Hosted by Design By Many, the Passive House for New Orleans competition challenged designers to design a single-family dwelling that is sustainable in the broadest sense of the term: affordable to build and purchase, long-lasting, with minimal impact on the local environment, and affordable to heat and cool throughout the life of the building.
The winning proposal, designed by sustainable.TO, is based on the vernacular shotgun typology. The affordable, low-energy, single-family low cost, low energy house will help to revitalize the existing neighborhood of the Lower Ninth Ward. More images and architects’ description after the break.
Before beginning to design, we researched traditional New Orleans residential architecture: shotgun houses. This style of residence surged in popularity in the Southern United States from the end of the American Civil War through to the 1920s. Typically, the rooms of the house would be aligned in a row, with no hallways as one would walk from one end of the house to the other by going through each of the rooms.
Shotgun houses are typically made from wood frame construction with wood siding. High ceilings and a lack of hallways allow for efficient cross-ventilation and cooling in each room. Variations of the conventional shotgun style have emerged to meet additional needs. A camelback shotgun house has a partial second storey at the back; a north shore shotgun house has a porch that wraps around three sides, and a double-barrel shotgun is two shotgun houses side by side, sharing a central wall. Our final design emerged from the results of a good ole-fashion design-off. We each worked on separate designs for a few days and then presented them. As expected, certain features were admired in each design and they were pieced together to form our final product.
The house reinterprets a traditional shotgun-style plan by mirroring two bedroom and bathroom units on either side of the main living space. The open living plan optimizes natural air flow and daylighting. The corridor opens southward to a flexible cantilevered side gallery that wraps around the house, providing shaded outdoor living space, similar to that of a north shore shotgun style. The flexible boundary between the corridor and gallery can adapt to the changing needs of the family throughout the seasons.
Organized linearly along a circulation corridor, the long axis of the house runs east/west. This organization addresses strategies of natural ventilation, daylighting, shading and solar heat gain. The south facade’s deep roof overhang provides passive solar protection for the building’s interior in the summer, while allowing passive solar heat gain in the winter. Sliding panels on the south facade offer flexibility and protection from the sun, rain and wind when required. Windows on the north facade provide abundant daylight and natural ventilation while limiting solar heat gain. If required for a north/south long-axis orientation, the facade with the large sliding panels would be the west facade, achieving many of the same benefits as the optimal southern exposure.
When designing this house, we employed a number of different strategies to achieve the Passive House Standard including:
- Highly reflective, recyclable galvalume cladding minimizes solar heat gain in the summer and provides a lasting ‘lifetime’ material. - Deep overhangs on the south are calculated to provide passive solar protection for the building’s interior and sheltered outdoor space, reducing inside cooling needs. The overhang is also calculated to allow passive solar heat gain in winter. - Openings on the east and west are also protected by overhangs. The north side is flat and exposed, increasing daylighting with a minimum solar heat gain. - Windows on opposite sides of rooms for cross ventilation and natural cooling. The high sloped ceilings induce air flow, allowing hot stale air to escape through operable vents. - Large sliding horizontal slat panels at the south facade acts as rain, sun and privacy screens while allowing daylight and air through. - Operable tilt and turn Pazen-manufactured windows are fiberglass wood clad, triple-glazed and thermally broken. - All exterior walls have a minimum R-47 envelope. Roxul insulation is made from recycled mineral slag, an industrial waste material providing high thermal resistance and is moisture, mould, and fire-resistant.
Additionally, two UltimateAir RecoupAerator Energy Recovery Units exchange stale air with clean fresh air, providing ventilation and air filtration. Return air pathway grilles and baffles located in the bedroom closets and washroom doors allow for the movement of air from the bedroom and living space to washrooms for extraction. Split-zoned Misubishi Electric M-Series ductless heating and cooling units located above the washrooms are energy-efficient and allow each indoor zone to operate individually. Reversible ceiling fans in all private and public spaces manage rising convective heat in booth summer and winter reducing air conditioning needs.
Compliant to post-Katrina building codes, guidelines and best practices, the structure is raised 7 feet above grade. This ensures security in case of flooding and allows air to circulate under the building. Additionally, this provides shaded living and parking spaces. Pier foundations minimizes disturbance to site while a water-permeable driveway surface minimizes environmental impact to the site.
Concrete floor topping provides thermal mass to absorb solar heat in the winter months and to re-radiate it into the space as required. Embedded hydronic heating also provides low-energy supplemental heating. The concrete floor is also beneficial during the summer as it is naturally cool. The use of low-cost, durable and long-lasting materials, and proven construction techniques assures value to returning homeowners. The high albedo, recyclable galvalume roof and wall cladding minimizes solar heat gain and provides a lasting ‘lifetime’ cladding material.