Building Enclosure

Parapet Parodies: Water, Air, Thermal, and Vapor Control

By Benjamin Meyer

September 09, 2025

Parapets are a critical interface where building aesthetics meet performance.

Parapets are a critical interface where building aesthetics meet performance. The parapet is so much more than the intersection of roof and wall. It's also the junction where building aesthetics meets structural performance, air and moisture management, energy efficiency, construction trade sequencing, and operational maintenance.

To better understand common parapet challenges, it is important to review continuity across the roof and wall systems, specifically the key four control layers: water, air, thermal and vapor.

These four key control layers should generally be continuous across all six sides of the building enclosure. The "pen test"—tracing each of the control layers across the building enclosure—is a helpful tool to design and communicate the intent of the critical components and functions of the building enclosure. The "pen test" is relatively easy in theory, but it can get complicated as we zoom in and consider the control layers at each condition, penetration and transition.

Key points to consider:

  • Water Control is managed by the roof membrane and the cladding.

  • Air Control can be managed at the deck level of the roof, which can more readily be married into the wall air barrier.

  • Thermal Control continuity is maintained by connecting the roof and wall insulation, which can be challenging.

  • Vapor Control can also be in the same plane as the air control layer.

Parapets are a critical interface where building aesthetics meet performance.

Click the link below to read the paper by Ben Meyer, Siplast's Building Enclosure Business Director. The paper is part of a 1.5 LU | HSW & IIBEC CEH course.


Parapet Parodies: Water, Air, Thermal, and Vapor Control

About the Author

Benjamin Meyer, AIA, NCARB, LEED AP is the Building Enclosure Business Director with Siplast. Previous experience includes: enclosure consultant principal, technical management, research, and education for enclosure products, commercial design, real estate development and construction management on a range of projects that included residential, educational, offices, and DuPont industrial projects. Industry positions include: Envelope Chair and Full Voting Member of ASHRAE 90.1, Fellow and past Director of the Air Barrier Association of America (ABAA), and past LEED Technical Committee member and Technical Advisor of the LEED Materials (MR) TAG. Mr. Meyer has MBA, B.S., and M.Arch degrees from the University of Cincinnati.

This blog contains information created by a variety of sources, including internal and third-party writers. The opinions and views expressed do not necessarily represent those of Siplast. The content is for informational purposes only. It is not intended to constitute financial, accounting, tax, or legal advice, or professional design advice as to any particular project. Siplast does not guarantee the accuracy, reliability, and completeness of the information. In no event shall Siplast be held responsible or liable for errors or omissions in the content or for the results, damages or losses caused by or in connection with the use of or reliance on the content. Consult a design professional to ensure the suitability or code compliance of a particular roofing system for any particular structure.