Saturday, 25 December 2010
7 More London is one of the UK's first speculative offices to achieve a top BREEAM rating at design stage.
There is a new landmark on the banks of London’s River Thames. Alongside Tower Bridge and across the river from the Tower of London is a new office building called, modestly, 7 More London. Despite its unassuming title this conventional-looking corporate building is significant because it is one of the first major speculative office schemes in the UK to have been awarded a BREEAM Outstanding rating at design stage. It is now working to the target of following up the interim rating with a full rating post-construction.
7 More London is the final and largest building to be constructed under the masterplan for the More London site. The 10 storey, 60 000 m2 building incorporates 48 000m2 of office space located above ground floor retail units. Construction of the building’s shell is complete; its glazed, symmetrical wings of offices open out to embrace the river revealing a hollow circular drum, housing the reception, at its core. Three curved bridges connect these two wings at levels two, five and eight, while at the rear the building’s southern elevation drops to seven storeys to respect the existing buildings along Tooley Street. Inside work is underway to fit out the offices ready for the building’s 6000 occupants, which will have moved in to their new home by May 2011.
The story of how 7 More London became one of the UK’s greenest office buildings started four years ago, when PricewaterhouseCoopers’ (PwC) decided to lease the ten storey office in order to consolidate its London operations. At the time, the building was still on the drawing board so it was regarded by PwC as having the potential to meet the firm’s sustainable vision. “We wanted this building to dispel some of the myths in the real estate world that occupiers are not interested in sustainable buildings, the so called ‘circle of blame’,” says Paul Harrington, real estate director at PwC. He says occupiers do want good sustainable buildings because “sustainability is good business practice”.
Sustainability was also seen as a differentiator between PwC and its competitors and Harrington was aware that most of the questions on the firm’s website relating to the move to new offices concerned what the organisation would be doing to enhance sustainability in its new offices. “The drive for sustainability was from the top down and the bottom up,” explains Harrington.
At the time PwC decided to lease the building it had a planning requirement to achieve a minimum environmental rating of BREEAM Very Good (2006). Accordingly, PwC pushed the developer and its design team along with PwC’s fit-out designer BDP to target the highest level of environmental performance attainable at that time, BREEAM Excellent (2006). As work on the building’s engineering design commenced, however, details began to emerge of an upgrade to BREEAM and the release of BREEAM Offices 2008. This was a major blow to PwC’s vision because the changes included the addition of a new elite rating of BREEAM Outstanding to the classification system. The result of which was that as it stood, PwC’s new building would no longer be the sustainable differentiator it wanted.
PwC upped the ante and set a target for the building to achieve BREEAM Outstanding (2008), under the revised criteria. “This is a building for the future and a building that will last us for the next 20 years so it would seem crazy not to go for the ultimate category,” says Harrington. To achieve this rating the design would have to achieve a minimum of 85 out of a possible 100 environmental points. This was uncharted territory.
To stand any chance of getting close to the threshold of 85 points, collaboration between the developer’s and tenant’s design teams was essential so that tenants and developers design teams grasp every opportunity to tease every last credit out of the scheme. “It was important that both project teams were involved, without this joint effort we would never achieve what we wanted,” Harrington says.
· A high performance building envelope, based on an argon-filled, low transmission glazing system fitted with extensive shading to minimise solar heat gains.
· A biofuel based tri-generation system to generate heat, power and cooling using absorption chillers (CCHP). The specification of the CHP engines was enhanced to enable them to run on any biofuel including used cooking oil. The system incorporated two engines each capable of developing 385kW of electricity along with 400 kW of heating and 416 kW of cooling.
· Plate heat exchangers were added to CCHP to units to increase the use of waste heat and extend the CCHP unit’s run time to enable it to provide up to 25% of the buildings total electricity demand.
· Also included in Roger Preston’s base-build design was a solar thermal hot water supply to the core’s toilet pods and a heat recovery ventilation system.
· To squeeze every extra credit out of the design a regenerative braking system was incorporated into the building’s 16 lifts.
· PwC were helped in their task of grabbing BREEAM points by the building’s structural designers Arup, who succeeded in using 80 per cent recycled aggregate for the first time in the building’s concrete structure; an achievement which merited the award of the first ever BREEAM point for innovation.
On the office floors, the enhancements to BDP’s design to achieve BREEAM Outstanding saw:
· The office fan-coil units replaced by active chilled beams. The amount of fresh air supplied to these units is minimised by linking it to CO2 concentration in the offices.
· The building’s electric perimeter heating was replaced by low-grade hot water heating system fed from heat recovery units added to the building’s roof-mounted chillers. The units supply low grade hot water at 45°C but the addition of the heat recovery system also improved chillers’ efficiency by 35 per cent and earned the design team another BREEAM point for innovation.
· In addition, a sophisticated control system was also developed with extensive sub metering to monitor cooling, heating, power and lighting loads on a zone by zone basis.
· The offices are also being fitted with an ultra efficient, high frequency, fully-programmable low-energy lighting system which is daylight-linked. The system is IP addressable which will allow it to be controlled by the building’s occupants via their PCs, within strict boundary conditions, and will incorporate time clock control and presence detection for out of hours working.
· In hospitality areas, restaurant, cafes and corridors BDP has opted for high efficiency LEDs to help reduce maintenance and save energy
“We’ve looked sensibly at what we’ve invested in,” says Harrington. As a result there were some technologies PwC did not utilise because their payback would have been over 50 years. “Some technologies have a payback of up to 15 years, but that still makes good business sense on the basis of a 20 year lease,” explains Harrington. “You have to talk commercially about sustainability; the days of windmills on roofs are gone, we now need to deliver things that are practical and cost effective,” he says.
The building has even been future-proofed to allow further environmental enhancements when these become cost effective. This includes strengthening the building’s structure in key areas to enable rainwater storage tanks to be installed in the future. There is also provision for the future installation of a solar electric array on the building’s roof – should it become cost effective for PwC to do so.
The good news for the design team was that the building succeeded in achieving a BREEAM Outstanding rating based on its design. It was also awarded an EPC A rating. According to Runicles the building will achieve “a 70% improvement in CO2 emissions over current (2006) Building Regulations Part L2.
“When we set out we wanted to demonstrate that BREEAM Outstanding could be achieved at a sensible price,” says Harrington. The good news for PwC is that the estimated cost increase of taking the building from BREEAM Excellent to BREEAM Outstanding was minimal. “We estimate it cost at £2.25 per square foot on the base price to achieve BREEAM Outstanding, which proves that good sustainable buildings need not cost that much more money if they are properly planned and specified,” he says.
Having achieved BREEAM Outstanding for the design, the next challenge is to ensure construction waste targets are met and the scheme gets an Outstanding rating under the BREEAM post-construction review. “We’re not being complacent, we’re working hard with the contractors to ensure that they meet these very challenging targets,” says BDP’s Runicles.
The design team scored 8 out of a possible maximum of 10 innovation credits to achieve BREEAM Outstanding including:
- The building becomes a learning resource by displaying environmental performance data to staff and visitors
- 80 per cent recycled aggregate used in the building’s concrete
- Exemplar performance under the Considerate Constructors Scheme
- Recovering heat from the chillers that would normally be rejected to atmosphere and using this heat in the perimeter heating system
- Water sub-metering
- Involvement of expert accredited professional BREEAM advice from pre-stage C (2 credits)
- Use of multi-fuel CHP engines
Project Team Box: Shell and Core
Client: More London Developments
Architect: Foster + Partners
M&E consultant: Roger Preston & Partners
Structural engineer: Arup
Construction manager: Mace
Project team box: Tenant fit out
M&E and interior design: BDP
Project and cost management: Turner & Townsend
Fit out contractor: Overbury
Friday, 24 December 2010
1.1 Importance of Building Energy Efficiency
- Buildings are significant users of energy and building energy efficiency is a high priority in many countries.
- Efficient use of energy is important since global energy resources is finite and power generation using fossil fuels (such as coal and oil) has adverse environmental effects.
- The potential for energy savings in the building sector is large.
- Energy efficient building design is location-dependent. The local climate must be considered when selecting appropriate design strategies.
- A cooling-dominated climate is assumed here. However, some of the general principles are also applicable to other climate types.
2. BASIC PRINCIPLES
2.1 Climate and Site
- Climate has a major effect on building performance and energy consumption. Energy-conscious design requires an understanding of the climate.
- Buildings will respond to the natural climatic environment in two ways:
- Thermal response of the building structure (heat transfer and thermal storage).
- Response of the building systems (such as HVAC and lighting systems).
- To gain the maximum benefits from the local climate, building design must "fit" its particular climate.
- When faced with unfavourable climatic conditions, optimal siting and site design may solve all or part of the problems. Site elements to be considered include:
- Topography - slopes, valleys, hills and their surface conditions.
- Vegetation - plant types, mass, texture.
- Built forms - surrounding buildings and structures.
- Water - cooling effects, ground water, acquifiers.
- The six important aspects of architectural planning which will affect thermal and energy performance of buildings are:
- Site selection
- Mutual relationship
- Architectural and landscape designs should be closely integrated. If possible, should provide wind breaks in cold winter and access to cooling breezes in summer.
2.2 Building Envelope
- Elements of the building envelope (= "protective skin"):
- Walls (exterior)
- Underground slab and foundation
- Three factors determining the heat flow across the building envelope:
- Temperature differential
- Area of the building exposed
- Heat transmission value of the exposed area
- The use of suitable thermal mass and thermal insulation is important for controlling the heat flow. Remember, the envelope components will respond "dynamically" to changing ambient conditions.
- Some people also consider the "embodied energy" (include energy for producing and transporting) of building materials when making the selection.
2.3 Building Systems
- Heating, ventilation and air-conditioning (HVAC) systems are installed to provide for occupant comfort, health and safety. They are usually the key energy users and their design is affected by architecture features and occupant needs.
- While being energy efficient, HVAC systems should have a degree of flexibility to allow for future extensions and change.
- To achieve optimum energy efficiency, designers should evaluate:
- Thermal comfort criteria
- Load calculation methods
- System characteristics
- Equipment and plant operation (part-load)
- Lighting systems is another key energy user and additional cooling energy will be required to remove the heat generated by luminaires.
- Energy efficient lighting should ensure that:
- Illumination is not excessive.
- Switching is provided to turn off unnecessary light.
- Illumination is provided in an efficient manner.
- General design strategies for lighting design:
- Combination of general and task lighting.
- Electric lighting integrated with daylight.
- The use of energy efficient lamps and luminaires.
- Use light-coloured room surfaces.
- Other building services systems consuming energy include:
- Electrical installations
- Lifts and escalators
- Water supply systems
- Town gas supply system
3.1 Passive Cooling and Sun Control
- Passive systems - internal conditions are modified as a result of the behaviour of the building form and fabric.
- General strategies for passive heating and cooling:
- Cold winters - maximise solar gain and reduce heat loss.
- Hot summers - minimise solar gain and maximise heat removal.
- Correct orientation and use of windows.
- Appropriate amounts of thermal mass and insulation.
- Provision for ventilation (natural).
- Strategies for shading and sun control:
- External projection (overhangs and side fins).
- External systems integral with the window frame or attached to the building face, such as lourves and screens.
- Specially treated window glass, such as heat absorbing and reflecting glass.
- Internal treatments either opaque or semi-opaque, such as curtains and blinds.
- For hot and humid climate like Hong Kong, extensive shading without affecting ventilation is usually required all year round. Shading of the east and west facades is more important.
- Daylight can be used to augment or replace electric lighting. Efficient daylighting design should consider:
- Sky conditions
- Site environment
- Building space and form
- Glazing systems
- Artificial lighting systems
- Air-conditioning systems
- The complex interaction between daylight, electric lights and HVAC should be studied carefully in order to achieve a desirable solution.
Figure 3 - Daylighting design in an atrium
- Advanced window technologies have been developed to change/switch the optical properties of window glass so as to control the amount of daylight. There are also innovative daylighting technologies now being investigated:
- Light pipe systems
- Light shelves
- Mirror systems
- Prismatic glazing
- Holographic diffracting systems
3.3 HVAC Systems
- Energy efficiency of many HVAC sub-systems and equipment has been improved gradually over the years, such as in air systems, water systems, central cooling and heating plants.
- Energy efficient HVAC design now being used or studied include:
- Variable air volume (VAV) systems to reduce fan energy use.
- Outside air control by temperature/enthalpy level.
- Heat pump and heat recovery systems
- Building energy management and control systems.
- Natural ventilation and natural cooling strategies.
- Thermal storage systems (such as ice thermal storage) are also being studied to achieve energy cost saving. Although in principle they will not increase energy efficiency, they are useful for demand-side management.
3.4 Active Solar and Photovoltaics
- Solar thermal systems (active solar) provide useful heat at a low temperature. This technology is mature and can be applied to hot water, space heating, swimming pool heating and space absorption cooling.
- The system consists of solar collectors, a heat storage tank and water distribution mains. An integrated collector storage system has also been developed recently to eliminate the need for a separate storage tank.
Figure 5 - Schematic of a typical solar hot water system
- Photovoltaic (PV) systems convert sunlight into electricity using a semi-conductor device. The main advantages of PV systems include:
- Reasonable conversion efficiencies (6-18%).
- PV modules can be efficiently integrated in buildings, minimising visual intrusion.
- Their modularity and static character.
- High reliability and long lifetime.
- Low maintenance cost.
- In practice, PV technology can be used for central generation or building-integrated systems (BIPV). The systems can be of the standalone type, hybrid type or grid-connected type. Although the cost of PV is still high at present, it may become cost-effective in the hear future.
Figure 6 - Grid-connected solar photovoltaic system
4. Evaluation Methods
4.1 Bioclimatic Design
- The integration of design, climate and human comfort -- the bioclimatic approach to architectural regionalism -- was first proposed in mide-1950s by Victor and Aladar Olgyay.
- Their intention was to highlight the belief that architectural design should begin with understanding of the physiological needs of human comfort and take advantage of local climatic elements to optimise these requirements naturally and efficiently.
- Building design itself is conceived as a natural energy systems that restores environmental quality to its site.
- The aim is to creat a supportive and productive environment that ultimately can contribute to sustaining the regional and global environment.
4.2 Building Thermal and Energy Simulation
- Nowadays, building energy design often require the analytical power to study complicated design scenerio. Computer-based building energy simulation will provide this power and allow greater flexibility in design evaluation.
- The simulation method is based upon load and energy calculations in HVAC design. The purpose is to study and determine the energy characteristics of buildings and their building systems.
- The cost effectiveness of any energy conservation measures will be a compromise between initial, maintenance and energy costs. Simulation techniques can provide the tools for assessing different design options based on their energy performance and life cycle costs.
4.3 Building Energy Audits
- Building energy auditing can be defined as "measuring and recording actual energy consumption, at site, of a completed and occupied building (expressed in units of energy, not monetary value); fundamentally for the purposes of reducing and minimising energy usage".
- Energy audits identify areas where energy is being used efficiently or is being wasted, and spotlight areas with the largest potential for energy saving. They are useful for establishing consumption patterns, understanding how the building consumes energy, how the system elements interrelate and how the external environment affects the building.
- There are different approaches to conducting a full building energy audit, but the following stages are often adopted:
- Stage 1 - An audit of historical data
- Stage 2 - Survey
- Stage 3 - Detailed investigation and analysis
- A proper energy audit is useful for more than energy conservation goals. Energy audits can be employed to assist in areas such as:
- Establishment of data bank and consumption records.
- Estimating of energy costs.
- Determining of consumption patterns and utility rates.
- Establishment of an operational overview.
- Building energy design challenges building designers to think about climate, orientation, daylighting, and the qualities of environment as part of the initial design conception.
- It also requires the architectural and engineering disciplines to work as a team early in the design phase and to conceptualise the building as a system.
- Architects and engineers who incorporate energy design concepts and methods into their design projects can play a significant role in reducing energy consumption and achieving sustainable energy structure for our society.
A group of researchers at UC Santa Barbara is looking to play a major part in that reduction. Professors Bud Homsy, Igor Mezic, Jeff Moehlis, João Hespanha, and Rich Wolski are leading research efforts into integrated building design, in which active control of indoor airflows could greatly improve the ventilation and efficiency of heating and cooling in buildings.
Current technologies—existing hardware combined with energy-efficiency modeling tools and algorithms, such as the Department of Energy’s “EnergyPlus”—offer energy savings of 10% to 30% when applied to the retrofit of extant buildings and the design of new ones. Far greater savings can be achieved, however, with modern analysis and control tools based on dynamical systems and control theory, when these tools are used to optimize the performance of the building as a fully integrated system.
Large buildings equipped with heating, ventilation and air conditioning (HVAC), data centers, and a myriad of sensors and wireless communication devices are complex systems whose operation includes multi-physics and multi-scale effects. Building systems are dynamically uncertain with respect to both the energy load and the environment, with dramatic changes in the number of occupants in the building, their energy demand, and ambient weather conditions.
A smart building containing an array of sensors and an integrated, optimized control system could dynamically adjust lighting and HVAC flows based on actual, real-time presence rather than scheduled occupancy. Energy and money are not wasted on cooling and lighting empty rooms. Mixing of airflows is a particularly important topic for energy efficiency in buildings, since good mixing avoids the wasteful temperature stratification which occurs, for example, when hot air rises to the ceiling and cold air falls to the floor.
Recent research in Mezic’s laboratory has established modeling techniques that enable design of efficient mixing in a variety of ambient conditions—the airflow can be directed to cool or heat the occupants much more efficiently. By combining sensor networks, active ventilation, adjustable lighting, and adjustable windows and doors into integrated and optimized compound systems, much higher quality living and working environments are possible, with 50% greater energy efficiency than current systems offer.
Data centers are an important, special case, whether as occupants of dedicated areas in general-use buildings or as single-purpose data center buildings. In data centers, there are few people but large heat loads from high power-density server arrays. Data center growth is causing the energy density of buildings to grow at a rate that is expected to be proportional to internet and server demand—and that demand is expected to double in the next few years.
Efficient energy use in data centers, far more than in typical office spaces and commercial buildings, requires especially efficient ways of redistributing cooling energy. Data centers present special and unique challenges, due to the coupling between the computer use and cooling systems. Mezic and Rich Wolski are spearheading an effort by faculty in UCSB’s Mechanical Engineering and Computer Science departments, developing new approaches and solutions for this special class of buildings.