Historic Pine St Passive House

This major retrofit modernized a 4-apartment circa 1845 rowhome located near Philadelphia’s historic Rittenhouse Square to achieve passive house performance, prioritizing repurposed, reused, recycled, and low-carbon materials.

The first-floor gut rehab converted therapists’ offices into a modern, three bedroom, three-bath apartment that accommodates the owner’s architecture office, art collection, and custom-designed furniture. A light color palette, vibrant accent colors, and mirrors offset the limited access to daylight.

Two units were converted into 2-bedroom, 2 bathroom apartments for flexible tenancy. Modernized, enlarged kitchens enhanced all upper flats; refurbished fixtures and casings, traditional millwork, and tilework adorned the upper floors. While the first-floor owner’s unit received local FSC flooring, the original ‘Philadelphia style’ oak and walnut floors of the upper units were refinished. The retrofitted building has all electric services from renewable services. Natural gas boilers and draft hot water heaters were removed from the building, making the building fossil fuel-free. Each apartment has Energy Star appliances, heat pumps, and ERVs for HEPA-filtered air.

The brick on the front and rear elevations was tested for water absorption using the Rilem tube test. The thermal envelope was modeled using PHPP and WUFI tools to prevent condensation and bio-growth, resulting in a healthy, airtight, and super-insulated design. Triple-pane, simulated double-hung windows, trimmed with high-density insulation milled to match the original profiles, enhance the historic Pine Street façade.

A café table, refurbished streetlight, and native plants enliven the sidewalk in this walkable neighborhood. A solar PV-ready canopy shades the shared garden roof deck. The retrofit produces higher rents and multi-year leases. People love living here.

Design & Construction team

Architect: BluPath Design – Laura Blau AIA, Kevin Davey

CPHC / Energy Modeler: Laura Blau CPHC / Kent Lessly, RA

CPHC Structural Engineer: Amy Rivera PE, Jean Gajary PE

General Contractor: GreenSteps LLC

Framing and Construction: Hivemind Construction

Air Sealing Specialist: GreenSteps LLC

Building Areas

Unit A (Basement + First Floor) = 1,686 sf
Unit B (Second Floor) = 1,207 sf
Unit C (Third Floor) = 944 sf
Unit D (Third + Fourth Floor) = 1,011 sf

Total Building = 6,493 gsf

Lot Area (20 ft wide x 90 ft deep) = 1,800 sf

AIR TIGHTNESS TEST RESULTS – UNIT A

Floor Area = 2,482.3 sf
Surface Area = 7,424.5 sf
Volume = 26,424.5 cf
Final Airtightness = Pressurized 515 CFM50 / 1.17 ACH50, Depressurized 477 CFM50 / 1.08 ACH50

ASSEMBLIES

Basement Slab = 4-6” XPS Underslab
Basement Parged Stone Wall = 6-10” Mineral Wool Board w/ lime plaster parging and/or liquid air barrier
Typical Brick Wall = 4-6” Dense Pack Cellulose w/ liquid, plaster and/or fabric air barrier
Windows & Doors, Tilt-N-Turn Triple Glazing = Pine Street – Klearwall (Ireland), Rear – Intus Windows
Ventilation = Zehnder America ComfoAir ERV
Heating & Cooling = Mitsubishi Minisplit HVAC
Dehumidification = None
Domestic Hot Water = GeoSpring Heat Pump HWH