The path to a low carbon future
The clock is ticking. The Government has set clear targets for buildings to become carbon neutral. With new homes and new schools facing a 2016 deadline, public sector non-dwellings required to become zero carbon by 2018 and other non-dwellings needing to comply by 2019.
The question is which technology should consultants opt for to meet these targets? And for all the hype and media coverage they generate, do renewables have all the answers?
The silver bullet
As a technology type, it’s true that renewables are seen by many as a silver bullet to cut carbon, comply with the Code for Sustainable Homes, score highly with EPCs and meet planning requirements which demand a 20% renewables target.
Wind, solar and biomass technologies undeniably have a role to play. Interestingly, aerothermal (energy in the air) and hydrothermal (energy stored in water) have now been recognised for the first time under EU law as sources of renewable energy. Following the European Parliament’s adoption of the EU Directive on the Promotion of Renewable Energy Sources in December. The context for this recognition is the use of geothermal, aerothermal and hydrothermal energy by heat pumps. However, it opens the door for a broader acceptance and understanding of the role that recovering energy can play in improving building efficiencies and cutting carbon emissions.
In my view, we have to be more explicit about the importance of recovering and re-using existing energy within our buildings, irrespective of how or from which source this energy was generated in the first place. This is true recycling, and, after all, it allows building occupiers to reduce consumption or even switch off mechanical equipment for longer periods.
Other areas within building services can offer heat recovery systems, but it is the air movement sector which is at the cutting edge of energy recovery solutions. In the residential sector, increasing regulation on air tightness is opening the way for the use of mechanical ventilation with heat recovery (MVHR) systems.
SAP Appendix Q listed ventilation solutions capable of 90% heat recovery with low specific fan powers, as being able to help reduce the DER (Dwelling Emission Rate) of new build properties. Changes to Part L and Part F of the Building Regulations are likely to conspire to make central extract or MVHR the preferred ventilation solution in the new build market place where adequate levels of air tightness are achieved.
As a whole house, multi-room ducted solution, MVHR systems combine supply and extract ventilation in one unit. Warm, moist air is extracted from wet rooms through ducting and passed through the heat exchanger before being exhausted to the outside. Fresh incoming air is preheated via the integral heat exchanger which recovers up to a staggering 90% of the heat energy that would otherwise be wasted. No background ventilators are required, so there are no heat losses and the opportunity for noise ingress will be reduced.
Similar principles and unprecedented energy recovery performance lie behind recoverable systems that can be applied in the commercial and public building sector.
Ventilation on demand
Take our Sentinel Totus D-ERV (Demand Energy Recovery Ventilation) system as an example. Designed to operate on the principles of on-demand ventilation, this system responds to the precise ventilation requirements of a room at any one time providing the right level of supply and extract airflow only when required, making it ideal for schools, hotels, theatres, offices and other environments with changing occupancy patterns.
It is capable of 90% energy recovery, not just heating but also cooling, from the extracted air, transferring it into the fresh air supply via the unit’s integral high efficiency counterflow heat exchanger. The result is a system which achieves required airflow rates and ventilates according to precise needs, significantly reducing fuel consumption, energy costs and cutting the carbon footprint of a building by up to 30% more than conventional crossflow energy recovery ventilation devices.
The system’s on-demand operation can be triggered by its response to room occupancy according to a range of different sensor readings. These can include PIR occupancy detection, to activate the unit, with additional proportional airflow control from a combination of sensors, CO2, humidity or temperature. These sensors communicate with the main unit which, in turn, drives the fan to the required speed to deliver the airflow and respond precisely to room conditions. Sensors can be combined to generate a hierarchy of control for the ventilation system and ventilation system operation can also be easily linked into a Building Management System via volt free contacts for monitoring, if required.
Automatic air-conditioning and heating interlocks enable systems, like Sentinel Totus, to optimise energy recovery performance further and provide free cooling during summer through bypass optimisation. A user enabled night-time purge facility can reduce the start up loads for a building’s air-conditioning plant and helps reduce over heat in summer from non air conditioned spaces.
Low carbon future
The value of energy recovery in cutting carbon emissions and boosting energy efficiency should be clearly recognised by all parties in the construction chain. They deserve a platform every bit as eye-catching and significant within the building services sector as that taken by renewables. That’s why they should be recognised as a category in their own right, and their use enshrined as an obligation within each and every relevant piece of legislation. Recoverables are, after all, at the heart of our low carbon future.