Heating and Ventilating

With specific CO2 reduction targets set out on both UK and European levels, how can the adoption of Passivhaus principles help companies meet these targets? Here, Tunca Sekban of Airflow Developments explains the theory behind Passivhaus and looks at one of the central technologies - Mechanical Ventilation with Heat Recovery (MVHR)
Increasing operating costs and rising fuel prices are a burden to any organisation, and with the energy use of non-domestic buildings accounting for approximately 18 per cent of the UK's total carbon emissions, it's no surprise that commercial properties are now being forced to think about their day-to-day operations on a number of levels, including efficiency, energy usage and their continuing carbon footprint.

Often thought of as a specific building process that applies primarily to domestic properties, the performance-based set of design criteria on which Passivhaus is based is actually relevant to all building types - and already thousands of offices and schools have been built to these standards across the world.

Structural airtightness is the primary focus in building to the Passivhaus Standard, and aims to diminish uncontrolled infiltration through cracks in the building and create a thermally efficient envelope that will benefit both the environment and the owner's energy bills. Status is therefore attained after a number of strict requirements have been met, including very high levels of insulation, extremely high performance windows with insulated frames, an airtight building fabric and 'thermal bridge free' construction. The installation of a mechanical ventilation system with highly efficient heat recovery is also a stringent requirement that influences Passivhaus status. Installing a mechanical ventilation with heat recovery (MVHR) system as part of a Passivhaus upgrade will allow for sufficient and comfortable ventilation to all areas of a building. The energy efficient system also contributes to minimising the loss of indoor heat and promoting a higher quality of air, maintaining a balance between extraction and supply. The system will conserve energy within a building by recovering heat from the extracted air and transferring it to the incoming air. Each unit features an advanced control system enabling management of a range of peripherals such as frost protection, heat supply and effectively setting parameters such as summer bypass temperatures.

There are currently only seven commercial MVHR units in the UK market that have been fully tested and approved by the PassivHaus Institute - four of these are Airflow's Duplexvent MHVR systems. The introduction of Passivhaus technologies over the past few years has provided significant potential for new commercial buildings to operate with almost no energy costs. The stringent requirements can be built into commercial spaces just as easily as they can with domestic buildings; the predominant consideration is the materials used.

Of course, even if a building isn't constructed to PassivHaus standards there is still a strong argument for incorporating MVHR. With heating costs generally accounting for over 50 per cent of consumption for commercial property, this has amplified pressure on building and facilities managers to find new ways to improve overall energy efficiency. Utilising MVHR with high thermal efficiency (85-90 per cent) can save approximately 40 per cent on heating costs, reducing the average payback period of the MVHR unit from 7.5 years to three years against units with only 50 per cent thermal efficiency, since the more air that is ventilated the more energy is consumed to heat this air volume.

MVHR also provides a clean and healthy air supply that combats sick building syndrome. This recognised condition includes symptoms like irritation of the eyes, nose or throat and skin problems, with one of the key causes of this condition being poor air quality. To combat this, MVHR systems have a high efficiency, inbuilt filtration system to clean out airborne particulates and VOCs while preventing damp, stale air from posing any threat to occupants.

Furthermore, advancements in IT continue to enhance system control, improving control efficiency - such as the Duplexvent Flexi Range from Airflow. These units feature intelligent controls, incorporating an internet server with service and user interfaces. With this feature a service technician can connect to the unit
remotely, check the status, diagnose any faults (if there are any) and instruct the user what to do immediately, saving service and downtime to both technician and client. Similarly the end user benefits from this by monitoring the indoor temperature, CO2 and humidity levels and accordingly changing the ventilation parameters if necessary in order to maintain the optimum indoor air quality at all times.

This innovative system offers greatly increased flexibility over control, with users also able to control the MVHR units remotely from laptops or smartphones. It also prevents users continually adjusting the output of the units - a common issue in workplaces and one that results in unnecessary, wasted electricity. Efficiency can therefore be equated to more than just the fuel use of the building; it can also be used to enhance the work productivity levels of the people housed within the building on a day-to-day basis.

Updated and incoming legislation will ultimately mark a huge change in the way that the industry looks at commercial and industrial ventilation, with indicators that MVHR units are witnessing an increase in popularity thanks to their ability to help reduce carbon emissions and to deliver over 90 per cent heat recovery. Ultimately, by using a Passivhaus certified MVHR unit in commercial spaces, users and the building owners will benefit from a healthier atmosphere and lower energy costs.