LOCKED strategy finish tier needs designer

LDD-11 · Exterior Envelope (IMP)

One-line intent

A robust, forgiving, high-performance environmental shell using insulated metal panels (IMP), with selective interior framed assemblies for acoustic + human warmth in habitable zones.

Locked decisions

Primary wall (outside → inside)

Factory-finished exterior metal skin (matte dark)
Continuous rigid foam insulation core
Factory-finished interior metal liner

Secondary interior wall (in habitable zones)

Optional service cavity
Independent wood stud framing
Mineral wool acoustic insulation (LOCKED)
Drywall and/or selective wood finish

Material strategy

Exterior: matte dark brown — Kynar 500 PVDF finish (LOCKED, per builder)
Color logic: dark brown integrates with Delaware mid-Atlantic landscape (deciduous canopy + native grasses + stream-adjacent context) more naturally than gray-black would
Interior: hybrid by zone — exposed IMP in infrastructural zones, layered drywall + mineral wool in living-oriented

Open items / engineer review

IMP panel thickness — 4", 5", or 6" (R-26 to R-42)
~~Panel finish tier~~ — Resolved: Kynar 500 PVDF, dark brown (per builder, 2026-05-15)
Vapor strategy — IMP is vapor-tight both sides; need air control layer detail at joints/penetrations
Air sealing detail at IMP-to-IMP, IMP-to-foundation, IMP-to-roof, IMP-to-glazing
Slab-edge insulation continuity at IMP-to-slab
Lightning protection for large metal building
Airtightness target (ACH50) — currently unspecified

Cost drivers

IMP wall ~13,500 sqft × $17/sqft avg = $230K. IMP roof $85–145K (LDD-01). Interior framing + mineral wool + drywall ~3,000 sqft = $66–105K. Exterior windows + doors $35–70K.

Air-gap concerns

Condensation risk on interior IMP liner — both sides vapor-tight. Hybrid mitigates in habitable zones; verify utility zone exposure.
Thermal bridging at fasteners + clips — verify effective R, not nominal.
Roof IMP at ½"/ft is below most manufacturers' preferred minimum for cold climate.
Acoustic underperformance for gym west IMP wall (low-frequency basketball impact).
Lightning + grounding — large metal shell needs bonding strategy.
Finish tier matters long-term. Kynar 500 holds color 25–35 years vs SMP 8–15 years. $1–3/sqft × 13,500 = $13–40K premium worth considering.
No airtightness target — without it, you don't know what you got. ≤1.5 ACH50 reasonable; ≤0.6 ACH50 is Passive House level.

Cross-references

← Inputs from

LDD-01 PEMB girts · LDD-02 slab edge · LDD-04 clerestory rough opening

→ Outputs to

LDD-18 habitable zone wall finish

Diagram

IMP envelope wraps the perimeter rectangle.