OPINION


Sound physics I could not agree more with John Harrington-Lynn that the CIBSE Admittance Method is based on sound physics (‘Admittance method provides accurate load methods’, Letters, August 2012, CIBSE Journal). The simplifi cation lies in the use of the fundamental frequency of a harmonic series. This simplifi cation allows for total transparency so providing a methodology that enables a good understanding of the thermal response of spaces within buildings. For these reasons I included


the complete algorithm describing the admittance method in the 2006 revision of Guide A. The algorithm, upon which the PDA is based continues in later revisions. That algorithm suffers in that only a constant ventilation rate is allowed. The introduction of variable ventilation is not well handled by a manual method (which was the original intention for the admittance method) although John has shown that it was possible if certain assumptions were made. A new variable ventilation algorithm that uses an hour-by-hour solution has been added to the PDA and is now under test. I believe that the widespread


the function of a technician and not a chartered engineer. Michael Holmes Consultant, Arup


First day at work for a building services graduate in the South?


Off the salary scale I have to say that I was surprised to read that building services graduates earn an average of £34,000 a year, or am I just living in another world ‘up North’ (£10 to save the world, August 2012, CIBSE Journal)? Current graduate salaries for sustainable/ built environment/engineers in this region seems to be in the low £20,000s, depending on the company and the graduate, assuming that they’re lucky enough to actually fi nd a job in today’s climate. Can I assume that this was a reference to the assumed earning potential several years in the future? Without


contributing to a political debate about the right or wrong of student fees, I agree with the


thrust of the article that monthly repayments of student loans do appear to be low in relation to salary levels when repayment is required and shouldn’t put anyone off going to university. Shona Williams, senior consultant CO2Sense CIC


use of black box tools (detailed thermal models) makes simplifi ed methodologies that are based on sound physics essential, as they may be the only way that people can obtain an appreciation of how spaces work. It may be necessary to use black box tools for compliance and detailed performance prediction; however, without understanding the physics that might be seen to be


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MANUFACTURER’S VIEWPOINT


The fl atlining UK economy needs defi brillating, and green investment could give it the necessary jump start, says Martin Fahey of Mitsubushi Electric


There is a lot of talk at the moment relating to the economy and whether plan A is working or whether we need to fi nd a plan ‘B’.


How about adopting plan ‘G’ – the green agenda?


Part of the government’s argument against a so-called plan ‘B’ is that, while it may lead to some stimulus for the economy, we would have to fi nance this by increasing national debt in the short-term. Yet the green agenda does seem to promise both immediate and long-term benefi ts for both the country and individual businesses and consumers, once we’ve got over the initial expenditure needed. When budgets are as tight as they are at the moment, it is natural to focus on what are perceived to be the ‘essentials’ and for many businesses, that means balancing expenditure and cash fl ow with salaries, while trying to simultaneously protect existing markets and grow new business. Yet a quick examination of almost anyone’s energy costs will show that they have risen year on year, and we know that most of our buildings are underperforming in terms of effi ciency. So fi nding ways to improve in this area would seem to offer real, tangible fi nancial benefi ts for both the individual energy consumers and the nation – in terms of helping reduce emissions.


News reports also talk of businesses sitting on capital, waiting for the economy to pick up. Surely a better use of any spare


fi nances would be expenditure that will offer a much better return on investment than any ISA or bank rate. One that will reap both short- term and long-term gain in terms of reduced energy bills month-on- month.


I would suggest that a lot of businesses, like a lot of households, only think of their


September 2012 CIBSE Journal 17


expenditure on energy costs when fuel prices increase. However, technology already exists that can reduce expenditure and it needn’t cost the earth in terms of up-front costs. For a typical offi ce, introducing a better control system wouldn’t break the bank but could pay for itself in the short-to-medium term. And replacing that 10-year-old air conditioning unit or boiler will rapidly repay the investment in terms of both lower monthly bills and a better performing system. There is even technology that will provide both air conditioning and hot water now utilising advanced, inverter-driven heat pumps. There are government incentives in the form of the Enhanced Capital Allowance Scheme, which allows companies to offset expenditure on new equipment against their annual tax bill. You will note that I have avoided any discussion on whether this government is for or against the green agenda.


That’s far too big a discussion for a simple column, but while we are all waiting for our politicians to decide the most economic and effi cient way to run the country, shouldn’t we all just get on with it and fi nd the best ways to run our buildings more effi ciently? Time for plan green!


Martin Fahey is sustainable solutions manager at Mitsubishi Electric. Join the debate by visiting the Green Gateway LinkedIn group, or following Martin’s Twitter account (@green_gateway) which offers followers a chance to receive up-to- the-minute news and views from those within and outside the industry, including key opinion leaders.


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