An Inside Look at the Phius Certified Windows Program Update Part I

Those of you who are familiar with Phius know that we certify projects, professionals, and products. The Phius Window Certification Program has always aimed to provide passive building practitioners with vetted, accurate, component-level performance data for windows, doors, and skylights and directly support energy modeling for buildings that seek Phius certification. To date, Phius has certified more than 800 windows and doors, making fenestration the largest category of Phius Certified Products.

Since 2013, Phius building standards have been updated at regular intervals to keep Phius performance targets in line with the growing number of refinements and optimizations to passive building techniques and strategies. Now known as Phius CORE and Phius ZERO, our flagship building standards remain the leading passive building standards in North America. 

New Phius Certified Product Database to Deploy this Year

The last year has also seen the release of the new Phius website and updated brand identity, and we’re not done yet. In 2023, we’ll also launch the new and improved Phius Certified Product Database. Manufacturers and practitioners alike will benefit from this complete overhaul of our certified product listings. Some noteworthy new features include:

• A comprehensive search feature
• Product filters based on key attributes
• Separate listings for windows and doors
• Individual product specification detail pages
• Unique serial numbers for each certified product

Upon release of the new database, Phius will sunset the existing Phius Certified Window listings. We’ll also replace all valid certificates for existing products with an improved format that will be available to both manufacturers and practitioners. We’ve received a lot of feedback over the years about how Phius Certified Window and Door certificates could better serve our practitioners – rest assured, we’ve heard you!

We took this opportunity to make some much needed updates to the Phius Certified Window Program in order to better align it with Phius building standards and important third-party programs. This program refresh will provide manufacturers with new, streamlined performance targets to earn Phius recommendations for each climate zone; practitioners will also benefit from simplified certification criteria and clearer climate zone recommendations for products. Let’s get into the details of the most significant changes.

Certification Criteria Updates

Since 2013, the combined experience of the practitioners and the Phius certification team has led to several cost and performance optimizations of the Phius building standards, especially in climate zones 5 and lower. We’ve updated the certification criteria to reflect what we’ve learned. Those familiar with the outgoing criteria will notice we’ve simplified our approach by removing the South and North/East/West differentiation for zone recommendations. We’ll also base these recommendations based on whole-window values, both for U-value and Solar Heat Gain Coefficient (SHGC). Generally, whole-window U-value requirements have been relaxed for zones 5 and lower.

Below are the 2013 criteria compared to the 2023 update:

Table 1 – Outgoing 2013 Criteria

Table 2 – Updated 2023 Criteria

Next, we’ll walk through the specific program changes in detail along with our rationale.

Changes to Whole-Window U-Value Ratings and Requirements

The whole-window U-value requirements have been relaxed in zones 5 and below based on alignment with the winter comfort criteria in Phius project certification standards. All zones will also see a bit of extra “relaxation” to the whole-window U-value due to the removal of the psi-install “penalty” found in the original 2013 program’s calculations.

The original 2013 criteria included the effect of a nominal installation thermal bridge coefficient (psi-install value) of 0.026 W/m.K (0.015 Btu/h.ft.F). This was essentially a built-in safety factor or “penalty” that de-rated products’ whole-window U-value for all climate zones. No other rating system uses this approach and actual installation situations vary widely. Therefore, we’ll stop applying this penalty to products’ whole-window U-values from 2023 onward.

Removal of U-COG Requirement

While the center-of-glass U-value is still necessary for building energy modeling and will still be published on products’ certificates, this figure will be removed from the zone recommendation requirements in favor of a combination of whole-window U-value and whole-window SHGC. The rationale for this change is listed below:

Change from SHGC-COG to Whole-Window SHGC Requirement

Zone recommendations will focus on cooling season solar protection with a maximum whole-window SHGC in warmer zones. There will no longer be minimum SHGC in cold zones.

No South/Off-South Designation

Like the decision to remove SHGC requirements for colder zones, we have also removed the south/off-south distinction for climate zone recommendations. The idea being that the issue of fenestration orientation is better dealt with in the context of designing the building to Phius project certification requirements, rather than at the product level.

Standard Model Sizes

This change offers a significant step in alignment with industry practices. Standard model sizes for the Orange Path have been reconfigured to align with those from the National Fenestration Rating Council (NFRC), which already apply to products in the NFRC Certified Product Directory (CPD); these NFRC standard sizes will continue to apply to Phius Blue Path certified products. The table of updated standard model sizes is shown below:

Table 3 – Phius Window Certification Program Standard Model Sizes

Combination units (e.g. two products mulled together) will receive a “Combination Unit” designation (rather than “One-Lite” or “Two-Lite”), and a model size that is a composite of the standard NFRC sizes in the table above according to the subsequent conditions:

Table 3a – Phius Approach to Standard Model Sizes for Combination Units

An important note for manufacturers: Combination units are not present in existing NFRC protocol.Therefore, any Blue Path products that aim to use their NFRC simulations as the basis for a Phius-certified Combination Unit must provide separate performance data and CPD numbers for each product that will comprise the Combination Unit. Phius Blue Path protocol allows for the creation of Combination Units from the data and simulations of each individual product that will be mulled together. Orange Path products that seek the Combination Unit designation will follow the same existing submission requirements as One-Lite and Two-Lite products.

So, what’s next?

If you’re a manufacturer, keep an eye on your inbox for an email from Phius’ Product Certification Manager, Michael Franco. We’ll work with all manufacturers who have existing certified products to determine their eligibility for migration to the new database and can expect the following:

• Products with unexpired certificates or those that would otherwise be eligible for renewal are also eligible for migration.
• Unexpired products will be automatically renewed as part of this undertaking.
• Migrated products will also be reevaluated and reclassified against the new 2023 criteria at no additional cost to manufacturers.
• Products that are expired or require recalculations due to design changes may be subject to modest renewal or recalculation fees prior to migration into the new database

We encourage manufacturers to email Michael Franco (mfranco@phius.org) with any questions related to the program changes or existing product migration.

Participating manufacturers will also receive updated customer-facing materials including a press kit which will include new Phius Certified Product marks and Phius logo/certification mark usage guidelines, allowing manufacturers to display any earned recommendations or certificates on their respective websites or print materials.

To all our practitioners: stay tuned for more information! We’ll notify professionals when the new database is ready for launch. Once we release the updated certificates for all products, we will clearly indicate a date at which all legacy product certificates will become void for use in project certification. Until then, please use the existing certificates found in our current product listings. If you have concerns about a project in progress that uses an existing product certificate, don’t worry. We aren’t making any changes that will affect the component-level data that you used for your building energy model. Since zone recommendation check marks are not a prerequisite to use a Phius Certified Window in a project, any changes to a product’s zone recommendations alone won’t affect its eligibility for use in a specific building.