Initial situation:   The existing five-story building in Woking, England was constructed in the 1980´s and was not energy efficient with very high operational costs.  It is located in central Woking, which is a built-up urban area with good access to all necessary amenities and services.

Description:  The refurbishment of the Hollywood House has created an energy efficient office space that now uses less than half the energy prior to the project.  Skanska UK's Rashleigh Weatherfoil divisional head office occupies two floors of the building for a total of  1,574 m2 of office space.

A photovoltaic (PV) array, solar domestic water heating system and heat pump were installed to generate renewable energy on site. The building was also fitted with sophisticated energy monitoring and control systems, and was connected to the local energy center, which provides renewable and low-carbon electricity and district heating. The project incorporated environmentally responsible materials, efficient waste management and the offices are equipped with comprehensive waste management recycling facilities. A rainwater harvesting system and water efficient fixtures were installed as part of the refurbishment. The project has also created healthier working environments, promoted more sustainable modes of transport and contributed toward sustainable urban development by reusing an existing building.  By reusing the existing building this has significantly extended its useful lifespan by modernizing and improving its resource efficiency.

Materials recycling and specification of green materials. 

Environmentally responsible materials

During the procurement stage, the project team prioritized products and solutions that contributed toward sustainability. For example, packaging was minimized or reused, such as light fittings being delivered in returnable packaging crates. Products were also prioritized with low embodied energy and high-recycled content, such as carpets, ceiling tiles and kitchen fittings that were made from bamboo. All adhesives, sealants, paints, coatings and carpets were low-VOC (Volatile Organic Compound) or non-toxic.

Regional construction materials

Construction materials that were sourced from the surrounding region included plasterboard, carpets, ceiling tiles, adhesives and paints.   Note:  Approximately 80 percent of the project workforce was from the south east of England.

Waste management during construction

Over 95 percent of construction waste was diverted from landfill by sorting waste materials into eight recycling streams. The waste management activities were linked to the procurement strategy to minimize waste accumulated on site. Furnishings such as storage cabinets, meeting room tables and chairs, and microwaves were reused in the project.

Office waste management

Skanska's offices have comprehensive waste recycling facilities to ensure that materials such as plastics, batteries, cans, printer toners, paper and cardboard are sorted and recycled off-site at appropriate facilities. Kitchen waste is also sorted on site and collected for recycling.

Promoting more sustainable modes of transport

24 secure cycle storage spaces, and shower and changing rooms were installed to encourage occupants to cycle to work. Several bus routes run close to the building and the Woking railway station is located within 300 m of Hollywood House. Car sharing parking spaces have been established and electric vehicle charging points were installed as part of the project.

Energy and Water Efficiency:

Renewables

A 140 m2 solar PV array was installed on the roof of Hollywood House, which is estimated to annually generate 15.6 MWh of electricity. The 20 kW system supplies the building with electricity and is connected to the national grid to allow any surplus energy generated to be sold. The array is fitted to the roof by a purpose built steelwork support frame manufacture by a Skanska fabrications facility. The peak output of the PV system is designed to meet Skanska's general office lighting requirements for both floors.

The building was also equipped with a solar domestic water heating system, which preheats the domestic hot water supply and reduces the building's heating demand. The 9.8 kW system includes 12.7 m2 of panels and is estimated to reduce the building's annual natural gas consumption by 940 m3.

Energy efficiency

The building's Energy Performance Certification (EPC) was  improved from an F to a C level (pending), to meet the current Part L 2010 building regulations.

The refurbished Skanska office floors (Skanska UK’s Rashleigh Weatherfoil divisional head office) are designed to annually use 219 kWh/m2 in total (excluding landlord services), which is 56 percent less than prior to the project and 46 percent less than the energy benchmark for the building.

Connection to local energy center

The building's gas boilers were replaced with a new plant room that sources efficient and low-carbon district heating from the Woking Energy Centre. The energy center is a small-scale Combined Heating and Power Plant (CHP) that also now provides Hollywood House with 100 percent low-carbon electricity from the CHP. Hollywood House was the first commercial office building to be connected to the centre.

A central heat pump provides both heating and cooling to the main meeting rooms and IT server room via fan coil units. The heat pump is deemed a renewable source of energy that produces approximately 3 kW of energy for every kW it uses. The meeting rooms are also heated with excess heat from the IT room during cooler months.

Water efficiency

The refurbished building now uses around 3.0 m3/person/year, which is approximately 55 percent less than what the UK Environment Agency considers to be 'good practice' for a UK office building. Skanska conducted a water usage reduction assessment prior to the project to identify how water use could be reduced. Bathrooms are equipped with water efficient toilets and taps, and occupant sensors, which promote water savings of around 35 percent in total compared with conventional taps and fixtures. The building was also equipped with a CHP, which collects rainwater from 360 m2 of roof for toilet flushing. The rainwater is filtered and stored in a 10,800 liter container in the basement, which is automatically topped up to ensure water is available for toilet flushing in dry periods. The hot and cold water systems, and the rainwater collection system, are linked to the BMS, which monitors the building's overall water usage.

Lighting and Ventilation

The daylight dimming control system regulates artificial lighting levels according to natural daylight and ensures a continuous lighting level of 350 Lux. 

A 7.8 W/m2 energy efficient lighting system was installed that uses 35 percent less energy than the CIBSE (Chartered Institution of Building Services Engineers) lighting design guidelines for medium sized offices. The system includes LED (Light-Emitting Diode) light fittings and a DALI (Digital Addressable Lighting Interface) control system that incorporates daylight and occupancy sensors to avoid unnecessarily wasting energy.

The offices are provided with natural ventilation through operable windows when conditions allow. One of the meeting rooms has a BMS traffic light system that advises occupants on the use of operable windows by considering indoor and outdoor temperatures, and indoor CO2 concentrations.

Skanska's offices also have a three-zone office area temperature and CO2 control that includes temperature sensors and control valves on each radiator to better regulate temperature.  The occupancy sensors also control the ventilation of spaces that are not permanently occupied to only ventilate on demand. The ventilation system has the capacity for nighttime cooling and the heat recovery unit was enhanced with CO2 control.

Heating storage and Cooling

One of Skanska's meeting rooms was fitted with 12.0 m2 of Phase Changing Material (PCM) ceiling tiles, which have a heat storage capacity of 2.15 kWh and help to regulate the temperature in the room by storing heat above 26˚C and releasing heat at 19˚C. The tiles provide passive heating and cooling, and are designed to work in conjunction with the room's mixed mode ventilation to store heat during high ventilation temperatures and provide nighttime heating to reduce traditional heating loads, particularly during cool periods of the year.

Other energy saving measures and building envelope

Includes floor slab insulation on the first floor, solar window shading, new high efficiency radiators, Energy star/A plus rated kitchen appliances, new elevator controllers that reduce energy consumption by nearly half compared with the previous models, and on-demand chilled and hot drinking water facilities to avoid unnecessarily wasting energy.

The offices have a centralized 'Power Off' function that automatically switches off office equipment during out of office hours to reduce energy consumption. However, the system has an override to enable individual occupants to work out of hours if required.

Energy monitoring

Skanska developed a Green Building Management System display together with technology partners that has been installed on both Skanska floors and is connected to both Skanska's and the landlord's BMS. The system allows the building's electricity, thermal and water performance to be monitored, managed and benchmarked, with warning indicators to signal when parameters exceed benchmarks. The system also enhanced BMS functionality with additional controls and displays, and will continue to be developed following feedback, technological advancements and better understanding of the data. The system is expected to further improve energy efficiency by between 2 and 5 percent in the first 12 months of post-refurbishment occupation by fine-tuning the BMS.

Other energy saving measures and building envelope

Includes floor slab insulation on the first floor, solar window shading, new high efficiency radiators, Energy star/A plus rated kitchen appliances, new elevator controllers that reduce energy consumption by nearly half compared with the previous models, and on-demand chilled and hot drinking water facilities to avoid unnecessarily wasting energy.

The offices have a centralized 'Power Off' function that automatically switches off office equipment during out of office hours to reduce energy consumption. However, the system has an override to enable individual occupants to work out of hours if required.

Energy monitoring

Skanska developed a Green Building Management System display together with technology partners that has been installed on both Skanska floors and is connected to both Skanska's and the landlord's BMS. The system allows the building's electricity, thermal and water performance to be monitored, managed and benchmarked, with warning indicators to signal when parameters exceed benchmarks. The system also enhanced BMS functionality with additional controls and displays, and will continue to be developed following feedback, technological advancements and better understanding of the data. The system is expected to further improve energy efficiency by between 2 and 5 percent in the first 12 months of post-refurbishment occupation by fine-tuning the BMS.

Raising awareness of more sustainable buildings

Skanska implemented a 'soft landing' approach into the entire evaluation, design, construction, commissioning and handover phases of the project to raise awareness of the building's efficiency features among the building's owners and occupants. The approach is intended to promote more efficient occupant behavior and the effective operational management of sustainability-related technical solutions. The Green energy display is shown on both the Skanska floors in Hollywood House and is intended to raise awareness of resource usage and occupant behavior to make further energy savings in the future. Following the completion of the project, the building's owner refurbished the remaining parts of the building by using the Skanska floors as a model.

Measures:   Benefits/ Results:   

• The building's Energy Performance Certification (EPC) was improved from an F to a C level (pending), to meet the current Part L 2010 building regulations.
• The 140 m2 solar PV array is estimated to annually generate 15.6 MWh of electricity.
• 12.0 m2 of Phase Changing Material (PCM) ceiling tiles which have a heat storage capacity of 2.15 kWh
• A 7.8 W/m2 energy efficient lighting system was installed that uses 35 percent less energy than the CIBSE (Chartered Institution of Building Services Engineers) lighting design guidelines for medium sized offices.

Operational carbon savings:  Skanska's floors are estimated to annually emit 59 kgCO2/m2 or 93 tonCO2 in total, which is around 55 percent less than the CIBSE Energy Guide F Standard (calculations are based on the Energy Centre's CO2 ratios of 0.3658 kgCO2/kWh for electricity and 0.1829 kgCO2/kWh for heat).  The building's PV solar and solar water heating systems are also estimated to annually save 8.3 tons CO2 and 2 tons CO2 respectively.

The Green BMS (Building Monitoring System) calculates, monitors and benchmarks carbon emissions resulting from Skanska's offices at Hollywood House to promote future savings. 

Notable achievement   

The Skanska floors were designed and refurbished according to LEED Commercial Interiors (LEED CI) Platinum certification, which is the highest level possible. LEED is a voluntary U.S. Green Building Council (USGBC) certification process intended to encourage and guide the construction of more sustainable and energy efficient buildings. The Skanska floors scored 96 LEED points, which at the time of the original publication, was the highest LEED CI score in the UK and among the highest scoring Skanska office renovations to date.

For further information:  
Skanska AB
www.skanska.com

Contact:  
Noel Morrin,
SVP Sustainability & Green Support

noel.morrin@skanska.se