Proving the future – how to keep up with Building Regulations

"From a standing start in 2006 to today, the builders have grasped the importance of air tightness testing as a proxy for quality of construction and the contribution good airtightness makes to energy efficiency" Mike Smith, Engineering Director

“From a standing start in 2006 to today, the builders have grasped the importance of air tightness testing as a proxy for quality of construction and the contribution good airtightness makes to energy efficiency” Mike Smith, Engineering Director

The rapid adoption of airtightness testing and the ability of the industry to achieve the right result first time in 89% of tests is one of the success stories of the UK construction industry over the past decade. The BSRIA Compliance team tested over 10,000 dwellings and 720 non-dwellings in 2012 and found the average dwelling airtightness value was 4.89 m3/(hr.m2) envelope area at 50 Pa (against a maximum regulatory value of 10 m3/(hr.m2)).

From a standing start in 2006 to today, the builders have grasped the importance of airtightness testing as a proxy for quality of construction and the contribution good airtightness makes to energy efficiency. The testing itself is rigorous, robust and, arguably, now at a very low economic price. It has respectability provided by UKAS accreditation for non-dwellings testing, the training of testers and, in the case of dwelling testing, registered testers through the Airtightness Testing and Measurement Association (part of the British Institute for Non-Destructive Testing).

The mantra should be “Build tight, ventilate right”. As fabric standards improve, driven on further by the 2013 Building Regulations, the role of passive and mechanical ventilation systems increases in importance. Unfortunately in the world of unintended consequences, we are seeing dwellings achieving better airtightness values than the designer intended which of course means less air leakage (and associated energy waste), but this is only useful if the designed-in ventilation systems can cope with these outcomes. In a nutshell the infrastructure supporting domestic ventilation engineering has not developed at the same pace as the improvement in building airtightness.

There is of course significant current activity to help remedy this problem but, as is so often the case, we are now on the back foot with increasing numbers of examples of poor installations and the inevitable questioning of the value of mechanical ventilation solutions.

The systems we are talking about are not complex but they are sensitive to errors. What is missing is not so much the technology or science but the widespread creation and adoption of proper codes of practice. Mechanical ventilation (MV) systems and the more complex MV heat recovery (MVHR) systems have to be site tested to ensure they are extracting and supplying appropriate amounts of ventilation. In the course of its compliance testing BSRIA is seeing two main kinds of problems.

The first is the performance of the specified equipment in a given situation, i.e. that the fan is correctly selected to match both the actual application and the inherent system losses that the system components will introduce. In simple terms this comes down to understanding the resistance characteristics of ductwork and its routing and the resistance of terminal units both inside and out. There is a widespread misunderstanding that ventilation fan outputs are usually quoted with outputs measured in “free air”. In reality they have to overcome backpressures from fittings. Even where kits are bought we see alternative terminal units used, usually to meet architects demands for aesthetics.

The second is the actual installation of the associated ductwork where there is a very poor understanding of the dramatic effect on performance that can arise from bad workmanship.

In a recent case BSRIA found approximately one metre of flexible ductwork that had been stuffed into the cavity wall for a straight through the wall installation that is approximately 300 mm thick. An additional 100 mm dogleg had been introduced on site to match the actual positioning of a porch structure. The result was a lot of fan noise with almost zero movement. The fan, when bench tested with zero back pressure, had a performance of 22 l/s, the designed performance including the ducting was 20 l/s however the actual performance was 5 l/s.

As part of the “catch up” in dealing with the rapid rise in the use of domestic ventilation we have identified that the act of measuring MVHR performance using published guidelines will give false results if the correct equipment or correction factors are not used. There is an easy remedy but not widely used at present. The automatic volume flow meter with pressure compensation – more commonly known as a “powered diff” will provide an instantaneous and accurate value. A more common hooded anemometer will impose a back pressure on the terminal, ducting and fan under test and the readings must be corrected (post use) specifically for both the anemometer model and the actual fan under test. More detail on this can be found in BSRIA’s “Domestic Ventilation Systems – a guide to measuring airflow rates – BG46/2013”.

And all of this is compounded by a lack of thinking regarding operational needs, limited controls, and poor instructions to the user, especially on what maintenance is required to keep performance at its peak.

So, airtightness demands have led to unforeseen consequences and something of a reaction against the use of mechanical ventilation. What then can be done to avoid making the same mistakes on other systems and concepts?

With fabric issues now largely dealt with in the Building Regulations it is likely that new focus will fall on the efficiency and operation of the MEP services in dwellings. If modelling and measuring the thermodynamics of a brick wall is difficult imagine how complex a multivalent heating system is going to be! And before being put into use, these complex integrated systems will need commissioning and possibly proving as well.

The Zero Carbon Hub has recognised that we will need to devise new test methods and regimes that, for example, will evaluate how the solar thermal collector performance meets expectations when linked with the ground source heat pump system that serves hot water generation, underfloor heating and thermal storage, in concert with a biomass boiler or room heater. Before regulation stimulates the market we need to have good practice guidance and proven on-site commissioning and test processes in place. This work is urgent and needs significant central support. With the next revision of Part L expected for 2016 – this time aimed at achieving zero (or nearly) carbon homes, time is not available to embark on a protracted negotiation with innumerable and varied industrial interests. Certainly industry’s support will be available but only for a properly directed and centrally funded programme.

If we fail to put into place a mechanism to improve the on-site verification of performance of new systems we will only have ourselves to blame for the next set of well publicised “failures to launch” and the consequent set back of achieving national aims.

BSRIA provides a range of Compliance Testing services for stress-free compliance to Building Regulations including airtightness (Part L), sound insulation (Part E) and ventilation testing (Part F).

Changes to Part L – is carbon neutral possible for 2016?

282px-AD-L_Part_2A2006 was a big year for building energy efficiency, the European Energy Performance of Buildings Directive started to be implemented. This triggered a radically new Part L, requiring all new building designs to meet CO2 emissions targets. The Code for Sustainable Homes was launched that year, and the government made bold plans to require new dwellings to be carbon neutral by 2016, non-dwellings three years later.

A glide-path to zero carbon was published with interim Part L changes planned for 2010 and 2013. Come 2010, and the first round changes took place, with a 25% reduction in CO2 targets. Then the following year, the government (now a conservative-led government claiming to be the greenest ever) watered down the definition of zero carbon to exclude appliances and cooking. Fair enough, absolute zero carbon perhaps wasn’t a feasible target anyway.

Fast forward to August 2013, and the second round of changes still hasn’t happened. The government has indicated that there will be a meagre reduction of 6% in CO2 targets for dwellings, and 9% for non-dwellings, and that these will kick in in April 2014. What this says to me is that the government, at the moment, aren’t all that interested in being green. Also, that 2016 is going to be very painful for housebuilders, who will have to make a huge leap to zero carbon. This zero-carbon commitment is still in place, and was even reaffirmed in the budget announcement in March. But of course, there’s another general election before 2016….

Getting life cycle costing right

Stuart Thompson

Stuart Thompson,
Senior Design Manager,
Morgan Sindall

A guest post by Stuart Thompson of Morgan Sindall 

The NRP (Norwich Research Park) Enterprise Centre project is an Exemplar Low Carbon Building, which is targeting BREEAM Outstanding and Passivhaus Certification.

The project for the University of East Anglia (UEA) is being delivered using a collaborative single point of delivery system by main contractor Morgan Sindall and its team, which includes architects Architype, civil, structural and environmental engineers BDP and Churchman Landscape Architects.

The centre has been created to achieve a 100-year design life and aspects of the development will be constructed using traditional methods. Locally sourced materials including Thetford timber, Norfolk straw and heather, chalk, lime, hemp and flint will be used and the lecture theatre will be constructed of rammed chalk while various buildings will be thatched. The development is expected to be completed in early 2014.

A key aspect of delivering the Exemplar Low Carbon Building at UEA is ensuring that the project has the lowest life cycle cost possible. The life cycle cost of a project is often discussed in construction but not usually followed through therefore it’s been fantastic to work with a client team which is happy to dedicate time and resources to evaluating this aspect of the development in such detail.

As part of the life cycle costing process, the design team met with consultants from BSRIA to consider how the building’s Passivhaus specification might affect its life cycle output. It was reassuring to know that the early analysis proved that the Passivhaus specification has life cycle benefits. You can watch a film about our workshop below:

 

Following the initial life cycle study, we followed up with a workshop that included a mixed group of various representatives from the client team. We learnt more about which issues were of particular interest to the various client representatives, such as predicted energy costs, climate change considerations, maintenance, robustness of filters and the type of finishes used. The debate did not simply focus on the initial capital costs, but also about legacy issues, robustness and replacement. We covered a full range of topics, including energy source, landscape materials, PV and roofing, lighting and floor finishes. The client maintenance team fed back to the group about their current issues and concerns too.

BSRIA's Peter Tse at the workshop

BSRIA’s Peter Tse at the workshop

What was interesting following such detailed debate was we were able to address the long term issues and this changed our initial concepts within the life cycle analysis. Our changes have made our project report totally specific and the real use and maintenance scenarios follow the life of the building. For example, how often timber windows will be re-painted, how often timber floors will be sanded and sealed and whether the LED light fittings will be able to handle the lamp life and transformer life claims. The workshop allowed the group to ensure that the life cycle analysis is extremely relevant and targeted to this specific project and we will now be able to use the information garnered during the process to shape the scheme over the next few months when detailed design commences.

This landmark project is part-funded by the European Union through the European Regional Development Fund (the largest single ERDF project in the region in the 2007-2015 funding round) in addition to funding from UEA, the Biotechnology and Biological Sciences Research Council (BBSRC) and BRE.

Sustainable Housing – defining zero carbon

In the last budget on 23rd March, the UK government, quite discretely, changed the definition of zero carbon.  The 2011 budget changed the requirements from having to balance all the regulated loads plus an allowance for cooking and appliances, to simply balancing the emissions from the regulated loads only.  In essence this is just the heating, hot water and lighting loads.   There appears to be a split in opinion on this issue, with some for the change arguing that it is a more realistic target for the construction industry to meet, while the other camp argue that the new definition isn’t really zero carbon.

I have been involved in a project that has just completed the construction of a Code 6 vicarageLevel 6 of the code for sustainable homes requires the building to meet “zero carbon”.  The new definition is effectively the requirement for Code 5 in the 2009 version of the Code for sustainable homes on the dwelling emission front.  With the old definition, there was no way out of producing a small power station for a house.  In the vicarage the south facing roof was covered in around 8 kWp of photovoltaic panels. The cost of these panels still significant, even with the feed-in-tariffs it is going to put a lot of people off the thought of installing them, and even thinking about going for Code 6.

2016 is still the target date for all new homes to be zero carbon, and built to Code 6 standards.  The pressure to meet this target is probably behind the change in the definition of zero carbon.  With this new definition, it is feasible to build a dwelling with minimal generating capacity, and so reducing the cost.  I’m sure the Passivhaus approach will come more into the frame – a more fabric first approach.  Reducing heat loss (or gain for summer months) simply makes sense.

Even with the definition of zero carbon changing, making it cheaper to build to Code 6, it will still be difficult.  Whether using the Passivhaus approach or not, the correct site is even more important than ever.  The Code for Sustainable Homes includes other issues, not just energy, that needs to be taken into account.  Things like ecology, cycle storage, water use and the lifetime homes standards have rarely stopped a house from being built in the past, but this may happen once Code 6 becomes the mandatory standard.

%d bloggers like this: