BUILDING PERFORMANCE 1 UNIVERSITY CASE STUDY 1998 occupant survey


1 1 1 1 1 1 1 1 1 1


7 7 7 7 7 7 7 7 7 7


Temperature in summer overall


1 = uncomfortable 7 = comfortable Temperature in winter overall


1 = uncomfortable 7 = comfortable Air quality in summer overall


1 = unsatisfactory 7 = satisfactory Air quality in winter overall


1 = unsatisfactory 7 = satisfactory Lighting overall


1 = unsatisfactory 7 = satisfactory Noise overall


1 = unsatisfactory 7 = satisfactory Comfort overall


1 = unsatisfactory 7 = satisfactory Design


1 = unsatisfactory 7 = satisfactory


Does the building meet your needs? 1 = very poorly 7 = very well Health


1 = less healthy 7 = more healthy Image to visitors


1 = poor 7 = good Perceived productivity


Decreased: -20% Increased: +20% Building Use Studies (BUS) occupant survey results for 1998 and 2011


The diagrams above show average responses by staff to 12 key questions in the BUS surveys in 1998 (on the left) and 2011 (on the right), just before the recent changes. For comparability, the 2011 survey excludes occupants in the converted kitchen and dining area. The satisfaction scales run from 1 (poor, on the left) to 7 (good), apart from the final question – the effect of environment in the building on perceived productivity – which goes from –20% to +20%. Green squares show where average scores are significantly better than benchmark values at the 95% confidence level. Orange circles indicate averages that are similar. For most occupant satisfaction variables, The Elizabeth Fry Building remains significantly above average. There are no red triangles, which would indicate scores significantly worse than average. The question about image (to visitors) was not asked in 1998. The score for overall comfort in 2011 is at the 79th percentile of the


reference data set, while in 1998 it was at the very top. Two things have happened since then: perceived conditions in the building are not quite


as good (e.g. the overall comfort score has fallen from 5.41 to 5.20), whilst buildings with better comfort levels have subsequently been surveyed. The 1998 result for Elizabeth Fry now falls at the 90th percentile of the 2011 reference dataset. The main influence on comfort is likely to be the higher occupation


density. The variable most affected is summertime temperature, where the average score has fallen from what was a very good 5.30 (the most comfortable in the 1998 dataset) to 4.24. The effect is exacerbated by a loss of perceived control in the open plan areas. Perceived air quality in summer has also fallen, but remains significantly above average. The average score for noise has dropped from 5.05 to 4.24, and is now indistinguishable from the average. The main causes are probably the creation of open plan offices and the growth in traffic on Chancellor’s Drive – particularly regular buses, which did not go past the building in 1998. Some people also mentioned noise from the ventilation plant.


Decreased: -20% Increased: +20%


1 1 1 1 1 1 1 1 1 1 1


2011 occupant survey


7 7 7 7 7 7 7 7 7 7 7


Air leakage Pressure tests reveal change


Envelope pressure tests have been carried out three times by building services research body BSRIA: • In December 1994, before the building was handed over. The result was 0.97 air changes per hour at 50 Pascals pressure, equivalent to an air leakage index of 4.2 m/h (cu m per hour per sq m of exposed envelope area) and an air permeability of about 3 m/h, 30% of the current limiting requirement • in Part L.


In February 1998, as part of the PROBE survey, giving an air leakage index of 6.5 m/h, equivalent to a permeability of 4.7 m/h. With the front


34 CIBSE Journal March 2012


The test in September 2011 gave the surprising result of a 5.3 m/h air leakage index (air permeability 3.8 m/h), better than in 1998. The main reason is thought to be the removal of the catering kitchen and its ventilation plant. BSRIA also thinks the lecture room ventilation plants may not have been sealed off as well in 1998. Smoke tests in 2011 confirmed similar leakage routes to earlier tests, including the entrance doors, particularly the main revolving door which needed new seals; the perimeters of the rooflights over the main


doors sealed, the air leakage • index fell to 6.2 m/h.


and escape stairs; and through the windows themselves, though their seals remain in good condition. A new leakage route had


also appeared under the cills of the windows, where the compressible foam plastic seals had begun to deteriorate and fall out. The mastic seals around the window and door frames were also cracking, but little air leakage was detected here.


More about the pressure test results can be found in: R Bunn, Elizabeth Fry, Ageing gracefully? DeltaT magazine 6-8, February 2012, published by BSRIA www.bsria.org.uk


a period when the main regenerative heat exchanger failed and the cold 2010-11 winter. In 1998 and 1999, the self-contained water


heater used as little as 3 kWh/sq m of gas, even less than in 1997. Consumption then rose to 4.4 kWh/sq m in 2000 and 5.5 in 2001, perhaps owing to temperature adjustments. In 2003-08, consumption nearly tripled to 12-14 kWh/sq m, owing to a change to 24/7 operation at 55C (65C on Sundays), resulting from concerns about legionella. In 2009 a new condensing water heater was fitted and its gas use fell to 11 kWh/sq m. Although the building is more heavily used, most of the extra consumption in relation to the PROBE survey data is thought to be from standing losses from lightly-insulated and uninsulated pipework. The box on the previous page shows an estimated breakdown of annual energy use


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