Energy Rating

UCL DOMESTIC ENERGY RATING Institute of Environmental Desing and Engineering University College London

by Amalia Vranaki

Contents DOMESTIC ENERGY RATING

01introduction 4 02methodology 4

BASE CASE 4 5 03calculations 5 50%reduction 5 70%reduction 6 90%reduction 7

7 04discussion 7

05conclusion 9

APPENDIX 1 | U-values

APPENDIX 2 | SAP inputs 12

10

01introduction Nowadays, due to the climate change and greenhouse effect from fossil fuel combustion, there is an emerging need for reducing CO2 emissions. These phenomena stem from the rising levels of energy demand. Thus, experts focus on two main goals; in reducing energy demand and in decarbonizing energy –especially electricity (UK Committee for Climate Change, 2011).

But, what is the role of the built environment?

As far as buildings are concerned, they play a key role in reducing consumed energy, as they comprise the 30-40% of total energy consumption (UNEP, 2009). Moreover, buildings’ emissions in 2006 were around 400MtCO2, accounting for 70% of total emissions in the UK (UK Committee for Climate Change). Improvements of the existing building stock, through retrofit and refurbishment, can make a serious contribution in reducing carbon emissions. Studies have proved that old houses lose 40% less heat than we believed in the past, but still, new technologies and materials can increase even more their thermal performance.

Having said that, aim of this report is to investigate ways in which there could be a reduction of emissions in existing buildings. For that purpose, a Victorian, semi-detached house is selected as a case-study. It situated in a conservation area in Campten, London. Objectives of the report are therefore:

1. The calculation of the fabric heat loss and Dwelling Emission Rate (DER).

2. To propose alternatives by which there could be a reduction of 50, 70 and finally 90% in carbon dioxide emissions 3. To evaluate the renovation and the different measures taken during the process in terms of cost and efficiency.

02methodology First of all, the original condition of the building was estimated, by calculating the DER, using the “Parametric Energy Calculation Tool” (PECT) (see Appendix 1, 2 for input values).

After that, gradual interventions were proposed in order to succeed in reducing emissions up to 90%. That included: Insulation • Replacement of single-glazed windows and frames • Increase air-tightness of the building • Exploration and proposal of heating and hot water systems • Renewable sources of energy The impact of each measure -in terms of CO2 emissions, energy and cost- were also calculated by using the PECT. Finally, an attempt was made to evaluate the measures in terms of cost and efficiency. For this process, the MAC Curve spreadsheet was used, as well as simple payback-method calculations.

BASE CASE In order to be able to complete the calculations and use the PECT, the following assumptions were made: 1.

Walls, roofs and ground floor were initially uninsulated 2.

The building has a timber-frame suspended ground floor, which was the typical floor construction of Victorian Houses (Baker, 2011) 3.

The roof is a timber-frame pitched roof. There is a habitable room in the top floor, something that will affect the insulation process.

4. There is a central heating system that runs on gas, with reduced boiler efficiency.

In Table 1 we can see the existing construction, materials and their calculated U-values (see Appendix 1 for calculations).

18.7tCO2/year TABLE 1: BASE CASE MATERIALS AND U-VALUES (CIBSE GUIDE A; Bull et al., 2011; Scottish Gov.,2011) ELEMENTS CONSTRUCTION U-values UNINSULATED ROOF timber frame, tiles 2.3 SOLID BRICK WALLS (UNINSULATED) brick, dense plaster 2.0 SINGLE GLAZING 5.6 UNINSULATED GROUND FLOOR Joints, chipboard 0.49 TABLE 2: BASE CASE DER AND tCO2/year and expected reduced values

BASE CASE 50% RED. 70% RED. 90% RED. DER (kgCO2/m2) 62.4 31.2 18.72 6.24 tCO2/year 18.7 9.35 5.61 1.87 Graph 1: Base Case tCO2/ year

03calculations 50%reduction First step is to reduce the fabric heat loss -through external walls, roof and ground floor.

This could be achieved through insulation, and installation of new windows. It is worth mentioning that this measure will also make the building more air-tight.

Figure 1: Insulation Process

2.1 Insulation Walls: Internal insulation is proposed, in order to maintain the traditional brick surface of the building.

Roof: A ventilated type of roof is suggested, insulated at rafter level. There were two main reason that determined this selection: • The existence of a habitable space –an insulated roof at ceiling level would reduce the size of the room, as well as, it would aesthetically degrade it.

• It is assumed that the roof is in a good condition and therefore the existing timber frame and tiling can be maintained, in order to reduce the cost of totally replacing the roof.

18.7tCO2/year

Ground Floor: For reducing the cost of the refurbishment, it is proposed to maintain the existing timber-frame floor. Thus, the proposed insulation (mineral wool) is placed under the floorboard and between the joists.

2.50

Windows: Replace existing windows with double-glazed, argon filled windows.

0.40

As we can see in Table 3, by optimizing the materials and insulating the building there was a reduction of approximately 60%.

4.00

2.40

Graph 2: benefit in tCO2/year for each measure taken Table 3. U-values in different scenarios. See APPENDIX 1 for calculations U- Values (W/m²K) BASE CASE 50% REDUCTION 70% REDUCTION 90% REDUCTION External walls 2.0 0.27 Roof 2.3 0.19 Ground floor 0.49 0.22 Window 5.3 1.8 DER (KgCO2/m²) 62.4 27.9<31.2 18.72 6.24

EXISTING ROOF

PROPOSED ROOF

λ (W/mK)

1.Tiles Repair tiles if needed 0.85 0.02 2.Timber battens

existing timber battens

0.13 (Cibse A)

3.HR sarking felt Existing HR sarking felt 0.20 (Handbook of Energy Data and Calculations)

4.Rafters insulation between rafters 0.04 (Scottish Gov,2011)

0.2 0.02

0.35

5.

- 50mm ventilation gap - 0.05 6.

- Rigid insulation with internal vapour protection layer 0.02 0.25 7.

- Service void 0.17 20-50mm 8.Plaster board plasterboard 0.21 0.012 1 rigid phenolic insulants for roof – kingspan-UK 2 CLEAR Comfortable Low Energy Architecture

70%reduction Infiltration and air leakage is another cause of heat loss. For achieving the 70% reduction, the air leakages should be minimized, i.e. to make the building even more air-tight, (0.25ach). Furthermore, a Mechanical Ventilation Heat Recovery system (MVHR) is proposed, in order to minimize heat losses through ventilation.

Next step is the selection of the appropriate heating system. In terms of CO2 emissions and installation cost, gas is the most effective option and therefore, a high-efficient condensing gas boiler is proposed to replace the existing system, with an efficiency of 89%.

18.7tCO2/year

1.70 1.20 2.50 0.40 2.40 4.00

Table 4. Case 3 | 70% reduction achieved

Graph 4: benefit in tCO2/year

U- Values (W/m²K) BASE CASE 50% REDUCTION 70% REDUCTION 90% REDUCTION External walls 2.0 0.27 0.27 Roof 2.9 0.19 0.19 Ground floor 0.58 0.22 0.22 Window 5.3 1.8 1.8 Other MVHR system Increase boiler’s efficiency to 89% DER (KgCO2/m²) 62.4 27.9 16.6<18.72 6.24

Table 5. Case 3 | 90% reduction achieved

U- Values (W/m²K) 50% REDUCTION 70% REDUCTION 90% REDUCTION External walls 0.27 0.27 0.27 0.27 Roof 0.19 0.19 0.19 0.19 Ground floor 0.22 0.22 0.22 0.22 Window 1.8 1.8 1.8 1.8 Other MVHR system MVHR MVHR Increase boiler’s efficiency to 89% Boiler 89% wood pellet Wood pellet stove boiler Solar Panels PV panels DER (KgCO2/m²) 27.9 16.6<18.72 5.8<6.24 4.8<6.24

90%reduction

The target for reducing CO2 emissions to 90% would be achievable if we consider to incorporate renewable sources of energy. By using a secondary heating system using wood pellet -wood pellet stove-, we achieve a reduction from 16.6kgCO2/m2 to 15.6 KGCO2/m2.

18.7tCO2/year

SCENARIO 1- Solar heating and PV panels Solar heating and PV panels can be used, since the roof and orientation of the building are appropriate (Southeast orientation of the main façade), and because of the low height of surrounding buildings. By adding solar panels of 10m2, we achieve a reduction to 42.8kgco2. Next step is the suggestion of PV panels. We need at least 5.5kWp of PV panels (occupying 50m2 of the roof area) in order to reach the goal of 90% reduction.

0.50

SCENARIO 2- Main heating system using biomass If the previous heating system is totally replaced by a biomass boiler -wood pellet boiler-, there is a reduction to 4.8KgCO2/m2, i.e. more than 90% without further changes or use of other renewable systems.

2.50

4.00

0.30 1.70

1.70

1.20

1.20

2.50

2.50

0.40

0.40

2.40

2.40

4.00

4.00

Graph 4: benefit in tCO2/yeaR

04discussion Cost analysis The cost analysis is a way to evaluate whether the suggested measures are “worth” implementing, and which of them are actually “good”. A measure is worth, when it can pay back its cost of installation in a sensible period of time, with a corresponding environmental impact. One can argue that a measure can be defined as “good” when it has a significant impact on CO2 reduction, and at the same time a negative marginal cost, or very fast payback.

MAC: £/tCO2

After producing the MACC curve, we can make the following conclusions: • Replacing the old boiler with a more efficient one, is a highly effective and negative cost measure.

Not only is a significant amount of money saved, but also carbon emissions are reduced, through the reduction of burning fuel.

• Wall and roof insulation is a low-cost refurbishment and it can be highly effective and negatively cost if it is installed correctly.

• PV panels, even if they are the most expensive measure, are very efficient in terms of CO2 reduction.

• Wood pellet systems are a high cost measure (SAP, 2009; DECC, 2011). In the first case a biomass

300 250 BOILER

200

wall insulation windows

150

roof insulation 100

floor insulation MVHR

50

PV PANELS

wood pellet stove 0

SOLAR PANELS

‐50 0

1

2

3

Tonnes of carbon saved/year

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

Graph 1: MACC Curve for scenario 1

MAC: £/tCO2

300 250 200

wall insulation roof insulation

150

windows floor insulation

100

MVHR

wood pellet boiler

50

PV PANELS SOLAR PANELS

0 ‐50 0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

Tonnes of carbon saved/year

Graph 2: MACC curve for scenario 2-wood pellet boiler

pellet stove was used as a secondary heating system, while in the second case the existing gas system was totally replaced by a biomass boiler. A closer look at the graphs, reveals that a wood-pellet boiler is far more effective and worth implementing in terms of CO2 reduction. The carbon price needed to reduce CO2 emissions by 70% (i.e.

Table 6: Simple Payback Method- the following prices were also used in the MACC Curve and are general estimations Simple Payback Method PROJECT COST ANNUAL BENEFIT PAYBACK YEARS LIFE EXPECTANCY (project cost/benefit) (used in MACC)

wall insulation* 700 640 1.1 100 boiler ** 1300 255 5.1 25 roof insulation* 2622 384 6.8 100 windows 1000 250 6.0 30 MVHR1 1500 100 15.0 30 ground floor insulation* 800 50 16.0 100 PV panels2 20000 541 37.0 30 solar panels3 2500 40 62.5 30 wood-pellet stove4 4300 45 95.6 50 wood-pellet boiler4 10000 -270 50 *insulation cost and life expectancy: Diez, 2014. Bull et al.(2014 **boiler cost and life expectancy: ASHRAE, Bull et al.(2014) 1 Solarcrest 2 K. Branker, M.J.M. Pathak, J.M. Pearce, 2011 3 Fraunhofer, 2013 4 Biomass Energy Center, Eco Solaris Inc.

Table 7: Capital costs and payback for the different scenarios.

The measures that were considered inefficient were not included

SCENARIO 50% 70% 90%

WALL £700 £700 £700 £700 ROOF £2,600 £2,600 £2,600 £2,600 BOILER £1,300 £1,300 £1,300 WINDOWS £1,000 £1,000 £1,000 £1,000 MVHR £1,500 £1,500 £1,500 WOOD PELLET £4,300 £15,000 PV PANELS £20,000

SUM COST £5,600 £7,100 £31,400 £20,800

ANNUAL BENEFIT £1,529 £1,629 £2,215 £1,104

PAYBACK (years) 3.7 4.4 14.2 18.8

by 13tCo2) is 70GBP/tCo2 in the Case 2, while it reaches the amount of 150 GBP/tCo2 in Case 1. The same pattern applies also for the 90% reduction -150GBP/tCo2 in Case 2, compared to 240 in Case 1. As indicated in Table 5, though, even if the total cost of implementing scenario 2 is lower than implementing scenario 1, the payback is faster in the first case, because the annual benefit is also higher. Furthermore, if we consider the 50% reduction scenario, we can easily understand that Case 1 is more efficient –due to the efficient gas boiler, which is a low cost and effective measure. Indeed, the reduction can be reached only by negative cost measures.

That proves that the process of evaluating a retrofit can be very complex. Depending on the desirable reduction levels and on the available budget, different options should be evaluated.

• Floor insulation does not worth the cost of installation, especially when compared to wall or roof insulation which are negative cost measures. It has a low environmental impact, because it is in contact with the ground, which has a high thermal mass and therefore, heat loss occurs at a very slower rate, compared to heat loss through walls or roof (Bull).

05 // conclusion Buildings can play a major role in reducing CO2 emissions. The measures taken in order to environmentally upgrade existing buildings aim in energy reduction through improved efficiencies and materials, as well as in the decarbonization of energy, by exploring renewable sources of energy and electricity. In the frame of this report different measures were overviewed, and their environmental and economic impact was analyzed. It is of major importance to propose retrofit strategies depending on the special features of each project; its historicity, location, materiality, as well as the reduction targets and available budget. Taking the above factors into account is the first step so as to propose effective alternatives for achieving zero carbon buildings.

06 // bibliography Baker P., 2011. Technical Paper 10:U‐values and traditional buildings:In situ measurements and their comparisons to calculated values, Historic Scotland: Endinburgh

BRE, 2009. SAP 2009 The Government’s Standard Assessment Procedure for Energy Rating of Dwellings, Garston, Watford WD25 9XX: BRE. BRE, 2006. Installing Thermal Insulation, BRE Press Bull J., Gupta A., Mumovic D.,Kimpian J., 2013. Life cycle cost and carbon footprint of energy efficient refurbishments to 20th century UK school buildings, International Journal of Sustainable Built Environment (2014) 3, 1–17

Diez R., 2014. Insulation: Can it last as long as your home? Available from: http://www. improvementcenter.com/insulation/ KINGSPAN, 2011. Insulation for tiled or slated pitched warm roof spaces, London: KINGPAN. Office of the Deputy Prime Minister, 2010. Approved Document L1B: Conservation of fuel and Power in Existing Dwellings, London: HM Government.

Scottish Government, 2009. Domestic Handbook, 6.A - Tables of U-values and thermal conductivity, Chapter 6, Edinburgh: Scottish Government Press.

Tomas, R., 1996. CIBSE GUIDE A: Environmental Desing, LONDON: CIBSE. UK Committee on Climate Change, 2010. Energy Use in Buildings and Industry: 4th Carbon Budget, London: UK Committee on Climate Change.

APPENDIX 1 | U-values For the U-values of the existing construction: 1. solid brick wall: MATERIALS λ (W/mK) width (m) R=width/λ(m²K/W) U-value(1/Rtotal) Rse 0.04 brick 0.77 0.22 0.29 plaster (dense) 0.58 0.02 0.03 Rsi 0.13 0.49 2.04

2. Uninsulated roof: 12.5mm plasterboard, no insulation, roof space, tiling: U-value 2.9 (CIBSE guide A) 3. Uninsulated floor: Table 3.20, CIBSE A Pf/Af=0.30, thus U-value for clay-soil equals 0.58 4. Single glazed windows, the values for typical single glazed windows were used, given by CIBSE Guide A, Approved Document L and Scottish Government (2009). In table 1, there is the methodology for calculating the proposed consturctions by calclulating thermal resistancies (width of material/thermal conductivity).

Proposed Construction TABLE 1: The U-values for walls and roof are shown in Table 1 and the values are also confirmed to be correct by Approved Document L1b (2014, p.24-25) MATERIALS

INSULATED WALL

Rse Existing Brick Existing Plaster (dense) Waterproof Expanded polysterene Plasterboard Rsi

λ (W/mK)

0.77 0.58 0.20 0.04 0.25

width (m)

0.22 0.02 0.01 0.12 0.02 SUM

INSULATED ROOF

INSULATED FLOOR

Rse tiles slate battens HR Insulation between rafter Ventilation gap rigid insulation plasterboard (fireproof) Rsi Chipboard Insulation (mineral wool Joints

0.85 0.13 0.20 0.04 0.02 0.25

0.02 0.20 0.02 0.20 0.05 0.25 0.02

0.14 0.04 0.14

SUM 0.019 0.15 0.15

R = width/λ (m²K/W) 0.04 0.29 0.03 0.05 3.00 0.08 0.13 3.58 0.04 0.02 1.54 0.10 5.00

U-value (1/Rtotal)

0.28

0.14 12.50 0.08 0.10 19.38 0.14 3.75 1.07

0.19

.

In the case of insulated floor, following the methodology given by CIBSE A for timber suspender floors, it is needed to calculate the total Rb for joints and the insulation between them which is given by the equation: Rb=[(Pm/Rm)+(Pn/Rn)]-1, where m,n are the different materials, P the proportion of area and R the thermal resistancies.

reproduced from CIBSE guide A

We assume, that we have joints of 50x200mm, every 400 centers and the thickness of insulation is also 200mm. Thus, Pm, insulation= 350/400=0.88 whereas Pn,joints=50/400=0.13.

Resistancies are shown in Table 1.

Thus, Rb=[(Pm/Rm)+(Pn/Rn)]-1= [(0.88/3.75) + (0.13/1.07)]-1 =2.86 Rtotal= Rchipb + Rb = 0.14+2.86= 3.00 From Table 3.20 in page 3-19 of CIBSE A, we have the Uvalue of the uninsulated roof for different proportions. In our case we have pf/af=0.3, therefore, Utotal=[(1/Uunins.) -0.2+Rtotal]-1 = [(1/0.58) -0.2 + 3.00]-1= 0.22

reproduced from Domestic Handbook, 2013, Tables of U-values and thermal conductivities, Chapter 6, Scottish Governement

APPENDIX 2 | SAP inputs gross floor area: total floor area=300m2 floors: 4 average room height: 3 width: 7m Depth: 12.1 glazing ratio: 0.28 glazing assymetry; 0.15 orientation: 45째 with respect to due South living area fraction: 0.14 (SAP table for habitable rooms: There are 15 habitable rooms in the house (excluding halls and WCs), therefore the living area fraction is 0.14 (SAP, 2009). wall area= total elevation area - windows/doors area

Figure 1: glazing asymmetry: proportion of windows on main facade

Figure 2,3: Rear and side elevations

Figure 4: exposed area to total area used for calculations (Pf/Af)