What is the fine-grained topic of the following text: Kappa pi2 provides complete and cost efficient solutions in residential and commercial air conditioning (cooling & heating), central heating and hot water using renewable energy (heat pumps, solar energy), photovoltaic installation, specialized ventilation (for restaurants, industrial), pool construction, water treatment (reverse osmosis, disinfection) and sewage treatment. Only return the topic.
Kappa pi2's multifaceted services in residential and commercial heating, cooling, and water treatment utilizing renewable energy.