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FLY OUT OF THE WINDOW The solution: thermostatic radiator valves


n a recent pilot project to quantify the energy efficiency benefits of electronic thermostatic radiator valves in a large public sector office block, the data showed some unexpected results. The radiator valves were installed as part of a gas-fired heating and hot water system but in addition to an 8% reduction in gas use over a 12-month period, the building’s electricity usage also fell, by an unexpected 12%.


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Steven Henry, Managing Director of Chalmor discusses a retrofittable fix that solves temperature fluctuations in problem zones within commercial buildings.


The explanation? Greater consistency of temperature had resulted in fewer office workers plugging in electricity-guzzling temporary space heaters. It is just one example of why we need to take into account the human factor if we are to move to the next level of environmental performance. When we design HVAC systems we work through a series of calculations to ensure that comfort conditions are within the required band. In reality, however, building occupants will always take matters into their own hands if they become uncomfortably hot or feel chilly due to spikes or drops in room temperature. The fact that the figures look fine on paper is of little consequence to the teacher opening all the windows on a sunny winter day, or the office worker who plugs in the space heater on chilly autumn mornings.


When comfort conditions are affected, for example by unseasonably cold or warm weather, these occupant interventions can very quickly undermine the energy efficiency of the building. Unless we can account for these behavioural responses to local temperatures, the building will only ever be as energy efficient as its occupants will allow it to be.


Heart of the problem


The key is to use energy data analysis to understand what triggers occupant interventions such as opening windows and switching on space heaters, and to install local temperature control devices to adjust comfort conditions before these occupant interventions occur. Our research into this area has revealed that it is the response time, rather than a lack of control technology, which is at the heart of the problem. If the weather is unseasonably chilly, the occupant often plugs in the space heater long before the Building Management System (BMS) can ramp up temperature in the room. Similarly, on sunny winter days, someone opens a window before the BMS (or a traditional TRV) has a chance to reduce the radiator temperature. When a window is opened, the BMS (sensing the drop in temperature) may actually ramp heating up instead of down and, where air conditioning is installed, you can become locked in a vicious circle where both the heating and cooling devices are fighting to restore comfort conditions.


uFigure 1


Research carried out in conjunction with London South Bank University, however, indicates that there is a simple, retrofittable solution to this problem involving smart radiator


valves. Chalmor eTRV electronic thermostatic radiator valves were installed as part of the research to analyse their ability to sense and react to local temperature changes. As can be seen in Figure 1, the faster response times of smart radiator valves compared to traditional TRVs achieved greater consistency of temperature, evening out the peaks and troughs that trigger building occupants to adopt their own local heating or cooling solutions. In addition, a boost button on the valve provides room occupants with the opportunity to trigger one hour’s heating manually if the room should feel chilly, providing a more efficient alternative to portable electric heaters (which, once switched on, are frequently forgotten about and left on unnecessarily). In addition, the latest generation of smart radiator valves (for example Chalmor’s eTRV+) incorporate Open Window sensing capability. When someone opens a window, the sudden drop in room temperature is detected by the smart radiator valve. The valve reduces the radiator temperature, preventing heat being supplied to the room unnecessarily, and preventing energy wastage (see Figure 2).


Government office savings


In the example already mentioned, for the Department of Work and Pensions, the pilot project delivered carbon savings of 29%, exceeding the Greening Government target of a 25% reduction. The trial of electronic thermostatic radiator valves was one of a number of ‘spend to save’ energy conservation measures applied across the whole estate of 750+ office buildings over several years. The building chosen for the pilot project was a three storey office block with a Job Centre on the ground floor, which is generally operating five days/week from 8am to 5pm, with some staff present until 7pm. Chalmor eTRV+ electronic thermostatic radiator valves including PAIR (Passive Active Infra-Red) were installed in offices, meeting rooms and customer facing areas. Corridors were set to 18°C, offices to 21°C, with a one hour boost facility to 23°C. The PAIRs provide occupancy based control in offices and meeting rooms, with a setback to 16°C when not in use, rising to 21°C when occupied. After tracking energy usage over a 12-month period, an 8% reduction in gas use was identified (broadly in line with expectations), but electricity consumption had also fallen, by an unanticipated 12%. Analysis revealed that this was because staff were no longer using portable electric heaters to enhance individual local comfort, as peaks and troughs in room temperature had been evened out by the eTRVs. With electricity costing up to 4 times as much as gas, financial savings exceeded expectations by 18%, giving a financial payback period for the project of just over 2.5 years, versus 3 years expected in the business case.


A key benefit of approaching the problem from the ‘radiator end’ is that it avoids expensive and complex customisation of the BMS. In addition, this is a retrofittable “fix” which can be rolled out incrementally, if required, using maintenance budgets (where finance for capital projects is unavailable). In addition it can solve temperature fluctuations in problem zones across sites that are difficult or costly to address from a central control perspective. Far better than allowing building occupants to take matters into their own hands.


www.chalmor.co.uk 16 BUILDING SERVICES & ENVIRONMENTAL ENGINEER APRIL 2016 VISIT OUR WEBSITE: www.bsee.co.uk ‘ The key is to use


energy data analysis to understand what triggers occupant interventions such as opening windows and switching on space heaters, and to install local temperature control devices to adjust comfort conditions before these occupant interventions occur.





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