Directorate for the Built Environment Building Standards Division

John Gilbert Architects

Improving the energy performance of existing buildings: Office building

June 2009

Report prepared by

John Gilbert Architects

on behalf of Building Standards Division, Directorate for the Built Environment, Scottish Government

Consultants

John Gilbert at John Gilbert Architects Ltd www.johngilbert.co.uk

Glyn Mountford at Energy Management Solutions www.energymanagementsolutions.co.uk

Vincent Farrel at Faber Maunsell www.fabermaunsell.com

David Young at Thomas and Adamson www.thomasandadamson.com

The opinions expressed in this report are those of the author.

Report commissioned by: Building Standards Division Directorate for the Built Environment Denholm House Almondvale Business Park Livingston EH54 6GA Tel: 01506 600 400 Fax: 01506 600 401 e-mail: buildingstandards@scotland.gsi.gov.uk web: www.sbsa.gov.uk © Crown Copyright 2009 Applications for reproduction of any part of this publication should be addressed to: Building Standards Division, Directorate for the Built Environment, Denholm House, Almondvale Business Park, Livingston, EH54 6GA

This report is published electronically to limit the use of paper, but photocopies will be provided on request to Building Standards Division.

Contents

Contents ................................................................................................................................. i

Acknowledgements .............................................................................................................. ii

Glossary................................................................................................................................ iii

Executive summary .............................................................................................................. 1

1 Background ................................................................................................................... 4

2 Energy requirements .................................................................................................... 5

3 The existing building .................................................................................................... 6

4 The new office wing.................................................................................................... 12

5 Detailed investigation of solar options ..................................................................... 16

6 Conclusions................................................................................................................. 20

Appendix A Energy Performance Certificate............................................................. 22

Appendix B Energy performance action plan............................................................ 23

Appendix C Structural and M&E report...................................................................... 29

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Acknowledgements We would like to thank SELECT, the organisation whose building was the subject of this case study, in particular Newell McGuinness, the managing director, and Mike Bowden whose role includes management of the building and the construction of the new wing:

www.select.org.uk/

We would also like to thank the following companies who were approached in the process of developing this report:

Wood fuel boilers

Dan Gates from Wood Energy Ltd www.woodenergyltd.co.uk/

Perthshire Biofuels in Dunkeld www.perthshirebiofuels.co.uk

Arbuthnott Wood Pellets in Laurencekirk www.hotstovies.com

Wood chip supplies www.pentlandbiomass.com

Solar photovoltaics (PV)

Andrew Baird at Solar Century www.solarcentury.com

Barry Griffin at Solar and Wind Applications www.solarwindapplications.com

Solar water heating

George Goodsmit at AES Systems www.aessolar.co.uk

Jim Norris at Solar Energy Systems www.solarenergysystems.co.uk

Ground source heat pumps

Colin Kerr at Ecoliving Ltd www.ecolivinguk.com

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Glossary BER Building Emissions Rate (from calculations of compliance with Building Standard

6.1 Carbon dioxide emissions

CO2 Carbon dioxide

EPC Energy Performance Certificate

M&E Mechanical and electrical

PV Photovoltaic

ROC Renewable Obligations Certificate

SBEM Simplified Building Energy Model (National Calculation Methodology for non-domestic buildings)

TER Target Emissions Rate (from calculations of compliance with Building Standard 6.1 Carbon dioxide emissions

iii

Executive summary The Sullivan report recommends “Consideration of a requirement for consequential improvements and research carried out on inequitability and compliance issues.” The Building Standards Division of the Directorate for the Built Environment, Scottish Government is undertaking a review of the building regulations which includes consideration of the energy performance of existing buildings at a time when alterations are made or the building is extended (consequential improvements). The Sullivan report also recommends “Introduction of legislation to require all owners of non-domestic buildings to conduct a carbon and energy assessment and produce a programme for upgrading”, which led to the inclusion of Section 50 in the Climate Change (Scotland) Bill. This is one of a number of case studies that considers ways in which the carbon and energy performance of existing buildings can be improved, the practicality of such improvements, and the cost impacts. This project has a particular focus on the perspectives of the organisation that owns and occupies the existing building.

This is a case study of a real design project where the host organisation, SELECT, is building a 1500m2 extension to its 2000m2 headquarters. It investigates options both to reduce energy consumption and limit CO2 emissions from the existing building and to introduce low carbon equipment, either to the existing building or the extension, to reduce CO2 emissions overall.

An initial energy audit was undertaken, including an energy performance certificate and investigation of cost-effective options both to reduce CO2 emissions and energy consumption. Several cost-effective improvements to the existing building were identified.

Suppliers of low carbon equipment (ground source heat pumps, wood fuel boilers, solar water heating systems, solar photovoltaics) were asked to advise on options for the building and to provide prices for budget costs. Each option was discussed with the organisation and their perspectives were taken into account in selecting those options that were investigated further. Considerations in the selection of options included the organisation’s building management and maintenance capability, concern for landscaping, cost, disruption, relationships with potential tenants, and messages that could be conveyed to its customers.

Two options, for solar water heating and photovoltaic systems, were selected for more detailed examination, with surveys by a structural engineer and an M&E engineer, and a tender exercise. This detailed investigation was pursued in order to identify the range of costs for installing particular technologies and to understand the implications of installing such technologies on the metal roof of the case study building and linking low carbon equipment to existing building services. It would also help to identify the scale of consultant costs that might be associated with installations to existing buildings and any concerns not previously recognised that might influence the selection of low carbon technologies.

The case study illustrates the following issues in attempting to improve the energy performance of non-domestic buildings.

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• The most cost effective measures are improvements to the existing building services

Adding a variable speed drive to the air handling unit supply fan at a cost of £2,000, would result in 14.8% savings on total emissions from the existing building, with payback within four years. This equates to a capital cost of £105 per Tonne of CO2 saved each year. Improvements to the efficiency of lighting in the entrance and reception area and the addition of heat recovery to the air handling system would each save 3.7% emissions, for payback periods of two and seven years respectively. • Low carbon equipment represents a relatively expensive way to reduce emissions

The cost of installing a 20.5 kW PV system, that generates 15,015 kWh electricity per year, saving 8.5 Tonnes of CO2, equates to a capital cost of £13,081 per Tonne of CO2 saved each year. It would reduce CO2 emissions from the existing building by 6.6%, but would not be sufficient to improve the EPC rating from D to C. A 50 kW or 75 kW woodchip boiler would reduce emissions by 12.5%, at a cost of £4,687 per Tonne of CO2 saved each year.

• It is difficult to raise EPC ratings from one band to another

The building owner was particularly interested in strategies that would improve the EPC rating, which they would be keen to publicise. The 20.5 kW PV system would not change the EPC rating, although it was attractive to the building owner as a very visible demonstration of their interest in reducing emissions.

Despite the substantial reduction in emissions that would be achieved by adding a variable speed drive to the AHU supply fan, by itself this did not change the EPC rating. However, the rating would move from D to C by combining this with improved lighting efficiencies in the entrance lobby and reception, for a total cost of £2,200.

• Remedying inadequate existing building services may not improve EPC ratings

The performance of the existing building is undermined by a lack of zoning, over-sized hot water storage, and lack of timer control on the electric immersion. Zone control could be implemented for £8,000 and a timer added to the heating element for £250, with payback periods of 7 years and 1 year respectively. However, the energy and emissions savings would not be reflected in the assessment for the Energy Performance Certificate.

• There may be limited opportunity for cost effective improvements to the fabric of the existing building

Certain parts of the building were identified as being at risk of overheating due to solar gain, and parts of the building has air conditioning to accommodate for this. Relatively simple installation of glazing solar film will reduce this solar gain and improve the asset rating of the building. It’s unlikely that other building fabric improvements will result in short payback periods.

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• The choice of improvement strategies needs to accommodate the building owner’s business concerns and fit with their facilities management regime

The organisation had no dedicated building maintenance staff, so that any measures adopted must demand minimal maintenance. This consideration precludes the use of biomass. Disruption to the landscaped grounds or car park was unacceptable, precluding ground source heat pumps. Wind turbines were excluded due to fears of planning delays. They were also concerned about the disruption that might arise from work to introduce zone controls to the existing heating system.

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1 Background The Sullivan report recommends “Consideration of a requirement for consequential improvements and research carried out on inequitability and compliance issues.” The Building Standards Division of the Directorate for the Built Environment, Scottish Government is undertaking a review of the building regulations which includes consideration of the energy performance of existing buildings at a time when alterations are made or the building is extended (consequential improvements). The Sullivan report also recommends “Introduction of legislation to require all owners of non-domestic buildings to conduct a carbon and energy assessment and produce a programme for upgrading”, which led to the inclusion of Section 50 in the Climate Change (Scotland) Bill. This is one of a number of case studies that considers ways in which the carbon and energy performance of existing buildings can be improved, the practicality of such improvements, and the cost impacts. This project has a particular focus on the perspectives of the organisation that owns and occupies the existing building.

This project concerns the extension to a building that is owned and operated by SELECT, a trade association for the electrical, electronics and communications systems industry. The organisation occupies offices and training facilities near Edinburgh which were completed in 2000. The building is largely single storey and covers 2,241m2. It has a gas fired boiler distributing heat to the building using a range of different distribution systems. Although the system is controlled by a Building Management System, there is no zoning to the distribution network.

SELECT is planning a new office building which will form a third wing of the present building and will provide a further 1,500m2 of space for commercial letting. The plans are well advanced and a building warrant has been applied under the current building regulations. The organisation is keen to reduce its energy consumption and would also like to be seen as setting a high industry standard. They would like to be able to demonstrate improvements through the Energy Performance Certificate (EPC) rating.

The Building Standards Division of the Scottish Government appointed architectural consultants, John Gilbert Architects, as an observer of the process of SELECT’s review of energy advice and of the possibilities of incorporating renewable technologies to the existing offices and the proposed new extension.

An energy consultant, Energy Management Solutions, was appointed to undertake an energy audit of the existing building, including an assessment for an energy performance certificate, and to provide further energy advice on options to improve the existing building.

Ballpark estimates for the technology options were obtained from several suppliers, with more detailed costings undertaken for certain options, in collaboration with Thomas and Adamson who are acting as the project manager for the extension. Some consideration was given to capital costs and energy cost savings, because the organisation was concerned about both initial investment and payback periods.

Building Standards Division also commissioned surveys of the existing building by structural and M&E engineers working for Faber Maunsell (now Aecom).

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2 Energy requirements The actual and predicted energy requirements for the new and existing building are included in the summary in Table 1. The building emissions rating of the new building exceeds the minimum requirements of the building regulations, as described in the Non-domestic Technical Handbook, Standard 6.1.

Table 1 Energy performance of existing building and new wing Existing building: as built New wing: design data Building fabric and services

Total area 2,374m2 1,199m2

U Values walls 0.45 W/m2K 0.30 W/m2K U values floors 0.25 W/m2K 0.25 W/m2K U values roof 0.25 W/m2K 0.25 W/m2K U values windows 2.12 W/m2K 1.7 W/m2K Air permeability 15 m3/h.m2 at 50Pa (assumed) 10 m3/h.m2 at 50Pa Hot water system 1,500 litres cylinder

48kw water heater to supply: 15 wash hand basins, 6 sinks

Direct point of use heaters, to supply: 14 wash hand basins, 5 sinks, 1 shower

Energy performance

Total energy demand 255 kWh/m2 (actual) 95.8 kWh/m2 (predicted)

Gas consumption 268,008 kWh 36,912 kWh (30.8 kWh/m2) Electricity including water heating and appliances

337,923 kWh

78,051 kWh (65 kWh/m2)

Electricity including water heating but excluding appliances

93,220 kWh 44,000 kWh (33.4 kWh/m2)

Annual cost of energy used (from 2008 bills, annualised pro-rata)

£10,707 (gas) £23,654 (electricity, including water heating and appliances) £33,306 (total)

-

Calculated annual CO2 emission rates: Notional TER BER

54 kg/m2 (from EPC)

- 38 kg/m2 (from SBEM) 29.1 kg/m2 (from SBEM) 21.2 kg/m2 (from SBEM)

Total CO2 emissions per annum

128.2 tonnes 25.4 tonnes

The total energy demand of the existing building is considerably higher than the good practice energy consumption of 79 kWh/m2 (187,546 kWh), recommended in BSRIA ‘Rules of thumb: Guidelines for building services.’

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3 The existing building

3.1 Summary of the present building services system

The building is designed for mixed mode cooling with a constant volume air handling system. It has a heating battery and chiller but no air conditioning. Energy is provided by a gas boiler which serves all of the offices. The building divides itself into four different areas each with a different approach to heat distribution:

• offices heated and cooled using floor mounted supply vents and a wall mounted extract air handling system with thermostatically controlled radiators in the office area;

• training section heated by fan coil units located at ceiling level;

• reception area heated by both radiators and under floor heating, and unlike the other spaces, opens into a top glazed atrium space;

• meeting rooms heated using thermostatically controlled radiators.

However, the heating system is not zoned to allow individual controls to be adjusted within each area in terms of flow temperature, which makes it difficult to balance the system.

The hot water supply is provided by a 1,500 litre hot water cylinder which is heated by a 48 KW immersion heater and water is continuously pumped around the system to ensure hot water is available at each outlet. The storage capacity far exceeds demand: there are 21 wash basins or sinks on the system with, on average, 22 -23 people being catered for, increasing on training days; the average hot water consumption for offices is 10 litres/ person/ day (or 15 litres/ person/ day where there is a canteen) which would result in between 230 and at most 750 litres (assuming max of 50 people and a canteen). This water heating system has proved to be expensive at an estimated running cost of £1,500 to £2,000 per annum.

3.2 Energy Performance Certificate and Energy audit report

The assessment for the Energy Performance Certificate gave the building a band D rating with carbon dioxide emissions of 54 kg per m2 per annum which would amount to total emissions of 128.2 Tonnes. If designed to current building standards, it would have a C+ rating, with CO2 emissions of 35 kg per annum, which would equate to total annual emissions of 83 Tonnes.

Approximate energy use was assessed as 171 kWh/m2 per annum resulting in 405,954 kWh. Energy use in practice, as derived from fuel bills, is 33% greater, at 605,931 kWh (see Table 1).

A number of recommendations for cost-effective improvements are included in the certificate, largely relating to lighting systems.

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The accompanying report prepared by the energy consultant (see Appendix A) detailed a series of recommendations some of which were discussed at follow up meetings:

• very efficient direct fired gas calorifiers would be cheaper to run than the current water heating system, an electric immerser, but they were relatively expensive at a cost of between £4,000 and £7,000;

• pumping the water around the hot water system at times when it is not needed unnecessarily increases electrical costs, so timing controls should be included;

• given the intermittent nature of the use of the training rooms, it might seem reasonable to separate the hot water supply from the offices and the training area as the demand requirements will be very different;

• the energy consultant initially advised that the total cost of adding solar water heating could be in the region of £20,000; later estimates showed that an appropriate system could be installed from around £8,000, but these differed from the tender prices which were closer to the original sum advised.

• the air permeability of the present structure has been assumed to be in the region of 15m3/h.m2 at 50Pa., but it would be useful to carry out an air permeability test to determine the actual infiltration rate and to use infra red thermography or a tracer gas decay test to locate any excessive losses which could help to reduce air leakage (although it might be found that the building was built to a tighter specification);

• the fan coil units in the training rooms could be replaced with radiant ceiling mounted heaters; this may improve the ability to control the variable temperatures and thus improve comfort levels, but it is hard to estimate the effect it might have on energy efficiency;

• lack of zoning seems to be the root of the problem in balancing temperatures within the building: under floor heating, radiators and warm air systems have different rates of response to temperature change and pre-heating requirements, to operate efficiently each should be on a separately controlled zone; however, adjusting the existing system to create separate zones would be very expensive.

Regarding this last point, the organisation said that balancing the present system had taken some time and they would be concerned if further adjustments had to be made.

Some measures that would improve the efficient use of energy would not affect the EPC rating:

• the introduction of zoning control (payback period 7 years);

• adding a timer to the water heating system (payback period 1 year); and

• replacing the fan coil units within the training room with radiant ceiling mounted heaters (impact is difficult to estimate).

Certain other measures would both improve the efficient use of energy and the EPC rating and are shown in the following table in order of priority:

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Table 2: Summary of options investigated for improving the energy usage efficiency and energy performance rating of the existing building

Annual CO2 savings

kgCO2/m²

Tonnes CO2

% total emissions

Estimate of capital

costs (£)

Annual financial savings

Payback (years)

Cost per Tonne

CO2 saved (£)

Variable speed drive on air handling unit supply fan.

8 19.0 14.8% 2,000 500 4 105.3

Improve lighting efficiencies

2 4.7 3.7% 200 100 2 42.6

Heat recovery from extract air for the open plan area to pre-heat air handling unit.supply

2 4.7 3.7% 3,500 500 7 744.7

Centralised direct gas fired water heater with storage capacity

1 2.4 1.9% 6,000 2,000 3 2500.0

Add solar pre-heat source to gas fired water heater

1 2.4 1.9% 20,000 550 30 8333.3

Solar film to South and West facing windows within open plan zone

2 4.7 3.7% TBA* TBA* TBA TBA

*It is not possible to estimate financial savings for solar film because present chiller demand is not known. Budget costs for solar film fitted on the inside of glazing can be based on approximately £35/m².

Of these measures, only the variable speed drive on the air handling unit supply fan would result in substantial savings, 14.8%, on total emissions from the existing building. However, by itself this did not change the EPC rating. The rating would move from D to C by combining this measure with improved lighting efficiencies in the entrance lobby and reception, which produces an additional 3.7% reduction. Payback periods are four and two years respectively. The addition of heat recovery to the air handling system also yields 3.7% reduction in emissions, but for a longer payback period, of 7 years.

3.3 Review of potential for low carbon equipment within the existing building

A number of different options were investigated to identify where low carbon equipment, including renewable energy devices, could be installed to reduce the carbon emissions of the building and reduce running costs.

SELECT said that it did not envisage that the present gas fired boiler system, which supplies the bulk of the energy to heat the building, would be changed and the interventions and adjustments which were recommended in the energy consultants report were all valid.

If the existing gas boiler had needed to be replaced, there could have been the opportunity to combine the heating supply for the existing building and the new offices into one power source. However, this is not required and there are advantages in keeping the existing offices and new extension on different systems, given that the main building houses SELECT and the extension will be let to tenants.

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a) Solar water heating

The large existing calorifier provides an opportunity to store solar energy as part of a preheat system and given the existing fitments are all plumbed to this point it could make good sense to retrofit a solar water heating system to the existing 1,000 litre calorifier.

Solar collectors with a total area of approximately 18m2 would be required to make a significant solar contribution to the system. This could be connected to an external heat exchanger before connection to the calorifier. The location and siting of the collector would need to be agreed. The pitch and orientation will affect efficiency and the ability of the panels to self clean. Initial discussions with suppliers suggested that it would cost in the region of £8,000 to £10,000 for the supply and installation of such a system (see Appendix A for budget costing), considerably less than the £20,000 that the energy consultant had indicated, but the final tenders were £14,750 to £19,130.

If the existing water storage calorifier were replaced with a new gas fired calorifier (or indeed a new replacement cylinder) then the actual storage capacity could be reduced to nearer 600 litres and be connected to 12m2 of solar water heating panels.

Solar water heating will reduce the energy used for hot water supply, often by up to 40%, but this depends on the pattern of use. and controls. In the case of the current hot water supply configuration, considerably higher savings might be anticipated. Cost and CO2 savings vary with the fuel displaced; the savings for the case-study building will be greater than if water were heated by gas.

The table below shows the estimated energy and CO2 saved for different solar panel sizes, calculated using Ofgem assumptions. Ofgem uses a benchmark of 396kWh energy saved per m2 of collector. Based on this, the following CO2 savings could be made for different solar water heating systems. There would be no routine costs in use, apart from electricity to run the pump but even this could be supplied by a dedicated PV panel. Solar energy would be displacing electricity in the case study building, but savings for displacing gas are given for information.

Table 3 Existing building: estimated energy and CO2 savings for solar water heating Solar water heating panel area

KWh per annum generated

CO2 saved when displacing electric hot water system*

CO2 saved when displacing gas fired hot water system**

4.4 m2 1,742 kWh 1.0 tonnes 0.34 tonnes

12.0 m2 4,752 kWh 2.7 tonnes 0.92 tonnes

30.0 m2 11,880 kWh 6.7 tonnes 2.30 tonnes

* Calculated using emissions factor 0.568, for electricity displaced from grid ** Calculated using emissions factor 0.422, for mains gas

b) Solar PV

Considerable savings in carbon emissions can be made by the installation of photovoltaic panels which generate electricity from solar energy. A number of options are available and we approached four suppliers for outline budget costs.

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A national supplier of PV panels attended a meeting with SELECT to discuss the different options for installing photovoltaics. They initially provided two options, both of which would cover as much of the existing roof as is deemed practical (estimated at 200m2). Another company was also approached in order to compare costs. The budget estimates for installing monocrystalline or polycrystalline systems are summarised in the following table. The suppliers state that there should be no routine costs in use provided the panels are positioned so that they self clean, but some cleaning may be required at pitches less than 20º.

Table 4 Existing building: Budget estimates and CO2 savings for PV panels

Installer/ supplier

PV type Energy yield per annum

Installed price

ROC gains per annum*

CO2 saved

Firm A 27.4kWp mono PV

22,055kWh £147,945 £1,860 12.5 tonnes

Firm A 25kWp poly PV 20,000kWh £147,500 £1,600 11.4 tonnes Firm B 32 kWp PV 25,600kWh £160,000 £2,000 14.5 tonnes * From April 2009 ROCs (Renewable Obligation Certificates) will increase to 2 ROCs per megawatt per annum. The value of ROCs has been estimated at £40 a ROC although sale of ROCs is by auction and values can fall as well as rise.

It was thought that the best available location for installing the PV panels was on the South facing roof above some of the training rooms. This was particularly attractive because the installation might be used in training sessions for electricians.

A pitch of about 45º is considered optimal for solar panels in central Scotland, due to the latitude. The pitch of the roof of the case study building is considerably more shallow, about 12º. Both sets of figures supplied assume that panels are mounted to largely South-facing roofs with preferred pitches of 30º – 40º degrees, which is more appropriate to southern England. The both have riders that lower pitches will lead to reductions in efficiency, although this would not be as critical as for solar water heating collectors.

None of the above systems are specifically designed to work with diffuse lighting conditions. Given that this is the predominant type of light we receive in Scotland, rather than direct sunlight, and given the low pitch of the case study roof, it could be more appropriate to consider amorphous silicone cells which are optimised for diffuse lighting. This means that they are as effective when laid at low angles as they are picking up diffuse lighting rather than direct sunlight.

Another firm which produces an amorphous silicone panel that can be adhered to each of the individual panels of a standing seam roof, was approached, but it was felt that there would be insufficient gains from such an installation.

In all cases, SELECT would not be eligible to receive a grant through the Low Carbon Building Programme as it does not comply with the requirement to be a non profit making organisation. This makes the capital cost more onerous assuming an installed price in the quoted region of £5,000 per kW. However, if grant aid is not sought, then there could be

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greater scope for procuring a system outwith the accredited contractors programme. Purchasing PV directly from manufacturers can sometimes lead to substantial savings.

Later, once SELECT decided that they might wish to pursue certain options, a formal invitation to tender was issued, for both solar water heating and PV systems.

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4 The new office wing A new two storey wing is to be built on part of the site, creating a courtyard space to the East side. It will provide flexible office accommodation for commercial letting. Construction is similar to the present offices, but with certain upgrades in specification. The building was programmed to start construction early in 2009.

The new wing will be built to a higher energy efficiency standard than the 2008 Building (Scotland) Regulations. The present proposal is to use a gas condensing boiler to provide heating to radiators with thermostatic valves. The hot water supply is specified as individual point of use electric heaters.

4.1 The potential for low carbon equipment for the new office wing

Building Standards Division asked the research project team to investigate whether low carbon equipment, including micro-renewables, could be installed in the new office wing to serve as a way of reducing the CO2 emissions from the existing building.

a) Wind turbine

Wind turbines were not considered, because it was assumed that planning permission would be difficult to achieve and would delay progress of the project.

b) Biomass boiler

The architects for the new building had considered using a wood fuel boiler at one stage but decided against it, largely due to fuel storage requirements. However, we decided to investigate the feasibility of a biomass boiler for the purpose of the research project.

A firm specialising in wood fuel heating systems was approached to provide budget costings for a wood fuel boiler. Because of the relatively small size of the system, they recommended a pellet boiler providing an output of 25kW. This would cost in the region of £40,000 to £50,000.

Due to the thermal mass of a biomass boiler, it does not respond well to changes in load requirements. This fluctuation will occur at night time and at weekends when the boiler is shut off, it can then take a significant time to start up again. The system would need to be designed carefully to match the predicted loads and to incorporate an ‘accumulator’ which works in conjunction with the boiler to store heat which can be used to provide a rapid recovery to start heating. The accumulator is basically a large thermal storage tank, in this case about 2,000 litres would be required.

A wood pellet store could be built below ground level to facilitate filling the chamber and avoid any extension to the ground floor area, although ideally a higher level hopper with sufficient capacity to accept a full load of pellets would be most efficient (a full lorry load is 16 tonnes or 24 cubic metres). Smaller loads become more expensive and need to be made more frequently. A chimney would also be required.

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It is estimated that by switching to wood from a gas heating system, 8 tonnes of CO2 could be saved per annum based on a 25kW system running at 2000 operating hours per annum (CO2 savings if replacing electrical heating would be 20 tonnes). The estimate of capital costs disregards additional construction costs, including costs associated with a chimney and storage, but these costs would need to be considered if the option were investigated further. Running costs would vary with the cost of wood pellets, although we understand that costs have been maintained to compete with gas. There are plans for a new wood pellet plant in Scotland, and in the meantime pellets can be sourced from a number of Scottish suppliers.

If both the existing building and the new building were being heated with biomass, then it would be more efficient to consider a woodchip boiler although a larger storage area and additional plant would be required for the fuel. There is a major supplier of wood chips near to the case study building, which would minimise the use of diesel for deliveries.

c) Solar hot water

The new offices present an opportunity to install solar panels because there is a South facing roof slope. However, the proposed pitch is only 5º and any solar collectors for water heating would need to be mounted on frames above the plane of the roof.

If individual electric single point heaters are used, the only way to contribute directly to the hot water costs would be a PV system. However, as the fittings are in close proximity to one another, a solar water heating storage tank could be used and linked to the new boiler system, allowing solar water heating panels to contribute to the hot water energy load.

One solar installer has supplied a quotation for a 4,4m2 system linked to a 250 litre cylinder. However, for the possible number of people using the offices, we think that a larger system should be used, say 10m2 with 500 litres of storage. This would supply 50 people assuming an average of 10 litres per person per day.

Estimates of the CO2 savings for both sizes of system are shown in the following table. In practice, it would probably be necessary to separate the costing of hot water between the two floors, because they are likely to be let to different tenants. There was some discussion of how investment costs might be recouped through rent levels and whether prospective tenants would recognise the benefits of solar water heating. Table 5 New office wing: Estimate of CO2 savings for solar water heating installation

Solar water heating panel area

kWh per annum generated

CO2 saved when displacing electric hot

water system

CO2 saved when displacing gas fired

hot water system 4.4 m2 1,742 kWh 1.0 tonnes 0.34 tonnes

10.0 m2 3,960 kWh 2.2 tonnes 0.77 tonnes

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d) Solar PV

Given both the issues of the pitch of the roof, the water supply system, and the relatively low level of savings, the new offices may present a better opportunity to install solar PV than solar water heating.

Prices were obtained from two firms for budget costs. These assumed that the overall area of 275m2 could be used and we have adjusted the figures to take into account the smaller area that was actually available. However, we have not adjusted the output figures which are based on panels installed at a pitch of about 30º.

The PV installations on the new wing could, at an optimum pitch, reduce CO2 emissions by nearly 13% compared with the emissions for the existing building, or by 50% for the new wing. A comparison of capital costs to annual tonnes CO2 would on average give £11,791 per Tonne CO2. These savings could be achievable in optimum conditions, but the suppliers would normally assume savings of no more than 10% of electricity consumption, which would greatly increase the cost per Tonne CO2 for the new wing, but not for the less efficient existing building. The suppliers advised that there should be no routine costs in use provided the panels are positioned so that they self clean, but some cleaning may be required at pitches less than 20º. See discussion of pitch in section 3.3.

There was some discussion of how investment costs might partly be recouped through rent levels and whether prospective tenants would recognise the benefits of solar generated electricity.

Table 6 New office wing: Budget estimates and CO2 savings for PV panels

Installer/ supplier

PV size, type Energy yield per annum

Installed price

ROC gains per annum

CO2 saved

Firm A 50kWp mono PV

30,325 kWh £196,000 £2,400 17.2 Tonnes

Firm A 45kWp poly PV

26,743 kWh £196,000 £2,080 15.2 Tonnes

Firm B 48 kWp PV 29,333 kWh £184,000 £2,320 16.6 Tonnes

* From April 2009 ROCs (Renewable Obligation Certificates) will increase to 2 ROCs per megawatt per annum. The value of ROCs has been estimated at £40 a ROC although sale of ROCs is by auction and values can fall as well as rise.

e) Ground source heat pump

The architects for the new building had already considered using a ground source heat pump but decided against it. We obtained a further estimate for both vertical and horizontal collector loop systems. The estimates were slightly lower than the costs previously obtained and similar to those for a solar PV system, but the building manager was not prepared to countenance the disruption to either their landscaped surroundings or car park.

f) Summary of options for low carbon equipment

SELECT dismissed the options of biomass and ground source heat pumps. The following analysis gives a ballpark summary of the options for solar technologies, which was presented to them for discussion, in order to decide whether they merited further investigation.

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Table 7: Summary of options investigated for low carbon equipment

Maximum annual performance (1)

Capital cost related to annual savings (4), (5)

CO2 saved

Size

Energy generated

kWh Tonnes % total

emissions

Estimate of capital costs (2) energy

£ / MWh CO2

£ / tonne

a) Existing building (total CO2 emissions: 128.2 Tonnes)

12.0 m2 4,752 2.7 2.1% £6,000 to £7,000(3)

£1,263 to £1,473

£2,222 to £2,593

Solar water heating

30.0 m2 11,880 6.7 5.2% £10,000 to £12,000

£842 to £1,010

£1,493 to £1,791

PV mono 27 kWp 22,055 12.5 9.8% £147,945 £6,708 £11,836

PV poly 25 kWp 20,000 11.4 8.9% £147,500 £7,375 £12,939

PV 32 kWp 25,600 14.5 11.3% £160,000 £6,250 £11,034

Biomass (5) pellet

25kW nil 8 6.2% £46,000 nil £5,750

Biomass woodchip

50 or 75kW

nil 16 12.5% £75,000 nil £4,687

b) New wing (total CO2 emissions: 25.4 Tonnes)

4.4 m2 1,742 1.0 3.9% £2,000 £1,148 £2,020 Solar water heating 10.0 m2 3,960 2.2 8.7% £7,700 £1,944 £3,500

PV mono 50kWp 30,325 17.2 67.7% £196,000 £6,463 £11,395

PV poly 45kWp 26,743 15.2 59.8% £196,000 £7,329 £12,895

PV 48kWp 29,333 16.6 65.4% £184,000 £6,273 £11,084

Biomass (5) pellet

25kW nil 8 31.5% £46,000 nil £5,750

Biomass woodchip

50 or 75kW

nil 16 63.0% £75,000 nil £4,687

(1) Solar technologies are assumed to be installed at optimum pitch. (2) Costs for equipment and installation, but excluding any ancillary construction cost. (3) Excludes cost of any new cylinder. (4) For PV, does not consider income from ROCs. (5) For biomass, excludes fuel costs in use, and routine maintenance. (6) Biomass options not investigated for installation in existing building, but savings from

installation in new wing shown relative to total emissions from existing building.

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5 Detailed investigation of solar options

5.1 Introduction

Following the initial investigations, SELECT rejected the option of a biomass boiler, in part due to the need for space for storage and the impact of the chimney on the appearance of the building, but principally because they did not employ staff who could attend to day-to-day maintenance of the system.

It was agreed with SELECT to commission a structural engineer and an M&E engineer to advise on the installation of both solar PV and solar water heating systems, with panels to be installed on the roof above the training workshops. It was also agreed to conduct a formal tender exercise in order to obtain detailed costings.

It was decided that the location should be the roof of the training workshops, partly to avoid issues of recovering costs from tenants, but also to allow guests to visit the installation.

5.2 Consultants’ reports

Reports from a structural engineer and an M&E engineer are shown in Appendix C. The main points arising are as follows:

a) Structural

• the existing rafters have the capacity to carry the weight of the panels, but if the panels were not sited on the main rafters, some additional steel purlins would be required;

• further steel would be required for fixing points for any elements that puncture the existing roof fabric and the weather detailing of such penetrations will be critical;

• puncturing the roof fabric may nullify any guarantees that may be in place for the roof and the building owner is advised to check this;

• the design and construction of panel frame support system must consider the wind and uplift forces on the roof plane, which faces the prevailing wind direction.

b) Mechanical and electrical

• the integration of the PV panels into the existing electrical services set-up would be better achieved via the electrical plant room and not the boiler room as proposed; however this may mean that the existing distribution board may have to be upgraded and his may be a major factor on whether or not the scheme is feasible;

• suggestion that the specification should be qualified specifically to consider the site conditions, to ensure that the PV panels are sufficiently robust;

• that the specification of the PV modules and array should take account of the difference between Standard Test conditions and the expected site conditions.

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5.3 Tenders for installation of solar water heating and PV systems

A full specification was prepared, including a plan of the existing roof, showing the location of the solar panels and the new office wing (see overleaf). An invitation to tender was issued for the following installations of solar water heating and photovoltaic systems.

• approx 17.7 m2 solar collectors connected to flat plate heat exchanger retrofitted to existing calorifier in plant room; panels pitched at 40 degrees (area A on plan);

• approx 150 m2 solar PV panels fixed to frame and fixed to existing roof construction; pitch to remain at 12 degrees (area B on plan);

• alternative array of approx 25 m2 solar PV panels fixed to framework fixed to existing roof construction.

Tenders were received from four firms for the installations of solar water heating and PV ystems. The results of the exercise are summarised below: s

a) Costs

• Installation costs for solar water heating range from £14,500 to £19,200

• Installation costs for PV systems range from £112,400 to £146,000

A number of clarifications were given on the tenders which demonstrate the range of issues that need to be considered in selecting a supplier and installer:

b) Warranties:

• Workmanship: range from 5 year warranty (backed by NICEIC) to 2 year warranty

• PV modules: range from 2 year warranty to 2 year warranty for all parts

• Performance of PV modules: no guarantee, or 25 year guarantee at 80% of the minimal rated power output and 10 year guarantee at 90%

• Inverters: range from a 2 year warranty to a 5 year warranty

• Solar collectors: 5 year warranty c) Work programme:

• Area A (solar water heating): 3 days

• Area B (large PV array): 7 days to 2 weeks

• Combined Area A & B: 2 weeks

• Area C (small PV array): 3 days to 4 days d) Supervision:

Varied considerably from continued attendance on site during works with one further site meeting, to one meeting prior to commencement and one further site visit. e) Statutory fees for planning / warrant applications:

Varied considerably from no provision, to inclusion of £5,550 for fees and associated costs.

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12º fall

5.6º fall

5º fall

12º fall

5.6º fall

5º fall

5º fall

5º fall

5º fall

AREA A: approx 17.7m2 solar thermal panels!connected to flat plate heat exchanger retrofitted!to existing calorifier in plant room.!Panels pitched at 40 degrees.

existing calorifier in plant room!approx size 1000 litres

AREA B: location of solar pv panels fixed to framework!fixed to existing roof construction. Total area approx 150m2.!Pitch to remain at 12º

AREA C: location of alternative array of solar pv panels!fixed to framework fixed to existing roof construction.!Total area approx 25m2

consider effect of potential overshadowing from higher roof

N

19,250

8,0

00

1,200

5m 10m 15m 20m

9° 24' 34"

plant room under

switch room under

Broderick aluminium standing seam!roofing with joint upstands at 525 crs

ROOF PLAN SHOWING!PREFERRED LOCATION OF SOLAR PANELS!ON EXISTING ROOF

NEW OFFICES TO BE ADDED TO EXISTING

It is not possible to make direct comparison with the estimates in Table 5 because the sizes of installations are different, but it is clear that the tender prices for the solar water heating systems are considerably higher than the estimates earlier obtained from suppliers, while those for PV systems are more similar.

Only one of the tenders included details of the size and output of the systems. The larger array would total 20.5 kW and estimated the output at 15,015 kWh per year. The smaller array would total 3.6 kW, with output of 2,643 kWh per year. These estimates did not consider shading. The tenderer recommended that the larger PV array would better be installed on the extension rather than the main building.

The performance claimed for the larger array equates to a cost of over £13K per Tonne of annual CO2 savings. It would reduce emissions by 8.5 Tonnes per year, a reduction by 6.6% of the total emissions from the existing building. This would equate to 3.5 kgCO2/m2, which would not be sufficient to change the EPC rating.

5.4 Cost of consultancies

The costs of the consultancies may not be truly representative of market prices, but it is worth noting that, apart from research project costs, the fees for the energy audit, the structural and M&E engineers’ report, and management and analysis of the tender amounted to £4,490.

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6 Conclusions The project explored ways to reduce CO2 emissions from an existing office building at the time when an extension was being built. The building is occupied by the organisation that owns it, SELECT, who are extending the building to provide letable office space. SELECT is interested in reducing energy costs and in demonstrating that it has improved the building to reduce CO2 emissions.

An energy audit evaluated the energy performance rating and identified several cost-effective options for reducing energy consumption and CO2 emissions: • A variable speed drive on the air handling unit supply fan (emissions reduction 14.8%, estimated capital cost £2,000, payback period 4 years)

• Improved lighting efficiencies in the entrance lobby and reception (emissions reduction 3.7%, estimated capital cost £200, payback period 2 years)

• Heat recovery from extract air to preheat the air handling unit supply (emissions reduction 3.7%, estimated capital cost £3,500, payback period 7 years)

• Centralised direct gas fired water heater with storage capacity (emissions reduction 1.9%, estimated capital cost £6,000, payback period 3 years)

The addition of solar film to south and west facing windows would reduce the electricity needed for the chiller, but it was not possible to estimate the payback periods due to lack of information about chiller loads.

Subsequently, options were explored for the installation of low carbon equipment, either to the existing building or to the extension. Wind turbines were excluded, due to concerns about the difficulty of gaining planning permission. Ground source heat pumps would not be acceptable to the building owner, due to the associated disruption of landscaping or car parking. Biomass was explored in more detail, but would not be acceptable to the building owner because no-one would be available to manage routine maintenance and cleaning.

Solar technologies were explored in detail, firstly with a feasibility study by structural and M&E engineers. This highlighted four main issues:

• the need to assess the capacity of all parts of the roof to support the solar panels, in case they were not supported by the main structural members;

• the possibility that penetrations of the roof would nullify any existing warranties on the roof;

• the possibility that the distribution board would need replacing, adding to the costs of the installation; and.

• the need to consider the robustness and performance of the PV panels in relation to the harsh conditions encountered on the site.

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Two companies had supplied informal, initial estimates for solar water heating and PV systems to give the building owner an indication of the likely scale of costs, then tender prices were obtained from four suppliers. Tender prices were considerably higher than the initial estimates for solar water heating, but were similar for PV systems.

An analysis of one of the tenders showed that the predicted performance of a large PV array would equate to a capital cost per Tonne of CO2 saved each year of over £13,000. The total annual CO2 savings would represent 6.6% of the total emissions from the existing building and the annual savings per square metre would be 3.6 kgCO2/m2, which is insufficient to improve the EPC rating from D to C.

The tender exercise also illustrated some other factors that should be considered in the selection of low carbon equipment, including the inclusion of all construction costs, statutory fees, and other ancillary costs and the scope of warranties for workmanship, equipment, and performance over time.

The tender exercise did not consider income from ROCs, or income from sales of electricity to the grid. The prospects for the viability of PVs would be improved if the proposed provisions for feed-in tariffs in the Energy Bill are introduced.

Costs for consultants’ fees amounted to £4,490. Given that this was a research project, this level of fees may not reflect market rates, but they are included to demonstrate that the cost of assessing options should be considered in the implementation of any new policies to improve the energy performance of existing buildings.

At the time of writing, the building owner had not discussed the tenders and it is anticipated that this report may be updated in future.

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Appendix A Energy Performance Certificate Energy Management Solutions assessed the existing building using SBEM and produced a draft Energy Performance Certificate:

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Appendix B Energy performance action plan Report by Glyn Mountford, Energy Management Solutions

1 Summary

This report outlines improvements which can be made to the existing building to improve its energy efficiency performance

It should be noted that some improvements will improve the buildings energy operational performance, but will not necessarily improve the Buildings Energy Performance Certificate Rating. This is because some improvements are identified which should improve how energy is used within the building, but will not improve the building asset parameters as defined within the EPC software options.

For the purposes of this report the recommendations are separated into two sections:

• Recommendations that will not affect the Energy Performance Certificate rating.

• Recommendations that will improve the Energy Performance Certificate rating.

Table 1: Recommendations that will improve energy usage efficiency but will not impact on the building asset energy performance rating

Annual Financial Savings

DeltaCO2 (+/-)

Estimated cost

Payback period

Recommendations (in order of priority)

(£) (kgCO2/m²) (£) (years) 1 Implement heating zone control to enable the open

plan, under floor reception and training area heating flow temperature to be regulated by the use of 2P valves and controlled by the demand of each respective zone

£1,200 N/A £8,000 7

2 Fit a timer control to the existing DHW heating element £300 N/A £250 1

3 Consider replacing the fan coil units within the training room with radiant ceiling mounted heaters to allow improved efficiencies from a Variable Temperature heating system

TBA* N/A TBA* TBA*

*It is not possible to assess the impact of this recommendation in real terms. It would not change the building asset rating. The change may well improve space comfort with some minimal energy savings dependant on how the controls are set up.

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Table 2: Recommendations that will improve energy usage efficiency and will impact on the building asset energy performance rating

Annual Financial Savings

DeltaCO2 (+/-)

Estimated cost

Payback period

Recommendations (in order of priority)

(£) (kgCO2/m²) (£) (years) 1 Fit variable speed drive on the air handling unit

supply fan 500 -8 2,000 4

2 Improve lighting efficiencies, by replacement of 50 watts halogen fittings to 11 watts GU10 in the reception and entrance lobby

100 -2 200 2

3 Install a run around coil heat recovery system for the open plan area extract air handling unit to supply pre-heat for the supply air handling unit

500 -2 3,500 7

4 Install a centralised direct gas fired water heater with storage capacity to supply the building DHW 2,000 -1 6,000 3

4a Combine recommendation 4 with a solar water heating pre-heat source 550 -1 20,000 30

5 Consider fitting solar film to South and West facing windows within the open plan zone of the building to reduce chiller demand within this area of the building

TBA* -2 TBA TBA

*Due to not knowing present chiller demand means that estimates of financial savings are not presently possible, but some budget costs to fit solar film are provided below. Budget costs for the fitting of solar film on the inside of the glass can be based on approximately £35/m². Some further recommendations were automatically generated by the EPC software current at the time of the study, for shading devices and optimum stop-start controls. However, we do not consider them appropriate to this building and we understand that the software will allow such suggestions to be manually deleted, as advised by the professional assessor responsible for compiling the EPC.

2 Recommendations that will improve energy usage efficiency but will not impact on the building asset energy performance rating

Priority 1 Implement heating zone control

There is no zone temperature control within the building such that all three major zones are fed at the same flow temperature which means that temperature control is less accurate in the respective zones leading to poorer comfort levels and increased boiler firing to compensate for the fact that centralised heating controls are set to serve comfort levels required by the remotest system zone.

Heating zone control would enable the open plan, under floor reception and training area heating flow temperature to be regulated by the use of 2P valves and controlled by the demand of each respective zone.

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Further detailed investigation and costing is required to evaluate the implementation of re-plumbing the main heating circuit to introduce separate heating circuits using two or three port valves, along with the associated optimising and compensating controls to vary flow temperature in line with building heating demand.

At the same time boiler sequence controls also needs to be reviewed as temperature differential between flow and return is critical to the systems operating efficiency.

Priority 2 Fit a timer control to the existing DHW heating element

It was noted that there is no programmable timer control for the Domestic Hot Water (DHW) tank heating element, which means that it is very possible for the heating element to remain energised when not required (e.g. during some periods when the building is not in use). Whilst the heating element will have thermostat control, the use of a programmable electronic timer will ensure that heating periods can be pre-set in line with heating demand patterns and can be overridden on request with a timed reset function. Care needs to be taken to ensure that timers are programmed to allow a pre-heat period such that any stored DHW will comply with Legionella requirements, with 60ºC being the recommended storage temperature during periods of DHW demand.

Priority 3 Replace fan coil units with radiant heaters

Consider replacing the fan coil units (FCUs) within the training room with radiant ceiling mounted heaters to allow improved efficiencies from a Variable Temperature heating system.

It is understood that at some point the Training Area radiator panels have been replaced with Fan Coil Units (FCUs). The efficiencies of these fan coil units will be in question as they are designed to operate using a Constant Temperature (CT) heating source, where as they may well be connected to a Variable Temperature (VT) heating source. This will mean that greater heating demand may be required to compensate for the increased heat loss from the fan coil units, which due to the lack of zone controls as highlighted earlier may be increasing the overall building heating demand.

It is very difficult to assess what, if any, savings would be generated or the likely payback ratios. It is likely that, with proper controls, some minimal savings could be obtained. We would not consider this to be a high priority project but we refer to it due to likely inefficiencies and poor comfort conditions that could arise due to heating a fan coil unit system through a variable temperature supply.

3 Recommendations that will improve energy usage efficiency and will impact on the building asset energy performance rating

Priority 1 Fit variable speed drive on the air handling unit supply fan.

The current main supply fan is thought to be running at constant speed regardless of heating requirement. This fan should be replaced by a variable speed device (VSD) which should be controlled by a close loop based on temperature control and or measured CO2 levels which will reflect the required Air Change rates based on occupancy levels.

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The above will have the effect of making the system a Variable Air Volume system which may contribute to some reduction in both heating and cooling demand.

We have estimated that varying fan flow rates according to temperature will reduce their electricity consumption by up to 15%, and will reduce heating consumption within the affected area by approximately 10%.

Priority 2 Improve lighting efficiencies

About 20 halogen fittings (50 watts) in the reception and entrance lobby could be easily replaced with GU10 CFL fittings which would have rated wattage of 11 watts. These fittings are only used as display lighting and therefore do not require a high power output.

Priority 3 Add heat recovery system to air handling unit

Install a run around coil heat recovery system for the open plan area extract air handling unit to supply pre-heat for the supply air handling unit.

Install a three-way diverting valve and a third recovery coil which can be used for winter heat recovery. Exhaust air vented from a building contains heat energy - energy that's going to waste. You can reduce your heating costs by capturing that heat and recycling it. This is achieved by the use of matched pairs of run-around coils. One coil extracts the heat from exhaust air, the other transfers it to a cooler stream of incoming air, and a pump keeps the system circulating.

A run-around coil heat recovery system is essentially self-contained. It consists of a matched pair of coil heat exchangers. The two coils are piped together in a continuous loop through which the heat-exchange medium (water or a water/anti-freeze mix) flows. A pump pack ensures that the medium keeps flowing in a single direction at a constant rate. Because the unit is sealed, it can transfer heat energy from contaminated exhaust air to incoming fresh air without degrading the quality of the incoming air.

Priority 4 Centralised direct gas fired water heater with storage capacity

Replace current calorifier with a direct gas fired gas boiler with an appropriate storage capacity to supply the building DHW.

In a gas-fired water boiler a reservoir of bulk water is indirectly heated by a gas burner-fired immersion tube. Direct fired water boilers provide one of the most energy efficient methods of heating water available on the market today. Low cost operation and consistent reliability of performance can be maintained during daily use with reduced heat recovery times due to the use of efficient burners, and high density boiler insulation which ensures minimum heat loss.

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Priority 4a Install solar water heating pre- heat source with centralised direct gas fired water heater with storage capacity

It is possible to install a package including solar water heating panels and commercial gas direct fired boiler. The package includes high quality solar collectors, single coil and twin coil duplex stainless steel cylinders, pump station, control unit and system expansion vessels.

The side of the building has a south / south west facing flat roof and there has been interest expressed in the possibility of installing solar panels here. Although the roof is sloped , its construction may require a frame to be constructed before panels could be installed, and there is some question of whether the roof could accommodate such a load and this would require further structural investigation.

Based on experience it is considered that a peak demand DHW demand for this building should not be in excess of approximately 16 KW (approximately 1/3 of the installed capacity), energised for say 20% (Utilisation Rate) would equate to an annual kWh of approximately 32,000 kWh.

This sizing is based on example projects and may be high for this building. It would be necessary to carry out a full feasibility study to accurately determine the required system capacity, and install a feed water meter to accurately measure the DHW demand profile. Payback figures of between 20 and 30 years are not untypical for solar water heating projects for office buildings in Scotland. To properly assess the asset impact we would need, following a feasibility study, to confirm the number of panels and the area, inclination, and orientation of each collector.

If flat panel solar panels are considered then these will have a % solar fraction (efficiency) of approximately 45%. Using this solar fraction of 45% (efficiency) and assuming an irradiation factor of 900kWh/m²/ annum1 (as based on UK annual solar irradiation factors), then a total surface (aperture) area of approximately 55m² of solar panel would be required to provide an estimated thermal heating capacity of approximately 22,000kWh per annum. This would require something like 10 x 4 off Zen type collector banks, with each collector bank providing a surface area of approximately 6.07m², but with a net aperture area of approximately 5.5m².

Typical dimensions and weights for each set of 4 off collector banks are provided in the following table:

Height mm Width mm Weight kg Aperture Area m² 3,433 1,776 117 5.50

It is estimated that the required cylinder capacity for such a solar water heating capacity will be in the range of 4,000 litres, so this also needs to be considered, to ensure that thermal capacity is not being restricted by insufficient cylinder capacity.

1 Data obtained from Solar Traders Association website.

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It should be noted that the efficiencies of the panels can be increased by using vacuum tube arrangements, which should increase the efficiencies from approximately 45% to 60%. This would mean that approximately a third less panels would be required to achieve a similar thermal heating capacity.

The above figures and values are extremely tentative and take no cognisance to efficiency variations (solar irradiation factor) associated with shading effects etc.

More detailed verification information would require a more detailed study, including some form of building structure survey to verify the level of loading that could be applied to the roof, and therefore the platform structure and mounting points etc.

For the purpose of a quick calculation it is assumed that preheating the water for these hot water heaters by using solar water heating would reduce the DHW supply demand by approximately 65% or approximately 14,300kWh.

Priority 5 Fit solar film to South and West facing windows

Consider fitting solar film to South and West facing windows within the open plan zone of the building to reduce chiller demand within this area of the building.

Fitting solar film to the glazed area can reduce solar heat gains by up to approximately 75%. In this case low reflective film is likely to be required which is would reduce heat gains by approximately 40% through the glazed area, and would only restrict light entering glass by approximately 35%.

Its difficult to estimate what consumption the present chilled water plant feeding the Supply AHU is taking, but the use of solar film should reduce the heating effect within the affected area/s by between 10 and 20%, which given good controls should reduce chiller demand by a similar ratio.

Due to not knowing present chiller demand means that estimates of financial savings are not presently possible, but some budget costs to fit solar film are provided below.

Budget costs for the fitting of solar film on the inside of the glass can be based on approximately £35/m².

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Appendix C Structural and M&E report Feasibility of solar panel installation on existing building roof This report advises on the feasibility of the installation of solar panels on the roof of the existing office building. On the 17th February 2009 Faber Maunsell visited the building and carried out a visual inspection of the plant room, the switch room and the roof structure beneath the proposed location for the solar panels. Our comments are as follows:

Structural Implications We have no specific details at this time of how the panels will be sited on the roof however for the purposes of this exercise our comments focus on the load capacity issues of the roof. The existing rafters are 357 x 171 x 45kg/m at 5.6m centres will have the overall capacity to carry the weight of the panels without any need for strengthening works.

However, we expect that if it is decided not to site the panels on the main rafters then there will be a requirement to provide some additional cold rolled steel, i.e. purlins spanning over the rafters, to cope with the additional weight from the panels. We would expect that items of tertiary cold rolled steel will be required to provide additional fixing points for any elements that will puncture the existing roof fabric. We would stress that puncturing the roof fabric may nullify any guarantees that may be in place for this roof therefore the building owner must be consulted on this matter. We would expect that the weather detailing of any such penetrations will be critical.

It should be noted that the roof plane in question generally faces the prevailing wind direction and is subject to considerable wind and uplift forces. This should be given some consideration when designing and installing the panel frame support system.

Mechanical & Electrical Implications

We believe that the integration of the photo-voltaic panels into the building’s existing electrical services set-up would be better achieved via the electrical plant room and not the boiler room as proposed. This however may mean that the existing distribution board may have to be upgraded to facilitate this retro-fit. This may be a major factor on whether or not the scheme is feasible.

We have some concerns regarding the robustness of the solar photo-voltaic panels to be located on Areas B & C of the roof. [The building owner’s representative] has advised that this South facing roof section is subject to extremely harsh weather conditions. The performance specification given to us states that “all systems should be designed for outdoor installation suitable for the climate of Scotland and robust enough to withstand high winds etc.” However we feel that it may be more prudent to narrow this qualification specifically to consider the site location.

We would also like to express some interest in the manufacturers data quoted in the “PV Module and Array Specification”. Have these figures been corrected to compensate for the difference between Standard Test Conditions and the expected site conditions?

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