Building Envelope Design - Best Practice

Case Study 6.1

Building Envelope Design Best Practice The Value of Field Mockups

“Bad times have a scientific value. These are occasions a good learner would not miss.�

Ralph Waldo Emerson

Building Envelope Design Best Practice The Value of Field Mockups The Intent of Mockups A building envelope field mockup is a replica of what will actually be constructed on the faรงade or building face. Mockups may include both vertical and horizontal surfaces. They may also be free standing, or constructed in place as part of the building exterior wall assembly. Architects use mockups for a number of reasons.

Types of Mockups Visual Field Mockups are used to provide an aesthetic reference. These are design focused and are used to assist the architect and owner decide on final selections of exterior materials, colors, and textures. In many instances, these are freestanding and include typical window and door types, masonry, metal panel/ siding, stucco surfaces, and other exterior materials.

Since there are so many traditional and new material types available, final selections can be challenging.

Variations in glass types, colors, reflectivity, and opacity can be difficult to judge when viewing a 12-inch by12-

inch sample. A large sample is typically required to obtain an accurate representation of the glazing material. Sometimes a shadow box needs to be constructed on the backside of the glass to help see the glazing as it will actually be perceived. Of course, it is not unusual for several

Provide an aesthetic reference using a visual field mockup.

glazing types to be used on a building; thus, all of these materials will need to be included in the mockup. Numerous coatings are available for metal extrusions used in windows, doors, and handrails as well as metal panels. The most commonly used finishes include fluoropolymer (Kynar),

project. The mockup will not only be used to help determine final

powder coatings, and anodized finishes, all available in numerous

material selections, it can also be used throughout the project as

colors with solid and metallic finishes. Materials like brick, stone, ceramic

a reference point for quality of construction, and control of color

tiles, Portland cement plaster, EIFS, fiber cement, and GFRC panels

and texture selections for exterior building materials. Material

must also be included so that the owner and the designers can see how

mockups can also be relatively small and cost very little. These

the materials and their colors and textures will blend and relate to one

would include 3’ x 8’ wall samples of brick, stone, cast stone,

another. Many of these mockups can be 30 to 40 feet in width and 15

plaster, metal panels, and other cladding materials. All of these

to 20 feet high, due to the number of materials and complexity of design.

field mockups can be used to determine visual compatibility of

It is not unusual for a mockup of this type to cost $100,000 or more to

various materials and assembly integration, which will show how

construct. However, the cost is relatively small when comparing it to the

materials meet, align and a 3D relationship of planes within the

millions of dollars that is spent on constructing a large mid-rise or high-rise

exterior wall assembly.

Chamber testing places window or wall assembly under negative pressure while water is sprayed on he exterior surface to determine moisture leakage resistance. the architect can choose to test field mockups at laboratory pressure without any reduction. If you choose this method, be sure that the glazers bidding the project understand they are bidding the work under more stringent requirements. Field mockups are also used to help the contractor sequence the work, and provide a final design at transitions between planes, different materials, and systems. Due to all the various materials available for construction today, it is critical to make sure compatibility and adhesion testing is performed prior to mockup construction to assure all components will work together to prevent premature deterioration. If any changes are made in the construction during the mockup phase, these should be reflected in revised shop drawings for the project Performance Field Mockups are another form of prototype used to determine whether

record. Exterior doorway mockups are especially

the exterior wall assemblies meet specified performance requirements. A chamber

important, since they need to provide waterproof

test that places the glazing or wall assembly under a negative pressure while water

construction and allow unencumbered access to

is sprayed on the exterior surface is a valuable test for determining air and moisture

the exterior. Depending on the building type, door

leakage resistance. Testing procedures are specified and detailed in both American

thresholds will need to meet Fair Housing, American

Society for Testing and Materials International (ASTM) and American Architectural

National Standards Institute (ANSI) or Americans

Manufacturer’s Association (AAMA) guidelines. The AAMA allows a 1/3 reduction of

with Disabilities Act (ADA) requirements, which limit

the laboratory test pressure for field testing as an adjustment for the differences between

the height of the threshold. Although it makes access

laboratory test environments and field testing. However, ASTM just specifies the method

easy, it makes waterproofing very difficult due to

of testing, and doesn’t specify pressures. By just specifying ASTM testing requirements,

the height restrictions. It is extremely important that a

Test whether the exterior wall assemblies meet specified air and moisture infiltration tolerances, since most litigation that occurs in construction is due to water leakage.

thorough evaluation of available products be made to ensure that they can provide both pedestrian access and waterproof construction.

Chamber Tests:

In most instances, performance field mockups are constructed in place, providing the exact conditions the contractors will encounter throughout the building process. Chamber tests are ideally performed prior to the contractor beginning installation on the project. Once mockups have passed all testing and are approved, the mockups may be left in place within the building envelope since they meet all project, manufacturer, and industry standards. Additional chamber tests are also typically performed at 30% and 60% completion to help assure quality control throughout the construction process. If failures occur during testing, it is typically recommended that at least two additional tests are performed for each failure. This expanded testing ensures that exterior wall assemblies are constructed to meet project requirements and industry standards.

Meeting Expectations In conclusion, building envelope field mockups help the architect make final aesthetic decisions and provide a means of determining whether proposed assemblies will meet industry standards and specifications. If a careful selection of materials and systems are included in the original design, it is just as critical that they be installed correctly in the field to ensure they meet project requirements and expectations.

A mockup helps the contractor to sequence the work, and provides for final design at transitions between planes, different materials and systems.

First Chamber Test

Before construction commences

Second Chamber Test

At 30 % completion

Final Chamber Test

At 60 % completion

Case Study Gables Park Tower, Austin, Texas Client: Gables Residential One of Austin’s newest boutique living experiences is nestled between Downtown and Lady Bird Lake.

The tower’s luxury homes offer stunning views of the city skyline, the Capitol, Lady Bird Lake, and the vast openness of the Texas Hill Country.

What was mocked up?

The contractor constructed a free standing wall that included all the various materials and components in the typical exterior envelope. This included a window wall, sliding glass doors, brick and stone masonry, balcony railings, deck coatings, metal panels, and wall vent assemblies. By constructing this wall assembly, the subcontractors worked out all the detailing required to coordinate installation of the materials and systems.

These mockups were used to make final selections of finishes. A small mockup of limestone, granite, and split-face CMU masonry was constructed to finalize selections prior to constructing the larger mockup.

During construction, in-place mockups were constructed and tested prior to large amounts of materials being installed. This is especially important with window and door assemblies. All typical window and door types should be water tested and pass, prior to additional units being installed in the building. If the mockups fail, required adjustments should be made and the unit retested until a successful test is achieved.

What was learned?

The materials installed on your building are supplied by various manufacturers. Even though you may think the paint coating on the window units, metal panels, or balcony railings will match other manufacturer’s components, it may not when you see it adjacent to the

other materials. Glass spandrel panels are another item that can be difficult

How did the mockup benefit the client?

to match until they are installed next to your vision glass, metal panels, and

Mockups allowed the owner and architect to make final

other materials. The color coating on the backside of the glass panel may

selections of materials to ensure the overall appearance

need to be adjusted to help coordinate with adjacent finishes. Materials

of the building was coordinated and acceptable.

like granite and limestone will always have variations in color due to the

They also ensured the exterior envelope was detailed

nature of the material. Different textures cut into the stone can also vary

and constructed correctly. Further, the large mockup

the appearance of these materials. Changes in the final selection of texture

was placed at the front of the building site. Potential

and range of color are made in the mockup prior to full scale construction

residents were able to see what the building was going

starting. Changes in details may also be required to ensure the envelope will

to look like before it was constructed. Therefore, it was

perform per the specifications and Industry Standards.

also used as a marketing tool.

“A mockup is used throughout the project as a reference point for quality of construction, and as a control for color and texture selections for exterior building materials.”

ABOUT the AUTHOR A graduate of Texas A&M University with a Bachelor’s in Environmental Design, a Master’s of Architecture and Masters of Science in Construction Management, Charles Middlebrooks has been with Ziegler Cooper for over 14 years since he joined the firm in 2001. With over 30 years of experience in architecture, construction, and consulting services, Charles serves Ziegler Cooper as Associate Principal and Senior Project Architect and is also the firm’s Waterproofing and Building Envelope expert. Over the years, Charles has strengthened his specialization in all forms of moisture control in building construction, applicable to roofing, waterproofing and curtain walls. He also specializes in energy conservation, green building design and specification development in the high-rise residential and commercial office markets.

Contact: cmiddlebrooks@zieglercooper.com | 713.374.0021

Ziegler Cooper 700 Louisiana, Suite 350 Houston, Texas 77002 713.374.0000 www.zieglercooper.com