Legislation


Tick the right SBEM box


Poor communication and confusing terminology are more than just inconveniences; they are a serious problem that often leads to inappropriate product choices and underperforming systems, says managing director of Lochinvar David Pepper


E


ngineers’ are often accused of having poor communication skills, and the profession is regularly lampooned for its love of technical detail and a tendency to over-complicate. Hence the old saying: “We are going metric…inch by inch.” However, when it comes to specifications, choosing the right terminology is a serious matter. Too often, the use of confusing terms has led to unnecessary and unexpected product and design changes and the incorrect application of building legislation. This can have long-term consequences: In a


recent study of 49 modern buildings, including supermarkets, offices, schools and health centres, Innovate UK found that modern non-domestic buildings “routinely” used 3.5 times the amount of energy they were designed to consume. It also revealed that carbon emissions were, on average, 3.8 times higher than predicted. When confronted with this ‘performance gap’, the industry tends to look at the individual technologies deployed and tries to analyse technical minutiae in a bid to establish where it is going wrong. However, in a very large number of cases, the underlying problem is actually quite simple and comes back to poor or missing communication.


Serious


Ambiguous terminology, which can create confusion at an early stage, leads on to much more serious problems further down the line. In the specific case of heating and hot water, honest attempts to comply with the Building Regulations are often thwarted. SBEM (Simplified Building Energy Model) is the most common software method used by system designers and specifiers to demonstrate compliance with the regulations, but experience shows that its terminology can be confusing and often throws specifications off course. For example, direct gas-fired water heaters have been widely used in the UK for more than 40 years and are well established as an efficient method of generating hot water for commercial and industrial buildings. They are often used to achieve the energy


22 October 2017


efficiency targets outlined in Part L of Building Regulations and would normally achieve a ‘pass’ for most projects when entered into SBEM. However, this is not inevitable because the performance data needs to be entered correctly, and that is not always as easy as it sounds. When it comes to generating hot water, there is often a grey area between what the software considers to be a boiler and what it defines as a water heater. As a result, many system designers have fallen into the trap of ticking the ‘dedicated boiler’ box instead of the ‘standalone water heater’ one. This sets them off on the wrong track and can effectively eliminate a particular type of water heater even though it could be the most appropriate selection. This is clearly an unintended consequence of the legislation. The SBEM process refers to a boiler providing hot water – it does not specify for what purpose. As a result, this leads many specifiers to select that category when beginning the process for working out the seasonal operating efficiency of a direct-fired water heater. By starting, effectively in the wrong place, they end up following a series of calculation steps that produce a completely erroneous result, which implies that the chosen product does not meet the requirements of the regulations even when it does. As a result, they assume they must only select indirect hot water production for their project when that might not be the most efficient or appropriate solution. Most engineers would probably define a gas-fired water heater as a “stand-alone water heater”, but there are a surprising number of people in our industry who refer to them as “boilers” for the purposes of calculation methodologies. Another menu option in the SBEM software refers


to boilers producing “dedicated hot water”. This refers to a boiler working in partnership with a separate indirect hot water cylinder, but many engineers take this to mean a direct-fired water heater. As a result, they end up answering questions


relating to indirect cylinders, rather than water heaters, and specifically about potential storage losses. There is a test methodology for calculating storage or standing losses in indirect water heaters,


David Pepper, Lochinvar MD


but the relevant measure for direct-fired water heaters is ‘Maintenance Consumption Value’, which is expressed in MJ/month. However, by selecting the wrong option in the first


place, the specifying engineer will end up with a calculation that, effectively, ‘fails’ the product for the application in hand.


Efficient


Ultimately, when the correct details are used, direct fired water heaters emerge as a good, energy- efficient choice for many projects, but if the incorrect details are entered because the wrong SBEM fields were selected, they frequently fail and are ruled out of the project.


This is not only deeply frustrating for manufacturers, who have gone to great lengths to ensure their products comply with the regulations, but should also be most alarming for engineers, and potentially their clients, who end up with a design they did not intend. Communication matters and using the right terminology can be crucial. While it is incumbent on the specifying engineer to make sure they are using the right words; it should also be part of the software provider’s role to ensure they do not add to the confusion by using inappropriate or, in some cases, out of date terminology. In fact, shouldn’t we go further and insist that any


such calculation methodology explicitly makes allowance for potential confusion by inserting clarifications and hints where the wording used to describe a technology could be ambiguous? In the case of SBEM, surely a ‘simplified’ model should make the process of selecting the correct solution as simple as possible.


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