The Office of the Deputy Prime Minister is on to that. It is considering pre-completion testing to check that build quality matches design content. This will put a lot of pressure on building control bodies and testers, however, and a more likely scenario would be the provision of robust details along the lines of those developed by the House Builders Federation for Part E of the Building Regulations. The ODPM says it could also be more realistic about build quality and ask for more insulation to be included.
Won’t robust standard details for Part L clash with the soundproofing robust standard details in Part E?
Yes, probably. The ODPM says it will consider integrating the two, but until that happens, Part E details will almost certainly need to be tweaked to meet the U-values laid down by Part L. For example, wider wall cavities mean plastic wall ties will have to go. Steel has the necessary strength but it is a good conductor of sound between homes. The housebuilders and the product manufacturers are very unhappy about these changes – understandably, because they have spent a fortune putting together robust standard details for Part E.
Am I right in thinking that if energy standards are set for the whole building I can install energy efficient boilers and not worry about U-values?
Some trade-offs will be allowed but minimum U-values for walls, floors, windows and doors still have to be met. There is some concern that a whole-building approach will tempt designers to install better heating, ventilation and air-conditioning at the expense of a thermally efficient envelope. The problem with this is a building envelope with a lifespan of 100 years could be traded for a super energy-efficient boiler with a lifetime of 10 years. When it breaks down, how will Building Control make sure it won’t be replaced by a less
Are there any other big changes in the calculation methodology for non-dwellings?
The way the efficiency of individual building components and systems is calculated is going to be radically altered. The same methodology that is used for domestic boilers will be adopted – each element will have an A, B, C or D rating, and only components in the upper bands will be allowed. Engineers will have fun working out
how all these components interact with each other so that they can arrive at an overall figure for the efficiency of each system. Whatever
it is, it will be fed into the new whole-building calculation method.
What about dwellings?
The whole building method for dwellings is likely to be based on the standard assessment procedure, or SAP, which gives a building a rating based on the energy it uses to heat space and water. However, the SAP ratings required will be made tougher, and it could be extended to include lighting within its scope and take account of new technologies such as microCHP.
And what about refurbishments?
The ODPM recognises that the bulk of carbon comes from existing buildings and would like a wider range of improvements to trigger Part L compliance. Also, change to a building’s use could require the whole building to comply with Part L even if, say, only 25% of it was being worked on. This is tricky, because the ODPM recognises that if the regime is too tough, it could deter people from improving buildings. Therefore refurbishment standards are likely to be less onerous than new-build.
How will the European Commission’s directive work out how energy efficient a building is?
The previous whole-building method is to be dropped. This gave a building a “carbon performance rating” depending on how much carbon dioxide it added to the atmosphere.
The problem is that it relied on a benchmark
and these only exist for office buildings, whereas a methodology is needed that can work for
all types. The idea is to switch to a new
whole-building method that brings more building elements into the calculation. Quite what that will be is currently the subject of much mental activity. However, an elemental-based method will be retained as back-up.
Is Part L going to require developments to include solar cells or similar renewable energy sources? I ask because the government’s energy white paper and the European Commission’s recent Energy Performance of Buildings directive demand greener energy sources.
The 2005 revision of Part L may not demand a certain percentage of energy is generated on site by wind or solar power but it may demand building designers give it serious consideration. The approved document is also likely to provide guidance on installing low or zero-carbon systems. However, renewable energy systems cannot be offset against the efficiency of the building envelope or building services systems. The possibility of making buildings “solar ready” – that is, ready for the later installation of photovoltaic cells and for micro-combined heat and power plants – is being investigated.
So once this lot is out of the way, will we have a breather before going through the whole hideous process again? And what are those changes likely to be?
Hard to say. Candidates include a requirement that a certain percentage of energy be generated on site from renewable sources and the requirement that a building’s shape and form maximise
energy efficiency. Maximum allowable levels of embodied energy in building materials is also likely to be included – and you can bet overall building energy performance will be increased.
What the producers thinkProduct manufacturers are directly affected by the changes as they have to retool their factories to manufacture the products that they have redesigned to conform to the new standards.
The ODPM paper entitled Possible Future Performance Standards has “got up the noses of a lot of people”, says John Tebbit, the CPA’s industry affairs director and chair of the working group to debate changes to a building’s external envelope.
Many subgroups within the working group are unhappy that the hike in standards will come into force a mere three years after the last significant changes. The glazing expert panel says that large investments and adjustments were made by to accommodate the 2002 changes, and that a demand for improvements in 2005, rather than in 2008 as first mooted, would be unfair.
The masonry panel says higher U-values will mean buildings will require a bigger footprint and result in higher material costs. The timber/steel frame panel says that 0.27 W/m2K is possible for walls but not 0.25. The roofing panel says 0.20 will be achievable but not 0.16. The curtain walling panel says it will need heavier frames and stronger hardware, which has cost and handling implications. John Garbutt, marketing manager of insulation manufacturer Kingspan says getting the industry to agree with the proposals is like trying to pull teeth but he senses that the ODPM will not be deflected. “I suspect ODPM won’t move much on these figures. If nobody can shoot down the proposals in the PFPS paper, then the plans will go forward. I’m confident we will get 0.25 for external walls.”