Clients were pleased to find their home had comfortable indoor air temperatures all year round.
The Mirboo house is designed as a zero energy strawbale home, located in the rolling hills of South East Gippsland, Victoria. The design of the house required modifying an existing timber post and beam structure, located on the 5.3 hectare farmlands site, and to use this as the base structure for the new home. The clients planned to retire and live a zero energy lifestyle in the Mirboo home, and to farm native Australian pepper.
The concept of zero energy buildings is logical and easy to understand. The total amount of energy used within the house is equal to or less than the renewable energy produced by the active solar electric photovoltaic systems. An energy building efficient home means that you use less energy in running the household which also means that the active electric system required is smaller. Basically, energy resources are fully utilized with minimal wastage.
BP Architects specialize in green architecture and ecological architecture. Being a green architect is important as more and more people are turning towards reducing their ecological footprint.
A Brief Description
The clients required their new home to be a contemporary sustainable building constructed out of strawbales, built around the existing modified post and beam structure. Several timber posts were removed, and concealed within new brickwork piers which also served to increase indoor thermal mass. Other posts were exposed within the house and within the strawbale walls. A new slab was laid around the existing posts.
Detailed Feature Description
In addition to the building being energy efficient, the design was also planned for low maintenance. Colorbond cladding was fixed to the high sections of the external walls, which reduced maintenance requirements for this section of rendered strawbales to zero.
The Weather Conditions
Gippsland is known for its cold winters and Hot summers. The Mirboo home was designed to accommodate both extremes of weather to design a comfortable home all year round.
To test the thermal performance of the house, data loggers were installed, inside and outside, to record air temperatures. The recorded temperatures found that the indoor air temperatures stayed between 20°C and 25°C whilst outside the temperature ranged from the extremes of cold winter weather to hot summer days exceeding 40°C.
The heating and cooling requirements of the Mirboo house are minimal.
“so it seems a well-designed and well-built house does indeed provide good thermal performance without any further energy input than the sun, wind and ceiling fans”. Colin Goodwin, Owner Mirboo Home
The house was designed with passive solar design principles in place. A north facing window wall optimized the thermal heat from the winter sun, whilst shaded by the roof eaves during summer. Strawbale external walls provided high levels of insulation with r-values of R4.8 – 5.5. Loose straw was filled around the windows and timber frames to prevent loss of heat via cracks and gaps in the walls.
Cross ventilation was achieved with unobstructed interiors and window placement. High clerestory windows allowed for secure night time cooling and exhausting of hot air.
Living areas and the master bedroom featured curved walls readily achieved with the modular system of straw bales. A mezzanine retreat fitted snugly above the utilities area, and overlooked the living room.
“the mezzanine is my peaceful haven away from the world”. Libby Anthony, Owner Mirboo Home
BP Architects are award winning architects and the Mirboo house was Highly Commended in the Sustainability Awards, Environ BPN.
House Size: 220.7sqm
- Low VOCs (Volatile Organic Compounds) materials and products
- Easy to clean surfaces for dust removal
- Thermal mass in the floor slab
- Tiled flooring
- High windows to exhaust hot air
- Rainwater tanks
- Ceiling fans
- Sun shading
- Passive solar design
- North facing windows
- Secure night time exhausting hot air
- Cross ventilation
- Light coloured Colorbond roof
- Ceiling Insulation: recycled PET eco batts R 4.0
- Roof sarking: reflective foil bulk insulation AirCell R2.0
- Engineered timber beams – salvaged recycled glulam beams (20 years old)
- Rafters: salvaged recycled 250 x 50mm F7 unseasoned hardwood (20 years old)
- Post & beam structure – salvaged recycled 180 mm dia. F7 treated pine poles (20 years old)
- Wall framing: plantation pine house framing
- Building membrane: Tyvek breathable building membrane
- Wall gap filler: loose straw
- Lightweight external walls & insulation: wheat strawbales R 4.8
- High walls & exterior clerestory: Colorbond wall cladding
- Interior walls: plantation pine frame plasterboard
- Kitchen cupboards: plantation pine
- Bathroom vanity, stair handrail, skirting’s: salvaged Blackwood from fallen trees on site, milled on site
- Windows & glass doors: composite timber & aluminum framed double glazed windows & doors.
- Skirtings & door & window frames: local hardwood local timber mill
- 2 separate photovoltaic arrays – grid connected and battery storage
- Worm farm composting system