EAST HILL LEED DUPLEX
LEED for the Home: Vernon Pilot Project
by Hugh Bitz
East Hill is a centrally located residential neighborhood within walking distance of downtown Vernon, BC. The majority of the neighborhood consists of single family homes constructed between 1950 and 1985, but there are also many heritage homes dating back to the early part of the century. Vernon’s official community plan recognizes the importance of sustainability in home design, including higher-density housing close to the city core.
The East Hill Infill project is a model for the potential infill of this neighborhood. An infill project is one where an existing structure in an established neighbourhood is replaced. In this case, the original home is replaced with a pilot project that exemplifies the potiential of sustainable design.
The project has achieved a LEED for homes Platinum rating and is one of the more exceptional sustainable builds in the Okanagan.
There are many early century craftsman style houses in the East Hill neighborhood. These homes are consistent in their raised floors, wide stairs leading from the street, linear covered porches, and the horizontal datum that they establish. Finish materials consist primarily of wood plank and shingle with some board and batten in evidence.
The East Hill infill responds to these features without sentimentality and without sacrificing its own uniqueness as a ‘Green’ home.
THE BUILDING'S DESIGN WAS INFLUENCED BY 3 KEY CONSIDERATIONS: It would be designed using sustainable principles and features; it would have simplicity in its construction and detailing, and it would be adaptable to different configuration of use and form. Also, the overall design was meant to establish continuity with the heritage character of the existing neighbourhood.
Sustainable Principles and Features
The infill replaces a neglected 1100 sq.ft. 1950’s era home with a duplex that realizes a fivefold increase in conditioned floor area while increasing the site coverage by just over half that. Local bylaws required that each unit have onsite parking for two cars. Without alley access the only option was to park in the front yard. An at-grade garage or parking area would have cut the units off from the street and forced a larger footprint.
The decision to partially raise the main floor and park under the house allows each unit a 1,300 sq.ft. back yard and results in a more open and immediate relation to the street. This relationship - in the form of the porch - allows people to participate in the public domain of the street. By incorporating the porch element into the design the pedestrian based nature of the neighborhood is reinforced and the stage is set for re-establishing a community based relationship that the automobile has made obsolete. A further result of this decision is the access to natural light/ventilation in the conditioned space behind the garage. Although bylaws currently prohibit secondary suites the design anticipates and allows for the possibility of a self contained suite in this space. Four families may potentially dwell where one occupied before.
The units are heated and cooled with a ground source heat pump that includes heat recovery. A de-superheater provides for domestic hot water. Despite this relatively low energy form of space conditioning, the design also encourages natural ventilation and conditioning by the careful placement of operable windows at either end of an axis interconnected via an open stair feature. Openings on the southern exposure are protected from the summer sun by the porch and shading pergola while allowing the sun to penetrate deep into the space in other seasons. On the second floor, light pipes allow natural lighting of interior washrooms.
Circulation core with open stairwell acts as ventilation chimney, prompting air movement through the house. Openings were placed to frame distant views and to maintain privacy.
The wall and roof assemblies were considered for their thermal performance and efficiency of use. Insulated concrete forms (ICF) walls are used on the load bearing axis’ where openings are limited or absent. The concrete provides superior stability, i.e. no shrinkage, and durability over framed walls.
The layout of walls and openings allowed for the whole or half block modules so that no cutting was required. There was no waste from these forms. In addition ICF walls have an R value of 22.7 and no thermal bridging - which effectively increases their performance over that value. The mass of the concrete provides some modulation to temperature swings.
Light framed walls were used on the south and north elevations where larger openings and greater transparency was desired. A soya based closed cell spray foam with recycled fiber (Polar Foam) was applied to the exterior framed walls resulting in an R value of 35. Polar Foam was also used to insulate floors suspended over unheated space, increasing the R value over traditional ‘batt’ insulation while also mitigating the thermal bypass (air gap) between insulation and heated space. Made to measure pre-engineered joists and beams where used throughout. These assemblies contributed to an estimated 60% reduction in construction waste. Finally, the extra deep roof trusses specified allowed for a vented roof with combined R59 batt with. The flat roof allows for the future provision of solar collectors or photovoltaic panels. Triple glazed windows and double glazed doors with argon filled spaces and low e coatings add to the thermal performance. Energy conservation will be further realized by the exclusive use of energy star rated appliances and fixtures.
Water conservation is critically important in the semi arid Okanagan, and the project responds by using 93% of the roof area to harvest rainwater. This water will be stored in 1800 gal storage tanks buried behind each unit to feed the drip irrigation system. To reduce the overall irrigation demand drought tolerant plants are used exclusively. Water conservation is further enhanced indoors by using very high efficiency fittings and fixtures.
Interior finishes were selected for their renewability, durability and low VOC content. Flooring consists of bamboo hardwood and green label wool carpet. Casework is made entirely from FSC certified wood. Clay-based paint and finishing system were used throughout the interior.
Simplicity and Adaptability
The clear span structure will allow for plan variations in design or for adaptive re-use without the need for structural modification. On the main floor, a street related ‘flex’ space with separate entrance and en-suite washroom anticipates a home based business, but will serve equally well as a family room or extra bedroom.
This ensuite is designed to accommodate persons with limited mobility and an adjacent area has been roughed in to allow the laundry function to be move downstairs. This will allow elderly occupants to spend most of their day on the main floor avoiding stairs. The unfinished basement allows for a future self contained suite but will satisfy a number of other uses.
Continuity
There are many early century craftsman style houses in the East Hill neighborhood. These homes are consistent in their raised floors, wide stairs leading from the street, linear covered porches, and the horizontal datum that they establish. Finish materials consist primarily of wood plank and shingle with some board and batten in evidence.
The East Hill Infill responds to these features without sacrificing its own uniqueness and a "Green" home.
Cementatious fibre (Hardie) siding was selected over wood because of its durability. Wood trim is used discretely in more protected areas and where they are ‘within touch.’
Article by Hugh Bitz
All photographs of this project are by Jeff Bassett
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