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Model project - Herman Miller UK HQSeptember 2009

BSRIA visits the Herman Miller HQ to find out whether the building's energy use and occupant satisfaction matches the design team's intentions.

Furniture firm Herman Miller is well known for creating innovative office equipment. So when the US company built its international headquarters in 2006, the building had to be something a little special.

What Herman Miller came up with was VillageGreen (sic). On the surface it does not have the look of a landmark building. It's also located in a standard office business park on the outskirts of Chippenham rather than in a city centre where it can display its credentials more ostentatiously. But looks can deceive.

What VillageGreen is able to boast - uniquely in the UK - are high ratings under both the BREEAM and LEED environmental assessment schemes.

Usually, clients and design teams opt for one or the other - not both. What drove Herman Miller was clearly a statement made by the firm's founder in 1953: "We will be good stewards of the environment'. This maxim is enshrined in what the company now calls its Policy 53. This led to the new building becoming a "living showroom" of good environmental performance.

A BREEAM Excellent rating was included as a contractural requirement. The decision to go for a LEED rating came later in the process, albeit a natural one for a US-owned company and a founder member of the US Green Building Council. The company's aim for this building and the desire for it to work effectively were highlighted by Herman Miller's marketing director, and Steve Jackson, the head of facilities, being included as part of the design team - a refreshing change to standard design practice. The building was designed to be an integral part of the firm's brand identity.

Building layout

The layout of the building is very simple. The ground floor is largely dedicated to sales and marketing of the company's products. Much of the floor space is a showroom with different styles of furniture laid out for clients to view and test. The rest of the ground floor contains training rooms, meeting rooms and the café area, as well as a small data centre for Herman Miller International, (the latter catering for all sites outside the US). The first floor is the conventional office workspace where everyone, from customer care and finance to the international president, is accommodated.

Environmental ratings

The building was assessed under the 2005 version of BREEAM. Although BREEAM 2005 had the same categories as the current 2008 version, some of the credits were different and there was no requirement for a post-construction review.

While it was possible to carry out a post-construction review with the 2005 version, in BSRIA's experience very few were carried out. So the BREEAM Excellent rating at VillageGreen is therefore based entirely on the design team's intentions.

The ground floor is largely dedicated to sales and marketing of Herman Miller's products. Much of the ground floor is occupied by a showroom with different styles of furniture for clients to try out.

That said, some aspects of the BREEAM assessment do not affect the later running of the building; they are all about the site and management of the construction process. The land use and ecology section, for example, only looks at the ecological effects of building on that particular piece of land, while the management section looks largely at commissioning. Additional credits were available in BREEAM 2005 for minimising the effects of construction activities and for the production of a building users' guide.

Other areas of BREEAM can really drive the design decision-making process and fit-out choices - affecting those things that can stay with the building for the rest of its life.

For example, the health and well-being section of BREEAM contains many issues involved with helping the workforce to be happy and productive while satisfying the environmental aspirations. At VillageGreen, this led to the use of natural ventilation.

Ventilation strategy

All the first-floor open-plan offices and the ground floor showroom are naturally cross-ventilated by using windows on either side of the building. Traffic noise was reduced by locating the building so that it is shielded from the busy A4 on one side by a retail store and from the A350 by another office block.

The windows have two openings: a motorised fanlight which is controlled automatically, and a main window which is controlled manually by the occupants. The fanlights also have an automatic override button to give occupants some local control. A night-cooling strategy operates during the summer months to purge the building of heat built up during the day.

Although the automatic controls are standalone and not connected to the building's building management system (BMS), they monitor the internal conditions through sensors in the floor slabs as well as external conditions such as wind speed and direction. Rainfall and solar radiation are also monitored.

The design team adopted a pulsed ventilation strategy, an approach that periodically opens windows for a short time to release stale air, rather than opening and closing windows on space temperature, and keeping them closed when it's cold.

This ostensibly straightforward ventilation system did not perform to expectations during the first full summer of operation. In other buildings where natural ventilation has delivered less than was expected, problems are often caused by poor design detailing, cost-cutting, inadequate commissioning, or a failure to manage the ventilation system properly in operation. But at VillageGreen, the problem stemmed from a conflict with the credit in the BREEAM health and wellbeing section covering glare control.

This credit is awarded for user-controlled glare control (blinds). Originally, venetian blinds were installed from the top of the window reveal. These blinds covered the fanlights and compromised airflow when the blinds were down.

Small break-out areas are dotted around the floor. Some have traditional table and chairs, while others are more homely with some armchairs and a lamp.

Once the clash was discovered, post-handover, the venetian blinds were replaced with roller blinds only covering the main part of the window. This enables the fanlights to open and for the air to flow easily. Anti-glare film was fixed to the fanlights on the south-facing side (and all other glass panels above blinds) to reduce residual glare.

Surprisingly, given the problems caused by clashes of this nature, conflicts between openable windows and inappropriate blinds are widespread.

Getting a tick in the box for a BREEAM credit is all well and good, but implementation really does need to be thought-through. There is no way that BREEAM could assess for this kind of problem as it would become a huge unwieldy monster with very complicated ifs-and-buts type questions to get credits.

Energy consumption

Energy is the main measure of a building's environmental footprint. A high BREEAM or LEED rating at the design stage is often held to be an accurate indicator of a building's operational energy use. While this might be the case, the two should not be confused. Not only is the association between design aspiration and in-use performance rather fragile, but energy is only one of several metrics in both BREEAM and LEED.

For the year to April 2009, VillageGreen used 530,000 kWh, or 260 kWh/m2 per annum, for electricity and fossil fuel. This is way above the ECON19 good practice benchmark for an open-plan naturally ventilated office (133 kWh/m2 per annum), slightly above the typical value (236 kWh/m2 per annum). However, against the Display Energy Certificate benchmark of 95 kWh/m2 per annum quoted in CIBSE TM46:2008, the building's performance looks rather worse.

Obviously this is disappointing for a building with strong environmental credentials. However, the building doesn't fit perfectly into TM46 and ECON19 benchmark peer groups, as it has a ground floor showroom and a data centre - things normally not associated with a naturally ventilated office.

Gas consumption for space heating and domestic hot water is 74 kWh/m2 per annum compared with the (good practice) benchmark of 79 kWh/m2 per annum, probably a reflection of higher insulation and airtightness standards in the Building Regulations. Electricity consumption over both floors comes in at 186 kWh/m2 per annum, which is high compared to the ECON19 good practice value of 54 kWh/m2 per annum, and also the typical value of 85 kWh/m2 per annum.

Although this performance looks poor, there are militating circumstances. For a start a data centre is not normal for a naturally ventilated office, and the one at VillageGreen serves more than one site. Meter readings from submeters to the data centre suggest electricity consumption of 123,500 kWh per annum, a sizeable chunk of the overall power consumption.

Then there is the ground floor showroom. The lighting here is manually controlled, and for aesthetic reasons is kept on for visitors or clients. In contrast, lighting in the first floor office space is much more energy efficient. Each individual luminaire has sensor control, detecting both lighting levels and movement. There is also a manual override for those times when light is absolutely necessary. The day of BSRIA's visit was bright, and while very few of the first floor lights were on, all of the showroom lights were on.

The difference in power consumption of the two lighting strategies is clear from the submeters. The first floor lighting consumes around 27,000 kWh per annum, while the showroom consumes 111,300 kWh per annum over a smaller floor area.

Even allowing for the age of ECON19 benchmarks, VillageGreen demonstrates the difficulties of benchmarking the energy performance of a building that doesn't quite fit in any of the benchmark peer groups. Benchmarking has to be done with great care. End-uses need to be separated out or at least highlighted.

If VillageGreen didn't have a showroom or a data centre, its performance would be more respectable. Fortunately the lighting and small power for the traditional office space on the first floor are metered separately. Lighting is about 27 kWh/m2 per annum, with the small power coming in at 34 kWh/m2 per annum. These compare to good practice benchmarks of 22 and 20 kWh/m2 per annum respectively in ECON19. The typical benchmarks are 38 kWh/m2 per annum and 27 kWh/m2 per annum. So lighting is within the right range and small power a bit high.

When the lighting and small power from the first floor is added to the energy use for heating and domestic hot water, this gives a rough value of 138 kWh/m2 per annum - very close to the good practice value in ECON19. While VillageGreen has room for improvement in comparison with the benchmarks, it's by no means the high energy consumer the headline figures suggest.

Summary results of the Building Use Studies occupant satisfaction survey. Green triangles represent mean values better or higher than the benchmark and amber circles are mean values no different from the benchmark.

Occupant survey results

BSRIA carried out an occupant satisfaction survey using the Building Use Studies (BUS) methodology. Figure 1 shows building's performance against the 12 BUS summary comfort variables.

In terms of overall satisfaction the building scored very highly, coming out in the top range of well performing buildings in the BUS dataset. Summertime comfort and air quality are close to typical for naturally ventilated office buildings while all other scores were significantly above benchmark.

The interesting score is that for image, which is very high. The occupant's perception of the building as being iconic and worthy will tend to breed forgiveness of any shortcomings the building might have. It cannot neutralise them, but it will tend to pull up scores for other comfort variables.

This is also true of the high score for the needs-related variables. Usually, this is a sign of diligent and effective facilities management. Herman Miller's decision to replace the blinds is clear evidence of this. In similar buildings where faulty systems have not been fixed and/or where facilities management is either lacking or absent, occupant satisfaction can plummet and any forgiveness that might exist is not strong enough to prevent negative feelings from developing.

The facilities manager's speed of response to problems voiced by occupants is also vital. VillageGreen had suffered from control issues with the radiators. The thermostatic radiator valves were sticking, removing the ability for people to control the environment and leaving them feeling too hot or too cold.

Performance assessment

So does VillageGreen live up to its high BREEAM and LEED scores? Does it prove that BREEAM and LEED create exemplar buildings?

While VillageGreen is an excellent building, it's possibly in spite of BREEAM and LEED rather than because of them. When asked about the LEED rating, the facilities manager Steve Jackson replied that it did not take much extra design effort above that needed already for the BREEAM rating. A small premium was paid (in terms of the design and construction) to get the BREEAM excellent rating, which probably helped.

So while the assessments drove the decision to put in waterless urinals, cycle racks and sustainable drainage, the overall building design stemmed from the company's environmental ethics and by a belief in high quality, hands-on facilities management. Yes, the building gets a bit hot in summer, and yes it uses a bit more energy than its peers, but VillageGreen is not a typical building.

Maybe VillageGreen could be even better if more of its flaws had been picked up at the design, construction and fit-out phases, leaving more time for the facilities team to optimise the building rather than get it to a working state. This is not uncommon.

Facilities managers may be led to believe that the newest building under their charge requires less attention than any older ones. They may have been led to believe that their new building is operationally ready at handover, that all the systems are fit-and-forget, and that no fine-tuning is needed.

New buildings are more like children; they need nurturing through the early years to get the best out of them. Neglect them, and they'll quickly end up behaving badly.

The overall message from Village Green is not about the importance of high BREEAM or LEED ratings, but more one of how to manage a building and its occupants properly to achieve the desired operational outcomes.

For more information on VillageGreen visit the Herman Miller website.


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