Achieve Phius CORE Prescriptive

Phius' newest standard was created to facilitate widespread adoption and scaling up, placing emphasis on quality, durability, healthy, safety, and cost-optimized conservation on the path to zero energy.

Phius CORE Prescriptive Standard Specifications

The Phius CORE Prescriptive Hybrid Approach

The prescriptive standard takes a hybrid approach with prescriptions for both envelope and mechanical elements of the building and allows for some performance tradeoffs within those categories. It comprises three types of requirements:

Universal Requirements

As in the name, universal requirements apply to all projects and most of the program requirements fall into this category. These are items such as banning fossil-fuel combustion, an airtightness threshold, maximum limit on window-to-wall ratio and maximum floor area based on planned occupancy, compact form regulated by the maximum envelope-to-floor area ratio, designing for limited moisture and condensation risk, thermal bridge elimination, 3rd party co-requisite programs, etc.

Climate Specific Requirements

These requirements are critical for climate appropriate passive building design. They include setting minimum thermal performance for the opaque and transparent enclosure, guardrails to limit window solar gain with guidelines on solar heat gain coefficients and overhangs, and minimum efficiencies for ventilation recovery and active heating/cooling systems.

Building Specific Requirements

These are the active conservation regulations that impact operational energy like water heater efficiency, major appliances, and lighting. There are two compliance paths in this category: one based on meeting the prescribed efficiency of each individual component and the other using a performance tradeoff between equipment to out-perform the component-based approach, on a predicted annual energy use basis.

Phius CORE Prescriptive Resources

A handful of resources were developed to support the prescriptive path. These free tools can be utilized to support the design of high-performance homes, whether the project chooses to pursue certification or not.

Phius CORE Prescriptive 2021 Checklist

This comprehensive checklist outlines all detailed requirements of the prescriptive program. It has useful tools built in, like an effective R-value calculator, whole-building UA tradeoff calculator, moisture design criteria for the opaque enclosure, condensation risk assessment for fenestration, and the appliance, hot water, and lighting performance tradeoff calculation. A completed checklist is required for certification submission.

Download the Checklist

Phius CORE Prescriptive Snapshot

The snapshot tool was designed to provide a quick look (snapshot) at is similar to the zone table, outlining mostly climate-specific requirements and some building specific requirements. Instead of zone-by-zone, the requirements are based on the individual city (climate data set). The snapshot is recommended for anyone designing a single-family home: throw in the general building size and climate zone and use the requirements as a starting goal for design, whether or not any Phius certification is being pursued.

View the Snapshot

Phius CORE Prescriptive Climate Map

The climate map provides almost all of the same data as the snapshot, except it's displayed on a map. It is often helpful to use this map to find the location/climate data set closest to your project site.

View the Requirements Map

Phius CORE Prescriptive Climate Zone Table

This zone table is the most broadly applicable resource. It provides a single table outlining the climate specific project requirements, displaying the range of thermal and mechanical equipment performance requirements based on the edges of the climate zone, as defined by ASHRAE 167-2019. This is especially useful for those designing in different cities across a zone; the conservative end of the range can be applied to all projects in that zone instead of looking city by city in the Snapshot.

Download the Zone Table

Phius CORE Prescriptive Provides

Healthy Living

Superb indoor air quality is a prerequisite for Phius certification – you can count on a healthy environment.

Affordability

Phius projects require minimal to no additional upfront costs, while guaranteeing substantial energy cost savings in the future.

Safety

Phius-certified buildings go through a rigorous quality control process, ensuring safety for the environment and the building inhabitants.

Comfortable Living

Superinsulation, high performance windows and efficient mechanical systems create a comfortable, quiet building

Resilience

Phius buildings have been proven to be more resilient in the event of natural disasters, such as wildfires and extreme heat and cold events.

A Sound Long Term Investment

The holistic design of Phius buildings and attention to detail in the enclosure make them extra durable and uniquely built for the long haul.

Read The Blog

Phius Project Certification Manager James Ortega outlines the Phius CORE Prescriptive path available for project certification.