Hotels are coming under increasing pressure to comply with energy requirements. Colin Hobart, director of RHWL Architects, explains

Hotel operators are usually aware of the energy implications of their properties. Many of them have policies set out in development manuals that are issued to developers for constructing the base buildings. However, the new Part L will require higher standards than operators demand at the moment and the concept of a carbon footprint will be new to many. The new process and cost implications will undoubtedly cause issues for some, but there are some who are taking a positive and aggressive line.

Energy-saving strategies

The first step to improving the carbon emissions of any building is to reduce the energy demands by making passive improvements to the building, then look at the services design and provision of renewable energy if necessary. RHWL Architects considers passive methods initially then liaises with the engineering specialists to develop an integrated strategy. These strategies are used to consider potential solutions, such as:

  • Building orientation and layout (ideally using an east–west axis) to optimise solar gain and daylighting, with suitable positioning of occupied spaces. In practice, this is difficult to achieve on many urban sites.
  • Glazing specification and particularly solar shading to minimise solar gain and reduce overheating and cooling requirements.
  • U-values optimised through the new Part L SBEM process, which leads to compliant specification, design and selection of materials.
  • Air permeability of the building fabric, which now has to be designed and specified.
  • Enhanced building services controls to efficiently control boilers, chillers, pumps and fans. For example, pumps and fans could be linked to a BMS, which in turn would monitor all major plant for possible energy wastage while ensuring environmental conditions were maintained.
  • Natural ventilation, which is increasingly relevant for public and circulation spaces as it can negate the requirement for fans and plant. It is also possible to make use of the free night cooling from outside air.
  • Laundry drying space – in hotels this can add significantly to the carbon emissions associated with washing machines and electrical drying equipment. Ideally the use of natural drying space could reduce electrical demand but this is difficult to achieve.
  • Incorporating vertically balanced boiler flue and natural ventilation system, despite its space requirements. This has no power requirements, unlike a flue dilution system.
  • High efficiency lighting, which significantly reduces power consumption and prolongs lamp life. The typical interior design, tungsten halogen spots are being replaced.
  • Enhanced lighting controls, with presence detectors, daylight detectors, more time clocks and infra-red controls, which all assist the reduction of power. RHWL is having to learn to light spaces in different ways. There will be quite an impact on public spaces, particularly at the luxury end of the market.
  • Power factor correction equipment connected to the main switch panel attracts a significant benefit from Part L.
  • Energy efficient lifts systems such as Kone EcoDisc type system, which use the energy required to power a motor in a much more efficient way. However, this is not considered in the new regulations.
  • Key card power off systems, which are operated by the hotel guests entrance card, are a major factor in hotels. Part L SBEM does not seem to explain how allowance may be made for this.
  • Reduction of hot water usage – a problem area in hotels. Guests like powerful showers but they use as much as a bath. Hoteliers are going to have to compromise here.

Renewable energy technologies

Having thus reduced the energy demands of the building as much as possible through the implementation of the above passive methods, the next step is to deliver the remaining power requirements in an ecologically sound, efficient and practical manner. Where the planning consent requires, this can be done through the use of low- to zero-carbon-emitting technologies as follows:

  • Wind power can be utilised in suitable locations to harness wind energy as an effective source of renewable electricity generation, but there are problems on high rise buildings and dense sites.
  • Photovoltaic technology is technically easy to use but is expensive for little return. It also affects the facade greatly if large areas are to be incorporated.
  • Biomass boilers are a straightforward solution but have space requirements. They burn wood chip, or wood pellets for best efficiency. This needs a large probably underground fuel bunker and lorry access, which is a major problem as hotel ground floor space is at a premium.
  • Ground source heat pump and cooling systems transfer heat from the sub-strata to either provide space heating or, in some cases pre-heating domestic hot water and swimming pools. For every unit of electricity used to pump the heat, 3-4 units of heat are produced generally, and the reverse process can be applied to generate chilled water, or combined for both heating and cooling. This looks like a winner, but the geology has to be right.
  • Solar water heaters are arrays of evacuated toughened glass or Pyrex tubes that are used to absorb solar energy and directly heat up water, which is of a low grade and thus normally used to pre-heat stored water for domestic use and swimming pools. Again this is a realistic technology for hotels with their high domestic hot water demand.
  • Another good option for hotels is trigeneration – an on-site CHP plant with an electricity generator heating and cooling capability. This can use typically 35% less primary energy than tradition generation because of the waste heat not being dumped and the reduced transmission losses. Hotels have a constant electrical load and a significant hot water heating load, so this looks a promising option.
  • Bio-gas has been discussed but doesn’t seem viable.
  • Hydrogen fuel cells such as CHP can produce electricity and heat for local use by using chemicals via a catalyst, rather than combustion. Again they seem to be a future rather than current development.