Can be adhered to with traditional silicone sealants without having to worry about adhesion to HDPE liners 33

34 Sealants have Limits Movement capability of materials A traditional sealant: Maximum compression 50% Maximum extension is 100% with the right sealant Precured materials can compress up to 75% and extend up to 300% Compression is harder on sealants than extension 34

35 Compatibility Between Components Dow Corning INTERNAL It is critical that all pieces of a system be compatible for them to perform long-term No unexpected material interactions Especially when exposed to UV light Compatibility also must include: Robust adhesion between components Allowance for movement between components 35

36 Solution Use similar chemistries for all components whenever possible Compatibility testing between components (ASTM C1087) Minimize number of products and manufacturers Consider environmental effects on materials 36

37 Adhesion and Compatibility Adhesion: Does it stick? Tested in the LAB per ASTM C794 Tested in the FIELD per ASTM C1401 Compatibility: Is there a negative chemical reaction that will impact the sealant? Test in the LAB per ASTM C1087

38 Order of Installation 38

39 Constructability Order of installation Sequencing of trades Air barrier contractor Fenestration contractor Waterproofing contractor Insulation contractor Other Timeline flexibility 39

40 How is the detail going to be installed? Dow Corning INTERNAL

41 Determine if the detail can be made simpler and the process leaner Make it simple! Limit number of steps Limit number of materials

42 Communicate The Detail 42

43 But how? Simplification If a detail is hard to draw, it s probably difficult to install in the field I can draw it but there is no way they can install it Minimize the number of materials Lower probability that the contractor can use the wrong material Easier to specify Include all members of the team

44 For Air Barrier Systems Define: Responsible party Scope of work Knowledgeable contractor Constructability Continuity

45 An Important Note No one wants to be responsible for the transition between the opaque wall and the fenestration Who has the contract? Involve a knowledgeable contractor in the conversation early to help ensure the details are able to be constructed 45

46 Water Resistance at Material Interfaces 46

47 Water: The Universal Find-its-way-er Systems can pass ASTM E283 for air leakage rate but may still fail water resistance Sealing of screw heads Extrusion must be lapped to shed water Forcing structural deflections of system and retesting for water and air may reveal failures 47

48 Two Traditional Solutions Traditional sealant joint Precured silicone strip 48

49 Precured Silicone Extrusions Allow for spanning gaps and angles that are difficult with sealant Must meet same air infiltration standards as sealant Allow for movement of large joints and transitions Window perimeters Floor slabs 49

50 What s Wrong With This Detail? 50

51 VIDEO

52 Performance of Intricate Assemblies Air Leakage Rate (ASTM E283) Static Water Pressure Resistance (ASTM E331) Dynamic Water Pressure Resistance (AAMA 501.1) Structural Performance (ASTM E330) 52

53 Structural Loading, Then Water and Air Standard testing Max load ±30 psf Overload testing Max load ±45 psf No tearing No loss of adhesion 53

54 What Is a Successful System? Air infiltration must meet system criteria of 0.04 cfm/ft 2 at 1.57 psf No water infiltration can be seen either before or after structural loading Water can be harder to pass when adding pressure and structural movement 54

55 How Does This Get Fixed? Video

56 Dow Corning INTERNAL Finally Understand the movement needed at the interface Refer to material requirements for compatibility, adhesion and clearances Think through the order and process of installation of the detail Determine if the detail can be made simpler and the process leaner Communicate the detail to the applicable construction team members for input on practicality 56

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