Boiling up a high BREEAM rating
Lots of BREEAM credits can be gained by paying close attention to boiler plant, as Liam Elmore explains.
Even the best designed energy efficient buildings can achieve substandard energy performance due to poor building management. 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, the extension of the BREEAM ratings to cover existing buildings represents a significant step forward in improving the efficiency of the UK’s building stock.
BREEAM ratings encourage responsible building managers to effectively upgrade their existing operations and do their bit to improve energy efficiency as well as reduce the building’s environmental impact. 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 to offset shortcomings in building design that cannot fundamentally be changed.
There are two main sections in BREEAM relating to boiler plant.
• Energy, where up to 15 credits are available for reducing carbon-dioxide emissions.
• Pollution, relating to NOx emissions, where up to three credits are available.
|Helping the Hive building in Manchester’s Northern Quarter achieve a BREEAM excellent rating is this installation of Hamworthy Wessex ModuMax condensing boilers.|
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% and 100% of the boiler output. For natural gas boilers, this must be a minimum 86% for new build and 82% in existing buildings, although boilers in existing buildings must achieve what is referred to as ‘an effective boiler seasonal efficiency’ of 84%.
With existing buildings, it may be necessary to gain credits (percentage points) to improve the minimum boiler efficiency from 82% to 84%. Of course, if the boiler seasonal efficiency is already 84% or above, then additional credits are not necessary to meet the minimum requirements.
Hamworthy pioneered modular boilers even before natural gas became the preferred choice of fuel, and the decentralisation of heating systems and modular boilers are examples of how efficiency credits can be built up in the SBEM calculations. Along with accurate boiler sizing, up to four 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 introduced a number of features designed to improve user control, such as optimised start/stop, boiler sequencing and temperature control. High-efficiency biomass boilers also feature automatic ignition and extinguish function to eliminate fuel waste and unnecessary emissions.
Embracing sustainable energy into a heating solution will bring additional benefits. Hamworthy biomass boilers have minimum efficiencies of 90 to 96%, amongst the most efficient on the market and far exceeding the minimum 75% efficiency for automatic wood chip or pellet boilers.
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 must be below 40 mg/kWh to gain maximum BREEAM credits. Putting this into context, electricity sourced from the national grid has associated NOx emissions of about 1200 mg/kWh.
|Up to three BREEAM credits are available for boilers with low NOx emissions.|
Overall, it makes sense to look at improving the efficiency of the existing building stock rather than solely focusing on trying to improve the efficiency of already efficient new buildings, both domestic and non-domestic.
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 achievement of Excellent and Outstanding BREEAM ratings.
Liam Elmore is northern regional sales manager with Hamworthy Heating.