Lightbox 23 net zero House, Portland Building, Sustainable Home, Oregon Real Estate, US Property Images

Lightbox 23 net zero House in Portland

Real Estate Development in Oregon design by Steelhead Architecture, USA

post updated November 4, 2022 ; Aug 14, 2018

Design: Steelhead Architecture

Location: Portland, Oregon, USA

Lightbox 23 net zero House

Photos by Josh Partee

Lightbox 23 net zero House

Lightbox 23 is a 2-unit net zero infill project in inner NE Portland. The project features super insulated wall, roof and sub-slab assemblies plus high performance mechanical and ventilation systems. Topping it off (literally) is a 10kW solar array on each unit. The project has been certified net zero by Earth Advantage.

The design is a split level floor plan with the floating stairs acting as the central spine. Each floor opens to the half level above and below through the open slot the stairs create. The exterior tube forms step up the facade to the corner view deck where Mt. St. Helens and Mt. Adams are visible to the north. Being a corner lot each unit faces a different street and the plans / facades are mirror images of each other.

Lightbox 23 is a speculative project by Lightbox Portland, who is dedicated to high performance, high density modern development. 3 more Lightbox Portland / Steelhead Architecture projects are currently in process.

Net zero construction simply means generating as much, or more, energy as is used by the building. On the supply side this means a 10kW solar array for each unit. That’s the easy part. Reducing the energy load is the more interesting part of the equation. Super insulation is a huge part, and relatively inexpensive.

Steelhead Architecture used 2×8 walls filled with blown in cellulose then added 2″ of EPS (rigid insulation) to the outside of the plywood / WRB for a thermal break. There are 3″ of EPS below the concrete slabs (no crawl spaces ever used). The roof assembly is similar to the walls with the combination of blown in and rigid insulation for a ventless assembly.

Our air barrier is another huge piece. Steelhead Architectureused Henry Blueskin as the WRB and air barrier over plywood (no OSB). With repetitive joint sealing and searching out leaks Steelhead Architecture achieved a blower door test of 2.36 ACH50 (air changes per hour at 50 pascals of pressure) which is 4-5 times better than an average house. All of these tight and super insulated envelope measures equals very little heat / cooling loss and therefore much less energy use.

For the mechanical system the architects used ducted heat pumps – all electric which have far greater efficiency the gas systems. There is in fact no gas used on site at all, again to increase efficiency and reduce penetrations. The system also includes an independently ducted HRV (heat recovery ventilator) to provide controlled air exchanges without losing energy.

Lightbox 23 net zero House, Portland, OR – Building Information

Project size: 5800 ft2
Site size: 5000 ft2
Completion date: 2018
Building levels: 3

Design: Steelhead Architecture

Photography: Josh Partee

Lightbox 23 net zero House in Portland images / information received 140818 from Steelhead Architecture, USA

Location: Portland, Oregon, United States of America

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