The Philly Passive House: What does a home without fossil fuels look like?

Inside a Francisville Passive House project, Green Philly attendees saw how airtight construction, insulation, efficient HVAC, and solar power can reduce home energy use.

To the untrained eye, 1931 and 1933 W. George Street look like any other construction job popping up across the city. To insiders (like those who attended Green Philly’s sold-out Passive House tour on September 16), these units make up an all-electric, net-zero energy residential development.

During the site tour, attendees learned about the future of sustainable housing from architect Jeremy Avellino of Bright Common; Deborah Solo and Alejandro Franqui of Solo Real Estate; general contractor Anthony Giacobbe of Red Oak Construction; and Neil Goldman, Passive House Institute US (PHIUS) rater and project manager.

Comfort is the foundation of these Francisville homes

LEED certification is the globally recognized standard of green building practices. While LEED focuses on the holistic sustainable picture, PHIUS standards focus on maximizing energy efficiency. Passive houses prioritize health and comfort, creating a quiet and serene environment with natural light, steady temperatures, and low humidity. 

To achieve net-zero performance, passive houses rely on:

• Continuous insulation
• An airtight envelope
• High-performance windows
• Low-emission materials and combustion-free appliances
• An ultra-efficient heating and cooling system

A passive home’s envelope is protected by continuous insulation – four inches of structural foam underneath, double the interior wall insulation of a traditional build, and four inches of exterior mineral wool – plus an airtightness layer, where an interwoven screen tightly wraps the slabs. This insulation keeps homes cool in summer and warm in winter.

Working with nature

Woonerf is a Dutch design concept where cars and pedestrians share public space equally. Each home sits on a 16-by-35-foot parcel, where a tiny alley meets a minimal sidewalk, followed by a stoop, EV carport, and living space. Inspired by Italian piazzas, the kitchen and dining room are on the first floor instead of the ground floor.

“When you’re siting a house, the longest part of the facade should face south to capture passive solar,” explained Avellino. “Passive houses factor in solar orientation but can still reach zero-energy design.”

“With energy modeling software, even without ideal solar orientation, you’re not fighting it – you can add insulation to the slab, walls, or roof, and optimize for comfort or cost. We look at these choices alongside the developer’s pro forma, designing with feedback from the building itself.”

The home’s large, triple-paned windows use daylighting and face south to optimize interior light and solar heat. Unlike traditional windows, they swing open like a screen door, preventing air leaks, water damage, energy loss, and mold.

The second floor holds the primary bedroom with an en suite bathroom, storage, and a laundry room with combustion-free appliances. The third floor has two more bedrooms and a shared bathroom. A solar canopy on the roof deck offsets 100% of future energy consumption.

Simple. Dependable. Reliable.

“Comfort comes down to two things: the envelope that separates indoor and outdoor air, and the heating and cooling system that handles what the envelope can’t,” explained Goldman. “Think of the building like a submarine: underwater, any leak is an air leak.”

Because the envelope performs so well, the HVAC systems can be smaller. Passive homes use an energy-recovery ventilator (ERV) – a whole-house mechanical system that continuously replaces stale indoor air with fresh outdoor air while transferring heat and moisture between the two.

Throughout design and construction, the project is verified against PHIUS standards: third-party inspectors review Avellino’s blueprints and give feedback, Neil inspects ducts for airflow and tests system efficiency, and Anthony reports roadblocks as they arise.

PHIUS-certified buildings perform up to 85% better than conventional buildings.

So how do the passive homes hold up for the people who live in them?

One tour attendee lives in another Passive House development by Bright Common and Red Oak. Despite another record-setting hot year, he said he only needed heat when temperatures dropped below zero and runs the AC just a handful of times each year.

Photos: Madasyn Andrews