Budget: $110,000
Original quote from Builder: $180,000 (saved $70,000 as owner builders)
Design period: 12 month period
Construct period: 6 month period
Constraints: the design required the new office to be built while the existing residence remained habitable.
Site: rectangular
Brief
The brief was to provide office accommodation as an addition to an existing Edwardian dwelling, including:
enhancement of the character of the existing Edwardian house
maximising water and energy efficiency by design, and choice of materials and appliances
use of sustainable and non toxic materials wherever possible
Time: The project was undertaken with no specific time constraints except to minimise impact on occupants
Site planning
The site planned was predetermined by the existing structure on the block.
Building planning:
The footprint of the existing Edwardian building dictated the scope of the design. Using this footprint as a basis, the office addition was designed to maximise natural light without detracting from the existing character of the site.
Technical systems:
The office computer system was designed with its own electrical circuit and will be connected to a UPS in the shed. This allows for a self-sufficient energy system using PV panels to be installed as funds become available.
Pre-design strategies
Judy and Andreas worked together to manage the design and construction and Andreas also took on the role of builder with carpenters working under his direction. This was quite straightforward as they had previously operated a business called Sunpower construction and were both experienced in the design and construction process. One advantage of working on site was that Sunpower were able to provide clear direction to carpenters and contractors on a day-to-day basis. Much of the work was undertaken by Judy, Andreas and friends, including sourcing all the materials, finishing, fixing (doors and architraves), internal painting and construction of the stairs.
The specifications for the project identified most of the materials to be used, however Judy and Andreas were keen to use this building as a research tool to test new ideas and products. This process was greatly enhanced by the commitment of contractors to the Sederof’s goal of achieving a sustainable building. Many of the ideas specified at the beginning of the project changed along the way with further research and input from everyone involved.
Design strategies
Over a period of twelve months ideas were discussed and explored to come up with the final design. The team at Sunpower Design were all involved in brainstorming ideas to ensure that everyone’s needs were met in the new office. The size of workspaces and open plan nature evolved with discussion over time. It eventually became clear that most of the staff preferred a collaborative open plan work environment while Judy wanted her own space to work.
For Judy and Andreas the project was one of tremendous synergy – once the decision was made to do the building the process from design through planning, employing contractors and construction. Contractors were enthusiastic and committed to the idea and implementation of sustainability. Everyone become excited by the idea of a sustainable building and put in extra effort to ensure the best solutions were employed.
Melding Edwardian and contemporary architectural styles was a major design challenge. Judy and Andreas were constantly on the lookout for examples of how other people were addressing this apparent contradiction in form. The final design solution for this aspect of the project was to retain the front roofline and set back the office addition to minimise the clash of styles.
Post-design and construction strategies
The process of evaluating the building’s performance is an ongoing process. While construction is complete a number of finishing touches are still required. The most significant of these is the adjustable blinds that will be installed on the north, east faces of the office to prevent glare and control heat loss.
Light
Use of natural light was far from a priority in Edwardian buildings and this house was no exception. To improve passive lighting all existing windows were enlarged to full height. Overshadowing vegetation was cut back, light-coloured internal finishes were used, and the new extension was designed to maximise northern light.
By following these principles the Sunpower team has found that internal lighting is not required during daylight hours due to the high degree of natural light in the office. All the internal and external lighting are compact fluorescent lamps or circular fluorescent lamps. These lamps were chosen not only because they use much less energy but also because they are much more durable than regular light bulbs.
External paths are lit with battery-powered lights that switch on automatically after dark. Integrated photovoltaic panels recharge the batteries automatically. The office entrance light is activated by a motion detector that incorporates a photoelectric cell to ensure that the light only activates after dark.
Heating (eg maximising use of passive heating strategies and using high efficiency equipment where active systems are required)
High levels of wool bulk insulation were installed in the walls (R2.5) and roof (R3.5), along with Astro-foil to minimise heat loss in winter and heat gain in summer. Astro-foil is a non-carcinogenic, non-asthmatic & non-irritant insulation that performs better than most standard insulation (R2.5+). The Astro-foil sheets were taped together to maximise their efficiency and extra care was taken to provide adequate sealing around window frames and sashes to further reduce heat loss.
A Bowan gas heater was installed to ensure comfort was maintained during the colder months. This type of heater was chosen for its energy efficiency (Australian Gas Association Energy Rating of 5.25) the level of NOx emitted into the environment is 1/10 compared with standards, minimising the level of air pollution in the environment.
The experience of the first four months of occupation has shown that this combination of strategies delivered a very high degree of comfort with minimal operating costs. Andreas estimates that during this period the occupants used around 60 hours of heating time in total, resulting in a significant reduction in energy bills.
Cooling and ventilation
The design of the concave roof over the main studio utilises Bernoulli’s Venturi theory to give extremely efficient natural cooling in summer. Even on still days the curve of the roof directs the hot air as it rises through the building and out of the high windows on the southern face of the studio. This air movement works on a principle where the hot air acts like a thermal chimney drawing the hot air out of the building.
Astro-foil was used instead of sisalation under the metal roofing to provide excellent summer performance.
The ceiling exhaust fan in the bathroom was an Expressair fan, which remains sealed when it is not in use. The fan was also ducted to the outside to ensure efficient operation. Ceiling fans were installed to ensure that air could be circulated in hot weather. Installing ceiling fans during construction is much cheaper than retrofitting.
Thermal and visual comfort
In order to minimise heat loss in winter and heat gain in summer most windows were double-glazed. Windows on the western face of the office were double glazed with ‘Azurelite’ tinting, a heat reflective glass used to reduce heat transmittal and minimise glare. A feature window on the north east corner of the office was constructed with Pilkington ComforTone® rather than double-glazing to allow but jointing to enhance the aesthetic presence of the window. Andreas estimates that the ComforTone® performs at around 70% the efficiency of double glazing, but also cuts up to 99% of ultraviolet (UV) radiation and reduces glare.
It is intended that adjustable external awnings on windows and a sun sail on the deck will be installed before summer. This will be particularly important for the east and north faces of the building to prevent glare on the computer terminals and control heat gain and loss.
Hot water
The hot water system in the existing building has been retained, however it is intended that a solar system will be installed once this system has reached the end of its life.
Appliances and equipment
A range of appliances and equipment were chosen for installation in the office including:
® the highest energy rating under bench fridge from Fisher and Pickle (R3.5)
® a reconditioned hand microwave (microwaves produce less than half the greenhouse gas generated by a conventional stove)
® a smoke detector which had no radioactive parts. These smoke detectors may be obtained from Going Solar at: http://www.goingsolar.com.au/
® an Expressair ceiling exhaust fan in the shower which is sealed when shut and spins opens once turned on. The fan is ducted to the outside not into the roof in the old way.
® ceiling fans were installed to ensure that air could be circulated in hot weather and while these might prove unnecessary given the design, it was much cheaper to do in advance.
Power generation
The main power source for this building is the grid, however the computer system has been designed with its own electrical circuit connected to a UPS in the shed. This will enable photovoltaic panels to be installed to establish a self-sufficient computers system once funds become available.
Roof cladding was removed from the existing house and reused to clad some external walls and part of the new roof.
Second hand jarrah was used for the entry door, structural mullions, feature doors and decking. This timber not only provide structural integrity but also provided an attractive design element.
Recycled products and materials
The Sunpower Design team broke new ground by using Easiwall panels in a load bearing capacity. Easiwall has a very low embodied energy as it is manufactured from compressed straw and recycled paper. This product is lightweight which makes it easy to install but provides insufficient thermal mass resulting in a very low R rating (R 0.75). This limitation was overcome by building up the depth of the panel membrane with battens and adding an extra 50 mm of polyester insulation. By trialing this new technique it was possible to improve the R rating of the external wall to (R 2) while at the same time improving the structural integrity of the panel.
Sustainable and environmentally friendly products and materials
Sustainable and environmentally preferable materials were used wherever feasible including:
® cypress macrocarpa was chosen for the door and window joinery and external cladding. Sunpower spent quite some time investigating the suitability of this product, and discovered that it is a plantation timber which is harder, more durable and a third of the price of western red cedar which is traditionally used for this purpose.
® a commitment to avoiding the use of old growth timber for any purpose in the construction.
® rendered fibre cement sheeting with a low embodied energy rating was also used for cladding on some of the external walls.
® desk construction using laminated pine sealed with bio paints lacquer.
® Enviroven timber veneer was used as a feature wall in the office meeting room. This product available from New Age Veneers is manufactured from plantation poplar grown in northern Italy, which is then figured by machine to give it a unique finish. A detailed Environment Impact Statement is available to explain the environmental performance of the product.
® flooring was constructed using CD grade pinus radiata laminated ply. The floor system used engineered floor joists from sustainable sources – HJ beams from Colt Harvey. This floor became the roof structure to the existing residence during construction. The advantage of this was that the existing dwelling remained habitable throughout the building of the new office.
The Sunpower Design team were aware that waste minimisation starts at the design phase of the project. By designing for standard sizes and measuring applications very accurately ordering materials on a just-in-time basis wastage was minimal. Companies supplying fibre cement sheeting and timber were happy to take back any material that was not used in the construction. Smaller offcuts were given to tradespeople to reuse on other jobs. Plasterboard was the most problematic as the Sunpower Design team were unaware that there are now viable recovery options in the Melbourne area. Companies such as Recovery & Recycling Industries ph: (03) 9314 8300, T&L Recycling Ph: 0407 867 133, Western Gypsum Ph: (03) 5342 2270 and Building Bitz Ph: (03) 5672 4021
Appliances were chosen with water conservation in mind including:
® a dual flush toilet.
® AAA rated shower head and water restricting values.
The team is currently reviewing options for installing a rainwater tank, however to date this has proved to be quite a challenge due to limited room and existing landscaping.
The designer’s commitment to use sustainable materials was also taken through to the choice of internal finishes. They also wished to address the problems of off-gassing and internal air quality by choosing products with low toxicity including:
® Berger ‘Breathe Easy’ Paint which was used on the main walls.
® Porters Limewash which was used on the feature walls.
® Linseed oil which was used to seal some timbers.
® Bio-Paints clear varnish which was used to seal the desks (zero toxicity)
® a tinted tongue oil was used as the finish for the meeting room table and as a final floor finish to cover the water stains on the ply flooring and resulted in a practical and stylish finish.
The Sunpower team consulted neighbours to ensure they would be happy with the affect of the structure on neighbourhood character.
The project design was consistent with the planning requirements of the day and enjoyed a smooth approval process. Since it was to be a planning approval was for a home office, it was important that the project team demonstrate that parking would not be a issue. This was not difficult given that the site is close to public transport and staff arrive by bicycle 8 out of 10 days.
There were a number of financial issues which affected the project including:
® a limited project budget of $110,000, which allowed for the majority of the owners requirements to be incorporated.
® a number of addition features that will be added in the short-term including blinds, awnings and the sail over the deck.
® a number of additional features will be added as funds become available such as a solar hot water system and a self sufficient power system for the computers.
® the cost effectiveness of using Easiwall ($33 per square metre) which allowed for investment in other products such as the second hand Jarrah which was not cheap.