Energy Credits Calculator: supporting information

Contents Supporting information .............................................................................................................. 1 Assumptions and background information ................................................................................ 1 1. Dwelling type..................................................................................................................... 2 2. Fabric performance........................................................................................................... 2 3. Ventilation ......................................................................................................................... 4 4. Heating.............................................................................................................................. 5 6. Lighting.............................................................................................................................. 6

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Supporting information The Energy Credits Estimator, produced by the Building Research Establishment (BRE), has been provided to the Energy Saving Trust to help familiarise housing professionals with the potential approaches and features necessary to achieve a range of energy credits within the Code for Sustainable Homes. It also incorporates a SAP2009 calculation engine so that designers may gain initial thoughts on the potential design changes necessary to be compliance with Part L1A as of the 1st October 2010.

This tool is provided free of charge and may be freely circulated and copied. However please note that no guarantee, warranty or support is implied. This tool is based on the April 2007 Code for Sustainable Homes Technical Guidance. Whilst many of the principals and concepts remain the same anyone seeking to achieve compliance with the Code for Sustainable Homes should employ a licensed assessor and follow the latest technical guidance available from www.communities.gov.uk/

Assumptions and background information The Energy Credits Calculator Excel spreadsheet contains a full SAP2005 and SAP2009 calculator - to provide a simplified Energy Credits Estimator the following assumptions have been used. This tool will remain password protected so no alterations to these assumptions are possible.

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1. Dwelling type The following areas are used:

Floor areas (m2) Dwelling type

Ground First Second

Wall areas (m2)

Roof Area (m2)

Four bedroom detached house 150 150 0 260 150 Three storey town house mid-terrace 70 70 70 145 70 Two storey three bed semi-detached house

55 55 0 158 55

Two bed back-to-back mid-terrace 42.5 42.5 0 46 42.5 Two bed bungalow 100 0 0 120 100 Two bed flat mid-floor 0 55 0 40 0

This Energy Credits Estimator only allows individual dwellings to be assessed, it is hypothetical, and thus assumes that items such as building orientation and window location can be adjusted. In reality however, for example with back-to-back dwellings this will not be possible. Within full Code for Sustainable Homes assessments it is also possible to average out the dwelling emission rates for groups of similar flats and this is not possible within this tool. The living area fraction for all dwelling types is 0.25

2. Fabric performance Walls, roofs and ground floors The U-values for walls, roofs and ground floors may be adjusted in this data entry section by using the provided drop down boxes.

Please note - in the case of the mid-floor flat that changing the U-values for the ground floor or roof will have no effect. Party wall Party wall heat loss is a new feature for SAP2009 and will only affect those results. The following assumptions are made with regards to the U-values assumed: Unfilled cavity with no effective edge sealing, U-value = 0.5 W/m2K. Unfilled cavity with effective sealing around all exposed edges and in line with insulation layers in abutting elements, U-value = 0.2 W/m2K. Fully filled cavity with effective sealing at all exposed edges and inline with insulation layers in abutting elements, U-value = 0.0 W/m2K. Windows and doors The areas of windows are calculated as a percentage of total floor area, the user may select a range of between 8-50% of total floor area using the information provided in the dwelling type table. The total amount of glazing facing south may be adjusted as well. The window types available are modelled using SAP conventions and common specifications - they are modelled within SAP using the U-value, frame factor and solar transmittance of the unit.

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Doors are assumed to have a fixed area in each case, they are as follows:

Dwelling type Door area (m2) Assumption Four bedroom detached house 3.7 Three storey town house mid-terrace 3.7 Two storey three bed semi-detached house

3.7 2 Doors

Two bed back-to-back mid-terrace 1.85 1 Door Two bed bungalow 3.7 2 Doors Two bed flat mid-floor 1.85 1 Door

Three door types may be selected including a solid door (U-value 3.0 W/m2), half-glazed (U-value 2.0 W/m2) and an insulated door (U-value 1.0 W/m2). Thermal bridging SAP takes account of thermal bridging at junctions between elements and around openings. Specific values for linear thermal bridges are not used within this tool and the calculation is undertaken using an allowance based on the total exposed surface area of the dwelling being examined. Further details of this methodology are contained within in SAP Appendix K.

Construction detail used Y-value Not compliant 0.15 Accredited 0.08 EST Enhanced 0.04

Thermal mass Thermal mass is now included within SAP2009, thermal mass has been modelled using generic thermal mass parameters:

Thermal mass TMP (KJ/m2K) Low 100 Medium 250 High 450

Changing the thermal mass has no effect on SAP2005 results.

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3. Ventilation Five values for the air permeability are provided, further information on air tightness can be found on the Energy Saving Trust website www.energysavingtrust.org.uk/housing/publications. Air Permeability (q

50),

m3/m2/h @ 50 Pa Buildability risk Recommended ventilation

system 10 Very low Natural ventilation 7 Very low Natural ventilation 5 Low - provided strategy is

adopted Natural ventilation or mechanical extract

3 Low to Medium - dependant upon experience and strategy adopted

Whole house mechanical (ideally with heat recovery)

1 High - requires experience and an exemplar design team & workforce

Whole house mechanical (ideally with heat recovery)

Please note that it is possible to use natural ventilation down to an air permeability in the region of 3 m3/m2/h @ 50 Pa - however at this point it is generally considered to be more robust and better in terms for overall CO2 emissions to specify whole house mechanical ventilation with heat recovery for most dwellings. An airtightness approaching 1 m3/m2/h @ 50 Pa is not uncommon to achieve Code level 6. SAP Appendix Q ventilation system is provided as an option, this is based upon typical 'best of class' with a heat recovery efficiency of 88% and a specific fan power of 0.6 watts per litre per second. Ductwork is 150mm rigid throughout.

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4. Heating The following heating system types can be selected, hot water is assumed to always be supplied from the primary system using a 150 litre hot water cylinder insulated to building regulations standards.

Primary heating Efficiency Notes A-rated Mains Gas boiler 91 A-rated LPG boiler 91 A-rated Oil-boiler 93

All boilers are regular (i.e. with separate cylinder), fanned flue, condensing

On-peak electric 100 Panel heaters with immersion heater for

hot water

Storage heaters 100 Modern slimline storage heaters, with dual

immersion for hot water

Air-to-Air heat pump 250 Auxiliary heating and immersion heater for hot

water included (typical practice) Ground-to-Water heat pump

300 Specified without auxiliary heating and immersion heating for hot water (typical practice)

Wood pellet boiler 88 Regular boiler, HETAS Approved Community heating (Gas)

88 Unit charge linked to use, pre-insulated distribution, separate hot water cylinder

Community heating (Biomass)

88 Unit charge linked to use, pre-insulated distribution, separate hot water cylinder

Community heating (Heat pump)

320 Unit charge linked to use, pre-insulated distribution, separate hot water cylinder

Secondary heating Efficiency None 100 Electric room heater 100 Gas flame effect 40 Solid fuel open fire 37 Wood pellet stove 67

Building regulations minimum control types are assumed throughout.

5. Cooling SAP2009 now allows fixed mechanical cooling to be included within the calculations, for the purposes of the Energy Credits Tool this is simplified to either 'none', or a packaged mechanical cooling system cooling 100% of the dwelling with an Energy Label Class (A to G). Heat pumps which are able to provide cooling are modelled in full SAP, but this is not accounted for in this Energy Credits Estimator. The mechanical cooling data entry will not affect SAP2005 results.

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6. Lighting The energy credits tool assumes a fixed amount of 30% low-energy lighting for the purposes of the Part L 2006 TER calculations, this includes the Code level 6 zero carbon calculation. For the SAP 2009/Part L 2010 results the actual amount of low energy lighting is given full benefit. Please consult the Part L1a documents and the Code for Sustainable Homes technical guidance for further information.

7. Low-energy appliances No supporting information required - please see Code for Sustainable Homes guidance.

8. Renewable technologies The following CO2 savings for renewable energy technologies have been calculated using SAP conventions.

Renewable system

Assumptions

Evacuated tube, each collector having an aperture area of 3m2

Zero-loss collector efficiency h0 = 0.8 Collector heat loss coefficient a1 = 3.5 Assumed to be orientated south at 30o

Solar hot water

No solar powered pump 1.25m2 215 watts peak each PV Assumed to be orientated south at 30o Blade diameter 1.75m The local annual average wind speed is 5 m/s or more. Hub height above building is 10m (Dense urban), 6m (low-rise/sub-urban) and 12m rural.

No part of the turbine blade dips below the level of the ridge of the roof;

Small scale roof mounted wind turbine Manufactures rated output of 1.25kW There are no obstructions significantly larger than the building within a radius of

10 times the building height.

Blade diameter 3.5m Hub height is fixed at 12m

Mast Mounted wind turbine Manufactures rated output of 2.5 kW All other assumptions as per small scale roof mounted wind turbine

Blade diameter 5.5m Hub height is fixed at 15m

Mast Mounted wind turbine Manufactures rated output of 6 kW

All other assumptions as per provided 2.5 kW example.

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Over shading is assumed to be 'little' (i.e. <20%) in all cases. Please see SAP for further guidance.

9. Miscellaneous energy credits All dwellings are assumed to have less than three bedrooms for the purposes for calculating credits for cycle storage provision.

Energy Saving Trust, 21 Dartmouth Street, London SW1H 9BP

Tel: 0845 120 7799 Fax: 0845 120 7789 bestpractice@est.org.uk www.energysavingtrust.org.uk/housing

CE312 © Energy Saving Trust November 2009. E&OE

This publication (including any drawings forming part of it) is intended for general guidance only and not as a substitute for the application of professional expertise. Any figures used are indicative only. The Energy Saving Trust gives no guarantee as to

reduction of carbon emissions, energy savings or otherwise. Anyone using this publication (including any drawings forming part of it) must make their own assessment of the suitability of its content (whether for their own purposes or those of any client or

customer), and the Energy Saving Trust cannot accept responsibility for any loss, damage or other liability resulting from such use. All technical information was produced by BRE on behalf of the Energy Saving Trust

Further information The Energy Saving Trust provides free technical guidance and solutions to help UK housing professionals design, build and refurbish to high levels of energy performance. These cover all aspects of energy performance in domestic new build and renovation. They are made available through the provision of training seminars, downloadable guides, online tools and a dedicated helpline. A complete list of guidance categorised by subject area can be found in Energy efficiency is best practice [CE279]. To download this, and to browse all available Energy Saving Trust publications, please visit www.energysavingtrust.org.uk/housing/publications or email bestpractice@est.org.uk