Fresh challenges for heating and hot water

Baxi Commercial Division, LZC, low carbon, renewable energy, boiler, space heating, DHW
Specifying in the future — Jeff House.

Revisions to Part L of the Building Regulations are set to take effect in April 2014. Tighter compliance targets and a gradual shift towards 2019 ‘nearly zero energy’ buildings will affect the specification of heating and hot-water systems, says Jeff House of Baxi Commercial Division.

Dealing with Part L (Conservation of fuel and power) of the Building Regulations, a critical piece of legislation, is perhaps the main policy driver affecting our sector. Indeed, set against a background of rising energy prices, media debate over energy production and an EU-wide policy mix designed to minimise CO2 emissions, the revisions to Part L could not be more topical.

The recast EU Energy Performance of Buildings Directive sets a number of new and revised requirements across all member states, many of which are transposed into UK legislation through Part L, hence the need for a revision this year.

Part L 2013 has, sensibly, taken a more flexible approach than previous versions to make it easier for the building-services industry to deliver a broad programme of low energy buildings. It has set a range of target improvements of 9% compared with the 2010 version of Part L for new non-domestic buildings, depending on the type of structure being constructed. The Government hopes this will make it easier for design engineers to produce solutions across a wider range of buildings and, therefore, deliver an overall improvement of 15 to 18% for new build.

Minimum ‘backstop’ values covering building fabric and services are still in place in the main documents, together with the Non-Domestic Building Services Compliance Guide, but have been altered in some instances from those used in Part L 2010. However, flexibility and reduction of demand are the overarching watch points.

For example, condensing heating appliances will be required in most instances, but in the retrofit commercial water-heating sector there is some room for manoeuvre. Replacing a non-condensing heater with a condensing equivalent can prove problematic dependent upon the installed flue-system arrangement and access to drainage for condensate disposal. Design engineers have, therefore, been given some leeway in this area to keep costs realistic, with non-condensing systems — still of sufficiently high energy performance — permitted to ensure low-energy improvements are made.

In general terms, design teams are encouraged to adopt a ‘fabric-first’ approach to new buildings, thereby reducing the requirement for heating and cooling and easing compliance with new target emission rating requirements. Even so, we are still many years away from completely passive buildings being a viable and sensible option.

Baxi Commercial Division, LZC, low carbon, renewable energy, boiler, space heating, DHW
The role of renewable energy to reduce carbon emissions needs balanced consideration.

From a pragmatic viewpoint it is still anticipated that heating and hot water will represent the predominant use of regulated energy in most building types, and a greater proportion of this energy will need to come from a low carbon or renewable source. This is where considered and correct application of low-to-zero carbon (LZC) technology is absolutely critical to achieve a positive outcome for the client.

Simplified Building Energy Model (SBEM) software is typically used to demonstrate compliance with Part L building emission targets and, again, a revised version will be made available to coincide with 2013 standards.

Given that there will be a greater demand for LZC to meet compliance, a sensible and considered approach will be critical; this is where joined-up thinking between SBEM assessors and mechanical design engineers is an absolute necessity. When it comes to correct application of LZC in a heating or hot water system, it is utterly essential to appreciate that SBEM is a compliance tool and not a design tool. Far too often we see the specification of LZC technology being driven by SBEM compliance. At its worst, SBEM is simply a box-ticking exercise to reach the desired compliance figure, which can lead to massively inappropriate specification requests, unless the implications are understood.

For example, we often see specifications for solar-thermal systems with huge arrays of collectors, yet only a moderate demand for hot water within the building, or CHP plant sized to cover way more than the building base thermal load. Clearly both are inappropriate solutions, yet when queried, the inevitable response is, ‘We need this for the building to pass planning.’ In extreme cases, mismatching of LZC technology and building loads can lead to a huge performance gap between SBEM estimates and actual in-use data.

Holistic design is the key to hit compliance targets, deliver a finished asset which will perform in the long term and represent a good investment in terms of whole-life costs. The specification of LZC to hit compliance targets, without due consideration of the application, has to end or the reputation of the technologies involved will be damaged irreparably.

Jeff House is marketing and applications manager for Baxi Commercial Division.

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