37°C Outside. 24°C Inside. Using Groundwater.

Can groundwater really keep an entire house comfortable during a heatwave using only a few watts of pumping power? In part 1, I tested whether the cold energy stored in groundwater could be transferred into a floor cooling system using a simple proof-of-concept setup. In part 2, I integrated that concept into the actual floor heating installation of my house by adding a plate heat exchanger, circulation pump, and switching valves. Now it's time for the first real-world results. In this video, I show what happened during several days of testing while outside temperatures reached up to 37°C. For the first time, the groundwater cooling system is actively cooling the entire house, allowing me to compare the results with previous hot days and evaluate how effective the concept really is. Along the way, I discover unexpected challenges such as condensation, temperature control, heat losses, and system stability. I also experiment with different pumps, buffer configurations, and flow rates to find a setup that delivers efficient cooling without creating new problems. This is not a theoretical project. Everything shown is built, tested, measured, and evaluated in a real house during an actual heatwave. What you'll learn • How the groundwater cooling system performed during several hot summer days • How cold groundwater can be used to cool an entire house through floor cooling • Why controlling flow rate is critical for preventing condensation • How supply temperature affects cooling performance • The role of the buffer reservoir in storing cold energy • Why smaller pumps sometimes outperform larger pumps • How temperature measurements reveal the actual heat transfer inside the floor • What happens when the floor itself starts acting as a thermal battery • The limitations and inefficiencies of the current prototype • Which improvements are planned for the next phase of the project Key results • Outdoor temperatures up to 37°C • Indoor temperatures maintained around 24°C • Floor cooling supply temperatures around 17–18°C • Temperature differences across the floor circuit of 2–3°C • Groundwater temperature around 12–13°C • Total daily energy consumption of approximately 5 kWh Why this project is useful Traditional cooling systems often require expensive equipment and significant electrical power. This project explores whether groundwater can provide meaningful cooling using infrastructure that already exists, while consuming only a small amount of additional energy. Potential benefits include: • Very low operating costs • Passive cooling using naturally cold groundwater • Reduced reliance on conventional air conditioning • Reuse of groundwater that is already being pumped for irrigation • Integration with existing floor heating systems • Potential for full automation • A scalable and highly energy-efficient cooling concept Links: • Project page, calculations, diagrams and updates: https://www.forestguybuilds.com/ Project overview 00:00 It's working during this heatwave! 01:28 High level overview of the prototype outside 03:18 The prototype inside 05:10 More details about the components outside 10:10 How everything is connected and condensation 12:05 The results, measurements and metrics 20:50 Evaluation and looking ahead to part 4 This is a practical DIY experiment focused on energy efficiency, creativity, engineering, and testing unconventional ideas in the real world. If you're interested in home energy optimization, sustainable cooling, DIY engineering, groundwater systems, hydronic cooling, smart home technology, or innovative HVAC concepts, you'll probably enjoy this journey. Keywords: groundwater cooling, floor cooling, passive cooling, DIY cooling system, groundwater energy, heatwave cooling, plate heat exchanger, hydronic cooling, floor heating conversion, home energy optimization, sustainable cooling, thermal storage, buffer tank, smart home engineering, low energy cooling, DIY HVAC, groundwater heat exchanger, energy efficient house cooling