Pure’s Environmental Credentials Update
14/08/09
When we designed Pure Offices, Swindon as a serviced office centre, one of our aims was to make the building as environmentally friendly as possible, within the limitations of a fairly standard steel framed/concrete floored/metal clad structure.
The scope to improve our environmental credentials therefore relied on the layout design of the building, how it was heated and cooled, and how the occupiers, our customers, could be persuaded to operate their individual offices.
We tried to take a pragmatic approach, and focus on how we could operate the building as efficiently as possible, whilst keeping the plant as simple as possible. The environmental impact of a building, once it has been built and commissioned, that is directly controllable by an owner/operator, is limited to the consumption of electricity, gas and water, and the production of waste.
Our innovative solution was to design a hybrid heating system powered by both a highly efficient Gas boiler, and an electrically driven Air Source Heat Pump (ASHP). In addition, all the individual offices have their own electricity meter, so occupiers are charged an economic rate for their power, which encourages them to conserve power.
The heating system is designed to run using the ASHP as its primary heat source, and only at times of extreme cold or demand does the Gas boiler kick in to supplement the ASHP. The idea behind the ASHP is that it uses one unit of electricity power to produce (under optimum conditions) 3 units of heat. This compares to a gas boiler that uses 1 unit of gas to produce 0.9 units of heat, again under optimal conditions.
So the theory sounded excellent. What have been the pitfalls? Well, we only opened Pure Offices Swindon in April 2009 and therefore have only experienced the ASHP for about two months including pre opening testing before the summer. We do know it works effectively at heating the radiators, and also that it is efficient. However, we have had difficulty balancing its use with the Gas boiler, and there is a slight conflict as the ASHP prefers to run constantly and build up heat slowly, whereas a multi-let office building has a varying demand for heat, and when it needs it, it needs it quickly.
Other issues we are faced with are the running costs. Whilst an ASHP is a relatively simple piece of equipment (a compressor and a heat exchanger) the costs of the electricity to create the heat is currently at least three times the cost per unit compared to gas. So whilst one unit of electricity produces three units of heat, its running costs are similar to gas. So there are no obvious running cost savings, just energy consumption. However, we knew that before we embarked on this project.
So our experience so far is that the system works effectively, it’s not as responsive as gas, and it won’t be any cheaper to run that a gas fired system. It also cost £20,000 more to install on top of the Gas system. On the plus side, it uses less energy, so produces less carbon, and by heating the Pure Office this way, the building earned a “B” Energy Performance Certificate, which is excellent for a building of this type.
We are persisting with this strategy at our next Pure Office development at Tachbrook Park, Leamington Spa, where we have installed a bigger ASHP than the Swindon model, which should be capable of providing all our heating requirement, even on the coldest days. We haven’t yet abandoned the trusty Gas boiler back up however.
Our other more standard building innovations are working well. Our occupiers are delighted with the small bills they are receiving for their power consumption, which vindicates our decision to meter the offices individually, and helps us minimise consumption.
We’ll update again once we get some reliable data and experience through the winter months, and see whether the ASHP/Gas hybrid is a viable solution moving forward.
Nick Smith
Pure Offices
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