Part L changes for DHW are not that big a deal

DHW, water services, Lochinvar, Part L
The limitations of legislation — David Pepper.

David Pepper welcomes the flexibility and practicality of the proposed changes to Part L of the Building Regulations, but questions their significance for producing domestic hot water.

It might seem a strange thing to say at the start of an article about Building Regulations, but there is rather too much weight put on legislation in our industry. You might get the impression from much of what you read that complying with legislation is the key market driver and an obsession for building clients. Nothing could be further from the truth.

Part L is definitely influential, and the European Performance of Buildings Directive (EPBD) has set a useful context for the technical developments in energy efficiency. However, clients are increasingly interested in achieving performance far above the ‘lowest common denominator’ benchmark set by legislation and ‘tick-box’ assessment schemes.

The changes proposed for Part L this year — and it is important to note that these are still just proposals and, in any case, will not come into force until October — do show an admirable understanding that legislation for energy efficiency should be ‘light touch’. To achieve the most energy-efficient solution, engineers need flexibility. This is not a one-size-fits-all industry, and overly prescriptive legislation is not appropriate.

Instead of going for a blanket energy-efficiency target for all buildings, legislators have allowed breathing space for those harder-to-treat places by setting a lower limit of an 11% improvement on 2010 levels, rising to 20% for those better built structures where higher efficiencies are achievable cost-effectively.

In the water-heating sector, legislators have resisted the temptation to slap a ‘condensing-only’ requirement on everyone by allowing engineers to design the most appropriate and cost-optimal solution for systems under 40 kW capacity.

All water-heater manufacturers have developed condensing technology, but it is a sensible move to allow some flexibility in the regulations so that non-condensing systems can be used where they are the right engineering solution. It can be difficult to get appliances to condense in some retrofit applications without making costly changes to the system, and the regulators have acknowledged this fact.

The initial proposals did include a condensing requirement on gas-fired water heaters for new buildings, but the ICOM Energy Association was able to point out that the application of condensing technology in lower output (up to 40 kW) water heaters is difficult to achieve without a substantial increase in cost.

One likely outcome of such a requirement would be the specification of gas boilers and indirect cylinders, in place of high-efficiency direct gas-fired water heaters, despite the lower operating efficiency of indirect systems due to their transmission losses.

Condensing boilers being used to provide hot water via indirect cylinders also will not operate at their best efficiency because condensing only occurs at return temperatures of 57°C or below, and there is usually a requirement to store hot water at 60°C or above to reduce the risk of legionella.

The likely higher cost of applying condensing technology to low-output water heaters could, therefore, produce the unintended consequence of encouraging end users to favour lower-cost, but less-efficient, solutions. It is understood that ICOM’s recommendations have been received and understood, so the revisions may stipulate condensing-only water heaters for new build — but only on products rated at 40 kW or above.

DHW, water services, Lochinvar, Part L
Condensing Technology is difficult to achieve without a substantial increase in cost for applications up to 40 kW.

This also reinforces the point that customer choice is the most important market driver, not legislation, making it vital that legislation is not so strict that choice is strangled. It is not healthy to have engineers designing just to meet legislation — they need to have the flexibility to select the technical option that will give the best energy performance for the project in hand. The proposed changes to Part L could well achieve this healthy balance.

Gas-fired technology has become more and more energy efficient in the past 20 years and is perfectly able to deliver much of the energy efficiency improvements the legislators are looking for. However, renewables will be needed to achieve the 20% target on higher-spec properties, but again the likely changes reflect the sensible approach that renewables are only used where appropriate and cost-effective.

The Government remains committed to its low- and zero-carbon pathway for buildings — with zero-carbon new buildings to be achieved by 2019. But the likely changes to Part L suggest it now realises there are several routes to that goal and that engineers can be trusted to make good choices.

Young engineers, in particular, seem to recognise the limitations of legislation and that good engineering is the real key to sustainable buildings.

‘I have a real problem with people saying the Government should do this and should do that. The Government can’t install anything,’ said former CIBSE ASHRAE Graduate of the Year Angela Malynn. ‘We are engineers, and it is up to us to show them the answers and demonstrate how to deliver sustainable buildings.’

This is a refreshing outlook that puts the whole role of legislation into perspective. Part L is influential and deserves to be better enforced by local authorities, but at the end of the day it is just a basic benchmark and should not be the basis for an engineering philosophy.

The proposed changes to Part L are to be welcomed if they turn out to be as flexible as they appear, but in any case, they are just a starting point.

David Pepper is managing director of Lochinvar.

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