The AECB building standards are offering the construction industry new routes to achieving high building standards. Enhabit’s Head of Building Physics & Consultancy, Dr Sarah Price, gives an overview of the recently-launched AECB Retrofit Standard.
Why is there a need for a new Retrofit Standard?
The Passivhaus standard is the ultimate goal for newbuilds and this is something the AECB completely recognises, seeing its own newbuild standard as a stepping stone to Passivhaus.
However, when it comes to retrofit, there are very few standards available, and while the Passivhaus retrofit standard, EnerPHit, is a brilliant aspiration for retrofitters, it can often be can often be unattainable and maybe too stringent for most homes in the UK. The AECB Retrofit Standard offers a pragmatic approach to the energy demand targets, which are still potentially lower than current UK new building regulations.
The main difference that sets the AECB standard apart is that it recognises that every home is unique, and focusses on managing retrofit risks to avoid unintended consequences. This is something that is at the core of the work we do at Green Building Store and Enhabit, independent of the final energy demand. The self-certification process offered by the AECB Retrofit Standard also helps to keeps costs down.
Energy & comfort requirements
The AECB building standard has a retrofit target of 50 kWh/m2 annum, but an exception may be applied for of up to 100 kWh/m2 annum. It has an airtightness requirement of 2 ach @50 Pa. The AECB Retrofit standard uses the Passivhaus Planning Package (PHPP) software as a design tool. By using PHPP modelling the AECB Retrofit standard ensure good thermal and comfort performance and avoiding the ‘performance gap’ of so many retrofit projects.
Managing retrofit risks is key to a good retrofit. The consequences of bad retrofit can be far worse than doing nothing at all. The AECB retrofit standard has the advantage of addressing the myriad of other issues surrounding retrofit, drawing on all the retrofit knowledge and expertise set out in its CarbonLite Retrofit course. The AECB Retrofit Standard also includes management of risks around moisture, flood, radon and fire, as well as requiring an excellent retrofit survey the ensures that the building is fit for retrofit in the first place.
Decarbonising our buildings
We know that not all buildings are going to meet the EnerPHit standard and that we need a moderate approach to retrofit with an average of around 50% carbon reduction by energy efficient fabric measures, with some buildings achieving more and some less.
The AECB Retrofit Standard will help projects to addresses retrofit risks and create warm, comfortable and safe buildings for the long term. This will support the decarbonisation of the grid and reduce peak heating load as we turn to electrical heating in our buildings.
Dr Sarah Price is Enhabit’s Head of Building Physics & Consultancy and was one of the technical authors of the AECB Retrofit Standard