Balancing Heat in Future Buildings
Buildings are responsible for nearly half of all UK carbon dioxide emissions, with non-domestic buildings producing 18%, principally from space heating and cooling, water heating, lighting and other building systems.
When designing new buildings, many organisations use Part L of the Building Regulations as a mandatory standard to ensure that they meet the exacting requirements for CO² emission reductions. The new Part L came into force in April 2014. It requires energy efficiency standards of new non-domestic buildings to improve by 9% on the 2010 regulations. The new rules also apply when specific building services work, including climate control, is carried out.
With these increasing demands for sustainable buildings, plus rising energy prices and a warming climate, the business case for reappraising whole building energy strategies for efficiency savings is clearly growing. For building designers to be able to meet these requirements they must consider how to deliver heat into all areas of a building in a balanced, energy efficient, controlled way.
There are multiple design considerations for building owners and managers who are looking to achieve the highest levels of energy efficiency while maintaining high levels of comfort but the easiest solution is to specify a whole building, VRV system with heat recovery.
The ultimate operating condition for VRV systems typically occurs during typical autumn and spring temperatures and demands in the building may balance to 50% heating and 50% cooling. This is where a VRV system operates at maximum efficiency, with almost no rejected energy.
For example, a typical office building requires cooling and heating to maintain the temperature typically between 20-24 degrees C, with 200 litres of water storage being required for washrooms and 150 litres of water storage for kitchens. By recovering the heat from indoor units in cooling mode, a Co-efficient of Performance (COP) of 4 can be achieved. In milder conditions, when 75% of the indoor units are in cooling mode with 25% in heating mode, the efficiencies rise to COPs in excess of 7. But when a VRV system is fully balanced between heating and cooling, efficiencies can increase even further.
To achieve these higher COPs, it’s vital to analyse right from the start a building’s multiple requirements, usage patterns and varying occupancy levels, to design an intelligent solution that optimises energy efficiency and heat recovery.
The key is to design the system so that it operates as close as possible to a balanced heating and cooling operation for the maximum amount of time, according to the building’s energy usage statistics. VRV systems can balance the heat usage of new buildings by integrating a number of peripheral functions such as re-using waste heat in multiple areas, heating water overnight and by connecting to low temperature hot water modules for optimal underfloor heating.