Part L, one year on

It has been a year since Part L of the Building Regulations was introduced, but parts of the construction industry are still struggling to understand it. They are also having to get to grips with the requirements of Planning Policy Statement 22, which requires that at least 10% of a development’s energy requirements be generated onsite from renewable sources.

Both these requirements are having an impact on the way the industry works, as teams struggle to comply and hard-nosed clients struggle to keep keep costs down. These teams will not be comforted by the thought that even tougher energy regulation is on the way, and that each revision of Part L requires greater complexity of analysis, and the mandatory use of standard calculation software. This last requires a good understanding of building physics and engineering services. The next revision to regulations is scheduled for 2010 and is expected to be as significant as 2006’s.

In preparing this piece we talked to a range of practitioners - suppliers, architects, engineers, sustainability and building control specialists. All have found their work affected in a big way.

THE EFFECT OF 2006 PART L ON BUILDINGS

Part L1A: New-build dwellings.

The introduction of the 2005 SAP calculation methodology does not appear to have dramatically changed dwelling design. Window sizes have reduced somewhat and fabric insulation values have increased. And getting electrical heating and hot water systems to comply is regarded as difficult by many, so there are more gas boilers being installed. However, M&E engineers report that careful adjustment of the SAP input data can still produce a pass with electrically heated dwellings.

Part L1B - Refurbishment and extension of existing dwellings

Put simply, if you work on a controlled element such as a wall, a roof, or a floor, or a fitting such as a window, a door, or services, you need to consider upgrading it. The process is simple: you either add insulation to the elements or change fittings and services such as the glazing, doors or heating systems.

Problems arise over the details. Window and door frames can be heavy-looking, and you can forget about once-popular design details such as stripping off the plaster and sandblasting the brickwork. However, if the building is of genuine historic interest, attractive features can be retained without extra insulation.

Building control bodies will often allow elements to offset each other – in other words, by upgrading one element above the minimum requirement, another can perform less well.

Part L2A: New-build non-dwellings

The dust has not settled here. The energy and engineering design professions expected that L2A would lead to the end of 100% glazed, sealed, air-conditioned office blocks. They are still with us! The reason for this is that to comply, a building must achieve a performance that is a certain number of percentage points better than a similar 2002-compliant building. This means it is easier to get an air-conditioned building to comply than a naturally ventilated building, because there is less scope to improve the performance of a naturally ventilated building; it is already energy efficient.

Another problem is that the old and new regulations describe engineering systems in different ways, and the new software is not sufficiently flexible to allow for the wide variety of engineering systems available. So comparison between 2002 and 2006 results appears to be rather imprecise.

L2B: Existing non-domestic

This section of Part L must be the cause of more confusion and wasted time in design teams than any other. The problem is the detailed wording.

Part of it is straightforward. If you work on controlled elements, fittings or services, then you should upgrade them, provided that the costs of doing so meet the technical and economic criteria set out in Part L. However, many fabric upgrades do not fulfil the economic criteria and are unnecessary. But it does require a lot of work to justify whether the work is required, and only a few QSs appear to be tackling this. On most schemes there is little regulatory pressure for windows to be changed to double-glazing.

The most controversial part of L2B is proving to be the consequential improvements aspect to buildings larger than 1000m2. This is where an improvement to one element of the building triggers general improvements to another, subject to the technical and economic criteria. A number of organisations have produced flow charts to ease the pain, but unfortunately they are all different and some practitioners disagree on their correct interpretation.

Commercial fit-outs are another area of concern. A new building fitted out to category A standard has to fulfil Part L2A. But the subsequent tenant fit-out has to comply with part L2B, which could trigger consequential improvements. Taken literally, adding a new fan coil to an office that has had the partitioning changed could trigger consequential improvements, although this is plainly nonsensical. It seems like a good idea to retain the category A approved inspector for the subsequent fit-out to avoid conflicts of opinion.

The response to L2B by building control bodies is variable. The best of them find that teams tend not to be knowledgeable and like to engage in a lot of pre-consultation. However, some bodies are not fully up to speed and education and training is going to be needed for the foreseeable future.

Problems with SBEM

The “SBEM” referred to in the regulations has been the subject of extensive criticism in the media, largely because the software had to be developed quickly to meet the 2006 deadline. The “S” stands for simplified and it is really only suitable for the simplest of buildings. This has led to reports of cases where a revised version of SBEM has caused the same building to slip from a pass to a fail. This would have serious implications for the design and construction teams.

Initially, SBEM was only available from BRE; now it has been incorporated in other popular software tools to make calculating compliance easier for engineers. There are reports that different software packages appear to give different patterns of energy consumption. This may have a significant influence on the energy strategy adopted and the choice of engineering systems. We hear of firms offering to run the same building on different software systems to come up with the cheapest compliant solution.

Senior energy designers find outcomes from SBEM are sometimes counter-intuitive, yet there is nothing they can do as the national calculation methodology that underpins it is hidden. They would like access to its details but it is in the hands of the developers for the time being. Without understanding how SBEM arrives at results, seemingly unclear outcomes remain unexplained, making an industry consensus on best practice solutions more difficult.

In the right hands, best value outcomes can be developed with the available software. However, it is also possible to manipulate the calculation inputs to favour one set of building components or elements over another. So, the fabric can be downgraded, requiring a higher spec lighting or HVAC system. Or alternatively, the air-tightness can be set to a higher standard to reduce the need for other more costly measures.

This can lead to the burden of compliance being passed down the supply chain. For instance, the services engineer can cut the cost of the HVAC system by stipulating a very low infiltration rate, creating a nightmare for the architect and builder when it comes to compliance testing. Equally, some architects are still expecting services engineers to overcome poor envelope design and achieve compliance by the clever use software and services design.

For many, the outputs from SBEM are accepted on face value, but considerable knowledge of envelope and engineering services design is needed to get accurate outcomes.

It is vital for the team and building control to manage the software development, input parameters and implied construction details right through the project. This has an impact on many trades. For example, changing a glazing spec could require a change of the HVAC system or the lighting concept. This has a big impact on the way contractors commonly work. Late changes of supplier are possible but the carbon impact must be assessed and the requirements transferred to the trade supplier.

DESIGN RESPONSES TO PART L

Teams are developing a new way of working. Uncomfortable as it may seem to many clients and architects, energy and sustainability advisers are being brought in at the front-end of projects. The M&E engineer, once the Cinderella of the

industry, is now in demand even on modest-sized projects. At a time of skills shortages, this is a challenge.

Specialist sustainability and energy consultants are sprouting up everywhere you look. Until last year, there were only a few hundred people active in UK practice and therefore, recognised as being reasonably competent.

As usual, when faced with a complex problem, people are searching for a magic bullet. Ground-source “heat pump boilers” biomass heating and CHP are being widely considered. Advanced construction methods such as Termodek are being considered on ever smaller schemes, and the methods themselves are being developed to stay ahead of the game as manufacturers rush to prove their renewable and low-carbon credentials.

Team responsibilities: a crunch

The complexity of the energy regulations is causing difficulties for many teams. Clear “ownership” of design and construction from inception to hand over is rarely allocated to a single party. Demarcation errors or failure to properly carry out the calculations and then inform all the relevant trade contractors are causing problems. We hear rumours that some buildings have had to replace elements as critical as windows in order to achieve compliance.

M&E trade contractors are becoming very concerned that their responsibilities are impossible to discharge unless they have clear instructions regarding the energy performance required from the kit they purchase. There are significant risks and the consequences in liability are as yet not fully known, because few buildings have gone through the full process.

Where clients do not pay for the work in advance, contractors may find the risks unacceptable. Certainly we can expect to see the cost of bidding rise if the risk is to be effectively managed.

The perceived solution so far has been to bring in energy advisers before planning applications are made. This helps, but the detailed work to achieve compliance reliably has to follow through the whole construction process. The following is a guide to the people getting involved in the energy design and process management at different stages, which includes new specialisms:

• RIBA Stage C: energy/sustainability consultant
• RIBA Stage D: M&E designer/energy consultant and building control body
• Design-and-build bid: contractor and M&E designer/energy consultant and building control body
• Construction, M&E aspects: M&E contractor
• Fabric: contractor, compliance specialists or M&E consultant
• Hand over: contractor/compliance specialists and building control body

Built environment consultant the BSRIA has produced a useful document (BG6) that schedules a huge amount of what has to be done and when. However, it is not a compliance checklist and it does not recommend who should do what! So teams still have to thrash this out.

On completion, the building control officers must decide whether a building passes or fails based on the evidence before them. In view of the number of parties and the potential responsibilities this task must be difficult to get right.

Summary

So, is new Part L working? Well, yes, to a degree, although the low carbon hopes of many have had to be tempered for the time being.

The jury is out as to whether the 19-28% reduction on 2002 standards will be achieved. The regulations will certainly result in better buildings than those of 2002, if only through increased energy awareness and the greater amount of design thought that must now go into them. Also, the improved air-tightness testing regime and the final compliance checklist will definitely deliver results. But until we get serious about energy rating certificates and measuring actual post-occupancy energy use, we will probably never really know. But that story is still to be told.