--- title: "Coimadai, Victoria: Geothermal Heating, Cooling and Ventilation for a New Build, SCOP 8.1" date: 2025-02-12T15:40:00+11:00 author: Darren Burch canonical_url: "https://sogeo.com.au/case-studies/case-study-sogeo-revolutionised-home-comfort-in-coimadai-victoria" section: Pages --- ![Coimadai]() # Coimadai, Victoria: Geothermal Heating, Cooling and Ventilation for a New Build, SCOP 8.1 Terry and Lynne Lefoe’s new build in Coimadai runs underfloor heating, cooling and heat recovery ventilation from a Stiebel Eltron geothermal system on four 99 m boreholes, drilled into mudstone in a single week. Measured SCOP: 8.1, the highest of any SóGeo project we have published. **Location**Coimadai, Victoria**Project**New build family home**System**Geothermal heating and cooling: hydronic underfloor heating, underfloor cooling, forced-air cooling and heat recovery ventilation**Ground loop**Four vertical boreholes, 99 m each, drilled into Coimadai mudstone in one week**Equipment**Stiebel Eltron geothermal heat pump and ventilation systems**Measured result**SCOP 8.1; heating, cooling and hot water bills cut by up to 70%**SóGeo’s role**Design, drilling, full ground source heat pump installation and connection of the interior systems## The brief Terry and Lynne set out to build their home around two things, comfort and sustainability, and asked SóGeo to deliver both from one system. The design brought together a geothermal heat pump feeding hydronic underfloor heating and cooling, forced-air cooling for the hottest days, and a heat recovery ventilation system that keeps the indoor air fresh while recovering the thermal energy that would otherwise leave with the exhaust air. ## The challenge The ground came first. The ground heat exchanger is four boreholes drilled to 99 m each into Coimadai mudstone, and the drilling was completed in a single week, which set the foundation for everything that followed. The build itself was a long one with the usual run of small surprises that come with a new home, and SóGeo kept the homeowners informed throughout and held the mechanical works to schedule while the rest of the project moved around them. 01 ![Coimadai]() ### The system Four deep boreholes, one Stiebel Eltron plant, and a ventilation system that gives heat back. At the centre of the home is a Stiebel Eltron geothermal heat pump drawing on the four 99 m boreholes. It feeds hydronic underfloor heating in winter and underfloor cooling in summer, with forced-air cooling for peak days, so the same plant covers the whole year. Stiebel Eltron equipment was chosen for its reliability and efficiency, and SóGeo managed the integration of every interior system so that heating, cooling and ventilation work as one. The heat recovery ventilation system is the quiet contributor to the result. It brings in filtered fresh air continuously and recovers heat from the outgoing air, which improves air quality and reduces the heating load the geothermal system has to carry. On a well sealed new build, that is a meaningful part of why the measured efficiency landed where it did. ## The results The system achieved a seasonal coefficient of performance (SCOP) of 8.1: across the season it delivered 8.1 units of heat for every unit of electricity it used. SCOP is a measured figure from the system in operation, not a laboratory rating, and 8.1 is the highest result of any project SóGeo has published. Terry and Lynne have seen their combined heating, cooling and hot water costs fall by up to 70% compared with conventional systems, and they describe a home that feels comfortable all year round while running at a fraction of the energy it would otherwise use. ## What made it work - **Deep bores in stable ground.** Four 99 m boreholes in mudstone give the heat pump a source that barely moves through the year, which is the single biggest driver of a high SCOP. - **Low-temperature distribution.** Underfloor heating runs on the lowest water temperatures of any emitter, and a heat pump’s efficiency climbs as the flow temperature drops. - **Ventilation that recovers heat.** The heat recovery ventilation system reduces the load the heat pump has to meet, so the plant spends more of its life at part load, where inverter heat pumps are most efficient. - **Built to outlast the house.** The buried ground loop has a service life of 50 or more years, and the heat pump can be replaced in twenty years without touching it. ## Related The technology: [ground source heat pumps](/ground-source-heat-pumps). Boreholes and rigs: [geothermal drilling options](/geothermal-drilling-options-for-tight-melbourne-sites). The distribution: [hydronic underfloor heating](/hydronic-heating-cooling/hydronic-underfloor-heating-comfort-efficiency) and [hydronic underfloor cooling](/hydronic-heating-cooling/hydronic-underfloor-cooling-efficient-comfort-for-your-home). Choosing a complete system: [geothermal heating and cooling systems in Australia](/blog/geothermal-heating-and-cooling-systems-australia-guide). More projects: [SóGeo case studies](/case-studies). *Building new and want the mechanical design settled before the slab is poured? [Start with a heat-loss calculation](/contact-us).* ![Coimadai hole]() ![Coimadai roof]() ## Our Partners [ ![Reece](https://sogeo.com.au/uploads/suppliers/_AUTOx96_crop_center-center_none_ns/Reece.png) ](https://www.reece.com.au/) [ ![Stiebel Eltron](https://sogeo.com.au/uploads/suppliers/_AUTOx96_crop_center-center_none_ns/Stiebel-Eltron.png) ](https://www.stiebel-eltron.com.au/) [ ![Mitsubishi](https://sogeo.com.au/uploads/suppliers/_AUTOx96_crop_center-center_none_ns/Mitsubishi.png) ](https://www.mitsubishielectric.com.au/) [ ![Purmo](https://sogeo.com.au/uploads/suppliers/_AUTOx96_crop_center-center_none_ns/Purmo.png) ](https://www.purmo.com/au) [ ![Viessmann](https://sogeo.com.au/uploads/suppliers/_AUTOx96_crop_center-center_none_ns/viessmann_wordmark_rgb_1_vitorange.png) ](https://www.viessmann.com.au/)