DEMScot 2: Scotland s Housing Carbon Model The extensions

Transcription

1 DEMScot 2: Scotland s Housing Carbon Model The extensions 16.0 CO2 emissions per year Mt CO Base Case Scenario 1: Base case including embodied CO2 Simulation including embodied CO April 2010

2 DEMScot 2: The extensions Summary This report summarises how DEMScot, the Domestic Energy Model for Scotland, was extended to incorporate new functions from February to April It is accompanied by a supporting report, Modelling Price Elasticity of Demand, Direct Rebound Effects and Recent Government Policy Initiatives in DEMScot, by Cambridge Econometrics. Contents Introduction 2 1. Price Elasticity of Demand 2 2. Rebound Effects 3 3. Maintenance and Replacement Costs 5 4. Floor Insulation 6 5. Other changes 7 Appendix 1: Replacement and maintenance 8 Appendix 2: Embodied CO2 of replacements 16 Cambridge Architectural Research 1

3 DEMScot 2: The extensions Introduction The Domestic Energy Model for Scotland, DEMScot, was developed in 2008 to It modelled 18 upgrades to Scottish housing, including a range of insulation measures, heating systems, and renewable technologies. It showed the effect of implementing these upgrades on energy use and carbon dioxide emissions through to The model is described in detail in our report on the Scottish Government website, Modelling Greenhouse Gas Emissions from Scottish Housing: Final report. However, the original DEMScot was not designed to include price elasticity effects (how demand for energy changes in response to price changes), or rebound effects (which mean, broadly, that upgrades aimed at reducing CO2 emissions achieve a smaller saving than expected). Nor was it designed to model the effect of floor insulation. The Scottish Government asked CAR and Cambridge Econometrics to extend the model to include price elasticity and rebound effects, and to add floor insulation to the palette of upgrades. We were also asked to include the maintenance costs of upgrades (e.g. servicing wind turbines and biomass boilers) and the costs of replacing upgrades as they wear out. This report explains how we changed the model. It is accompanied by a supporting report, Modelling Price Elasticity of Demand, Direct Rebound Effects and Recent Government Policy Initiatives in DEMScot, by Cambridge Econometrics, which describes why we implemented the price elasticity and rebound effects as we did. This report is in four parts: 1. Price Elasticity of Demand 2. Rebound Effects 3. Maintenance and Replacement Costs 4. Floor Insulation, and 5. Other changes. Price Elasticity of Demand The original DEMScot included Cambridge Econometrics projections for energy costs to households through to This was used to show how the cost of domestic energy will change under different upgrade scenarios. However, there was no link between energy cost and households use of energy. There is robust evidence 1 indicating that in fact householders do use less energy when the price rises, and more when prices fall. Debate continues about the precise magnitude of these effects, but Cambridge Econometrics work recommended a value of (This means that, if fuel prices increase by 100%, demand will fall by 6%, or conversely if prices 1 This is reported in full in Cambridge Econometrics (2010) Modelling Price Elasticity of Demand, Direct Rebound Effects and Recent Government Policy Initiatives in DEMScot, CE, Cambridge. Cambridge Architectural Research 2

4 fall 50%, demand will rise by 3%.) CE concluded that this value reflects soft behavioural changes in response to price changes, i.e. changes in how people set their heating controls, use lighting and appliances, and ventilate their homes in the heating season. It does not (and should not) incorporate physical upgrades, which are already dealt with by the model. DEMScot 2 users can now select Including price elasticity in the Economics effects options on the Total CO2 emissions worksheet. This automatically adjusts CO2 savings, energy use and energy costs to reflect changes in prices. When users choose anything apart from Constant (SAP) energy prices in the Future energy costs options, demand falls for energy price rises and increases for energy price cuts. The factor by which demand changes (technically, the price elasticity of demand ) is set by default at 0.06 in cell B248 on the Upgrade parameters worksheet. This aggregate figure (the elasticities of all fuels taken together) can be altered by users. Users may also change the individual elasticities of demand for different fuels in cells B250 to F250 in the same worksheet. We suggest that users monitor new research into price elasticity of demand for household energy, and update these figures as more robust data becomes available. As to how these changes in energy demand are achieved in practice, it is not possible to say. Many different combinations of different heating set-points, lighting controls, ventilation and other aspects of household behaviour could achieve the changes in demand. If users wish, they can alter the number of high, medium, and low users to achieve the same effect, by trial and error. This may make it easier to communicate the effects of price elasticity, but there is inadequate data to say exactly how behaviour might change. Rebound effects Actual fuel and CO2 savings that result from energy-efficiency upgrades are almost always less than you would expect based on building physics models. There are many reasons for this, and the best understood is the notion of takeback, where householders take part of the saving from better insulation or heating system efficiency as improved thermal comfort. Effectively, as it becomes easier and cheaper for people to heat their homes, they run their homes warmer. Similar effects apply to electricity use: appliances and lighting. Strictly speaking, these changes in behaviour that work against energy saving are called direct rebound effects. These are the effects we have added to DEMScot 2. As with price elasticity, research into rebound effects is at an early stage, and the magnitude of these effects is still contested. However, CE s report advocated using an average rebound effect of 20% (implying that an expected saving of 1 tonne of CO2/year translates into an actual saving of 0.8 tonnes). The Scottish Government was also keen to define higher rebound effects in the model for groups at risk of fuel poverty: pensioners and CERT priority groups. (It is likely that these groups take back a higher proportion of savings as warmer homes.) As for price elasticity, DEMScot 2 users can now select Including rebound effect in the Economics effects options on the Total CO2 emissions worksheet. This automatically adjusts CO2 savings, fuel use and energy costs to adjust expected savings from building physics to the actual savings we are likely to see in Scottish homes. The modelled rebound effect implies that improvements in gas efficiency result in a rebound effect shared proportionately across all uses of gas, while any electricity efficiency Cambridge Architectural Research 3

5 gains are shared proportionately across all uses of electricity. This is because householders will not know where savings in their (gas or electric) bills come from - they will simply see a saving in one of their utility bills. The 'product' in question is energy, and there is no evidence to suggest that whether gas is used for hot water or space heating, or electricity is used for lights or appliances, makes any difference. The rebound effect is set by default at 20% in cell B255 on the Upgrade parameters worksheet. As with price elasticity, this aggregate figure can be altered by users. Users may also change the individual elasticities of demand for pensioners, CERT priority groups and others in cells B258 and D258 in the same worksheet. If they wish, they may also change the magnitude of the rebound effect for different fuels, in cells B262 to F264. Once again, we suggest that users monitor new research into rebound effects for household energy, and update these figures as more robust data becomes available. (In reality, every household has a different rebound effect, depending on their individual circumstances, and in particular their income and base case heating temperatures. However, we do not have access to such data, so it is not possible to use this for greater disaggregation of the rebound effect.) As with price elasticity effects, there is no way of knowing exactly how behaviour would change as a result of the rebound effect (longer heating periods, higher set points, more water use, more lights or appliances use...). There is no robust data on this. As before, though, users wish to estimate an 'equivalent behaviour change' by trial and error, using the User behaviour worksheet to match the loss in savings to the rebound effect. (In developing this extension to DEMScot, we also considered, but rejected, building a separate rebound effect into each upgrade. However, this would mean having to make assumptions about the use of each upgrade and how this affects behaviour, and there is no data available for individual upgrades. In reality, we only have data on aggregate rebound effects, so and trying to break this down to each of the 19 upgrades would be guesswork with no greater accuracy or reliability.) Limitations of the model In reality, rebound effects for heating upgrades are different from those for other upgrades, for several reasons. First, not all upgrades result in lower fuel use (using biomass heating, for example, does not necessarily make it easier or cheaper to heat a home). You would not expect a rebound effect from upgrades that do not result in an efficiency improvement, but DEMScot 2 does currently show a rebound from such upgrades. Second, several of the heating upgrades (biomass boiler, ground-source heat pump, and air-source heat pump) often result in fuel switching (e.g. from coal to biomass heating). The model assumes that there is a rebound effect on the original fuel (i.e. that coal use will not fall as much as predicted because householders will take back some of the saving in better comfort. However, in reality there is no rebound effect (or in some cases a reduced rebound effect) when upgrades result in fuel switching. Again, because a more sophisticated approach was not possible, we have applied the usual rebound effect. Third, some households (especially poorer households, and those with solid fuels) are likely to be under-heated before they were upgraded. Arguably, these homes may show higher rebound effects than other homes, but we have not implemented this to avoid double-counting this effect pensioners and CERT priority groups can already be set to have higher rebound effects. Cambridge Architectural Research 4

6 Overall, we calculated 2 that the worst-case scenario for rebound effects and heating upgrades would result in an over-stating of the rebound effect of 4.9%. (i.e., for all heating upgrades selected, DEMScot will show a 20% rebound for the default settings, when it should really be 15.1%.) However, the under-heated homes (where the rebound effect is probably under-stated) offset these other special cases (where the rebound effect is too high). Users should bear in mind that the rebound effect is likely to be 2-3% too high when they model large numbers of heating upgrades. Maintenance and Replacement Costs The original DEMScot included projections of some whole life costs, but not all of them. While it showed future energy costs, and allowed users to compare these to initial capital costs, it omitted maintenance costs and the replacement cost of upgrades. This meant, for example, that it showed the initial capital cost of installing a wind turbine, along with the subsequent energy cost savings, but it did not include the cost of servicing the turbine each year, or replacing the turbine at the end of its life say, 25 years after installation. Service lives of building components are notoriously difficult to estimate, and uncertainty about service lives is even more intense for new, renewable energy technologies (which have only been installed in any volume for a few years not enough time to know with real confidence how long they will last). Similarly, maintenance costs for homes can change from dwelling to dwelling, depending on location and construction. There may also be a significant difference between the recommended frequency of maintenance and how often householders actually maintain their equipment. (This applies just as much to existing equipment, like a boiler, as it does to new renewable energy technologies.) Notwithstanding these difficulties, we assembled the best available data about service lives and maintenance costs for all upgrades (and the base case, with no upgrades, see Appendix 1). We also obtained quotes from Scottish companies that can carry out maintenance to all upgrades to estimate maintenance costs. The data we have used is included as Appendix 1 to this report. These are all defined in DEMScot in Upgrade parameters, and can be changed by users. Heating system maintenance costs Heating systems and boilers are something of a special case, because maintenance costs are significant, and because (unlike all other upgrades), even the base case (no upgrades) scenario will incur substantial maintenance costs. (To clarify, not installing a wind turbine or PV does not imply maintenance costs to the householder, whereas not upgrading a boiler means that the householder still needs to maintain their existing boiler.) For this reason, we have assigned maintenance costs to both the base case and all heating upgrade options, using figures from Scottish boiler servicing companies, see Appendix 1. 2 Based on the permutations of the number of homes that could take each heating upgrade, their original heating fuel, whether the rebound effect applies, and estimates of the actual rebound effect that would apply in each case based on expert judgement. Cambridge Architectural Research 5

7 Users should be aware that nearly all existing boilers in homes will need to be replaced over the next, say, 20 years, because they will fail, or because replacement parts are no longer available. It is not now usually possible to replace an existing boiler with anything other than a high-efficiency condensing boiler. This means that, even without a conscious effort to improve boilers, the average boiler efficiency will rise over time. It also means that by around 2030 there will be no non-condensing boilers installed in Scottish homes. For this reason, users should ensure that their scenarios include replacing all boilers by (Even if users are applying other upgrades, they should remember to include the replacement of boilers in line with the expectation that all existing boilers will be replaced by 2030.) Embodied energy of upgrades We have included embodied energy for replacement upgrades, and shown it as a separate line on the 'Total CO2 emissions' graphs. The figures used are consistent with those we used for the embodied energy of initial upgrades, and are included here as Appendix 2. They are defined in DEMScot 2 in the Upgrade parameters worksheet, and may be changed by users as more data becomes available. In reality these values would change over time as the CO2 intensity of grid electricity changes with lower embodied CO2 per upgrade in the future if the upgrades are made in the UK. However, it would be complicated to include the effect of changes in grid electricity over time, because we'd need to work out the proportion of electricity vs. heating and transport fuel for each upgrade, and we'd need to know where the upgrades are being made - because CO2 intensities of electricity differ between countries. Floor Insulation The original version of DEMScot allowed users to model the effect of installing roof and wall insulation, but not floor insulation. (Floor insulation is a less common upgrade because it is relatively expensive and more disruptive to install than other types of insulation.) For completeness, the Scottish Government asked us to add this to Version 2 of the model. In part because floor insulation is an unusual upgrade to homes, and in part because the approach to insulation depends on the construction of a dwelling, there is almost no published data about the cost of insulating floors. This made it difficult to obtain a robust cost for upgrading floors. Similarly, because of uncertainty about construction types and achieved u-values for insulated floors, we had to make five assumptions in the model, all of which can be changed. Our assumptions are: 1. Floor insulation consists of 50mm of high impact polystyrene, achieving a u-value of 0.23 W/m2K. This is the same for solid floors and suspended floors. 2. There is no change to airtightness when solid floors are insulated, but suspended floors have airtightness improved from 0.2 to 0.05 air changes per hour through the floor % of the housing stock is available for upgrade (20% of dwellings have no ground floor heat loss - suggesting that they are flats above a heated space, and Cambridge Architectural Research 6

8 31% of the remainder have a floor u-value of less than 0.45, suggesting that they are already insulated.) 4. It costs 1,200 to insulate the ground floor for either solid or suspended floors. (This is a weak link - there is no published data on the cost of floor insulation apart from 'DIY' costs that are about a tenth of this. CAR has actual cost data for one project that insulated a suspended floor, last year, at a cost of 1,200, and another large dwelling with a solid floor which cost 2,000, but it remains rare for individual householders to insulate their floors.) 5. The embodied CO2 of floor insulation works out at 319 kgco2 for high impact polystyrene. (Solid walls, for comparison, are 577kgCO2, at a cost of 5,500.) To summarise the outcome of the new floor insulation upgrade, applying ground floor insulation to all available homes saves 7% of total kwh, or 6% of total CO2, compared to the base case. This upgrade would cost 1,546m at 2008 prices. Other Changes We have also added a discounting function for all of the future costs calculated in DEMScot 2. This uses the Treasury Green Book discount rates of 3.5% for the first 30 years, then a rate of 3% through to the end of the simulation. The discounting can be turned on using the Discounting and cost base switch on the Cost Worksheet. The discount rates used may be changed in cells F277 to F299 in the Upgrade parameters worksheet. Finally, we have added DECC s latest energy price projections to the model. DECC has published four sets of time series energy costs (for gas, electricity, oil and solid fuel), which run to 2060: - Low - Medium - High, and - High-high. These are held in the Annual input data worksheet, with graphs beneath so users can see how DECC anticipates energy costs could change. DECC updates these forecasts periodically, and users can paste the new projections over the top of the existing data as DECC revises its projections. The energy price projections become particularly important when price elasticity is turned on in the Costs worksheet. Cambridge Architectural Research 7

9 Appendix 1: Replacement and maintenance Summary As part of Stage 2 of CAR and CE s work for the Scottish Government, we were asked to extend the model to include the replacement costs and maintenance costs of upgrades. No other UK models of household energy use and cost include these costs, but they are clearly important in long-term decision making. However, the data on both replacement and maintenance costs is extremely limited partly because carrying out fabric upgrades and installing renewable energy systems are new phenomena. There is currently no well-recorded history of the actual cost of maintaining and replacing components in upgraded buildings. Similarly, there is extremely limited published data on the service lives of the upgrades in DEMScot. We have used the limited published information available on these costs, and our judgement, to estimate replacement and maintenance costs, and service lives, of 18 upgrades in DEMScot. They are summarised in the table below. No. Option Service Life (years) Maintenance Cost (per year) 1 Changed user behaviour N/A N/A N/A Replacement Cost 2 Cavity wall insulation ,000 3 Solid wall insulation ,500 4 Loft insulation Ground floor insulation Lifetime of 0 1,200 building 6 Short term upgrade package 5 years for draughtexcluder, 0 30 for draughtexcluders 50 years all other upgrades 7 Low energy lights Solar water heating ,000 9 Double or secondary glazing , Advanced heating controls Boiler upgrade , Biomass boiler , Combined heat and power (CHP) 14 Ground Source Heat Pump (GSHP) 15 Air Source Heat Pump (ASHP) 16 Community heating with CHP , , , /dwelling 2,000/dwelling Cambridge Architectural Research 8

10 17 Improved electrical appliances 18 Photovoltaic , Wind turbine ,400 Introduction A weakness of the original DEMScot model was that the ongoing cost of maintaining fabric upgrades or renewable energy systems were not included. For example, it is accepted that biomass boilers need an annual service. Wind turbines may also need periodic checks and re-greasing of bearings or gearing. These costs should be factored into the total costs of carrying out upgrades. Similarly, DEMScot 1 omitted the replacement costs of upgrades when they reach the end of their service lives. For example, most double-glazed windows are expected to last around 25 years, at which point they need to be replaced if they are to maintain their thermal integrity. An air source heat pump has a shorter expected service life, and this too will need to be replaced. Such replacement costs can be considerable (doubling or even trebling the total capital costs of an upgrade over 50 years), so this really shouldn t be left out of the decision to upgrade. However, to date none of the existing UK housing energy models include these costs partly because there is so little robust data about the costs of maintenance and replacement, and so little robust data about service lives. (Both stem in part from the fact that many of these upgrades are new, so there are few projects where maintenance and replacement costs have been significant, and recorded.) CAR has examined the literature about fabric upgrades and renewables, looking in particular for comments relating to post-installation costs and service lives. Overall, we found very little published material. Where there was information, it sometimes only reflected DIY costs which underestimates the true costs. We have tabulated the data we did find, recording any information about maintenance costs, replacement costs, and service lives separately. For ease of reference, we present the tables here in the order of the numbered upgrades in the model. 1. Changed User Behaviour Estimate Maintenance Cost N/A Replacement Cost N/A Service Life N/A 2. Cavity Wall Insulation Maintenance Cost Replacement Cost 0 National Insulation Association * National Insulation Association /house ESRU TIED 2005 Service Life 25 years Cavity Insulation Guarantee 2009 Agency (CIGA). Cambridge Architectural Research 9

11 40 years BRE - Delivering Cost effective 2007 CO2 savings *Initial capital cost (actual replacement cost would be higher strip out cost) 3. Solid Wall Insulation Maintenance Cost Replacement Cost 0 EST Website National Insulation Association * EST Website 2009 ~ 700* BCIS Greener Homes Price Guide * ESRU TIED Report 2005 Service Life years EST Website 2009 * These values are known to be too low. CAR has data about five houses where internal and/or external insulation was used, and the average cost was 5, Loft Insulation Maintenance Cost 0 EST Website 2009 Replacement Cost 500 National Insulation Association ESRU TIED 2005 Service Life 40 years AE Insulation Ltd years BRE Delivering Cost effective CO2 savings 2007 There is good consistency between an insulation installer and the BRE about the service life of loft insulation. However, while the thermal performance of loft insulation may decline somewhat over time (as the insulation gets compressed and/or damaged), it will still provide some insulation to the house. Unlike double-glazing, the upgrade is not visible either, so arguably the insulation could stay in place for much longer than 40 years. 5. Ground Floor Insulation Maintenance Cost 0 EST Website 2009 Replacement Cost 500 (DIY) National Insulation Association ,000 BCIS Greener Homes Price Guide 2008 Service Life Lifetime of building Quinn Therm years BRE Delivering Cost effective CO2 savings 2007 There is a wide variation on the cost of ground floor insulation, depending on materials and construction type. CAR knows one upgraded house where the cost of insulating the floor was around 1,200, which suggests that the BCIS figure may be too high. BRE s estimate Cambridge Architectural Research 10

12 of the service life also seems conservative given that floor insulation is protected and unlikely to be damaged in the usual use of a home. 6. Upgrade Package Maintenance Cost Replacement Cost Service Life (Radiator Insulation per radiator, Pipes , cylinder insulation 120, Shutters 200 per window) Varies BCIS Greener Homes Price Guide Low energy lights Maintenance Cost 0 Replacement Cost 4-8 per bulb* BCIS Greener Homes Price Guide 2008 Service Life hours Ethical Consumer Magazine Issue hours National Energy Foundation 2009 *The cost of low energy bulbs has fallen since 2008, and it is likely to fall further as manufacturers benefit from increasing economies of scale, and consumers benefit from more competition by suppliers. We have taken a cost of 4/bulb, and assumed there are 10 bulbs in an average dwelling. We assume that the replacement cost of low energy lights is lower than the initial capital cost because, although some light fittings may need to be replaced initially to accommodate low energy lights, this will not be necessary when the bulbs fail. 8. Solar Hot Water Heater Maintenance Cost every 3-5 years EST website 2009 Replacement Cost NHBC Review of Microgeneration Technologies Service Life 30 years NHBC Review of Microgeneration Technologies Double Glazing Maintenance Cost 0 EST website 2009 Replacement Cost EST website /per window ESRU TIED 2005 Cambridge Architectural Research 11

13 Service Life years* EST website 2009 *EST s estimate of the service life of glazing sounds over-conservative. The presumption in whole life costs for major PFI projects is that glazing will last, on average, 25 years. In a domestic setting windows often actually last longer. 10. Advanced Heating Controls Maintenance Cost Replacement Cost Service life 0 300/house for full ESRU TIED 2005 controls package We could not find any information on the service life of heating controls. We assume therefore that they will last more than 50 years. 11. Boiler Upgrade Maintenance Cost /year Boilerguide website 2009 Replacement Cost 800 ESRU TIED 2005 Service Life 15 years EST website Biomass Boiler Service Life 25 years NHBC Review of Microgeneration 2008 Technologies Maintenance Cost 250/year TRECO (Manufacturer) website 2009 Replacement Cost 6,000 for 25kW Boiler NHBC Review of Microgeneration Technologies Micro CHP Maintenance Cost /year Boilerguide website 2009 Replacement Cost 3,000 Eon Website 2008 Service life years Building Magazine Air Source Heat Pump Maintenance Cost 790/year EST Website 2009 Replacement Cost 5-9,000 EST Website 2009 Cambridge Architectural Research 12

14 5-10,000 Carbon Trust Website 2009 Service Life years Office of Energy Efficiency (Canada) years Carbon Trust Website Ground Source Heat Pump Maintenance Cost Replacement Cost years (50 for heat coil) $0.17/sq.ft./year 6000 (excludes heat distribution system) NHBC Review of Microgeneration Technologies Washington State University Energy Programme NHBC Review of Microgeneration Technologies Service Life 20 years Chartered Institute of Plumbing and Heating Engineering The ground-couple of a GSHP should not need to be replaced within 50 years, and nor would the heat distribution system (pipework and radiators). We therefore restrict replacement costs to just the heat pump. 16. Community CHP Maintenance Cost 150/dwelling Combined Heat and Power 2009 Association Replacement Cost 2000/dwelling Carbon Trust 2009 (1000KWe) Service Life 15 years Intelligent Energy Europe years Carbon Trust website Improved Appliances Maintenance Cost Replacement Cost Service Life years machines with motors; 15 years cold appliances EST website 2009 CAR s best estimate 2010 There are two types of appliances relevant here: washing machines/dishwashers, and cold appliances like fridges and freezers. We assume that the former last, on average, around eight years, while the latter last, on average, 15 years. For DEMScot 2, we propose to take the average: 11.5 years, and the average cost of both appliances together: 600. Cambridge Architectural Research 13

15 18. Photovoltaics Maintenance Cost 1% total hardware PV Resources 2010 cost 50/year + 80 CLG Code for Sustainable Homes inspection every 5 years Impact Assessment Replacement Cost 7m kwp Solar Century/DEMScot system Service Life years National Renewable Energy 1999 Laboratory (USA) years Photovoltaics World Magazine years Carbon Trust years BRE Delivering Cost effective CO2 savings 2007 There is good consistency in these estimates of service lives, but in fact some PV installations in the US are known to be functioning even 40 years after they were installed. In fact, the output declines slowly over time, but manufacturers say it would be very unusual for the panels to stop generating power completely. Some photovoltaics contain heavy metals, and they are likely to be considered special waste at the end of their service lives, which means disposal costs will be higher than other building components. We have allowed 500 for disposal costs in our total cost of replacement for PV. 19. Wind Turbine Maintenance Cost 1.5% and 3% of cost University of Strathclyde 2006 of turbine 1.5-2% cost of Danish Wind Industry Association 2003 turbine per year MET Office Small Scale Wind Energy 2008 Technical Report Replacement Cost 15-20% of cost of Danish Wind Industry Association 2003 turbine Service Life years American Wind Energy Association years Renewable Energy Focus Magazine 2009 Cambridge Architectural Research 14

16 Heating system maintenance costs Heating systems and boilers are a special case, because maintenance costs are significant, and because (unlike all other upgrades), even the base case (no upgrades) scenario will incur substantial maintenance costs. (To clarify, not installing a wind turbine or PV does not imply maintenance costs to the householder, whereas not upgrading a boiler means that the householder still needs to maintain their existing boiler.) For this reason, we have assigned maintenance costs to both the base case and all heating upgrade options, using figures from Scottish boiler servicing companies, see below: Heating system Company Maintenance Cost Gas Boilers (condensing or standard) React Fast Boiler Services Scotland 95 flat fee including VAT Oil fired boiler Oil Care Scotland 214 per year inc. VAT Biomass Boilers Eco Energy Base rate 400 plus VAT and travel (say 500 total) Ground Source Heat Pump Solid fuel heating (open fires or stoves) Ground Source Heat Pump IHS Energy Firework Sweeps, Inverness Abel Sweeps, Lanarckshire travel per year (or can extend normal 2 year warranty for 275 per year) 45 for a standard sweep or 65 for a powersweep using a special rotating brush. (inc. VAT) 50 for domestic chimneys, inc. VAT The Guild of Master Chimney Sweeps UK suggest these frequencies for sweeping: Smokeless fuel: At least once a year Wood: Quarterly when in use Bituminous coal: Quarterly when in use Oil: Once a year Gas: Once a year For simplicity, we are assuming annual sweeping for all solid fuels, and two chimneys per home, at a total cost of 95. Cambridge Architectural Research 15

17 Summary The data on costs and service lives is patchy and incomplete. However, there will inevitably be large variations in costs and the frequency of maintenance and replacement from home to home depending exactly how the upgrades were implemented. This means that, taken together with CAR s database of projects, the literature work presented here is sufficiently robust to predict maintenance and replacement costs in DEMScot 2. The actual service lives and costs we propose to implement in the model are shown here a more detailed version of the table on page 7. No. Option Service Life (years) Maintenance Cost (per year) 1 Changed user behaviour N/A N/A N/A Replacement Cost 2 Cavity wall insulation ( 500 strip out replacement) 3 Solid wall insulation Loft insulation ( 200 strip out replacement) 5 Ground floor insulation Lifetime of 0 1,200 building 6 Short term upgrade package Varies Low energy lights per bulb = 40/dwelling 8 Solar water heating Double or secondary glazing Advanced heating controls Boiler upgrade Biomass boiler Combined heat and power (CHP) 14 Ground Source Heat Pump (GSHP) 15 Air Source Heat Pump (ASHP) 16 Community heating with CHP 17 Improved electrical appliances (50 for coil) /dwelling 2000/dwelling 8 (washer/dryer) 17 (fridge/freezer) Photovoltaic disposal 19 Wind turbine a Existing boiler b Solid fuel heating (open fire or stove) N/A 95 N/A Cambridge Architectural Research 16

18 Appendix 2: Embodied CO2 of replacements Cambridge Architectural Research 17

19 References Books The Greener Homes Price Guide BCIS, 2008 Sustainable Energy without the Hot Air David Mackay, 2008 Innovation for a Low Carbon Economy (Market Transformation: Innovation Theory and Practice) Mark Hinnells and Brenda Boardman Edward Elgar Publications 2008 Reports/Articles Putting a Price on Sustainability BRE Trust/Cyril Sweett, Watford, 2005 Energy Conservation Field Studies in Domestic Heating G.A Pickup, AJ Miles Examining the Carbon Agenda via the 40% house Scenario Brenda Boardman Building Research & Information, Volume 35, Issue 4 July 2007, pages From Pre-Pay to Pay as you save David Adams, Knauf Insulation, January 2009 Code for Sustainable Homes: Impact assessment Communities and Local Government December 2009 Refurbishing Victorian housing - Guidance and assessment method for sustainable refurbishment Tim Yates, BRE Construction Division, October 2006 Delivering Cost-effective CO2 savings John Henderson for DEFRA, 2007 Delivering Renewable Energy to the Cambridge sub-region Energy for Sustainable Development with Global to Local, 2004 Community Heating Using New Sources Carbon Trust, Energy Saving Trust, 2007 Costing Energy Efficiency Improvements in Existing Commercial Buildings Cyril Sweett for IPF Research NHBC Review of Microgeneration Technologies BRE, 2008 Cambridge Architectural Research 18

20 ESRU Thermal Improvement of Existing Buildings (TIED) Jan 2005 Small Scale Wind Energy Technical Report MET Office August 2008 Cost Analysis of The Code for Sustainable Homes DCLG 2008 Insulating UK Homes IInsulation Strategy Group of the Energy Efficiency Partnership for Homes August 2008 Meeting Climate Change Targets The role of microgeneration and energy efficiency Encraft, 2005 Websites Cambridge Architectural Research 19