Honesty is the best policy

The issue of misleading information provided by manufacturers to building services engineers is damaging, unethical, unfair and potentially expensive for end clients.

The industry has a patchy record in delivering buildings that meet their target performance goals. The CarbonBuzz benchmarking exercise supported by CIBSE and RIBA uncovered the hugely disappointing – but sadly not surprising – fact that many buildings use between 1.5 and 2.5 times the energy predicted during their design. This includes many new constructions supposedly built to modern energy efficiency standards.

As energy costs rise; this has serious implications for the long-term running costs faced by building owners and occupants. Designers are making mistakes; many of which are exacerbated by problems with the way contracts are structured and specialist trades are managed. However, manufacturers are also contributing to the problem. Many of those initial mistakes are the result of assumptions based on incomplete information, which means we have a duty to behave professionally and ethically.

Sadly, many product suppliers leave out crucial details about their product or seek to deliberately mislead the specifier in order to secure a sale. By doing so they are, effectively, asking the building services engineer to deliver improved system performance with one hand tied behind his or her back.

This is all too common in a range of product areas, but hot water radiant panels are a prime example. A new European standard for ceiling mounted radiant panels was introduced in 2003 to smooth out variations in the data quoted by rival manufacturers and to ensure the information provided to consulting engineers was reliable and consistent.

EN14037 (Parts 1, 2 and 3: 2003) sets out technical specifications and requirements; test methods for thermal output; and the rating method for calculating radiant thermal output of panels. The testing regime that underpins the standard provides a standard method to ensure that designers can rely on the test data for correct sizing of products.

The surface temperature and the emissivity of the panel surface are the critical factors in establishing the useful radiant heat output of the panel using water flow rate and temperature difference, but the upper insulation on a ceiling mounted radiant panel has a significant impact on the thermal performance.

Where a building has been designed to take advantage of the characteristics of radiant heating then the amount of heat emitted through convection from the upper surface or rear of the panel – due to inadequate insulation – must not exceed the anticipated proportion of the total heat output, particularly if heat is convected into a ceiling void.

Where radiant panels are installed below a ceiling it may be acceptable for the convective element to be more significant as this heat will still be entering the space; although this depends on there being mechanisms in place to ensure effective distribution.

To make it possible for specifiers to compare products on an equal basis, the EN 14037 standard clearly states that the upper insulation provided for testing output should be a “layer of 40mm mineral wool with vertical fibre, covered with aluminium foil delivering heat conductivity of 0.04 W/mK at 40°C and a density of 25kg/m³”.

It has become apparent that some manufacturers are providing test data derived in accordance with the standard, but then marketing a product which is very different to the tested design. Many supply the product with either no insulation on the upper surface or insulation with inferior insulation properties. This allows them to increase claims for total heat output, but at the expense of the radiant performance of the installed panel.
As well as misleading and confusing the design engineer, this also has significant commercial implications and creates an unfair competitive advantage for certain suppliers over those adhering closely to the requirements of the standard. A panel with no upper insulation could achieve a total heat output as much as 70 per cent higher than the EN14037 test, although the referred percentage of radiant output will be much lower.

Foil faced bubble wrap type insulation, is offered by some manufacturers and, while this type of insulation is effective in reducing the radiant heat from the upper surface of the panel, it has a ‘U’ value typically 10 per cent of that for the insulation specified for the EN14037 test, and considerably less mass. As a result, the panels supplied will perform very differently to those tested.

Responsible manufacturers are solidly behind efforts to ensure radiant panels are rated in accordance with a common standard. Product claims must match actual test standards otherwise how can a consulting engineer rely on the figures supplied to achieve the energy performance goals set out in their overall design?

It should be a source of considerable shame to our sector that many consultants take it for granted that they will receive incomplete or inaccurate data and just work around the problem. This wastes their valuable time and compromises their design calculations. Even more seriously, less experienced engineers often take the performance data at face value and make assumptions that will have significant running cost implications for the building occupant and manager.

Honesty is surely always the right policy. All manufacturers should aspire to being part of the solution to the ‘performance gap’ – not a major cause of the problem.

 

www.dunham-bush.com

 

Mike Holding is managing director of Dunham-Bush.