In addition to the default inventory and screening methodologies described in Section 2 of the HPD Open Standard, the HPD provides “Special Condition,” or non-default, policies. These are alternative methodologies to inventory and screen materials and substances on the HPD.

Because these methods may evolve at a pace different from the typical HPD methodology, Special Conditions are documented on HPDC’s website as Best Practices. There may be updates to this guidance, and additional sets of instructions added to this online area between formal releases of the HPD Open Standard. Therefore, it is important to review the Best Practices when creating an HPD. If any Special Conditions are applicable, reference the Special Conditions version number used in the Inventory and Screening Notes. 

If using an automated, HPD-compliant tool like the HPD Builder to complete your HPD, you will be prompted with up-to-date Special Conditions instructions and notations will be incorporated automatically based on your responses. 

HPDC Special Conditions policies are required to be used for each applicable type of content. Exceptions are noted within those policies. 

The creation and ongoing maintenance of Special Conditions is overseen by the HPDC Technical Committee and its technical sub-groups. HPDC regularly reviews existing Special Conditions and proposals for new Special Conditions in response to industry feedback.

Special Conditions for Materials

Many building products consist of various substances that are mixed or reacted to form materials and ultimately a finished product. The default inventory and screening methods described in the HPD Open Standard work well to report a product’s chemical substances that are easily identified by CAS RN.

While all materials can in theory be analyzed in terms of the substances that make them up, in practice it doesn’t always make sense or improve our understanding of a product’s health characteristics to inventory and screen material content at the substance level. It is for these situations that several Special Conditions have been defined.

For example:

  • Biological and Geological Materials: The chemical composition of wood and stone is inherently complex and highly variable or unknown. Wood and stone also have distinct hazard profiles compared to their constituent substances. The HPD Open Standard describes procedures for manufacturers to inventory and screen wood (and other biological materials such as wool, cotton, etc.) under a Special Conditions policy for “Biological Materials,” and stone (and other mined and quarried products) under a policy for “Geological Materials.” 
  • Metal Alloys and Float Glass: In contrast with the previous examples, the chemical composition of these materials is well-defined and transparent. However, their health characteristics as materials are distinct from the characteristics of their constituent substances, and this difference as well as other factors warrants a specific methodology.

See Best Practices on the HPDC website for complete, up-to-date Special Conditions for materials.

Special Conditions for Substances

There are also circumstances where the HPD Open Standard default reporting method for inventory and screening of chemical substances identified by CAS RN has limitations that warrant the use of Special Conditions.

For example:

  • Form-Specific Hazards: The mechanism of the toxicity of a substance may be directly caused by its physical form rather than its chemical composition alone and thus strongly influenced by its context in a material.
  • Polymers: Single CAS RNs often used for polymers are frequently insufficient to fully inventory the multiple substances that are relevant for a complete inventory and hazard screen of a polymeric material.

See Best Practices on the HPDC website for complete, up-to-date Special Conditions for substances.

Special Conditions and LEED v4

HPDs developed using HPD-defined Special Conditions will be able to qualify for the key LEED v4 credit, “Building products disclosure and optimization: Material ingredients,” Option 1.

Specific modifications to the HPD Open Standard include:

  • Ability to characterize, screen, and/or identify a Special Condition according to emerging Best Practices guidance and receive a "Yes" or “Yes except Special Conditions” indicator.
  • Specific instructions for data fields that define information to be provided and format for that information.

Detailed information on Special Conditions is available in HPDC’s Emerging Best Practices guidance.