Multifamily developer Location: Columbus, Ohio Property: 220-unit, 4 buildings, 3-story garden-style wood-frame, new construction Project Type: Full thermal envelope — open-cell walls + closed-cell rim/penetrations Project Duration: 11 weeks across staggered building sequence
The Challenge The developer was building to Ohio’s 2017 Residential Code (still active for multifamily Type V-A under 4 stories) but marketing the property as “high-performance” to justify above-market rents in a competitive submarket. They needed envelope performance that supported a marketing claim, kept utilities low enough to win renter reviews, and met FHA financing requirements for the construction loan. Three competing bids from foam contractors ranged $312K to $498K. The GC needed schedule certainty more than the lowest number — the previous foam contractor on a sister project had missed 11 inspection dates.
Scope of Work
- 2×6 exterior wall cavities, all 4 buildings: 5.5″ open-cell spray foam (Demilec Heatlok HFO Pro 2.0)
- Garage ceilings under living units (Type V-A 1-hour separation): 6″ open-cell + intumescent coating system
- All rim joists, band joists: 3″ closed-cell
- Attic floors (vented attic assemblies per architect spec): air-sealed all top plates, can lights, fan housings before blown cellulose by separate contractor
- 880 unit-to-unit demising wall sections: 3.5″ open-cell for STC performance
- IRC R806.5 unvented attic option NOT used (developer chose vented for warranty simplicity)
- Total foam volume: ~92,000 board feet
Deliverables Met
- Met inspection at every scheduled date across 11-week run (44 inspections, zero misses)
- Sample unit blower door testing across 12 units: average 2.4 ACH50 (code is 3.0 for CZ5)
- STC field testing on demising walls: STC 54 average (code minimum is 50)
- Developer secured $0.18/sf utility allowance from Columbia Gas based on envelope spec — translated to ~$39,600/year reduction in operating costs across the property
- Property leased up 14% faster than developer’s other comparable asset in market — leasing team credited “low utility bills” as a top-3 amenity cited by renters
- Zero envelope-related warranty calls in first 18 months of occupancy
