Overheating Analysis and Remedial Works Recommendations Report

Transcription

1 Overheating Analysis and Remedial Works Recommendations Report Gallery Space & Glazed Corridor AAD Building (East) University of Lincoln Brayford Pool Lincoln LN6 7TS Project No.: Revision: * Date: Richard Tibenham Consulting All Rights Reserved

2 1 This report has been produced by: Richard Tibenham (Director) Greenlite Energy Assessors 11 Yarborough Terrace Lincoln LN1 1HN T: E: For: Estates & Commercial Facilities Department University of Lincoln Lincoln Lincolnshire LN6 7TS Revision Notes: Revision: Date Notes: Assembled by: * Based on information provided by client and site survey data. RT

3 2 Contents 1.0 Introduction Description of the Spaces Strategy for Achieving Thermal Comfort Investigated Options; Summary The Thermo-Dynamic Models Model 1; As Specified Model 2; Addition of a room thermostat to control HRU Model 3; Addition of a room thermostat to control HRU01, plus the inclusion of heat recovery by-pass damper Model 4; Addition of high capacity extract fan to the apex of the atrium, plus amended curtain glazing assembly to rear fire escape door Model 5; Addition of louvered glazing to the atrium, plus amended curtain glazing assembly to rear fire escape door Model 6; Addition of top hung open roof lights to the atrium, plus amended curtain glazing assembly to rear fire escape door Model 7; Air conditioning to gallery floor space Investigation into the Impact of Reduced Solar Gains Relative Humidity Levels and Potential for Drafts Résumé of Options Conclusions and Recommendations 56 Appendix A X-Plane CFD Air Temperature Outputs 58

4 3 Executive Summary The University of Lincoln Estates and Commercial Facilities department have appointed Greenlite Energy Assessors to undertake analysis of the gallery space and glazing corridor link within the newly constructed AAD (east) building at the university s Brayford Pool campus. The gallery space incorporates a large, unshaded, glazed atrium to the south of the room. The glazed corridor, which links the new building with the existing AAD (west) building features glazing to the entirety of the roof and wall. The glazed corridor is located on the south elevation of the building and is unshaded during the majority of the day. The gallery space is assessed to yield peak solar gains of approximately 12.5kW, and the glazing link around 43kW. Despite the clear potential for very high solar gains, little or no consideration appears to have been given to overheating risk in these spaces, in either the architectural design or mechanical systems specification. As a consequence, both spaces suffer from chronic overheating problems during a large proportion of the year, rendering the gallery space unusable and the corridor very uncomfortable. Within the gallery, this is not only poor for human comfort, but also for the display and storage of artefacts in room. The south facing internal wall within the gallery has been calibrated as reaching 56 C this summer. These temperatures make the wall unsuitable for placing artwork, which is its intended purpose. Greenlite Energy Assessors have been appointed to investigate remedial measures which can be employed within the spaces to reduce internal temperatures to acceptable levels. Through the use of Dynamic Thermal Modelling (DTM) and Computational Fluid Dynamics (CFD) software, various investigations have been carried out to assess the merits of various remedial approaches. It is concluded that a number of options are available to address the overheating problems being experienced. Of these however, only three are probably viable; a mechanical extract option, a full natural ventilation option or air conditioning. Reductions in solar gains are demonstrated to be of some benefit, but not sufficient in isolation. The introduction of glazed louvers to the glazed corridor is assessed to be a highly successful option. Disclaimer This report provides advice on options available to achieve thermal comfort within the UoL AAD (east) gallery space and glazed corridor, using IES VE simulation software. The results provide an illustration of the thermal conditions likely to occur during a hot summer. The report does not however guarantee that over heating within its widest terms does not occur based upon any proposed strategy, as this is dependent upon personal tolerance to high temperatures, metrological conditions, and the performance and design of the systems installed. This report goes to some degree to illustrate many of the considerations which must be made when adopting a particular strategy, however the responsibility to ensure thermal comfort remains with others.

5 4 1.0 Introduction Dynamic Thermal Modelling (DTM) and Computational Fluid Dynamics (CFD) modelling of the AAD (east) building has been undertaken using the IES suite of simulation software modules. As part of the investigation, both the AAD (west) and Engineering Hub have been modelled in order to accurately account for solar shading from these two prominent topographical features. Concise modelling of the gallery space, glazing corridor link and all adjacent rooms has been undertaken to account for suitable boundary conditions within the critical analysed zones. All inputs into the initial simulation are based upon information provided by the client or gleaned from site visits. These inputs include architectural geometry, architectural specifications, HVAC specifications and so forth. Where inputs concern occupancy densities, internal gains from lighting and equipment etc, suitable inputs have been made based upon observations made at site. All simulations utilise the CIBSE Nottingham design summer year weather file for analysis, which accounts for high summertime temperatures. Through discussion with the client, it has been agreed that operational temperatures of C within the gallery space should be targeted. Conditions within the glazed corridor link are considered less critical. The analysis utilises the as-specified simulation as a template for exploration into the remedial options available to achieve this. The considered options are; 1. Addition of a room thermostat to control HRU Addition of a room thermostat to control HRU01, plus the inclusion of a heat recovery by-pass damper. 3. Addition of a high capacity extract fan to the apex of the atrium, plus amended curtain glazing assembly to the rear fire escape door. 4. Addition of louvered glazing to the atrium, plus amended curtain glazing assembly to the rear fire escape door. 5. Addition of top hung open roof lights to the atrium, plus amended curtain glazing assembly to the rear fire escape door. 6. Air conditioning to the gallery floor space. This report begins by describing the context of the overheating problems within the rooms and the reasons for this, and continues to assess the various remedial options described above. Each option is assessed in terms of its ability to deliver the thermal conditions necessary and the likely operational costs. Capital costs should be attained for the considered options and when combined with the assessed running costs, can be used to compare options in respect of financial considerations.

6 5 2.0 Description of the Spaces The AAD (east) building is a new build construction which adjoins the existing AAD (west) building. The building features a fully glazed corridor which adjoins the two buildings and a heavily glazed gallery space. This area of the building is illustrated below, with the glazed corridor shaded in red and gallery in blue. These two zones are the principal focus of this report. In section, the rooms are shown below. The glazed link is separated from the gallery by means of a deep section stud wall construction. The gallery comprises a single height section to the rear of the room and two storey glazed atrium to the south. Neither room is specified with opening windows, therefore any solar gains entering the spaces are contained within them, resulting in very high internal temperatures during certain times of the year. The glazed link in particular experiences extremely high internal temperatures during the summer. Construction fabrics used around these two zones are predominantly of a lightweight construction. All partition walls, including the partitions between the glazed corridor and gallery, and between the gallery and first floor shared use space are lightweight constructions with limited thermal mass. There is an area of exposed first floor construction to the rear of the gallery, and the ground floor is of a polished concrete construction. The ground floor to the glazed corridor is a concrete ground floor slab with slate grey floor tiles.

7 6 3.0 Strategy for Achieving Thermal Comfort The high internal temperatures occurring within the building are the product of; Very high solar gains. No ability to purge warm air from the building once it is present. Low thermal mass within the structure. The high internal temperatures are not the product of; Internal gains resulting from occupancy density, equipment or lighting. In order to address the overheating issues within the space, one or more of the highlighted issues must be addressed. The context of this particular building should be considered when making these choices. The following is a brief summary of the considerations necessary; Measures to Reduce Solar Gains; Solar gains are the principle heat source to both rooms during the summer. A reduction in solar gains will yield a reduction in internal temperatures. Measures to reduce solar gains can include; Reduced glazed area. Low-g solar glazing. External solar shading such as bris soliel or blinds. Internal shading such as blinds or curtains. External shading is generally the most effective for limiting solar gains, however the low-g glazing can also be effective. Solar shading or low-g glazing can have limited effect when located on east or west elevations due to the lower sun altitude. In this case however, glazing is orientated south, where the effect of either is optimised. Internal shading is limited in performance, due to the fact that once solar gains are within the insulation envelope of the building, they cannot leave so easily. The use of internal blinds within the glazed corridor would have little effect if windows remain fixed closed, as the accumulated heat gains between the glazing and the blind would re-radiate back into the room. All the above options will also reduce the availability of natural light. Given the light and airy nature of the glazed corridor, and requirement for natural light within the gallery, it is suggested that reductions in solar gains are not the first aspect to be addressed. Furthermore, it is unlikely that reductions in solar gains alone will provide the results required. Reductions in solar gains may form part of the solution, but will probably need to be accompanied by the ventilation methods suggested below.

8 7 Measures to Allow the Purging of Warm Air from the Building; Overheating is partly the result of accumulated solar heat gains. The considerable quotas of glazing provide very high levels of solar gains. The glazed corridor is assessed to be up to ~43kW and the gallery up to ~12.5kW. Once these gains are within the building, there are no mechanisms in place to allow them to be discharged. Both the gallery space and atrium begin the day with the highest temperatures occurring within the upper roof space. As the day continues and solar gains continue to occur, high temperatures occur progressively lower down, until very high temperatures are experienced at ground level. In order to rectify this problem, mechanisms must be put in place which allow warm air to exit the building, being displaced by cooler air entering the building. This can be achieved through several means, which can be broadly grouped into; Natural ventilation strategies Mechanical ventilation strategies Air has a very low thermal capacity, which means that in order to dissipate the high levels of solar gains occurring with the spaces, large volumes of air at the external air condition must be drawn through the building in order to reduce the internal temperatures. Alternatively, smaller volumes of air at a lower temperature can provide the cooling effect required which implies the use of mechanical cooling (air conditioning). Because the partition wall located between the gallery space and glazed corridor is intended to be used as a display area, air transfer grilles cannot be located within this wall. This divides both spaces and precludes both rooms from operating under a single ventilation system. As such, separate approaches must be applied in each room. Geometry used within the IES simulations:

9 8 The Existing Ventilation System: The gallery space is equipped with mechanical ventilation via heat recovery unit 01 (HRU01). This is located within the ceiling space of the sculpture room. However, this system is drastically limited in its scope to address high internal temperatures, due to; The flow rate from the unit being regulated based upon CO 2 concentrations only. The heat recovery unit being permanently active. There is no by-pass damper fitted. The mechanical ventilation flow rate is regulated only CO 2 concentrations only there is no control based upon internal temperature. The supply rate will only increase when the CO 2 concentration within the room increase beyond a certain threshold. As the space is infrequently occupied, this results in the system not becoming operational. The system is also regulated using a time-clock, which currently only operates the system during the day. The introduction of a simple room thermostat, and extension of the active period to cover a 24/7 period would allow reaction of the existing mechanical ventilation system to internal temperatures at any time. Heat recovery ventilation allows ventilation to occur without the thermal losses usually associated with natural ventilation. Heat is recovered by means of a heat exchanger matrix, which draws heat from the extracted air and uses it to heat the incoming supply air. During the heating season, this is desirable as it reduces the heating demand. However in the summer, where the internal temperatures are possibly higher than desired, the pre-heating of supply air is not desired. For this reason, heat recovery by-pass dampers are often installed to allow the heat recovery unit to be by-passed, therefore allowing air to be supplied at the external air condition. There a few examples where a heat recovery by-pass damper would be more critical than within the gallery space. However, for some reason, this has not been specified -despite only being a small additional cost. As a result, air being supplied to the room is calculated to reach up to 38 C, as it recovers around 75% of the heat from the out-going extract air. The inclusion of a by-pass damper would allow supply air to be delivered at the external temperature condition; circa C through much of the summer. Where a by-pass damper is fitted to the existing HRU (if possible) and the unit is controlled using a room thermostat and extended time-clock setting, this option will provide a quota of space cooling. It is however limited in scope, in that the ventilation rate cannot be increased any more than is installed, and the system is only capable of effecting the ground floor level high temperatures are likely to remain within the atrium area, where artwork is required to be located. It should be noted that the operation and maintenance manual for the building does state in section General Ventilation, that the ventilation system to the building shall be in accordance with the following standards and recommendations.overheating criteria CIBSE Guide A Not to exceed 28 C for 1% of the occupied period. Clearly this level of performance is not achieved within the gallery space, and it would appear to have received limited or no regard in respect of the specification of the currently installed heat recovery unit.

10 9 Natural and Mechanically Assisted Natural Ventilation: Options exist to allow warm air accumulating within the atrium space to be discharged. In doing so, this can draw air through the remainder of the room, providing space cooling as a result. In order to be successful, this approach requires the system to work in harmony with the natural buoyancy of air. Warm air rises, so should be extracted from as high in the zone as is feasible. In order for the warm air to escape, balance air must be introduced into the space to balance the pressure. Where cooler air is introduced at low level, the resulting temperature imbalance results in a stack effect convection current. This phenomena can occur naturally, or can be assisted using mechanical assistance (fans etc). The gallery space lends itself to this strategy, as the very high solar gains will actually help drive the convection current the system is self-regulating; higher solar gains mean higher ventilation rates. Within the gallery, this effect can be produced by introducing cool air at the rear of the zone via louvers or other suitable openings introduced in the fire escape door curtain glazing assembly. Being located at the north of the building, and being in permanent shade, means that air being introduced into the building at this location will be as cold as possible without incurring mechanical cooling. Warm air can be extracted from the upper atrium area by means of; Opening roof vents (windows). Glazed louvers to the vertical elements of glazing. Mechanical extract fans located within the upper zone and discharging to the flat roof space. Mechanical extract fans located within the glazing, or opaque glazing replacement. With respect to the glazed corridor, there are few opportunities to integrate mechanical ventilation. A natural ventilation approach is likely to be most feasible. As with the gallery, this requires warm air to be allowed to escape easily at the highest part of the zone, and cool air to be introduced at the base. This could take various guises, however possibly the most appropriate option would be to introduce several glazed louvers to the corridor, which allow large free-opening areas for both inlet at the base and outlet at the height of the zone. These could be automated or manual, however a manual device is likely to be less utilised. The illustration below describes this approach, in this case using glazed louvers throughout. An example of glazed louvers is also shown to the right:

11 10 Mechanical Cooling; Mechanical cooling, or air conditioning as it is more commonly known, remains an option to provide the necessary space cooling. However, this option should be given carefully consideration owing to the high operational costs which could be incurred. In its current form, installing air conditioning into the gallery space is much like installing air conditioning into a greenhouse it makes very little sense to be incurring very high solar gains and addressing these gains using very high cooling loads. A more prudent approach would be remove the problem initially, by allowing warm air to escape naturally, as described in the previous section, or if these options are cost prohibitive, at least apply a degree of solar shading in order to reduce solar gains prior to installing a system. Mechanical cooling could take two forms. Air conditioning cassettes could be located within the lower gallery space to provide direct space cooling, or, a cooling coil could be introduced to the existing mechanical ventilation system in order to introduce chilled air. Both options would address temperatures within the lower gallery space. High temperatures would most likely maintain to be observed in the upper atrium area, which may cause deterioration to artwork located there.

12 11 Introduction of Further Thermal Mass: One factor in the causation of high internal temperatures experienced within the building is the low thermal mass, lightweight construction methods employed. All partition walls to the zones are constructed using lightweight stud wall constructions and incorporate limited thermal mass. As a result, the thermal storage capacity of these elements is minimal, and it only takes a small amount of thermal energy to be input into the material to raise the temperature. As a result, surfaces respond quickly to changes in solar gain, and will attain an energy equilibrium very quickly where by the solar energy into the material is equal to the thermal energy radiated out. This results in surfaces achieving high temperatures when exposed to prolonged solar gains. The use of higher thermal mass fabrics would allow for solar gains to be absorbed by the material to a greater degree. The time taken for an energy equilibrium state to be achieved is delayed by the materials ability to absorb higher levels of thermal energy. The inclusion of higher thermal mass materials would allow materials to heat during the day and cool during the night (with the aid of a night-time purge ventilation strategy). However, the retro-fitting of thermal mass is not easily feasible. Short of removing the existing walls and creating heavy weight concrete walls in their place, there are few options available. One option is the use of phase change materials (PCM) which use the latent heat capacity available within paraffin wax and similar materials to absorb thermal energy through a change in state; solid to liquid. These materials are however expensive. Furthermore, the very high solar gains with the spaces are so high that vast amounts would be necessary the equivalent of half meter thick concrete walls, or thereabouts. This really makes the introduction of further thermal mass non-viable and it is suggested that the previous two options are exploited prior to investigating this option.

13 12 Resumé of Remedial Measures easures: 1. Reduce solar gains by means of internal or external shading or low-g glazing. Internal shading is likely to have little effect, external shading is likely to have a more pronounced effect. The likelihood of success though the reduction of solar gains alone is unlikely. 2. Introduce a means of purging warm air from the building. This may take a number of forms; mechanical or natural ventilation, or mechanical cooling. The likelihood of success by means of purging warm air from the building are high, and may be complimented by the addition of reduced solar gains. 3. Introduce additional thermal mass to the structure. This option is unlikely to be feasible.

14 Investigated Options; Summary The existing specification and a further six exploratory investigations have been carried out in order to assess the performance available via each option. These options are; 1. Model 1; As existing. 2. Model 2; Addition of a room thermostat to control HRU Model 3; Addition of a room thermostat to control HRU01, plus the inclusion of a heat recovery by-pass damper. 4. Model 4; Addition of a high capacity extract fan to the apex of the atrium, plus amended curtain glazing assembly to the rear fire escape door. 5. Model 5; Addition of louvered glazing to the atrium, plus amended curtain glazing assembly to the rear fire escape door. 6. Model 6; Addition of top hung open roof lights to the atrium, plus amended curtain glazing assembly to the rear fire escape door. 7. Model 7; Air conditioning to gallery floor space. In addition, the inclusion of introducing louvered glazing to the glazed corridor is investigated in options 5 & 6, and the impact of bris-soleil and low-g glazing is also investigated.

15 14 Reporting into each option is laid out as follows; Name and description of ventilation/cooling philosophy: The ventilation/cooling strategy is described and illustrated where necessary. Thermal outcomes of the option during July: July is assessed to be the highest temperature month. Graphical outputs are provided to indicate the air temperature within the gallery space and corridor where applicable. Thermal outcomes for Friday 27 th July: The 27 th of July is selected as a typically hot summer day within the Nottingham design summer year weather file. This day is purely selected as a means of benchmarking various options against one another, using common metrological data for a typical hot summer day. Sizing equipment based on this data will allow the necessary performance criteria to be achieved for the large majority of time, however during particularly hot periods, higher temperatures will result. Surface temperature of art display wall: Surface temperatures of the art display wall which forms the partition between the atrium and shared study space are quantified. This will help in assessing an option for its suitability with displaying art in this area and potential for degradation. Air flow patterns: Where necessary, air flow patterns are illustrated and discussed. CFD thermal x-pl x plane section s of building at 15:30 on 27 th July: CFD calculations have been carried out where applicable to illustrate the air temperature at a fixed time. 15:30 on July 27 th is selected as the hottest time within a typically hot summer day. Illustrations help in understanding the thermal performance available via each option. For the purposes of benchmarking, all images use a temperature range of C. Larger images are provide in Appendix A. CFD thermal z-pl plane section of building at 15:30 on 27 th July: As above, but using a Z- plane section at 1.8m (head height) to indicate air temperature. (Animations for the above are provided electronically with this report submission). CFD air velocity x-plane x section s of building at 15:30 on 27 th July: CFD calculations have been carried out where applicable to illustrate the air velocity at a fixed time. 15:30 on July 27 th is selected as the hottest time within a typically hot summer day. Illustrations help in understanding the air velocity occurring within each option, in order to evaluate the likelihood of drafts etc. For the purposes of benchmarking, all images use a velocity range of 0-2m/s. CFD air velocity z-plane section of building at 15:30 on 27 th July: As above, but using a Z-plane section at 1.8m (head height) to indicate air velocity. Annual operation cost: The annual operation cost for each option is estimated. For the purposes of this assessment, systems are accounted to be active if necessary 24/7, in order to prevent high temperatures occurring within the space which could damage artwork (eg during weekends when otherwise systems may be inactive). As such, running costs will be higher than if systems are only operational during occupied time. For comparison purposes, an electricity cost of 13.4p/kWh has been used. Acoustic considerations: A brief summary of acoustic disturbance risks is provided.

16 The Thermo-Dynamic Models 5.1 Model 1; As Specified Model Name/Description: Thermal outcomes of option during July: As specified. Mechanical ventilation only via HRU01, controlled using CO 2 sensor only. No heat recovery by-pass. There is no apparent cooling strategy. Air temperatures are shown below for the gallery space. The highest temperatures occur within the upper roof area of the atrium (green). Lowest temperatures occur within the fire escape stairwell (yellow). External air temperatures are shown in purple. Temperatures experienced within the atrium void register peak around 50 C and the bottom and around 60 C at the top. This is consistent with the peak 56 C measured at site, taken from the sill beneath the internal windows between the gallery atrium and shared use space.

17 Air temperatures within the corridor are shown below. Note that the very high temperatures achieved are an average of the very high temperatures occurring at the glass surface and cooler temperatures in the center of the room. 16

18 17 Thermal outcomes for Friday 27 th July: Air temperatures are shown below for the gallery space. External air temperature is shown in red. Peak temperatures at ground level occur around 15:30. Peak temperatures at ground level exceed 50 C. Surface temperature of art display wall on 27 th July: Surface temperatures for the art display wall are shown below. Peak temperatures occur around 15:30 and exceed 60 C. Air flow patterns: n/a

19 18 CFD thermal x-plane section of building at 15:30 on 27 th July: Air temperatures occurring within the space are shown below. Section taken through rear opening to stairwell. Scale shows 20 C (blue)-40 C (red). Due to the calibration of the scale, air temperatures above 40 C are not distinguished. CFD thermal z-plane section of building at 15:30 on 27 th July: Air temperatures occurring within the space are shown below. Section taken through z-plane at 1.8m CFD air velocity x- plane section of building at 15:30 on 27 th July: CFD air velocity z- plane section of building at 15:30 on 27 th July: Annual operation cost: Acoustic considerations: n/a n/a n/a None

20 Model 2; Addition of a room thermostat to control HRU01 Name/Description; Thermal outcomes of the option during July: Mechanical ventilation only via HRU01. Controlled using CO 2 sensor and additional room thermostat. No heat recovery by-pass. HRU01 assigned to deliver up to 400l/s (design air flow rate). Air temperatures are shown below for the gallery space. The highest temperatures occur within the upper roof area of the atrium (green). Lowest temperatures occur within the fire escape stairwell (yellow). External air temperatures are shown in purple.

21 20 Thermal outcomes for Friday 27 th July: Air temperatures are shown below for the gallery space. External air temperature is shown in purple. Peak temperatures at ground level occur around 15:30. Peak temperatures at ground level exceed 45 C. Surface temperature of art display wall: Surface temperatures for the art display wall are shown below. Peak temperatures occur around 15:30 and exceed 60 C. Air flow patterns: n/a

22 21 CFD thermal x-plane section of building at 15:30 on 27 th July: CFD thermal z-plane section of building at 15:30 on 27 th July: CFD air velocity x- plane section of building at 15:30 on 27 th July: CFD air velocity z- plane section of building at 15:30 on 27 th July: Annual operation cost: Acoustic considerations: Not calculated option not viable. Not calculated option not viable. Not calculated option not viable. Not calculated option not viable. Not calculated option not viable. No more risk of acoustic disturbance than is already present.

23 Model 3; Addition of a room thermostat to control HRU01 plus the inclusion of heat recovery by-pass damper Name/Description; Thermal outcomes of the option during July: Mechanical ventilation only via HRU01. Controlled using CO 2 sensor and additional room thermostat. Heat recovery by-pass specified, regulating between no by-pass when extract air temp. <22 C, to full by-pass when extract temp is >25 C. HRU01 assigned to deliver up to 400l/s (design air flow rate). Flow rate regulates between 0l/s when room temp <22 C and 400l/s when room temp >25 C. Flow control subject to CO 2 concentrations remains present. Air temperatures are shown below for the gallery space. The highest temperatures occur within the upper roof area of the atrium (green). Lowest temperatures occur within the fire escape stairwell (yellow). External air temperatures are shown in purple.

24 23 Thermal outcomes for Friday 27 th July: Air temperatures are shown below for the gallery space. External air temperature is shown in purple. Peak temperatures at ground level occur around 15:00. Peak temperatures at ground level exceed 40 C beneath the atrium and around 38 C at the rear of the gallery space. Surface temperature of art display wall: Surface temperatures for the art display wall are shown below. Peak temperatures occur around 15:00 and almost reach 60 C. Air flow patterns: n/a

25 24 CFD thermal x-plane section of building at 15:30 on 27 th July: Air temperatures occurring within the space are shown below. Lower temperatures are achieved to the rear of the room, but remain above target temperature range. Section taken through supply air grille. Scale shows 20 C (blue)-40 C (red). Due to the calibration of the scale, air temperatures above 40 C are not distinguished. CFD thermal z-plane section of building at 15:30 on 27 th July: Air temperatures occurring within the space are shown below. Section taken through z-plane at 1.8m. CFD air velocity x- plane section of building at 15:30 on 27 th July: Air velocities within the space are shown below. Section taken through supply air grille. Scale shows 0m/s (blue)-2m/s (red). Air velocity is within tolerable bounds.

26 25 CFD air velocity z- plane section of building at 15:30 on 27 th July: Air velocities within the space are shown below. Section taken through z- plane at 1.8m. Air velocity is within tolerable bounds. Annual operation cost: Acoustic considerations: ~ 238/yr No more risk of acoustic disturbance than is already present.

27 5.4 Model 4; Addition of high capacity extract fan to the apex of the atrium, plus amended curtain glazing assembly to rear fire escape door 26 Name/Description; Mechanical ventilation as currently specified via HRU01. Controlled using CO 2 sensor only. Heat recovery by-pass not specified. 4m³/s inverter driven extract fan assigned to upper atrium zone, discharging via ductwork through shared use space and out through flat roof, as pictured below: Balance air to be provided via top hung opening windows above stairwell fire door, capable of opening to 45, and a louvered glazing or opaque infill panel adjacent the fire escape door, as pictured below: Both the mechanical extract fan and the opening windows to the stairwell fire door are assigned to be regulated using a thermostat located within the gallery, beneath the atrium at head height. The extract fan is assigned to extract 0l/s when the air temperature is <22 C, with and the inverter driven motor increasing capacity to provide 4000l/s extract at >25 C. Windows and louvers are assigned to be shut when the air temperature is <22 C increasing to full opening at >25 C. It is important that both systems work in unison.

28 27 Thermal outcomes of the option during July: Air temperatures are shown below for the gallery space. The highest temperatures occur within the upper roof area of the atrium (green). Lowest temperatures occur within the fire escape stairwell (yellow). External air temperatures are shown in purple. Internal temperatures are aligned much closer to external temperatures with this option. Thermal outcomes for Friday 27 th July: Air temperatures are shown below for the gallery space. External air temperature is shown in black. Peak temperatures at ground level occur around 15:30. Peak temperatures at ground level do not exceed 25.5 C.

29 28 Surface temperature of art display wall: Surface temperatures for the art display wall are shown below. Peak temperatures occur around 14:00 and do not exceed 38 C. Air flow patterns: CFD thermal x- plane section of building at 15:30 on 27 th July: n/a Air temperatures occurring within the space are shown below. Section taken through rear opening to stairwell. Scale shows 20 C (blue)-40 C (red).

30 29 CFD thermal z- plane section of building at 15:30 on 27 th July: Air temperatures occurring within the space are shown below. Section taken through z-plane at 1.8m. CFD air velocity x- plane section of building at 15:30 on 27 th July: Air velocities within the space are shown below. Section taken through opening to stairwell. Scale shows 0m/s (blue)-2m/s (red). Air velocity is highest through the stairwell/gallery opening, however remains within tolerable bounds. CFD air velocity z- plane section of building at 15:30 on 27 th July: Air velocities within the space are shown below. Section taken through z- plane at 1.8m. Air velocity is within tolerable bounds. Annual operation cost: Acoustic considerations: ~ 199/yr Moderate risk of acoustic disturbance from extract fan.

31 Model 5; Addition of louvered glazing to the atrium, plus amended curtain glazing assembly to rear fire escape door Name/Description; Mechanical ventilation only via HRU01. Controlled using CO 2 sensor only. Heat recovery by-pass not specified. Natural ventilation provided via a bank of louvered windows to the atrium, as shown below: Balance air to be provided via top hung opening windows above stairwell fire door, capable of opening to 45, and a louvered glazing or opaque panel infill adjacent the fire escape door, as pictured below: Both the louvered windows to the atrium and the opening windows to the stairwell fire door are assigned to be regulated using a thermostat located within the gallery, beneath the atrium at head height. Windows and louvers are assigned to be shut when the air temperature is <22 C increasing to full opening at >25 C. It is important that both systems work in unison.

32 31 This simulation also accounts for 3Nr panels within the glazed corridor being replaced with louvered windows, operated via actuators controlled via a local room thermostat. Louvers are assigned to be shut when the air temperature is <22 C, increasing to full opening at >25 C, as with gallery. Louvered panels to the glazed corridor are shown below: The ventilation/cooling strategy is to draw cooler air in at the base of the zones and allow warm air to escape at the top, as shown below:

33 32 Thermal outcomes of the option during July: Air temperatures are shown below for the gallery space. The highest temperatures shown on the graph are for the atrium zone up to the height of the top of the glazed louvers. Higher temperatures will be achieved within the small zone above this level. These results are not shown for clarity. Lowest temperatures occur within the fire escape stairwell (yellow). External air temperatures are shown in red. Shown below are the air temperatures within the glazed corridor. Temperatures do not exceed 36 C in this option.

34 33 Thermal outcomes for Friday 27 th July: Air temperatures are shown below for the gallery space. External air temperature is shown in grey. Peak temperatures at ground level occur around 15:30. Peak temperatures at ground mid level do not exceed 30 C. The zone at the height of the atrium roof, above the level of the glazed louvers does not exceed 65 C. Shown below is the same information, but without the zone at the height of the glazed roof shown:

35 34 Surface temperature of art display wall: Surface temperatures for the art display wall are shown below. Peak temperatures occur around 15:30 and do not exceed 40 C. Air flow patterns: Air flow through the glazed corridor windows is shown below at 15:30 on the 27 th July. The louvered window arrangement works well, drawing air in at ground level and exiting at the height of the louver.

36 35 Air flow through the atrium louvered windows at 15:30 on July 27 th is shown below. The image shows warm air exiting at the top of the louver and entering at the bottom. This is not the design intent of the strategy. A stack effect convection current is not established as a result. The air flow at the fire escape door lobby is shown below. Because a stack effect convection current is not established with this arrangement, hot air is leaving at the stairwell openings, rather than cool air entering. This is not the design intent of the strategy.

37 36 CFD thermal X- Plane section of building at 15:30 on 27 th July: CFD thermal Z- Plane section of building at 15:30 on 27 th July: CFD air velocity X- Plane section of building at 15:30 on 27 th July: CFD air velocity Z- Plane section of building at 15:30 on 27 th July: Annual operation cost: Acoustic considerations: Not calculated option not behaving as intended. Not calculated option not behaving as intended. Not calculated option not behaving as intended. Not calculated option not behaving as intended. ~ 0 Probably Minimal, but dependent upon external sources -external sources will be more audible when windows are open train line etc.

38 5.6 Model 6; Addition of top hung open roof lights to the atrium, plus amended curtain glazing assembly to rear fire escape door 37 Name/Description; Mechanical ventilation only via HRU01. Controlled using CO 2 sensor only. Heat recovery by-pass not specified. Natural ventilation provided via bank of top hung windows to the highest point on atrium, as shown below: Balance air to be provided via top hung opening windows above stairwell fire door, capable of opening to 45, and a louvered glazing or opaque panel infill adjacent the fire escape door, as pictured below: Both the louvered windows to the atrium and the opening windows to the stairwell fire door are assigned to be regulated using a thermostat located within the gallery, beneath the atrium at head height. Windows and louvers are assigned to be shut when the air temperature is <22 C increasing to full opening at >25 C. It is important that both systems work in unison.

39 38 This simulation also accounts for 3Nr. panels within the glazed corridor being replaced with louvered windows, operated via actuators controlled via a local room thermostat. Windows and louvers are assigned to be shut when the air temperature is <22 C increasing to full opening at >25 C, as with gallery. Louvered panels to the glazed corridor are shown below: The ventilation/cooling strategy is to draw cooler air in at the base of the zones and allow warm air to escape at the top, as shown below:

40 39 Thermal outcomes of the option during July: Air temperatures are shown below for the gallery space. The highest temperatures occur within the upper roof area of the atrium (green). The lowest temperatures occur within the fire escape stairwell (yellow). External air temperatures are shown in cyan. Room temperatures are shown to closely follow external air temperature with this option. Air temperatures within the glazed corridor are shown below. Temperatures do not exceed 36 C with this option:

41 40 Thermal outcomes for Friday 27 th July: Air temperatures are shown below for the gallery space. External air temperature is shown in dark red. Peak temperatures at ground level occur around 15:30. Peak temperatures at ground level do not exceed 26.5 C. Surface temperature of art display wall: Surface temperatures for the art display wall are shown above. Peak temperatures occur around 15:30 and do not exceed 38.5 C.

42 41 Air flow patterns: Air flow patterns in the atrium work well and support the design intent. Air flow through the opening top hung roof lights is almost entirely exiting the building. A stack effect convection current is established: Air entering the building at the fire escape door lobby is entirely cool air entering the building, as a result of the convection current occurring within the atrium.

43 42 As part of the investigation into this strategy, it was established that when sizing roof light openings, a reasonable benefit was had from larger roof lights up to around 1m in depth. Beyond 1m, the returns of a larger roof light diminished in respect of the internal temperatures achieved. The table below shows the peak internal temperature on the 27 th July at floor level beneath the atrium for various sizes of roof light opening: Roof light opening depth: Peak temp at floor level: 0.3m C 0.5m C 1.0m C 1.3m C 1.5m C 2.35m C CFD thermal x- plane section of building at 15:30 on 27 th July: Air temperatures occurring within the space are shown below. Lower temperatures are achieved to the rear of the room, however a good spread is achieved throughout. Section taken at opening between gallery and stairwell. Scale shows 20 C (blue)-40 C (red). CFD thermal z- plane section of building at 15:30 on 27 th July: Air temperatures occurring within the space are shown below. Section taken through z-plane at 1.8m.

44 43 CFD air velocity x- plane section of building at 15:30 on 27 th July: Air velocities within the space are shown below. Section taken through opening between gallery and stairwell. Scale shows 0m/s (blue)-2m/s (red). Air velocity is very low, within tolerable bounds. CFD air velocity z- plane section of building at 15:30 on 27 th July: Air velocities within the space are shown below. Section taken at 1.8m. Scale shows 0m/s (blue)-2m/s (red). Air velocity is its highest through the gallery/stairwell opening, however remains very low and within tolerable bounds. Annual operation cost: Acoustic considerations: ~ 0 Probably Minimal, but dependent on external sources -external sources will be more audible when windows are open eg train lines etc.

45 Model 7; Air conditioning to gallery floor space Name/Description; Mechanical ventilation only via HRU01. Controlled using CO 2 sensor only. Heat recovery by-pass not specified. 2Nr 10kW air conditioning cassettes are assigned to the ceiling void within the rear gallery space. Units assigned to provide no cooling when room is <22 C and maximum cooling at >25 C. The units account for a cooling coil total capacity of 10kW each, and each unit accounts for a fan speed of 825l/s. Both the fan and cooling coils are assigned to be inverter driven. The units are located in the recessed ceiling within the rear gallery space as shown below:

46 45 Thermal outcomes of the option during July: Air temperatures are shown below for the gallery space. The highest temperatures occur within the upper roof area of the atrium (green). Lowest temperatures occur within the fire escape stairwell (blue). External air temperatures are shown in yellow. Thermal outcomes for Friday 27 th July: Air temperatures are shown below for the gallery space. External air temperature is shown in purple. Peak temperatures at ground level occur around 15:30. Peak temperatures at ground level does not exceed 25 C. Higher temperatures occur within the atrium void, achieving ~53-73 C.

47 46 Surface temperature of art display wall: Surface temperatures for the art display wall are shown below. Peak temperatures occur around 14:30 and reach approximately 55 C Temperature ( C) :00 02:00 04:00 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 00:00 Date: Fri 27/Jul Surface temperature: Internal wall (UoL AAD Model 7 Full AC.aps) Surface temperature: Internal window 1 (UoL AAD Model 7 Full AC.aps) Surface temperature: Internal window 2 (UoL AAD Model 7 Full AC.aps) Air flow patterns: CFD thermal x- plane section of building at 15:30 on 27 th July: n/a Air temperatures occurring within the space are shown below. Lower temperatures are achieved to the rear of the room beneath the AC cassettes. Higher temperatures occur within the atrium void. Section taken beneath allocated AC cassette. Scale shows 20 C (blue)-40 C (red).

48 47 CFD thermal Z- Plane section of building at 15:30 on 27 th July: Air temperatures occurring within the space are shown below. Section taken through z-plane at 1.8m. CFD air velocity x- plane section of building at 15:30 on 27 th July: Air velocities within the space are shown below. Section taken beneath allocated AC cassette. Scale shows 0m/s (blue)-2m/s (red). Air velocity is highest beneath AC cassette. Rates may be considered a distraction if in an office environment, but probably tolerable for the activity type of the gallery.

49 48 CFD air velocity z- plane section of building at 15:30 on 27 th July: Air velocities within the space are shown below. Section taken at 1.8m. Scale shows 0m/s (blue)-2m/s (red). Rates may be considered a distraction if in an office environment, but probably tolerable for the activity type of the gallery. Rates at head height are shown to be acceptable. Annual operation cost: Acoustic considerations: With 4.0 SEER air source heat pump ~ 940/yr With 5.0 SEER air source heat pump ~ 626/yr Potential acoustic considerations from prolonged high power cooling operation.

50 Investigation into the Impact of Reduced Solar Gains Solar gains form the predominant heat gain within the gallery space and glazed corridor during the summer period. As such, the reduction of these gains will result in a reduction in internal temperatures to some degree. Investigation has been carried out to assess the impact of reduced solar gains through the application of the following to the gallery space; Bris soleil to the south facing glazing only. Bris soleil to the south facing glazing and low-g glazing (g-value 0.4) to the roof lights. Low-g glazing (g-value 0.4) to both the south facing glazing and roof lights, with no bris soleil. Bris soleil has been assigned to the vertical glazing as pictured below, accounting for a 200mm deep fin, orientated horizontally at 300mm spacings.

51 The graph below shows the solar gains occurring within the atrium space, from the bottom to the top of the vertical element of glazing. Further gains occur above this space, within the upper roof zone, directly beneath the roof lights. 50 The graph shows that solar gains to this segment can be reduced by circa 30% through the application of bris soleil. A further reduction of 5-6% can be achieved through the application of low-g glazing to all windows. Total solar gains can be approximately halved through the application of bris soleil to the vertical glazing and low-g glazing to the roof lights. When also accounting for the zone above, including the roof lights, total peak solar gains to the gallery can be reduced from 12.5kW to 7.86kw when applying bris-soleil to the vertical glazing and low-g glazing to the roof lights.

52 The graph below shows how these reduced solar gains translate into reductions in internal temperatures within the gallery space. The graph shows the internal temperatures occurring within the gallery floor space beneath the atrium during July for each option; 51 The graph shows that internal temperatures can be reduced by up to 20% where bris soleil is applied to the vertical element of glazing and low-g glazing is applied to the roof lights. However, internal temperatures remain well above the target temperature, exceeding 45 C at times. As such, reductions in solar gains can be considered as part of the solution, but will be incapable of offering a complete solution in themselves. A further consideration is that any reduction in solar gains will reduce the availability of natural light within the gallery, which may be detrimental to the intended use of the space. A daylight assessment can be conducted to assess the impact of various shading strategies on the availability of natural light within the space if necessary. The same issue shall be the case within the glazed corridor; whilst reductions in solar gains shall offer some benefit, in order to achieve the target internal temperatures, additional mechanisms must be employed to remove the accumulation of warm air in the space.

53 Relative Humidity Levels & Potential for Drafts Due to the very high level of solar gains occurring within the spaces, there is the potential for the overheating to occur even during the winter. The model indicates several occurrences of space cooling becoming activated even during periods of sub-zero temperatures, where solar gains are high due to clear weather conditions. Though the focus of this exercise is predominantly on the performance of strategies to provide space cooling during the summer, the likelihood of overheating during the winter should not be overlooked. Any cooling via ventilation strategy runs the risk of incurring low relative humidity levels and may cause cold drafts. Cold air has a lower moisture carrying capacity than warm air. Therefore, where cold air is used to cool and warm space, the relative humidity in the space shall fall. During the winter, when external air temperatures may be sub-zero, this effect can become pronounced. The graph below shows the lowest relative humidity occurring within Model 6; natural ventilation with top hung windows. The graph shows direct solar gains to the rear gallery space (black) reaching 850W (although almost 8kW occurs through the atrium itself), incurring internal temperatures (green) to rise to 24.5 C. As a consequence, the natural ventilation system becomes gradually active, and in doing so, reduces the relative humidity (red) to 30% -uncomfortably dry. The external air temperature (yellow) ranges from -5-0 C. The likelihood of cold drafts occurring around the rear stairwell opening is therefore high when the ventilation is in operation, however this only occurs for a short duration as the internal temperature within the room falls rapidly as a result of the low supply air temperature. Under this option, the relative humidity within the room is assessed to be below 40% (a minimum comfortable level) for 29% of occupied time, which is predominantly during the winter and spring seasons.

54 Though this assessment has been run using Model 6, the same issues shall occur with any system using ventilation as a means of cooling, where mechanical cooling is not present. The only system type which shall not incur this effect is the use of air conditioning, which cools the air in the space, rather than supply external air at a lower temperature and humidity level. Taking these issues into account, the following are suggested if considering a space cooling strategy via ventilation; Consider de-activating the natural ventilation system during the period December to May and provide space cooling via the existing ventilation system only -operating the HRU via a room thermostat and, if necessary, a heat recovery by-pass damper. Consider operating the system at a limited trickle rate only during the winter/spring seasons. This may result in temperatures exceeding 25 C for short periods, but will avoid the potential for low humidity and cold drafts. Consider operating the natural ventilation system at a limited trickle rate when external temperatures fall below a threshold temperature, based upon the input from an external thermostat. Consider operating the natural ventilation system using an internal humidistat to work in conjunction with an internal thermostat to reduce the ventilation rates if humidity levels become too low. The occurrence of space cooling during what is normally consider the heating season could lead to excess heating demand if the two systems work in a manner which oppose one another. This should be given careful consideration in order to avoid situations where the heating and cooling systems alternate during a single day. 53

55 Résumé of Options Analysis of the available options has been discussed within section five of the report. Below is a brief summary of each option; Model 1; As existing. Unacceptably hot during the spring/summer autumn. Model 2; Addition of a room thermostat to control HRU01. Only achieves minimal improvement in thermal conditions due to no heat recovery bypass damper. Supply air can reach nearly 38 C due to the temperature of extracted air and inclusion of the heat exchanger. Option not viable. Model 3; Addition of a room thermostat to control HRU01, plus the inclusion of a heat recovery by-pass damper. Provides a marked improvement in internal temperatures compared to options 1 & 2, but the flow rates specified remain insufficient to achieve the target temperatures. Cooler temperatures are achieved to the rear of the room, but temperatures to the front of the room beneath the atrium can still be expected to exceed 35 C. Model 4; Addition of high capacity extract fan to the apex of the atrium, plus amended curtain glazing assembly to the rear fire escape door. When specified as described with a 4m³/s extract rate and sufficient openings to the fire escape door curtain glazing, this option is capable of achieving the target temperatures for the large majority of time and provides some of the lowest temperatures on the art display wall. Model 5; Addition of louvered glazing to the atrium, plus amended curtain glazing assembly to the rear fire escape door This option will not generate a stack effect convection current, and as such is not recommended. Lower internal temperatures can be achieved than those in models one, two and three, however the natural ventilation design is not optimised.