Low Cost, Low Energy House

A Passive House for New Orleans

Hosted by Design By Many, the Passive House for New Orleans competition challenges 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. Competition requirements included:

• Homes should meet post-Katrina building codes, guidelines and best practices
• Homes should be shotgun typology and strive to create cohesive neighbourhoods
• Program - 1000 sq. ft. treated floor area to include (2) bedrooms, (1) full bath, (1) half bath or 1250 sq. ft. treated floor area to include (3) bedrooms, (2) full baths
• First floor elevation - +5' above grade
• Design should strive to achieve Passive House Standard:
  • Airtight building shell < 0.6 ACH @ 50 pascal pressure (simple, well-detailed construction
  • Annual heating and cooling requirement < 15 kWh/m2/year
  • Primary Energy < 120 kWh/m2/year

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 - 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.

Preliminary design sketches

Based on the vernacular shotgun typology, the affordable, low-energy, single-family Low Cost/Low Energy House will help to revitalize the existing neighbourhood of the Lower Ninth Ward.

View from southwest

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.

View down corridor

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.

View down gallery

When designing this house, we employed a number of different strategies to achieve the Passive House Standard:

• 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 structures 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.
• North facing windows allow abundant indirect daylight while limiting heat gain.
• Windows on opposite sides of rooms allow for cross ventilation and natural cooling, reducing air conditioning needs.
• Ultra high-efficiency on-demand water heaters in each of the washrooms reduce primary energy needs.
• 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.

To achieve Passive House Standard, this house employs an airtight, thermal-bridge free and super-insulated envelope combined with passive shading in summer and solar heat gains in winter; concrete floor topping for thermal mass to temper solar heat gain and to re-radiate the heat into the space as required; daylighting; natural ventilation and cooling; highly reflective self-venturing galvalume cladding; a balanced energy recovery ventilation system and split-zoned high-efficiency heating and cooling units with an ultra-high-efficiency on-demand hot water heater for domestic hot water and supplemental radiant floor heating. The use of low-cost, durable and long-lasting materials, and proven construction techniques assures value to returning homeowners. In accordance with post-Katrina build codes, guidelines and best practices, the house is raised 7 feet above grade, securing its safety during flooding and providing shaded parking, storage and outdoor living spaces. The high albedo, recyclable galvalume roof and wall cladding minimizes solar heat gain and provides a lasting 'lifetime' cladding material.

Sidenote: naming something is always a challenge, whether it is a baby or a building. This house was no exception. From many options including Clam House, C-Section, Shade House, PHNOSS (which stands for Passive House New Orleans Shotgun Style in case you didn't catch that), we opted to keep it simple and obvious with Low Cost/Low Energy House.

The Home Sweet Home competition was aimed at post-secondary students to design an environmentally friendly home for Brad Pitt, Angelina Jolie, and their six children. The competition required the design of a structure which would aim to meet four goals; be a healthy and comfortable for the occupants; be efficient, effective, and economical; be ecologically and socially responsible; and be affordable and marketable.

The intention of Sun House is not only to demonstrate the superior performance of green building strategies, but also to create an inspirational, and beautiful environment for a family to inhabit. The house allows nature to naturally ventilate, heat, and cool during the summer whilst during the winter, the interior of the house is well protected from the harsh Kapuskasing climate. By creating a comfortable and liveable space year round, Sun House uses green building technology to create the most natural house as possible.

Exterior Render

Sun house creates a very comfortable environment for the occupants and a healthy home to grow in. The house takes advantage of its location, allowing the continuous view of the natural surroundings. Being a naturally ventilated, heated, and cooled space, the house works with nature to create a comfortable living environment. Natural light is able to fill all areas of the space daily, reducing the needs of artificial light greatly. The house is designed to provide as large amount of space to the large family, but to also use this space effectively. Built with earthy materials such as straw, wood clay, and concrete, the house creates a comfortable and inviting environment. Low VOC paints were used and formaldehyde free carpentry was installed. Because of the natural materials used in Sun House the occupants enjoy a very comfortable home.

Floor Plans

The plan of the house was developed off a simple symmetrical grid which allows for reductions in cost and construction. The layout of the house does not require more than 4 exterior corners, further simplifying the design. Straw bale is the main material used in the house, and is also the main insulator. The straw bale is very affordable and can be locally sourced. When combined with a plaster finish on the interior and the exterior, the building envelope becomes quite simple. The straw bale is used extensively, taking advantage of its cheap costs. As the site consists of 100 acres with a large amount of wooded area, wood is an excellent local building material used in the project. The wood would be selectively harvested from the forest and locally milled to the required sizes. It must then undergo a drying process before being installed. Once installed the wood beautifully furnishes the interior, whist still being relatively economical to the family. Roxul, and polystyrene insulation were used where straw bale was not appropriate (during areas which could encounter moisture problems) in order to maximize efficiency of the project. Insulation was also installed to follow a simple ratio of efficiency R10 for basement under slab, R20 for basement walls, R40 for exterior walls, and R60 for roof of house. This current ratio was adapted for greater insulation to be located under the basement slab, due to its increased temperature caused by the radiant floor heating. The house does is not embellished with intricate details, and is instead creates a beautiful space through its symmetry and composition.

There are three main benefits to sourcing as much local materials as possible. It is affordable, it is environmentally aware, and it encourages social interaction and a dialogue with the community. Locally sourced material, such as the wood selectively harvested from the site, is inexpensive and has minimal direction to travel. Using local materials also allows for increased interaction with the community. When constructing a straw bale house, much help is needed, but little skilled labour is required. Local neighbours and inhabitants of the future house work together to successfully create an environmentally responsive structure. Millwork details completed by a local carpenter also allow for interaction amongst community. By involving the community in the construction process, it not only provides education of green building practices, but it also takes of one of the greenest resources; a community.

The open concept of the main floor allows the space to be slightly modified to fit the intentions of any client. The master bedroom, located on the lower level provides all of the sought after features of a new modern home, without extreme cost. By locating the less used space (mechanical, vestibule/recycling area, and bathrooms) north of the interior straw bale wall, all of the mechanical plumbing is significantly reduced. The building operates off grid. This allows the home owner to monitor their own energy, water, and heat usage without having to pay for it. The second level of the home, although comfortably configured for 6 children may be transformed in to any additional programmatic space. The disassembly of the interior partitions allow any part of the space to become an artist's studio, fitness center, home office, or secondary living space. This is possible as there are no load-bearing walls or columns, no plumbing, and no awkward space restrictions. By orienting the building along a central wall, not only does the building benefit from stack effect, it also is organized efficiently along a central spine. Thus circulation space doubles as living space in almost all areas of the home. With its natural interior finishes, programmable areas, and breathtaking natural views the off grid house appeals to a wide variety of clients.

The most advantageous aspect of this home`s design is its flexibility. Organized on a central spine the home can shrink and contract based on the needs of the builders. Additional living space can be achieved by continuing the grid established. The second floor plan of the house allows the house to be personally adjusted to meet the needs of any group or individual inhabitant. The house is not built around technology to achieve its goals. Although the house uses wind and solar to generate electricity, it could easily be operated by alternative forms of energy if opportunities are presented from an alternate site or future technology. Simple straw bale construction and wood finishes do not require skilled and specialized labour to build. This allows the house to be built locally, in any locality. The main benefit of Sun House is that it is flexible enough to adapt to multiple clients, technologies and communities.

As well as achieving these four main goals, the project has to be specified in depth:

Energy Specification

Area, Insulation, R-value

In Sun House different insulation materials were used to follow a ratio of R-10 for basement slab, R-40 for exterior walls, and R-60 for house roofs to maximize efficiency (as heat rises). The slab was given increased insulation as it contains radiant floor heating. Straw bale was used as it provides around R-40 and is local, environmentally friendly, and affordable. Roxul insulation was used because of its recycled waste content, its performance, and its resistance to water damage and fire.

Windows:

Most windows were oriented due south as to provide maximum heat gain. Additional smaller windows allow east and west light to enter into more private areas. As these windows are small and due east/west they result in minimal thermal gain during the summer months, and are thus not shaded. The south facade is shaded by the large overhang of the roof on the second floor, and the ground floor is shaded by a deck which extends the length of the building. The deck provides the optimal shading required in the summer, whilst proving more usable than a simple trellis.

Doors:

Two Madawaska exterior doors serve as fire exits for the house. Due to the location of the car park is it the most convenient entry is west facing. This door is designed to enter on to an interstitial vestibule, with a second sealed door which enters into the living space of the house. This system prevents cold winter air from cooling any part of the living space while occupants enter or exit. Madawaska wood doors are made with excellent quality wood, they use no toxic glues, are durable and long lasting, as well as locally available.

Space Heating:

Ventilation Section

The house is oriented due south to maximize the amount of thermal heat gain received from the sun. When solar gain can not satisfy the heating needs of the home, during the harsh winter months, radiant floor heating delivers heat to the home. Radiant heating, unlike a typical furnace, is efficiently used through the circulation of water, opposed to air, and provides a more even and comfortable space without the restraints of duct work.

Space Conditioning:

The house is not air conditioned, as is rare that the temperature in Kapuskasing would approach a severely uncomfortable temperature. The south facade of the building is designed to be entirely shaded on the 21st of June which results in no access thermal gain. Due to the north facing clere storey windows, the house may take advantage of stack effect to naturally ventilate all areas of the house as desired.

Water Heating:

Solar hot water heating is installed on the roof. This preheats the water, so the tankless water heater requires less energy to bring the water to its desired temperature. The tankless water heater does not keep a large volume of water hot for long periods of time, and thus does not drain power. It is only used when it is demanded. By using the sun to preheat the water the energy savings during peak sun times could be significantly reduced.

Power Generation:

Power Generation

Sun house uses two renewable electric generation systems; solar and wind. This diversification makes it less possible for weather conditions to stop the generation of power completely. During the winter, when the amount of sunlight is lower, wind power may substitute the needs of the home. During the summer solar photovoltaic may carry the energy demands of the home.

Lighting:

Daylight Section

LED lighting will be used in the house as its electricity usage is the most efficient form of lighting. The house will be furnished with abundant task lighting. There will be no shortage of electrical outlets allowing the occupants to make use of task lighting. Task lighting would allow a corner of the living room to be lit, instead of the entire living area; saving energy on a daily basis.

Interior Render - Summer

Interior Render - Winter

Water Specification Form

Water Reuse:

Rain water collection was not used to the point of being filtered as there are no storm water issues in Kapuskasing, and the occupants will access free clean drinking water through a well. Rain water is collected in a barrel for plant drip irrigation only. The waterloo bio filter uses bacteria to break down chemicals in grey water and black water. This water will be released downstream from the house, although the output of the system is clean. The conditions of the waterloo bio filter are that no highly toxic chemicals be flushed down any of the drains in the house. This is because toxic chemicals would kill the bacteria in the bio filter and render it useless. Thus the system reaches beyond rainwater treatment and ensures that natural and more eco-friendly cleaning solutions be used in the home at all times.

Water Conservation:

'Proficiency 3L toilet' from Proficiency; Ultra High Efficiency Toilets only requires three liters per flush. This is because it uses air pressure to assist in the flushing process. This toilet is more efficient than a dual flush toilet; as the minimum flush on a dual toilet is 3 liters, and the maximum is 6 liters Toto low flow faucets allow for only 5.68 liters per minute to be used, and Toto low floor shower heads use only 6.6 liters per minute, creating further water savings.

Water Conservation Outdoor water use:

Situated by a lake in Kapuskasing, it is would be unnecessary to use a rain water collection system to reduce storm water, as there is abundant water on and around the site. However, Brad and Angelina may wish to grow their own food during the summer months. A rain barrel will located at the north-east corner of the house, which could be able to provide drip irrigation for plants frown by the family. Permeable paving was used in the driveway and gravel was added installed around the perimeter of the house. The gravel was added to help protect the plaster from any water damage caused by splashing.

Materials Specification

Exterior Siding:

Interior Render - Second Floor

A cement based plaster would be applied to the straw bale, despite cement's environmental damage, as cement's water resistance is necessary. The plaster would be applied in eight, 1/8th inch layers, ensuring that fractures in the plaster do not align. Large five foot overhangs help to protect the plaster from rain. The base edge of the plaster is located three hundred millimetres above grade and the perimeter of the house is lined with an area of gravel which will reduce the damage caused by splashing of rain water.

Exterior Roofing:

Galvalume metal roofing is used for the roof. This is preferred over cedar shingles as there is a relatively low pitch. The galvalume sheets are long enough that there would be no seams length wise. Self-sealing screws would be used to install the roof as to ensure it would not damage the ice damning/roof membrane underneath. The Roof also would support the hot water system and the photo voltaic panels. The 5/8th inch plywood which is located underneath the ice damming would be used prior to its installation to protect existing tree roots from damage caused by the concrete truck. As the truck drives into the site, the plywood distributes the weight of the wheels, ensuring it will not damage the intricate root structure below.

Interior Flooring:

The only interior floor that was used was concrete. 2 " of concrete was applied over tong and groove wood slats, which sit on wood joists on the second floor. The concrete incorporated 35% recycled potash into its mix. All of the wood used in this floor assembly was be taken from selective harvesting from the forest, cut at the local saw mill, and dried on site. Limited concrete was used as to allow the use of a wood structure and because of concrete's harsh environmental impact. Radiant floor heating is installed into the floor, allowing back up heating/heat distribution to take place.

Interior wall finishes:

The majority of the interior walls of the house are the straw bale walls. These would be finished in two ways. The first, where thermal gain is possible with the low winter sun angles, would be a clay finish allowing heat to be stored inside the 2 inch deep plaster. The second, used where thermal gain is not possible (no direct sunlight) would involve a finish of a Venetian plaster. The Venetian plaster applied to the straw bale wall would use waste marble dust in its mix. This would result in a stone like finish, which is light enough to reflect large amounts of light. This combination would create a bright space whilst maximizing thermal gain. The other interior partitions (Bedrooms/Bathrooms) would be made from wood which would be locally harvested and screwed together, allowing for easy deconstruction and re-use if desired in the future.

Countertops:

The countertops would be made using local wood from selective harvesting from the 100 acre lot. Butcher block countertops could be created by a local carpenter without using toxic glues or finishes and FSC certified wood products. By using the skills of a local carpenter, the occupants can connect with the local community, and save the environment from the unnecessary costs of increased transportation/delivery associated with box store`s products and installations.

Cabinets:

The wood cabinets of the house were, similar to the countertops, made by a local carpenter with formaldehyde free glues and FSC certified wood products. By hiring a local carpenter the occupants support connections with the community. It also reduces travelling costs associated with box stores, and can result in a much better quality of product.