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Case study on the energy performance of the Zuckerman Institute for Connective Environmental research (ZICER) building.

ABSTRACT

In the early 1990s, the University of East Anglia in Norwich, UK, established a low-energy policy toward building design. In 1994, the first energy-efficient educational building was constructed on campus--the Elizabeth Fry building, which utilizes a hollow core ventilation system. Independent reviews at the time demonstrated that this was one of the best energy performing buildings in the UK. Several additional educational buildings of similar design have been built on campus, one of which is the Zuckerman Institute for Environmental Connective Research (ZICER) building, completed in 2003. The construction of the ZICER building is unusual. The main building envelope is served by a hollow core ventilation system, high in thermal mass, highly insulated and airtight, but on the opposite spectrum, a light weight, highly glazed structure made up of photovoltaic cells was added onto the building to make up the "Top Floor," home to an exhibition area and seminar room. This paper investigates the energy performance from the ZICER building's long-term submonitoring results and explains how the heating and cooling strategies evolved to meet half the building's energy consumption.

INTRODUCTION

The University of East Anglia (UEA) was established in 1963 on a campus approximately 4 km west of the city of Norwich. The initial development phase of the campus centred around buildings constructed in the mid to late 1960s, many of which represent wasteful energy approaches to building design but are now Grade II buildings (buildings in the UK of special architectural or historic interest, warranting efforts to preserve them), so the scope for improvements in thermal performance is limited.

Since the early 1990s, energy savings and conservation through technical means of low-energy building design, good building energy management, and awareness raising have been important aspects of policy and research at UEA. Over this time the campus has expanded in size, which has resulted in the construction of many new structures built to strenuous green design guidelines.

Among these buildings are four, soon to be five, educational office buildings employing the hollow core ventilation system: the Elizabeth Fry building (EFry), the Medical School (MED), the Zuckerman Institute for Connective Environmental Research (ZICER), and the School of Nursing and Midwifery (NAM).

The hollow core ventilation system used is a mechanically ventilated, low-energy heating and cooling system that utilizes concrete hollow core ceiling slabs as supply air ducts to the space (see Figure 1). The high thermal mass of the concrete slabs is used to store heat and coolness at different times of the year. The hollow cores running through the slabs enhance the access to this thermal capacity, which releases heat to or absorbs heat from the air that passes through. The hollow core ventilation system is used in conjunction with regenerative heat exchangers to recapture energy by transferring the heat or coolness from the exhaust air to preheat fresh incoming supply air in winter and to precool the supply air in summer. High insulation standards and good airtightness is also required.

[FIGURE 1 OMITTED]

This paper focuses on the energy performance of the third hollow core ventilated building to be built on the UEA campus, the ZICER building.

CASE STUDY DESCRIPTION

Case Study Building Details

The ZICER building (see Figure 2), built in 2003, is four stories plus a basement, with a total floor area of 2860 [m.sup.2] and a conditioned floor area of 2633 [m.sup.2]. The building is divided into two construction types.

The main building envelope encapsulates the basement, the ground, the first and second floors, and the main plant room and stairwells on the third floor. This main part of the building is served by the hollow core ventilation system. The envelope is high in thermal mass. Dense concrete blocks with a thickness of 23 cm were used for the external walls. These concrete walls are exposed to the interior with the insulation on the outer surface. The envelope is airtight, with an air permeability of 2.84 [m.sup.3] x h x [m.sup.-2] at 50 Pa. The U-factor for the external walls and floor is 0.2 W[m.sup.-2] x [degrees][C.sup.-1], the roof has a U-factor of 0.13 W[m.sup.-2] x [degrees][C.sup.-1], and the triple-glazed low-emissivity windows have a value of 1.1 W[m.sup.-2] x [degrees][C.sup.-1]. These insulation standards exceed the current UK building regulations.

The basement of the building is a virtual reality suite. It has an extensive amount of computer equipment but is infrequently used. The ground floor and the first floor are large open-plan offices for post-graduate students and researchers. These floors have cellular offices along the west of the building for faculty members. These two floors have high internal heat loads due to many people and lots of computing equipment. The second floor is entirely composed of cellular offices. This floor is for senior members of faculty and administrators.

[FIGURE 2 OMITTED]

The remainder of the third floor, referred to as the "Top Floor," is light in construction with a low thermal mass. The space is divided between an exhibition area and a seminar room. The southern facade and roof of the Top Floor are almost entirely glazed by photovoltaic (PV) cells. The heat losses and heat gains are high due to the large expanse of glazing. The glazed Top Floor is a demonstration project for the integrated PV cells.

The Operation of the Hollow Core Ventilation System

The operation of the main part of the building served by the hollow core ventilation is illustrated in Figure 3. Incoming air through the centralized air-handling unit (AHU) is preheated in winter and precooled in summer by the regenerative heat exchanger (RHE) and supplied to the hollow cores in the pre-cast concrete slabs via the supply duct for each floor. Each floor has its own heater battery to increase the supply air temperature if required. The circulating air passes through the hollow cores at low air velocities to allow prolonged contact between the air and the slab in order to transfer the heat or coolness to the supply air. After passing through the ceiling slabs, the air enters the internal occupied spaces through circular ceiling diffusers. The return stale air for each floor is extracted via the grilles in the bulkhead, up the extract duct and out through the AHU via the regenerative heat exchanger.

[FIGURE 3 OMITTED]

In summer, when the nights are cool but the days are hot, the fabric of the building is precooled overnight. During the day the air passes through the cool hollow cores in the ceiling slabs, precooling the air before it enters the occupied interior (referred to as free-cooling). The precooled concrete slabs also absorb the heat from the occupied interior, e.g., from body heat, office equipment, and solar radiation, like a radiator in reverse. The demand for space cooling has been eliminated in all areas except for the virtual reality suite in the basement due to the extensive amount of computing equipment. This specialist IT equipment requires additional space cooling from the district cooling system.

During the daytime in the winter, the concrete slabs absorb and store the heat from office equipment, passive solar gain, etc. As the preheated air from the regenerative heat exchanger circulates through the hollow core concrete slabs, heat is transferred to the supply air from the concrete before entering into the room. At night the building is sealed to reduce the heat loss from the building to retain the daytime heat gains. In the evening when the concrete slabs become warmer than other surrounding objects, the heat stored in the concrete from the day is released back into the room (via radiation). Supplementary heating from the 3 MW combined heat and power plant on campus is used via heater batteries if the slabs fall below the setpoint heating temperature.

The Operation of the Top Floor

The Top Floor has heating and cooling strategies independent of the main part of the ZICER building. Further space heating is consumed by the Top Floor. The exhibition area is heated by perimeter heating, which runs parallel and adjacent to the PV facade; it utilizes natural ventilation for cooling via an automated set of high and low louvers. The seminar room has its own, separate AHU (with no heat recovery), which supplies the room with all its space heating and cooling needs. The operation of the Top Floor is discussed in more detail in the "Results and Discussion" section.

Benchmarks

ECON 19 (DETR 1998) is an energy consumption guide for four types of office buildings located in the UK:* naturally ventilated cellular, naturally ventilated open-plan, air-conditioned standard, and air-conditioned prestige. Benchmarks for energy consumption, cost, and carbon dioxide are described for the four types of office buildings in order to compare the performance of office buildings in practice. New building design should aim to improve upon the stated good practice benchmarks. A summary of the annual delivered energy consumption for good practice and typical offices for the four office types is shown in Table 1.

The ZICER building's energy benchmarks were based on the energy performance of the EFry building, the first hollow-core-ventilated building constructed on the UEA campus (in 1994). Both the ZICER and the EFry structures are built to similar construction, with the same function and approximately the same hours of use. The only major difference between the two buildings is the ZICER building's lightweight Top Floor, which is absent on the EFry building.

The EFry building's heating consumption outperforms the good practice energy guidelines. The record year for space heating consumption was in 1999, when the heating consumption dropped to 27.3 kWh x [y.sup.-1] x [m.sup.-2] (normalized to the area's average weather conditions). The impressive energy performance of the EFry building gained it the title of being one of the most highly commended energy-efficient buildings in the UK by the Post-Occupancy Review of Buildings and their Engineering (Probe Team 1998), a research project in the UK that ran from 1995 to 2002. The ZICER building was constructed to slightly higher insulation standards, with better air tightness and better windows than the EFry building. The upper limit to the ZICER building's space heating goal (for the main part of the building) was 50 kWh x [y.sup.-1] x [m.sup.-2], but it was expected to be lower than the EFry building's heating consumption. The Top Floor was designed as a demonstration project for the PV cells. It was thought that this area would require more heating than the main part of the building per square meter, but the scale of difference was uncertain.

THE MONITORING PROCEDURE

Daily monitoring of the ZICER building's space heating and hot water (combined) and space cooling energy usage began in November 2003, almost immediately after the building first became occupied. However, it was not until March 2004 that appropriate sub metering was installed to separate the energy loads between the main part of the ZICER building, the exhibition area, and the seminar room to determine where energy was being used within the building. Due to a fault with the cooling sub meter, the separation of the cooling between the seminar room and the basement of the ZICER building was delayed until August 2004.

A weekly energy consumption monitoring regime was set up by the Energy Manager at the UEA upon completion of all the hollow-core-ventilated buildings. The results between the hollow core ventilated part of the ZICER building and the EFry building are compared on a weekly basis. The EFry building runs on three stand-alone gas boilers, whereas the ZICER building runs off the university's district heating system. In the latter case, the monitoring results do not include boiler losses; therefore, for a fair comparison between the two buildings' heating demands, the heat consumption data from the EFry building is multiplied by a factor of 0.9 to compensate for the boiler losses experienced in the EFry building. Both sets of data are adjusted for conditioned floor area.

RESULTS AND DISCUSSION

The First Set of Monitoring Results

Through the monitoring procedure it was recognized that the main part of the ZICER building was not meeting the energy performance criterion. Figure 4 shows the weekly heating and hot water comparison between the EFry building and the main part of the ZICER building (served by the hollow core ventilation system) from the end of March 2004 to mid-September 2004. By subtracting the estimated base load hot water requirements from both sets of figures, the heat usage of the main part of the ZICER building was calculated as a proportion of that of the EFry building. Over the time period shown in Figure 4, the ZICER building used 84% more space heating per square meter than the EFry building. As explained in the "Benchmarks" section, this should not have been the case. The poor heating performance of the main part of the ZICER building was investigated.

[FIGURE 4 OMITTED]

Investigation into the High Heat Load of the Main Part of the ZICER Building

The space heating and free-cooling strategy originally in place in the main part of the ZICER building operated using two different control temperatures. During the daytime, the building management system (BMS) analyzed the return air temperatures from each floor to determine whether heating or free-cooling was required. During the nighttime, the BMS analyzed the temperature of the hollow core concrete floor slabs through temperature sensors in the concrete slabs, a process known hereafter as slab control. If the temperature of the hollow core floor slabs was above the set point temperature range, then free-cooling was brought into action; if it was below the set point temperature range, heating was brought into action.

It was observed that during the daytime this heating and free-cooling strategy was very reactive. The AHU was switching from heating the incoming air with heat recovery to the free-cooling mode in quick succession many times a day. Figure 5 shows a typical day in spring 2004 of the AHU recuperation. The AHU switches from free-cooling to cycling with heat recovery at intervals as short as one minute.

[FIGURE 5 OMITTED]

This succession of heating and free-cooling at short intervals did not allow the mass of the building to take control in the way that it was designed to operate. High thermal mass requires a long period of heating or cooling to change its temperature, without which the concrete slabs are unable to store or remove heat. This poor use of thermal mass in the original heating and free-cooling strategy of the ZICER building meant that the building was wasteful in terms of its heating consumption.

Experience Gained from the EFry Building

A higher than expected heating load was observed early on in the operation of the EFry building. After experimentation by the UEA Estates team, the heating and free-cooling strategy was fine-tuned and put on 24-hour slab control. This strategy suited the EFry building and, once introduced, decreased the space heating consumption (see Figure 6).

Modifications to the Space Heating and Free-Cooling Strategy of the Main Part of the ZICER Building

The main part of the ZICER building did not originally adopt the 24-hour slab control heating and free-cooling strategy that worked well in the EFry building. The EFry building has a greater thermal mass than the ZICER building (its internal walls are dense block-work as opposed to lightweight stud partitions, and there are more internal walls due to the cellular offices). For this reason it was originally thought that the thermal mass of the ZICER building would not be able to regulate the internal temperatures so well as in the case of the EFry building. Therefore, the return air temperature from the floors was chosen during the day to determine whether heating or free-cooling was required, switching to slab control only at night.

With the energy monitoring results as proof of poor operation, the BMS for the ZICER building was reprogrammed to operate on 24-hour slab control. If this strategy used more energy or if there were complaints about the indoor temperature, then the option to revert to the original space heating and free-cooling strategy was available.

[FIGURE 6 OMITTED]

The Second Set of Monitoring Results

Moving the ZICER building away from air sensing to operate on slab control was a success. Toward the end of 2004, the ZICER building's heating and hot water consumption became more comparable with that of the EFry building (see Figure 7).

It was evident from the results that the main part of the ZICER building still consumed more space heating and hot water than the EFry building in the inter-seasonal months and at the start of the summer months. The cause of this was identified. It was observed that the few radiators that exist in the ZICER building (in the shower room, rest rooms, and basement stairwell) were on even during the summer. Upon this discovery in mid-July 2005, the radiators were manually switched off. The effect of this is shown in the reduction of the ZICER building's space heating and hot water after mid-July 2005 in Figure 7. The occupants of the ZICER building are free to turn these radiators back on if these areas get too cold. As of late September 2005, these radiators have remained off.

The scale of reduction in the space heating consumption between the original and new heating strategy of the main part of the ZICER building is illustrated in Figure 8 (only data points less than the UK's base temperature of 15.5[degrees]C were used to construct the graph).

Under the new heating strategy, the space heating consumption has been reduced by 57%. In September 2005, the annual rolling heating and hot water consumption for the main part of the ZICER building stood at 42.8 kWh x [y.sup.-1] x [m.sup.-2]. The value for the EFry building stands at 46.8 kWh x [y.sup.-1] x [m.sup.-2], but when a reduction in the space heating and hot water consumption is accounted for from the boiler efficiency, it is reduced to 42.1 kWh x [y.sup.-1] x [m.sup.-2]. At present, the ZICER building's figure is marginally above the rolling annual figure for the EFry building. Now that the cause of the ZICER building's higher heating load in the inter-seasonal and summer months has been identified, its value is likely to decrease below the annual space heating and hot water consumption of the EFry building.

[FIGURE 7 OMITTED]

[FIGURE 8 OMITTED]

Electricity Usage Associated with the Hollow Core Ventilation System and Regenerative Heat Exchangers

It has been described that the heating and hot water demand for the main part of the ZICER building was reduced by the change in the building's control strategy. The heating figures are now lower than good practice benchmarks for naturally ventilated office buildings as outlined in ECON 19 (DETR 1998). However, the AHU and regenerative heat recovery units installed in the ZICER building form an integral part of maintaining low heating and cooling demands in the main part of the ZICER building. These units run off electricity and operate from 8 a.m. to 6 a.m., Monday through Friday. The electricity usage of these units was monitored on two occasions, one week in October 2004 and one week in May 2005. In addition to the electricity usage from these units, the monitored results also incorporated the electricity consumption of the seminar room's AHU and the operation of the louvers in the exhibition area.

From the two periods of monitoring the electricity consumption for all the mechanical ventilation requirements in the building, the operation of the regenerative heat exchangers was estimated to be 19.1 kWh x [y.sup.-1] x [m.sup.-2]. If the electricity attributed to the ventilation and regenerative heat exchanger operation is considered in primary energy terms, the value would increase to 55.2 kWh x [y.sup.-1] x [m.sup.-2]. This value is then greater than the heating demand for the main part of the building. However, it is normal for modern offices, especially open-plan offices, to be equipped with mechanical ventilation, and the ZICER building figure of 19.1 kWh x [y.sup.-1] x [m.sup.-2] is below the good practice energy consumption value of 22 kWh x [y.sup.-1] x [m.sup.-2] for AHUs in a standard air-conditioned office building (DETR 1998). For more information on the ZICER building's electricity usage, see Raydan and Turner (2005).

Heating, Hot Water, and Cooling Requirements for All Areas of the ZICER Building

So far only the space heating of the main part of the ZICER building (including all the hot water requirements of the building) has been discussed. Further space heating is consumed by the Top Floor and cooling is used in the basement (due to an extensive amount of computer equipment) and in the seminar room. The rolling annual energy results for all areas of heating, hot water, and cooling are shown in Table 2, updated to September 2005.

The results in Table 2 show the excessive energy consumption from the Top Floor of the ZICER building in comparison to the main part of the ZICER building served by the hollow core ventilation system. The Top Floor represents 10% of the total conditioned floor area yet uses 53% of the overall heating and 74% of the overall cooling. The Top Floor increases the heating and cooling energy consumption on a square meter basis by 96%. The Top Floor has also been subject to many complaints from users that satisfactory temperature levels are not being achieved.

Due to the nature of the Top Floor, i.e., it is low in thermal mass and highly glazed, it was expected that the energy consumption would be high compared to the main part of the ZICER building, but the magnitude was unknown until submonitoring of the individual areas took place. After careful evaluation of the situation, it was thought that the Top Floor energy consumption and thermal performance could be improved as well as the basement cooling. Following is a summary of events that have occurred to address these issues.

Seminar Room. Under the original strategy, the AHU (with no heat recovery) for the seminar room would become operational if the return air temperature was above or below the programmed cooling or heating set point temperatures in the BMS. Incoming fresh air from the AHU would be heated or cooled to the set-point temperature before entering the seminar space. If the return seminar room temperature was between the boundaries so that heating and cooling became operational, then the return air would be recirculated into the seminar room without being heated or cooled.

Three issues under this original strategy were raised whereby the energy consumption could be reduced. These three issues and the respective actions taken are shown in Table 3. The last of the modifications in Table 3 took place in July 2005. Early results suggest that these improvements have reduced the energy demands for the seminar room. Estimated figures for 12 months' time are shown in Table 4. The heating demand of the seminar room is expected to be reduced by 80% and the cooling demand is expected to be reduced by 63%.

Exhibition Area. Heating is activated in the exhibition area when the room temperature drops below the lower set point temperature. The original heating strategy is shown in Figure 9. In order to create a flow of air through the perimeter heating, the bottom louver was opened. External air was forced through the heater where it would be heated up to the design set point temperature. Under this strategy, the energy and thermal performance of the area was poor. Heating the air from outside temperatures to the indoor design temperature uses more energy than if the indoor air was recirculated around the room, topping up its temperature when required. Therefore, the correct operation of the heating strategy required the creation and maintenance of air circulation around the exhibition area without having to open the louvers unless high carbon dioxide levels are detected in the exhibition area by sensors that then override the recirculation. Several minor physical alterations were made in September 2004 to promote air circulation with the louvers shut (see Figure 10). Monitoring results infer that no improvements in the energy consumption of the exhibition area were made despite the change in strategy. On the positive side, improvements have been made in the thermal performance; the design set point temperature in winter is now reached.

[FIGURE 9 OMITTED]

Basement Cooling. Submonitoring results revealed that initially the basement was using a high cooling load, between 14 and 60 kWh of electricity per day. Under investigation, this high cooling load was soon rectified.

The cooling system in the basement has the facility to be switched on or off by the users of the control lab when cooling is required. The users had never been informed that they had the option to switch the chilling unit off. At this discovery, clear instructions were given to the main users of the lab that cooling should be switched on (at their discretion) when the control lab is in use and switched off when not in use. A sign with this information was also attached to the chilling unit.

Using the cooling in the basement as and when necessary has improved the thermal working environment for the users of the control lab and has improved the energy performance, only rising to previous figures on days when the chilling unit is switched on.

The current annual rolling figure for the basement is 7.0 kWh x [y.sup.-1] x [m.sup.-2], but as the old figures filter through from the days when the chilling unit was permanently on, it is expected to reduce to 5.0 kWh x [y.sup.-1] x [m.sup.-2].

[FIGURE 10 OMITTED]

CONCLUSION

The initial monitoring of the ZICER building's energy usage highlighted that the heating performance of the main part of the building (served by the hollow core ventilation) was not meeting its design target of being on par with if not better than the heating consumption of the EFry building (approximately 35 kWh x [y.sup.-1] x [m.sup.-2]). The results showed that the ZICER building was using 84% more space heating than the EFry building per square meter of floor area. When this was identified, the monitoring results of the AHU recuperation mode were investigated. It was observed that on the original return air temperature control strategy, the AHU switched from free-cooling to cycling with heat recovery at intervals as short as one minute; hence, the heat that was put into the building one minute was removed from the building the next. With this in mind, the building management control strategy was put on 24-hour slab control to allow the mass of the building to deter-mine whether heating or free-cooling was required, which ultimately would stop the fluctuation between free-cooling and heating.

Re-monitoring the heating performance of the main part of the ZICER building proved that this change in the control strategy was a success during the winter months. Over this time, the ZICER building's heating consumption had become compatible with that of the EFry building. However, it was evident that during the inter-seasonal months the ZICER building still consumed more space heating than the EFry building. From general observation it was discovered that the few radiators in the ZICER building were left on unnecessarily over this period. These radiators were manually switched off and the improvement in the heating consumption could once again be seen in the monitoring results that followed.

By September 2005, the rolling annual heating for the main part of the ZICER building served by the hollow core ventilation had decreased by 57% from the first set of monitoring results and had reduced to 36.4 kWh x [y.sup.-1] x [m.sup.-2]. This figure is much below the ECON 19 good practice energy benchmarks (DETR 1998), and it is estimated that over the next 12 months the effect of switching off the radiators when their use is not required will decrease the heating by an additional 18%.

As described previously, a building designed to be low energy should not be taken as given. A monitoring regime should be set up to assess the actual energy performance of a building, which will identify any discrepancies in the energy load. If the data show that a problem exists, it can be investigated further and any modifications then made to the energy demand can be evaluated against past data collection. The whole monitoring procedure that has taken place for the ZICER building has shown that effective record keeping, analysis of the results, and good management is essential to achieve the full potential of a low-energy building.

The highly glazed, low thermal mass Top Floor of the ZICER building represents 10% of the total conditioned floor area yet used 53% of the building's total heating demand and 74% of the overall cooling. This increased the heating and cooling energy consumption of the whole building on a square meter basis by 96%. The heating energy performance of the ZICER building worsened when the original figure for the main building's heating was combined with that of the Top Floor heating. The ZICER building went from being good practice to being only slightly better than figures for a naturally ventilated office.

The monitoring procedure and changes to the heating and cooling strategies were also carried out on the Top Floor. Early results suggest that improvements have reduced the heating and cooling in the seminar room but that no improvements have occurred in the energy performance of the exhibition area. The energy consumption of the Top Floor has been estimated from the early monitoring results, and since the improvements have been made, the seminar room heating is estimated to be over three times the heating per square meter of the main part of the ZICER building with 100 kWh x [y.sup.-1] x [m.sup.-2], and the exhibition area is estimated to have a heating load ten times the demand for the main part of the ZICER building with 298.4 kWh x [y.sup.-1] x [m.sup.-2]. Even though the thermal conditions in the exhibition area during winter have improved, this area still suffers from many complaints from occupants.

From this particular case study it has been shown that the glass construction Top Floor has reduced its overall energy demands through modifications to the physical structure and changes to the control system, but it has not met good practice energy benchmarks outlined in ECON 19 (DETR 1998), and it does not achieve a high thermal acceptability from the users of the space.

ACKNOWLEDGMENTS

The authors would like to thank Martyn Newton, Assistant Director of Estates, UEA, UK; Mel Pascoe, Energy Manager, UEA, UK; Paul Totton, BMS Manager, UEA, UK; Research grant--UEA, UK and DTI, UK; Davis Langdon, Project Managers, UK; Northcroft, Quantity Surveyor, UK; RMJM, Architects and Service Engineers, UK; Whitbybird, Structural Engineers, UK; Willmott Dixon, Contractor, UK; and the ASHRAE reviewers.

REFERENCES

Carbon Trust. 2005. Historical UK degree days data. http://www.thecarbontrust.co.uk/energyCMS/CarbonTrust/items/Documents/Resources/AugustDegreeDays__120.pdf. Accessed Nov 2005.

DETR. 1998. Energy use in offices. Energy Consumption Guide 19. UK: Department of the Environment, Transport and the Regions.

PROBE Team. 1998. Probe 14: Elizabeth Fry building. Building Service Journal: The Magazine of the CIBSE 20(4):E20-E25.

Raydan, D., and C.H. Turner. 2005. A learning experience through applied research in energy efficient design. Proceedings of the 22nd Conference on Passive and Low Energy Architecture, Beirut, Lebanon, November 13-16.

DISCUSSION

Ken Fulk, Principal, Reed, Wells, Benson & Co. Consulting Engineers, Dallas, TX: (1) Do you filter the return air exhausted through the energy recovery wheel? (2) What was done to keep concrete cores clean to prevent dust, dirt, and debris from being distributed into the occupied space? (3) How many zones of control were provided on each floor? (4) Were all control zones similar in regard to heat gain/loss? (5) How were zones addressed that had significantly higher or lower heat gains than the typical zone? (6) How was building relative humidity controlled? (7) Did condensation occur in the concrete cores? (8) How did you prevent condensation from occurring in the cores? (9) Could mold develop in the cores under condensate conditions? (10) How would concrete cores be cleaned (mold/dust/dirt, etc.)?

C.H. Turner: (1) In the ZICER building there is a regenerative heat exchanger. There is no filtration on the return air, only on the incoming air into the building. However, the incoming air is not in direct contact with the return air path. The School of Nursing and Midwifery mentioned in the paper (the same design as the ZICER building) does utilize an energy recovery wheel, and the air is filtered on both the incoming and the return air.

(2) Initially the cores should be cleaned to a UK cleaning ductwork standard, the HVCA TR/19 Guide to Good Practice "Internal Cleanliness of Ventilation Systems." The air is then filtered before entering the building to prevent dust and dirt from entering the occupied space. Additional cleaning of the cores should take place every five years.

(3) Each floor is taken to be a different zone.

(4) The ground, first, and second floors all have similar heat gains/losses. The basement has a different heat gain/loss for several reasons. First, in the basement there is no solar heat gain. Second, the basement is only used intermittently. Therefore, when it is not in use there is a low heat gain due to little computing equipment operation and no people (hence, no body heat). When the basement is in use there is a high heat load due to lots of high-tech computing equipment in the space and also lots of people in a small area. Third, the basement is underground, leading to a heat loss different from the floors above.

(5) The basement has lower heat gains than the rest of the building when it is not in use. Thus, if the concrete hollow core ceiling slabs in the basement are below the setpoint temperature, more heat is input into basement concrete slabs. High heat gains are likely when the basement is in full use; therefore, it is actively cooled, as explained in the paper.

(6) In our buildings of this particular design, the relative humidity is not actively controlled but the humidity is passively moderated by the concrete slabs absorbing and giving out humidity.

(7) No, condensation did not occur in the concrete cores.

(8) The air is prevented from going down to a temperature where condensation occurs (approximately 12[degrees]C for the UK climate).

(9) If condensation conditions occurred then perhaps it could, but it is not allowed to take place. Concrete is also very alkaline; not many spores can live under those conditions.

(10) They can be cleaned by a Jet Vent Cleaning technique that uses compressed air to dislodge particulate contamination, which is then carried away to an extract unit for filtration collection (in accordance with COSHH regulations) and removal off site. Access to the cores for cleaning purposes is via the supply inlets into the rooms and through two specially designed inlets per concrete slab in the bulk head.

Richard Kelso, Professor, University of Tennessee, Knoxville, TN: (1) How was slab temperature measured in the second control strategy? (2) How did change in control strategy affect occupant comfort?

Turner: (1) Several temperature sensors are embedded in the concrete slabs on each floor. The average of these temperature sensors on each floor are used to determine whether heating or free cooling is required for the floor in question.

(2) The change in the control strategy had little effect on the thermal comfort of the occupants. Thermal comfort questionnaires were completed by the occupants of the ZICER building before and after the change in control strategy. Both sets of questionnaires indicated that a few occupants find the internal temperature too hot and a few occupants find the internal temperature too cold, but overall the majority of occupants and the average of the results show that a neutral temperature has been achieved; i.e., the occupants are neither too hot nor too cold.

C.H. Turner

N.K. Tovey, PhD, CEng

C.H. Turner is a PhD student in the school of Environmental Science and N.K. Tovey is the HSBC Director of Low Carbon Innovation, University of East Anglia, Norwich, UK.

* The UK has a temperate climate with marked changes between the spring, summer, autumn, and winter seasons. The 20-year average degree-days for East Anglia, where the ZICER building is located, are 2263 based on a balance temperature of 15.5[degrees]C (Carbon Trust 2005).
Table 1. Annual Delivered Energy Consumption for Good Practice and
Typical Offices for the Four Office Types in kWh x [m.sup.-2] of
Conditioned Floor Area (DETR 1998)

 Naturally Ventilated Naturally Ventilated
 Cellular Open-Plan
 Good Good
 Practice Typical Practice Typical

Heating and hot 79 151 79 151
 water--gas or oil
Electricity (without 33 54 54 85
 computer room)

 Air-Conditioned Air-Conditioned
 Standard Prestige
 Good Good
 Practice Typical Practice Typical

Heating and hot 97 178 107 201
 water--gas or oil
Electricity (without 114 208 147 253
 computer room)

Table 2. The Rolling Annual Heating, Hot Water, and Cooling Results for
All Areas of the ZICER Building (Figures Updated to September 2005)

 Area Size Energy Consumption
Energy Load ([m.sup.2]) (kWh x [y.sup.-1] x [m.sup.-2])

 Overall hot water 2633 6.4
 (estimated)
Heating of the main part 2364 36.4
of the building
Seminar room heating 90 499.9
Exhibition area heating 180 298.4
 Overall heating 2633 70.1
Basement cooling* 271 7.0
Seminar room cooling* 90 59.9
Exhibition area cooling* N/A N/A
 Overall cooling* 2633 2.8
 Overall ventilation and 2633 19.1
 regenerative heat
 exchanger electricity
 Total overall hot water, 2633 98.4
 space heating, cooling,
 and ventilation

* The cooling figures are in electricity consumption equivalents.

Table 3. Issues and Modifications Made to the Heating and Cooling
Strategy of the Seminar Room of the ZICER Building

Issue Modification

Heating and cooling The heating and cooling strategy was modified to
of the seminar make use of a carbon dioxide sensor and a heater
room from outside or cooler battery in the ductwork of the seminar
temperatures to the area that were both fitted during construction of
indoor setpoint the ZICER building. Now, if the return air
temperature via the temperature is above or below the setpoint
AHU proved to be temperatures for cooling or heating, the BMS looks
inefficient. at the C[O.sub.2] levels in the room. If these
 levels exceed the limits then, like the original
 strategy, the seminar room is heated and cooled by
 the AHU. If the C[O.sub.2] levels are below the
 limit, the return seminar air is circulated
 through the heater or cooler battery, where the
 return air is brought back within the temperature
 setpoints, before returning to the seminar space.
 If no heating or cooling are required and the
 C[O.sub.2] levels are below the limits, then the
 seminar room air is recirculated, above the
 C[O.sub.2] limit, and fresh air is brought in via
 the AHU.
The seminar room is A movement sensor was retrofitted to detect motion
used sporadically in the seminar room. When the sensor is activated,
throughout the the BMS decides what action is required. It is
week, yet under the reactivated every 15 minutes if people remain in
original strategy the seminar room. The BMS has also been programmed
it was heated and to activate the heating or cooling if the
cooled to remain temperature gets too low or too high when the room
constantly within is unoccupied.
the setpoint
temperatures.
Thirty-minute Adjustments were made to the setpoint temperatures
monitoring results to ensure that heating to the upper setpoint
of the seminar room temperature did not then activate cooling to the
revealed that lower setpoint temperature, which in turn would
heating and cooling activate heating.
were used in
conjunction with
one another within
the thirty-minute
time period.

Table 4. Estimated Annual Heating, Hot Water, and Cooling Results for
All Areas of the ZICER Building (Figures Estimated for 12 months' time,
September 2006)

 Estimated
 Estimated Reduction
 Energy From
 Consumption Current
Energy Size (kWh x [y.sup.-1] x Figures
Load ([m.sup.2]) [m.sup.-2]) (%)

 Overall hot water 2633 6.4 0
 (estimated)
Heating of the main 2364 30.0 18
part of the
building
Seminar room 90 100.0 80
heating
Exhibition area 180 298.4 0
heating
 Overall heating 2633 50.8 30
Basement cooling* 271 5.0 29
Seminar room 90 22.0 63
cooling*
Exhibition area N/A N/A 0
cooling*
 Overall cooling* 2633 1.3 54
 Overall 2633 19.1 0
 ventilation
 and regenerative
 heat exchanger
 electricity
 Total overall hot 2633 77.6 27
 water, space
 heating, cooling,
 and ventilation

* The cooling figures are in electricity consumption equivalents.
COPYRIGHT 2006 American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2006 Gale, Cengage Learning. All rights reserved.

Article Details
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Author:Turner, C.H.; Tovey, N.K.
Publication:ASHRAE Transactions
Geographic Code:4EUUK
Date:Jul 1, 2006
Words:6901
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