Premessa
I nuovi uffici del Building Research Establishment (BRE) della Gran Bretagna sono destinati a servire da modello. Si tratta infatti della prima costruzione nata da un programma di risparmio energetico negli edifici adibiti ad ufficio, il progetto Energy Efficient Office of the Future (EOF).
Tale progetto è diretto dal BRESCU in collaborazione con un gruppo di produttori, progettisti, società di servizi, imprenditori e promotori. L'équipe ha redatto gli standard, per l'efficienza degli uffici del futuro, ai quali ci si è informati per la costruzione dei nuovi locali del BRE.
Il progetto prevede che nel contesto di un ambiente di lavoro sano e confortevole, si cerchi di ridurre al minimo, se non di eliminare, la ventilazione e la climatizzazione meccanica, di ridurre l'illuminazione artificiale incrementando quella naturale, di sfruttare la forma e i materiali di costruzione dell'edificio per contribuire alla sua climatizzazione naturale, di utilizzare sistemi di comando e di modulazione più convenienti.
L'articolo spiega brevemente come la progettazione dell'edificio risponda ai suddetti obiettivi. La sua realizzazione era prevista per la fine del 1995.
(La pubblicazione ci viene concessa dalla Royal Architectural Institute of Canada)

Background
The project is a building containing offices and seminar facilities to be constructed at BRE's main site at Garston, near London. Intended initially to house staff relocating from BRE's old Fire Research Station in Borehamwood, this new building will also be the first to carry the title Energy Efficient Office of the Future (EOF). The title arises from its association with a broader EOF project being run by BRECSU for the Energy Efficiency Office, in collaboration with a number of commercial concerns representing manufactures, designers, fuel utilities, installers and property developers. The project was initiated under BRECSU's Best Practice programme to encourage energy efficient solutions to likely future developments in office requirements. To this end, the aims for the EOF project are:
- to encourage progress towards an office building that will satisfy both tne energy and environmental targets of the early part of the 21st century,
- to stimulate, earlier than might otherwise have been the case, the development of new technologies, products and systems for low energy design,
- to produce a performance specification and to apply this to the design and construction of a demonstration building (eg. the new BRE office building),
- to monitor and alayze the design process and to carry out extended monitoring of the building in use, and
- to disseminate the results and to promote the demonstration building as an energy-efficient office of the future throughout the construction industry.

Regular meetings of the EOF group have produced an EOF Performance Specification. This is not intended to be a design of the clients and their design teams on energy issues and to provide a check lists of issues to design process. Its emphasis is on energy use rather than the broad environmental issues which are dealt with by the BRE Environmental Assessment method (BREEAM).
The performance specification gives a series of performance targets for maximum energy consumption and carbon dioxide emissions per unit floor area. These are shown for both narrow and deep plan buildings, and for gas and electricity use (non-European readers should note that narrow floor plates with an emphasis on natural ventilation and daylighting are the norm in many European countries). The targets are based upon a 30% improvement over current best practice and are further split into end uses to allow a realistic building evaluation to be undertaken. They would need to be adjusted for a specific building, taking into account, for example, a mainframe computer or heavy catering loads. Sample total annual energy consumption targets, with the corresponding carbon dioxide emissions, are given in Table 1.

OFFICE OF THE FUTURE
To achieve a significatn reduction in energy use, current strategies identify four main areas for improvement:
- avoiding or minimizing the use of air conditioning,
- minimizing the use of artificial lighting while maximizing the use of daylighting,
- maximizing the benefits of the building fabric to reduce or shift peaks in heating or cooling demands, and
- using the appropriate level of controls.

Energy efficiency is only achieved, however, when the resultant design leads to a comfortable and healthy working environment. The EOF Performance Specification therefore considers thermal, visual and aural comfort; environmental and health issues; and indoor air quality. Effective post-occupancy operation of the building is a vital accompaniment to low energy design in achieving the required energy consumption targets, so building automation, maintenance and management were examined.

The new building
The new office building at BRE is designed, built and monitored utilizing input from the EOF Group, in the form of innovative products and expert support to BRE's appointed design team. The EOF Performance Specification formed a key part of the design brief given to the design team. Design work is almost complete, with site work planned to start this fall and completion scheduled for November, 1996.
Althought BRE is in some ways a unique client, this building is intended to be relevant to a wider audience, by embodying design principles and demonstrating the performance of products that are likely to have a future impact on the market. Results of the post-occupancy monitoring will therefore be widely disseminated by the Best Practice programme.

Table 1 - Samples of total annual energy consumption targets with corresponding carbon dioxide emission targets

Building Type	Energy Consumption kWh/m2			Annual CO2 emissions kg/m2
Narrow plan, gas and electric	Gas:	47	34
	Electricity:	36
Narrow plan, all electric	Electricity:	68	46
Deep plan, gas and electric	Gas:	47	39
	Electricity:	43
Deep plan, all electric	Electricity:	75	51

Design Snapshot
The following strategies represent a "snapshot" of the current thinking of the client and the design team. They will be subject to refinement and detailed design consideration before being incorporated into the final design scheme.

Natural ventilation and high thermal mass
The building has been designed as an essentially naturally ventilated building, and therefore incorporates large openable windows. Five solar stacks on the south side have been included to assist ventilation on hot and still days. In keeping with the passive design, exposed ceilings of high thermal mass have been included to moderate temperature swings. In addition, the designers have attempeted to push the boundaries of natural ventilation further by integrating air paths into the structure by using a "folded" slab for the first and second floors, thereby allowing almost unrestricted cellularization of the office space without resorting to mechanical ventilation.

Night cooling and minimum fresh air
The design will utilize night or free cooling using vents controlled by the computerized Building Management Systems (BMS). One option being considered is to use these vents during occupied hours to ensure that minimum fresh air is always delivered via the air paths created by the folded slab. In this scenario, outside air will pick up heat from the slab as it passes through there air paths, and a capacity for additional heating of outside air will be incorporated to ensure that air is at a comfortable temperature when introduced into the occupied areas.
Under this option, some vents would be closed in colder weather, reducing the amount of cold outside air being delivered. Other options being considered for supplying adequate fresh air includes the use of trickle ventilators. During summer conditions, the slab will be cooled at night and will therefore be able to cool the incoming warm ventilation air.

Goundwater cooling
While the strategies for natural ventilation, high thermal mass and night cooling are expected to meet the internal conditions of the EOF specification, the BRE design team and the EOF Group were keen to exceed these targets as a demonstration of low energy cooling.
Underfloor cooling by groundwater is therefore being considered as a means of reducing peak internal summer temperatures.

Maximizing daylighting
The designers have attempted to maximize the use of daylighting as far as is practicable. To overcome the problem of solar gain through the south-facing glazing, a system using movable external glass louvres is being explored. The attraction of such a system is that the view out can be maintained while markedly reducing solar gain.

Lighting
The design is likely to include a new lighting system (see News, page 1) developed by Philips, an EOF Group member. Based on a newly developed 16 mm fluorescent tube and electronic high frequency ballast, the system's primary benefit will be a very low energy consumption. The new system is being developed to allow the control of lighting to be fully integrated into the BMS.

The design of artificial lighting is still being worked out, but it is likely to consist of fluorescent lamps in suspended fittings. Given the curved soffit, the height and design on the lamp fittings is crucial - the last thing the designers want is zebra stripes across the floor.

Seminar spaces
The seminar spaces will employ basically the same strategies as in the office areas: natural ventilation, high thermal mass and groundwater cooling, althought the latter will be essential here to ensure that internal conditions can meet the requirements of the EOF specification.

Future of the EOF project
BRE's demonstration building only addressed the EOF's objectives for a greenfield site. To fulfill its wider aims, the EOF Group has identified the need for two more demonstration buildings, one covering urban development and the other a retrofit. Opportunities in there areas are currently being examined, althought it must be noted that this route is only one of several future courses the EOF project could take.

EOF Group members
Arup Research and Development
Pilkington Glass
Eastern Electricity
British Gas
Caradon Trend
Stanhope Properties PLC
Laing Technology Group
Philips Lighting
Hepworth Building Products
Electricity Association
Colt Group
Building Research Establishment

Design Team
Bernard Williams and Associates; project managers
Fielden Clegg Design; architects and leading design team
Max Fordham and Associates; services engineers
Buro Happold; structural engineers
Turner and Townsend; quantity surveyors
Nicholas Pearson Associates; landscape architects

DEGW; space planning advisors
Symons Travers Morgen; planning supervisor

(Fonte: Advanced Buildings)