Designing Robust Details for Resilient Buildings Andrea Wagner Dow Corning dowcorning.com/construction
WHERE BUILDING ENVELOPE DETAILS GO WRONG
So What happens when the different components of a building enclosure come together?
Many Substrates, One Corner Dow Corning INTERNAL
A Corner + a Window = Tight Tolerances
Why do these details happen!?! Inadequate Details Unrealistic Tolerances Poor Installation Difficult Substrates
How do we get to the RIGHT DETAILS
Window-to-Wall Transitions Variety of Substrates Movement Accountability Code requirements for continuous air and vapor barriers
Continuous Air Barriers Dow Corning INTERNAL
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.
How do you complete this detail? Dow Corning INTERNAL
RIGHT DETAILS, RIGHT PROCESS
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
Movement Within a Wall System 14
Thermal movement 15
Live load deflections between columns 16
Seismic and wind sway 17
Elastic frame shortening and creep 18
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
The Performance of Your Wall System Relies on Details 20
FOUNDATION DETAILS 21
WINDOW OPENING DETAILS 22
PARAPET DETAILS 23
PENETRATION DETAILS 24
Resilient Material Interfaces 25
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
The Details Are Not Always Simple 27
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
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
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
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
Flashing Window Perimeters Place for frequent premature failures Fragile substrates Sheet-applied membranes require complex cutting and layering to wrap a window perimeter. 32
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
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
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
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
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
Order of Installation 38
Constructability Order of installation Sequencing of trades Air barrier contractor Fenestration contractor Waterproofing contractor Insulation contractor Other Timeline flexibility 39
How is the detail going to be installed? Dow Corning INTERNAL
Determine if the detail can be made simpler and the process leaner Make it simple! Limit number of steps Limit number of materials
Communicate The Detail 42
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
For Air Barrier Systems Define: Responsible party Scope of work Knowledgeable contractor Constructability Continuity
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
Water Resistance at Material Interfaces 46
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
Two Traditional Solutions Traditional sealant joint Precured silicone strip 48
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
What s Wrong With This Detail? 50
VIDEO 0002 51
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
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
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
How Does This Get Fixed? Video 0003 55
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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