Is It Time to Retire the Metal Sill Pan

Windows Energy Use Water Management Air Barriers

Course Description

Metal sill pans have been used beneath windows for centuries to successfully protect the openings into which we install them. But is there a better way? Fluid and self-adhered membranes can conform more easily to complex geometries (origami with metal is difficult!) and any membrane at the sill can be continuous with whatever membrane is used at the jambs, reducing risk. But can fluids reliably span the gaps at openings? And are membranes less durable than their metal counterparts? This short presentation discusses both approaches to detailing windows at the sill (metal and membrane), showing examples (photos and sketches) of each, and makes the case that membrane sill pans are typically the more reliable choice.

Course Instructor Christine Williamson

Course Length 12:30

Published 18 Aug 2022

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Keywords: building science, energy efficiency, air barriers, air tightness, window details, sill pans, window detailing, water management

About Building Science Fight Club

Christine Williamson - Assoc. AIA

Building Scientist | Instructor

Christine Williamson has spent her career in building science forensics, discovering why buildings fail and working with owners, architects, and builders to remedy the problems. She is the founder of the Instagram account @BuildingScienceFightClub, an educational project that teaches architects about building science and construction.