Total impact

On the road to the 2016 zero carbon homes target, Building Regulations and the Code For Sustainable Homes are raising the bar on efficiency. Ian Mitchell, Residential Product Manager at Vent-Axia, reveals how mechanical ventilation with heat recovery systems (MVHR) are the ideal carbon cutting solution.

In May, Grant Shapps the coalition housing minister confirmed that the Government was committed to making new homes zero carbon from 2016. This announcement followed fast on the heels of the publication of the new Building Regulations, due to come into force in October, and represents a key stage in meeting this target.

Core to the Government’s aim to cut the UK’s carbon emissions, Part L’s (Conservation of Fuel and Power) new Target Emission Rate (TER) represents a 25% sweeping improvement over the previous 2006 Building Regulations and is in line with achieving Code for Sustainable Homes Level 3. Thus the Building Regulations cement Code Level 3 as the current stage private housebuilders need to attain on their developments, while upping the game for publicly funded housebuilders who need to pave the way with Level 4. The challenge is how to easily gain credits to keep up with the moving target levels.

Meeting the challenge

It is a huge challenge to meet the zero carbon housing deadline by 2016 and one that the property sector has recently been arguing is unrealistic. It is true that providing zero carbon housing by 2016 is a huge challenge but this is why it is essential for housebuilders to press ahead with the staged Government targets laid out by the Code for Sustainable Homes.

To achieve Code Level 3 a home needs a 25% better energy rating than the 2006 Building Regulations standards. For a home to meet this it is necessary to reduce the air permeability of the building to the minimum consistent with health requirements. As a result, changes to Part F publish guidelines for airtight properties with infiltration rates tighter than 5m³h/sq m at 50pa. For Intermittent System 1 and Passive Stack System 2 approaches, in airtight dwellings the guidance increases background ventilation rates by 50%. This looks set to cause some developers to re-evaluate their designs and move any new planning applications away from intermittent fans since the previous provisions in Approved Document F 2006 have already been difficult to achieve when using trickle ventilators in windows.

The changes to Part F and Part L favour continuous ventilation since it performs better in SAP, is easier to specify and easier to standardise, as trickle vents are not required. For Continuous Mechanical Extract, System 3 approaches, the guidance removes the requirement for background ventilation in dwellings designed with infiltration rates above 5m³h/sq m. It is likely that these factors, along with the Dwelling Emission Rate (DER) benefits of SAP Appendix Q will combine to boost the adoption of whole house Mechanical Extract Ventilation systems (MEV and dMEV) and Mechanical Extract Ventilation systems with Heat Recovery (MVHR).

Reduce consumption

Building more airtight homes is, of course, desirable in the impact it will have on reducing energy consumption. On the other hand, without an effective ventilation strategy, this approach could have a detrimental effect on air quality and occupant comfort. The carbon footprint needs to be reduced even further to meet Level 4 with homes needing to achieve a 44% reduction of CO2 compared with 2006 dwellings. As a result air permeability in homes needs to be reduced to very low levels.

MHVR systems therefore look set to become an increasingly popular choice with housebuilders to comply with the Building Regulations and the Code. For new build properties MVHR can be installed as whole house, multi-room ducted solutions, combining supply and extract ventilation in one unit. Typically, warm, moist air is extracted from wet rooms through ducting and passed through the heat exchanger before being exhausted to outside. Fresh incoming air is preheated via the heat exchanger which recovers between 70-95% of the heat energy that would otherwise be wasted.

Whole house MVHR systems can prove very effective at reducing the heat load in energy efficient homes since they recover heat which would have otherwise been vented outside and therefore lost. The system offers dual speed options, either continuous trickle ventilation or high speed boost extract flow, and the more airtight the property, the more energy efficient the heat recovery system will prove, which is ideal for new dwellings that need to meet the Sustainable Code. Not only is heat recovery ventilation good at saving energy, it brings other benefits as well.

Heat recovery ventilation reduces excessive moisture in the air, combating condensation and subsequent mould growth, saving money on maintenance and decoration in the long and short-term. Tenants are further aided through better indoor air quality which has the duel health benefits of reducing microscopic fungal growth and eliminating the conditions in which house dust mites thrive, both of which are linked to allergic reactions and asthma. With MVHR systems, pollutants in the home, such as dust and VOCs, are extracted and are simultaneously replaced with fresh air.

Saving energy

MVHR systems comply fully with the requirements of Building Regulations Part F 2010 and Part L1a, including SAP and Appendix Q. Housebuilders and developers can thus identify those systems which offer an improved SAP rating over and above the default product types. For instance, Vent-Axia’s Lo Carbon Sentinel Kinetic wholehouse mechanically ventilated, heat recovery system consumes less energy than it recovers, is listed in SAP Appendix Q and offers 90% heat recovery, so helping to reduce the DER of new build properties. The unit’s energy saving Vent-Axia DC motors further improve its efficiency and carbon reducing capabilities, with the Sentinel Kinetic boasting 0.72w/l/s SFP.

This lightweight and quiet-running unit is suitable for installation in kitchen cupboards. The system’s exact ventilation rate can be set on the LCD display at normal, boost or purge speeds to match the volume of the property. This operation is then further enhanced by a range of internal and external, plug and play control and sensor options which can account for changes in humidity, air quality, PIR (Passive Infra Red), CO2 and temperature. In addition, the operating temperature settings can be pre-programmed for automatic operation of the summer bypass, providing free summer cooling. Wireless control options are also available, allowing controls to be located in the most convenient position.

Meanwhile, for larger newbuild properties and light commercial applications (such as student accommodation), Vent-Axia offers the Sentinel Kinetic Plus. Designed to supply a maximum airflow of 400m³/hr at 150Pa, the Sentinel Kinetic Plus is a SAP Appendix Q eligible ventilation solution capable of up to 92% heat recovery.

The Sentinel Kinetic range not only offers good air quality but also maintains it, another key issue in Part F of the Building Regulations 2010. The unit can maintain pre-set airflow irrespective of system pressure (e.g. blocked filters) via a Constant Volume option. It also features a Constant Pressure option which maintains system pressure by adjusting airflow when Constant Pressure dampers open or close. Featuring a clean filter indicator the Sentinel Kinetic range is also easy to access for cleaning. Constant Pressure minimises energy consumption by only ventilating the room which has sensed the demand.

MVHR technology is proven to tick all the right boxes. It ventilates the home in a remarkably efficient way, saving energy, satisfying all relevant legislative requirements and making a big impact on cutting fuel bills for homeowners.

An effective solution

With the increasing efficiency demands of the Sustainable Code and rising energy costs, the ventilation goalposts have changed. With dwellings becoming increasingly airtight, MVHR systems have become the solution to both energy efficient and healthy ventilation. And with carbon targets tightening to meet 2016 zero carbon levels MVHR systems look set to offer a simple but effective answer to meeting the Code for Sustainable Homes.

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