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Part L 2013 – Finally…

Well first up this is only half the story. There’s still no sign of the ADs for L1B and L2B although we’re not expecting any changes to the technical requirements here. We’ll keep an eye out for those…

So we’re still on for our release date of the 6th April 2014. So this means if you want to avoid the new requirements then you need to register your site with Building Control before this date AND start work on site before the 6th of April 2015. This could include drainage works or foundations but doesn't include any demolition works.

Future of Zero Carbon

There’s also a small clue to the future of Zero Carbon in there. Whilst the Government seems to be committed to Zero Carbon from 2016 onwards (a subject of much political arm wrestling apparently) there’s a small section in Part L1A that states that nearly Zero energy buildings will not come into force until 2019 at the earliest.

Will our 2016 target for Zero Carbon move? It would seem sensible, considering that in reality we won’t have any meaningful performance data on completed Part L 2013 houses until 2016 at the earliest. But back to 2013 Regs. For Part L1A we now have both the Target Emission Rate and the Target Fabric Efficiency Rate (see our previous blog) under Criterion 1. For the TER we’re looking at a 6% reduction over the Part L 2010 TER. Whilst this doesn’t seem a huge jump, we believe it will push the fabric first approach further, with wall U values coming down. The TFEE requirement will also put more emphasis on solar gain and passiv design. Not a luxury everyone can design towards, but it will certainly help.

The TER and the TFEE will both be measured using SAP 2012, the beta software for which has unfortunately not been released yet. Given the process to update SAP is not a quick one, we’d expected commercially available approved software to be released just before or maybe on the 6th April next year! But hopefully when we get our hands on the interim beta software we’ll get able to get a good idea of what compliance looks like. ADL1A also says that block compliance can be used on developments of multiple dwellings in the same building for both the TER and TFEE which is good news, and means that north facing flats have a means to comply.

As before the SAP will need to be completed before work starts on site. Probably a good idea given the more stringent requirements!

It’s also worth noting that regulation 25A (stay with me) has now been written into Part L. This basically states that a developer should asses the viability of renewable and high efficiency alternative system before starting work on site. This report should also be available to Building Control if requested.  These technologies don’t need to be installed under the Building Regs, but their suitability should be assessed. Another box to tick on route to compliance.

U-Values remain the same...

The AD's also confirm what we thought, that the limiting U values remain unchanged from Part L 2010.

  • Wall: 0.3

  • Roof 0.2

  • Floor 0.25

  • Party wall 0.2

  • Openings 2

  • Air perm 10

The reality is that these U values will need to be much lower in order to comply. For the first time in Part L history we have been given a definitive means of compliance, an elemental recipe, or as the ADs call it Model Designs (Section 5 if you’re really interested).

This Model Designs, list the specification that is used by SAP to calculate your TER. And on that basis if you build exactly to this specification you’ll comply with both the TER and the TFEE. I wouldn't say it’s the most cost effective way to comply but it’s certainly a good starting point:

  • Wall: 0.18

  • Roof 0.13

  • Floor 0.13

  • Party wall 0

  • Openings 1.4

  • Air perm 5

  • A rated Gas boiler with twin zone control and weather compensation.

Fabric First Approach

So you can see there’s a lot of emphasis on a fabric first approach, with some pretty low U values. This won’t be everyone’s cup of tea and there will be ways of building to a higher wall U value, but this will need to be offset elsewhere in SAP.

One thing that really stands out in this Model Design is the importance of thermal bridging. The TER will effectively use a Y value of 0.05 in the calculation. This means that if you are using the standard Accredited Construction Details you will in effect be penalised, making compliance harder to achieve. This will ultimately encourage the use of better detailing and more efficiency thermal bridging design. The Enhanced Construction Details (from the Energy Savings Trust) and the Constructive details) would both help lower thermal bridging heat loss.

For Part L2, there aren't too many changes. Whilst the limiting U values are the same, the TER has been cut by approximately 9%. I say approximately as this target will vary depending on the type of building being assessed (the same process applied in Part L 2010). The calculation has however been adjusted so it doesn't penalise small warehouses – difficult to get through under Part L 2010.

There’s also a Model Design for Part L2A – a specification that will achieve compliance. It’s a bit more complicated than the recipe for Part L1A, and given there are so many ways to heat, ventilate and light a non-domestic building, it’s certainly not the only route to compliance. it does however, serve to give a good starting point for U values. The rest is then down to the performance of building services, by far the biggest influence on the SBEM calculation. Lighting efficiency have been improved along with heat pump standards.

As with all things SBEM, the nature of the building down to it’s room usage really defines the performance so unfortunately there are no hard and fast rules for compliance.

That’s about it for the main changes brought along by Part L 2013. As soon as the Beta SAP and SBEM software is released we’ll run some sample calculations, so we can make some more sense of all this paperwork!

If you would like to keep bang up to date on the changes you can follow us on Twitter @EnergistUK or join the UK Building Regulations group on LinkedIn.

Jon Ponting

Author: Jon Ponting

This article was published by Jon Ponting on 18.11.2013.