Towards top BREEAM status
Even the best designed energy efficient buildings can achieve substandard energy performance due to poor building management – but nowhere is the role of building management more pronounced than in established buildings, constructed well before modern materials and design principles were established. As such, last year’s extension of the BREEAM ratings to cover existing buildings represented a significant step forward in helping to improve the efficiency of the UK’s current building stock.
As well as contributing to the Government’s carbon-reduction targets, the BREEAM ratings encourage responsible building managers to effectively upgrade their existing operations and do their bit to improve energy efficiency plus reduce the building’s environmental impact. And since temperature control and hot water generation are among the main areas of a building’s energy consumption, it makes sense to improve boiler plant efficiency.
Improving the performance of commercial boiler plant is considered low cost, relative to building fabric improvements and sustainable energy technologies, yet produces a significant reduction in emissions and energy consumption, in turn providing building owners and occupants with substantial energy cost savings over the life of the plant.
However, since retrofitting requires contractors to work within the existing frame of the building, there is likely to be an even greater emphasis on boiler plant efficiency and associated controls in refurbishment projects which seek to meet BREEAM’s excellent and outstanding ratings, in order to offset building design shortcomings which cannot fundamentally be changed.
There are two main sections in BREEAM relating to boiler plant: Energy, where up to 15 credits are available for the reduction of carbon dioxide emissions, and Pollution, relating to NOx emissions, where up to 3 credits are available.
The energy parameters are provided through the National Calculation Methodology (NCM), using tools such as SBEM to calculate carbon dioxide emissions from new buildings. The BREEAM assessment of energy efficiency and carbon dioxide emissions is based on the outputs from SBEM, and is in accordance with the guidelines set out in the Building Regulations 2010, approved documents Part L2 for non-domestic buildings.
A key factor in these calculations is the boiler seasonal efficiency, which is the “weighted” average of the efficiencies of the boiler at 30 per cent and 100 per cent of the boiler output. For natural gas boilers, this must be a minimum 86 per cent for new build, and 82 per cent in existing buildings, although boilers in existing buildings must achieve what is referred to as “an effective boiler seasonal efficiency” of 84 per cent.
With existing buildings, it may be necessary to gain credits (percentage points) to improve the minimum boiler efficiency from 82 per cent to 84 per cent. Of course, if the boiler seasonal efficiency is already 84 per cent or above, then additional credits are not necessary to meet the minimum requirements.
The Building Regulations are being updated this year and there is expected to be tightening of the minimum boiler seasonal efficiency levels for new build but not for existing buildings.
Hamworthy pioneered modular boilers even before natural gas became the preferred choice of fuel, and the decentralisation of heating systems, as well as the use of modular boilers, are examples of how efficiency credits can be built up in the SBEM calculations. Along with accurate boiler sizing, up to 4 credits can be added for these, to boost the effective seasonal efficiency data.
Having sized and selected the boiler plant, controls then become the focus, where again further credits can be claimed for functionality. Manufacturers such as Hamworthy have long recognised the importance of effective boiler controls, and have introduced a number of features designed to improve user control, such as optimised start/stop, boiler sequencing and temperature control. The high efficiency biomass boilers also feature automatic ignition and extinguish function, to eliminate fuel waste and unnecessary emissions.
The Pollution section in BREEAM considers NOx emissions, which are atmospheric pollutants contributing to acid rain and climate change.
European standard EN 483 sets the rating for NOx performance, with the best being Class 5, less than 70 mg/kWh. However, NOx performance for heating and cooling appliances must be below 40 mg/kWh in order to gain maximum BREEAM credits. Putting this into context, electricity sourced from the national grid has associated NOx emissions of approximately 1200 mg/kWh.
Wessex ModuMax 250/750 modular condensing boilers, for example, were installed in the Hive in the heart of Manchester’s Northern Quarter. The choice of this boiler was steered by both commercial and environmental considerations and takes full advantage of the advances in multiple boiler design, use of full modulating capability and its low NOx emissions across the range, at less than 40mg/kWh.
As a cost-effective measure of helping to improve the performance of an existing building, we can only see boilers playing an increasingly significant role in the attainment of low carbon buildings.
www.hamworthy-heating.com
Liam Elmore is northern regional sales manager at Hamworthy Heating
