One of Transition Town Letchworth’s area of interest is reducing the carbon associated with both existing and new housing stock. We have been eagerly awaiting the update to Part L of the Building Standards in the hope that this legislative driver would fill the gap left by dropping the Code for Sustainable Homes and move the UK swiftly to the position where all newly built homes are capable of being operated as affordable zero carbon homes.
UK builders already have access to the technology and materials to build zero carbon dwellings, and we believe this is what the 2020 update of Part L should require. Once the grid decarbonises all new homes built from 2020 onwards should automatically operate as affordable zero carbon homes. However, analysis of the 2020 changes proposed for Part L identifies that the carbon associated with new homes will be largely due to decarbonisation of the electricity grid, not to a tightening in the Part L energy efficiency standards. Thus, it will not take builders on a journey to improving build quality to deliver zero carbon homes which is now so desperately needed.
The Future Homes Standard 2020 does not promote a well-insulated building fabric due to the loss of the fabric energy efficiency standard (FEES). Additionally, the two options proposed deliver either 20% or 31% energy efficiency reductions, neither of which push fabric, comfort and well-being hard enough. The more we can insulate our homes the less energy they will use for heating. We should not be designing and building homes that will need retrofitting in the future.
Under Part L 2013 there is a Fabric Energy Efficiency Standard (FEES) metric which helps prevent homes being designed with a fabric worse than the ‘notional’ building, the 2020 consultation is proposing to drop the FEES target. This means that homes can be designed using the ‘minimum’ building fabric u-values as long as the building passes the carbon and primary energy targets. Where an energy efficient heating system (such as an air source heat pump) is specified the building is able to pass these targets with a poor building fabric. This is a loophole that overrides the need to have a well-insulated fabric and is likely to impact on running costs for homeowners.
LETI have undertaken analysis of the proposed standard which illustrates that new homes could be less efficient in 2020 than under Building Regulations 2013. Such a retrograde step in minimum requirements should be seen as unacceptable. New buildings should be built to impose a minimal load on the national grid and thereby help the UK to achieve net zero carbon emissions. If there is a serious commitment to improving building fabric this must start now by setting more challenging 2020 fabric standards or setting higher FEES standards.
Zero carbon homes usually have an air permeability of less 3m3/m2.h at 50Pa and this requires mechanical ventilation. This is what Part L and Part F should be seeking but currently it is still planned to include guidance for homes with significantly higher air permeability.
Local Authorities Zero Carbon Plans
Local authorities are much better placed to assess local need and viability of their area. Until the government implements a Part L to deliver zero carbon homes, the UKs ability to slow climate change rests with local authorities’ ambitious response and their zero carbon plans. Government should therefore not be seeking to take this away until they have put in place legislation that requires affordable zero carbon homes. Instead they should be supporting local authorities and give them greater freedom to impose a faster journey to affordable zero carbon homes. There is already evidence where local authorities have set local targets beyond that of Building Regulations which have proved viable and successful.
Switching from Gas
New homes represent a small proportion of the UK housing stock. Having sufficient trained engineers to install heat pump systems into all new homes in 2020 should be deliverable and so the target to not have gas supplied to any new homes could and should be implemented earlier than 2025.
Measuring the Energy Efficiency of New Houses
It is time to move from setting housing performance targets relative to current building standards and switch to targets which are focused on the end goal of all new builds achieving zero carbon with affordable energy running costs. We believe standards should be set based on the actual energy a building consumes in operation (regulated and unregulated energy), for example, kWh/m2/year, rather than a percentage reduction over a notional building model. This will be less confusing than the current standards and can be understood by the wider population.
In summary the proposed building regulations appears not to have acknowledged the urgent need to tackle climate change and has underestimated the ‘rate’ of change that is possible in the building industry. If the code for sustainable homes had been implemented as initially planned, we would now be building zero carbon homes. The knowledge and technology exist to deliver affordable zero carbon homes and this is what should be done. If forced to change the construction industry will change so now is the time to put in the legislative drivers.