A Comprehensive Guide to the Glass Selection & Sampling Process: Technical + Practice

Selecting the right glass for a facade is a critical step in any architectural project, especially when low-e coatings are involved. With advancements in technology, more and more glass coatings are being introduced into the market, each offering a wide variance in color, transparency, performance, and quality. While this variety opens up exciting possibilities, it also makes it extremely challenging for architects to choose the right glass that meets both aesthetic goals and performance requirements such as thermal efficiency, solar control, and structural integrity.

This blog highlights the importance of a collaborative approach, particularly during sample reviews, and emphasizes how involving facade consultants early in the process ensures alignment across all stakeholders.

Here’s an in-depth look at how the glass low-e coating selection and sampling review process unfolds:

1.       Design Development - Glass Selection

Key Contributors

At the heart of the design development phase is a team effort that brings together expertise from multiple stakeholders. This phase begins with defining the project's goals, balancing aesthetic ambitions with technical feasibility.

Key activities

Key factors effecting the visual appearance of glass

Glass selection - a balancing act

Importance of Sample reviews and benchmarking

Physical samples play a crucial role in visually evaluating the range of glass coating options available in the market. These samples allow reviewers to appreciate subtle differences in color and reflectance, offering an essential tactile experience for understanding the material. Reviewing the samples under the correct conditions and format is critical to the effectiveness of the process.

• Sample reviews are best carried out outside under sunny conditions at project site;

• Samples should be viewed from different angles to appreciate the difference in colour under different lighting conditions, particularly the reflective colour of the coating;

• Ideally with a black box/block out to resemble interior lighting condition

  
  

However, such samples still come with inherent limitations. A small 300x300mm sample cannot fully replicate the appearance of a thirty-story facade under real-world conditions. Factors such as the dynamic play of light, reflections, and the presence of the building's interior all contribute to the final aesthetic. This discrepancy often requires reviewers to stretch their imagination to envision how the material will perform at scale, hence why benchmarking existing built projects is an invaluable tool for designers when selecting glass. Architects and consultants can explore completed project images using platforms like GlasLab to assess how specific glass coatings appear in more realistic contexts.

2. Contract Documentation - Glass Specification

Documenting the glass specification and preferred coating

Once process advances to the contract documentation phase, the facade consultant takes a leading role in preparing the glass specification in the Facade Perforamnce Specification. This critical document outlines the glass make up, preferred coatings, and their performance characteristics, ensuring that all stakeholders are aligned on the project's technical and aesthetic requirements.

It is essential that the selected benchmark glass coating is clearly referenced in the contract documents, including both Architectural Specifications and Facade Specifications, to ensure the intended design aesthetics and performance standards are communicated to the contractor.

Pre-setting parameters for review process of substitutions in D&C contracts

Facade procurement often follows a Performance-Based Design and Construct (PBD&C) process, facade contractors may suggest alternative glass suppliers or coatings that differ from the specified benchmark. To navigate this effectively while optimizing costs and efficiency, it is also vital to include provisions for further sample review processes in the contract documents, including submission of samples, full size sample review and Visual Mock-Up Reviews. This ensures that during the construction phase, any proposed glass alternatives are thoroughly reviewed and approved by key stakeholders before final selection. By doing so, the project team can safeguard the original design vision while meeting all performance criteria.

3. Construction - Final Glass Selection Process

During the construction phase, the final glass selection process is undertaken. This critical stage relies on close collaboration between the architect, consultant, client, builder, and facade contractor to confirm that the final glass selected fulfills both the design intent and technical performance requirements before it's procured and goes into fabrication.

Prior to making final decisions, thorough visual evaluations are conducted through several key steps:

Step 1: Small sample reviews:

Alternative glass coatings proposed by the contractor are compared directly with the benchmark samples. This ensures that the alternatives closely match the specified color, transparency, and reflective properties.

Step 2: Full-size glass sample review:

Large-scale full size samples are essential to enable an accurate review of color consistency, transparency, and reflectivity under real-world conditions. These samples must be large enough to resemble actual project design, and provide an accurate representation of the glass’s transmitted color, reflective coating appearance, and level of transparency when viewed from both the interior and exterior. For the most realistic evaluation, the samples should be reviewed under conditions as close to actual use as possible, ideally installed with an enclosed setting behind to mimic their final application.

Step 3: Visual mockup review (VMU):

Although construction programmes often result in VMUs being constructed after glass selection, this step remains crucial. The mockup provides an opportunity to assess the glass fixing methodology, fabrication details, and overall quality of the installed facade. It ensures that the glass meets both functional and aesthetic expectations when integrated into the final design.