Part L has been revised several times since the turn of the millennium, but this is a more momentous change as this is the first time Part L is being split in two: There will be one version to cover England and a separate version for Wales. In the commercial sector, there are some significant changes to Part L between the two countries – all signs point to Wales being a much tougher place to build when these new documents go live from July 31st.
20% cut in Emissions
Firstly, and most importantly, there is a 20% cut to the Target Emission Rate (TER) compared to the current standard. This target is being calculated using a list of fixed values called the ‘Elemental Recipe’. In theory, if you build to this recipe, you can show compliance… but it may not be the preferred route to take (as we’re about to find out)... As well as the TER, there is a new, mandatory requirement called the Target Primary Energy Consumption (TPEC) which is measured in kilowatt hours per metres squared. This second target only looks at the fixed building services (heating, lighting, hot water and ventilation), so the quality of your building fabric will have no influence on this second target at all.
A Guide to the Recipe
The ‘Elemental Recipe’ used to calculate these targets will vary depending on building size and type, but here’s a general guide: For building materials, you should focus on U-Value of 0.22 for floors, 0.26 for walls and 0.18 for roofs. Glazing is 1.6 or 1.8, lighting efficiency is 65 lumens per circuit watt and heating is based on a 91% efficient mains gas boiler (different allowances are made for units without gas boilers). Air permeability in the recipe varies between 3 and 7, and cooling (where fitted) is based on a SEER efficiency of 4.5. The recipe also includes heat recovery ventilation at 70% efficiency. Just like all other sections of the recipe, you have the flexibility to construct in other ways (so you can use intermittent fans to wet rooms as an alternative ventilation system), providing you make improvements elsewhere to re-tip the balance.
There is an elephant in the room, which is unfortunately quite an eye-watering addition to the Elemental Recipe. Photovoltaic panels... For every 100sqm of floor area in your commercial building, the recipe for the new Target Emission Rate will be based on 5.3 sqm of PV panels… that’s a floor area to PV ratio of more than 1/20th. PV isn't a mandatory requirement, but is going to be extremely difficult to escape from without using low-carbon heating systems or alternative renewable technologies. If you are unable to prove at design stage that your commercial building design and specification complies with these two Targets, your building will not be deemed compliant with Part L2, and you’ll not be allowed to start work on site.
Key Elements remaining...
Aside from this, all other key elements which make up Part L2 are remaining as they are. This includes maximum U-Values (which are not being reduced) and air testing targets (which will remain at a maximum of 10). The full set of Welsh building regulations for Part L, including the new Elemental Recipe, are available from the Welsh Government website. For more details about Part L and how the changes may impact you, contact Energist UK on 08458 386 387. You can also follow us on Twitter @EnergistUK for regular updates or join the UK Building Regulations Network on LinkedIn.