Architecture at Zero Tetris Block Render

Duane B. Carter, Mike Stopka, Simon Mance, Scott Farbman, and Courtney Brower received the special recognition award at the 2013 Architecture at Zero competition for their near net zero energy design entry, Tetris Block. This is the third win for a team that used Sefaira in the AIASF and PGE sponsored competition (see more on the other two entries here and here.) The submission was praised by the jury particularly for its solar gain management strategy. The brief was to design 150 residential units over a ground floor grocery store within a 22,341sf site in downtown San Francisco, all with net zero energy use. The team used Sefaira for whole building modelling – its parametric analysis capabilities allowed them to optimise the envelope, HVAC, water and renewable strategies. Below are some of their key strategies for getting to a near Net Zero energy design.


Selecting an L-shaped building helped create a residential courtyard and the grocery store entrance was placed on the prominent street corner. The mandatory outdoor space was marked out on the 8th floor with 70% of the roof surface dedicated to solar PVs.

Solar Towers

Five solar towers drive the building’s passive ventilation strategy, creating a stack effect that benefits the residential units and common areas. They also act as light wells that bring light deep into the floor plan.

Diagram showing passive ventilation strategies


The team created an efficient facade system with the aim of nullifying the need for a mechanical cooling system. Simple rain screen panels tilt to accommodate exterior roller shades and angle on the south and west facades to provide shading. Selected panel colours reflect or absorb solar radiation where appropriate, creating an aesthetic pattern across the facade.

Detail section of the facade showing shading devices


Heat from the ground floor grocery store is harvested for use in both summer and winter months. It is sent to the solar chimneys in the summer to quicken the stack effect and in the winter months, the heat is collected by a heat exchanger and used to supplement the heat supply to the residential units from geothermal wells.


Strategy Impact and corresponding EUI Calculations

The Tetris Block submission consciously avoided any untested sustainability strategies, only specifying solutions that are readily available in today’s market. Although this hindered them from achieving the Net Zero status, their selected strategies enabled them achieve a 47% reduction in total EUI, settling on commendable EUI of 10kBtu/sf/yr. It also means that these strategies could be adopted by building developers to create better performing housing  today.