How Is MEP Designed for a Mass Timber Office in the Pacific Northwest?

The shared model is the project's single source of truth. The MEP engineer builds ductwork, piping, conduit, cable tray, and sprinkler mains in the same coordination model as the timber structure, and clashes are resolved in the model — not in the field, where moving a duct means re-cutting timber. The engineer sets routing hierarchies early: gravity systems (drainage, condensate) get first claim on slope, then large ducts, then sprinkler mains, then conduit and tray. Sleeve locations through CLT panels and glulam beams are frozen before timber fabrication, because the panels arrive from the factory with openings cut — a missed sleeve means a very expensive field modification or a visible reroute. The engineer also designs for the installer's reality. Exposed systems need hanger details that look intentional: trapeze hangers aligned in rows, seismic bracing that reads as part of the architecture, and pipe and duct supports anchored to the timber with fasteners the structural engineer approves. Access panels for dampers, valves, and control devices are located where maintenance staff can reach them without lifts through finished space, and the engineer documents every concealed device location because there is no ceiling tile to pop.

Fire performance at penetrations is designed around how mass timber actually behaves. CLT chars at a predictable rate, which is what gives it a fire-resistance rating — but a penetration that breaches the char layer needs a tested firestop system that restores the rating, and the engineer specifies systems listed for timber substrates rather than assuming a concrete detail transfers. Sprinkler coverage is designed for the exposed timber hazard, with the engineer confirming that the occupancy's sprinkler design criteria match the actual fuel load of an office with wood structure and finishes. Acoustics get engineered at the same crossings. The engineer seals every MEP penetration through floor panels with acoustic sealant, isolates vibrating equipment — fans, pumps — from the timber with spring isolators so structure-borne sound does not travel through the stiff wood, and coordinates the floor buildup above the CLT with the acoustic consultant's impact-isolation requirements. For moisture, all cold-air ductwork in the exposed zone is insulated with sealed vapor retarders, and the engineer reviews the building's humidity control strategy so the timber deck never sees sustained condensing conditions that could stain or degrade the exposed finish.