Sustainable design is a goal across communities large and small. However, sustainable food production often depends on climate, knowledge and design. These factors are used to positive effect in a sustainably designed greenhouse in the remote Great Lake region of Tasmania, with a design able to produce year-round food for their community.
The traditional greenhouse
Greenhouses have been used for centuries to grow food and plants within a controlled environment, converting light energy into heat energy in a simple yet effective way.
But in parts of the world where outside temperatures are particularly cold, a greenhouse requires an additional heat source to maintain the growing environment all year round, adding costs to the process.
In the Great Lake region of Tasmania, the odds were stacked against them for a traditional greenhouse. The winter period is snow laden and the costs to heat a greenhouse far outweigh the benefits. Finding another solution that could reduce operating costs and support the community with its primary purpose of food production was essential.
HED Consulting in Hobart took on the challenge of a sustainable design for a greenhouse for the Great Lake community. With a passive solar design already earmarked, HED Consulting were tasked with applying the principle to the Great Lake environment for a Tasmanian first.
Why a passive solar geothermal greenhouse was the choice
The Great Lake community are strongly connected to their environment and are passionate about utilising its strengths whilst minimising environmental costs. Sustainable choices are something committee members seek out for their community. Looking at similar environments overseas, they discovered the option of passive solar to operate a greenhouse of the scale they needed.
At the heart of passive solar is harnessing the sun’s energy through thermal mass and storing it for when required. It’s cost effective, reliable, and environmentally friendly, with a low carbon footprint where electricity use is minimised.
Here was an opportunity for a passive solar geothermal greenhouse designed for renewable climate control and year-round produce growing, with a significantly reduced impact on the environment and at a fraction of the cost of a traditional HVAC system.
The Great Lake greenhouse sustainable design
When it came to designing the greenhouse, David Abel at HED Consulting said, “We looked to the technology developed and refined from physical science principles around the world. We then visited the site to understand the environment and applied these principles to Great Lake.”
Water Recycling The greenhouse will be connected to rainwater storage tanks and a tray system will be hosted below the mezzanine structure. The tray will gather the water from watering plants above, redirecting the water into a 600L tank in the storage room for future re-utilisation.
Heat Heating within the greenhouse will be regulated by a GAHT (Ground-to-Air Heat Transfer system) and climate controls components. Using a GAHT system (Ground-to-Air Heat Transfer) helps acclimatise the internal temperature using the heat generated by the energy from the sun and channelling it through a reticulation system underground. This acts as a heat bank, pushing the cool air from beneath to the surface. The opposite effect happens when the temperatures drop at night. The heat stored in the underground thermal mass (heat bank) can be released to the surface with fans’. The GAHT system has been fine tuned with the collaboration of CERES Greenhouse Solutions in Boulder, Colorado USA, experts in this innovative technology for Australia.
Insulation The design incorporates thick insulation cladding and sealing thermal bridges to retain the heat as much as possible for efficiency. Importantly the greenhouse is oriented to the north to get the best sun and heat capture.
Ventilation Ventilation will be regulated by passive and active measures, like automated solar-powered roof vents, windows with hydraulic openers sensitive to temperatures, internal ventilation fans, dehumidifiers and mechanical ventilation components that will be fine tuned over time.
Mezzanine floor An additional mezzanine in the design is intended as a flexible space for growing and other greenhouse activities. In the warmer and sunnier months, there will be a plantation of seasonal produce. During the colder months, the goal is to add LED growing lights to support the crops.
On site learning As with all design, the theory and environment simulation will meet the actual environment when the greenhouse takes it home in the Miena location. The greenhouse will be connected to the grid to power some illumination, powerpoints and the initial mechanical ventilation system components. Plant growth will be designed and oriented to the conditions as the internal conditions are tested over time, with tweaks and fine tuning for the optimal functioning of this unique project.
With design documentation prepared by HED Consulting and submitted to the local council, the Great Lake community greenhouse now has its planning permit. Next is the building permit for construction to be given the green light. The committee continues to seek funding partners to complete the project.
Can these sustainable design principles apply to housing?
The principles of passive solar greenhouse design are transferable to housing design and it’s exciting to see more homeowners and builders investing in environmentally friendly options. Sustainable design means working with the environment to orientate, insulate and adapt a house to thrive and survive the cold, heat, fire, snow, rain, earth and atmosphere unique to each building location.
With heating and cooling increasingly significant costs in maintaining a home’s comfortable year-round temperature, there are now many more design and product options available. It’s worth investing in the skill of design experts to achieve the long-term success of a sustainable home.
Applying sustainability to homes and communities across Tasmania can only benefit its people and the planet for future generations.
HED (Hobart Engineering & Design) Consulting is a Hobart-based consultancy servicing the Tasmanian residential construction industry. With consulting engineers and an expert team, they ensure each build has the complete design, structural and statutory bases covered before construction begins. Contact us for more information.
