BSRIA Residential Network launch

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This blog was written by Saryu Vatal, Senior Consultant and Researcher for BSRIA Sustainable Construction Group

The BSRIA Residential Network was launched on the 11th of September, kindly hosted by the Wellcome Trust and well attended by over 50 delegates, comprising of both members and invited guests.  Ian Orme Business Manager for the Sustainable Construction Group welcomed the delegates and introduced briefly the intention of the network and how BSRIA would like to engage with all stakeholders to help make residential development better.

The event was chaired by Richard Partington of Richards Partington Architects, architect advisor for the Zero Carbon Hub and co-chair of the steering group for their Performance Gap project.

The day started with a summary of the current policy context for energy efficiency standards in new homes and challenges and opportunities for low energy retrofits.

The recently concluded Performance Gap project for the DCLG provided a starting point for discussing issues that impacted new build residential developments. For this project, an extensive evidence gathering and review exercise was carried and over 60 issues were identified as contributing to the gap between the designed and measured energy use in homes.  Of these the ones prioritised for action and further research, along with the shortcomings in skills and knowledge highlighted through the end-to-end process review of over 20 new developments,  formed the core of the Hub’s recommendations to the Government.

Rick Holland was present to give an update on the Government’s continued support for funding research into construction processes via Innovate UK (previously Technology Strategy Board), both for domestic and non-domestic buildings.

A major programme from this funding stream looking at Building Performance Evaluation is coming to a close at the end of September and early stage findings from meta-data analysis were presented by Ian Mawditt of Fourwalls.  This focused on the common issues found with the design, installation and operation of MVHR systems and data from whole house co-heating tests. The final findings will be disseminated via Innovate UK and will include information from all projects across the seven funding tranches.

The analysis of key design specifications that would impact the performance of the mechanical ventilation systems raised some interesting observations about common assumptions made at early design stages.  Common themes from the commissioned air flow rates were also discussed.  The performance of homes built to Passivhaus standard was notably better, which emphasised the importance of process control on site, but also highlighted the fact that, when needed, the industry was able to deliver a high quality product (homes).

The presentations of the day concluded with a summary of how BSRIA would like to engage with its members to try and address various shortcomings identified through research.  Members are invited to put forward areas where there is a need for additional support, in the form of training, guidance and impartial technical expertise.

Calculator leaned on a little house with red roofA panel discussion was facilitated by the event chair in which a range of topics were discussed.  These included issues around the effective design, installation and modelling of district heating in residential and mixed use schemes and variations in standards and assumptions between the EU and the UK.  Ashley Bateson was able to provide an update on standards being developed by CIBSE.

The conflict between supporting innovative technology and the confidence in product and performance data to allow these to be accepted into mainstream and within compliance tools was also highlighted as an area of concern.

The impact of users on the actual energy performance in homes has not been included in some key research projects although in reality this has significant impact.  While this lies beyond the scope of a developer’s influence, key decisions about the complexity of services, controls interface and handover procedures all contribute towards the usability of homes.  Instances of how internet based tools and were successfully employed in some projects to engage with occupants to develop a feedback and learning mechanism were highlighted.

There were concerns voiced about the problem of overheating in new and newly refurbished homes, especially when dealing with vulnerable occupant groups like the elderly.  The Zero Carbon Hub are working on a project looking at the evidence and aim to help develop the assessment standards and methods for evaluating and mitigating risks in new homes.

BSRIA sees itself well-placed to engage with its members and the wider industry to help address the various shortcomings and areas of concern highlighted.  Subsequent network events have been planned to focus on specific topics in detail and we are seeking feedback from members to help structure our efforts in the most effective and useful manner.

Presentations from all speakers can be found on the networks page of the BSRIA website.

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).

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