Understanding EPC Calculations

Mark Sreevesand

Lisa Dores

Who are National Energy Services?

• Established 1990

• Based in Milton Keynes

• Own and operate NHER and SAVA

• Co-developed RDSAP

• One of the first Accreditation Schemes for Domestic Energy Assessors

Presentation Overview

• Background• EPBD requirements for dwellings• SAP scale, 2001 and 2005• RDSAP development• Sensitivities

• Case Study• DEA process in example property• EPC Online• Relevant RDSAP conventions

RDSAP Methodology

• Energy Performance of Buildings Directive (EPBD) requirements

• Existing approaches & the need for a faster SAP

• Developing the dataset and methodology

EPBD January 2003

• Article 1, overall objective to reduce energy consumption

• Article 3, appropriate energy calculation methodology

• Article 7, energy performance certificates

• Article 10, ‘independent’ ‘experts’

• Article 15, transposition into law

EPBD Summary

• Energy Performance Certificate (EPC)

• Energy assessment methodology

• Independent energy experts

• Delivery legislation

RDSAP Methodology

• Energy Performance of Buildings Directive (EPBD) requirements

• Existing approaches & the need for a faster SAP

Standard Assessment Procedure

For any given dwelling :-

• An estimate of the energy costs for space heating, hot water and lighting

Utilising :-

• Standard occupancy criteria

• Standard weather conditions, geographical location and other geographical factors.

The SAP Scale

SAP 2001 - SAP 2005

0

20

40

60

80

100

120

140

160

-2 -1 0 1 2 3 4 5 6 7 8 9 10

ECF (£/m2/year)

SA

P

SAP 2001

SAP 2005

Why Not Use Full SAP ?

• Full SAP requires full dataset

• Large number of data items

• Some items only available through new build design process

• Inferences and assumptions required for existing dwellings

Using Existing SAP Methods

• Different systems in existence :-• NHER, Elmhurst & MVM systems• Other software providers• Stock profiling systems

• Directive requires “a common approach to this process”

Common Approach: Other Reasons

• Comparison: • “Consumers to compare and assess energy

performance of the building”

• Encouragement: • “Promote the improvement of the energy

performance of the building”

• User confidence: • Surveyors - don’t want complaints from customers• Government - legal requirement, don’t want

criticism

RDSAP Methodology

• Energy Performance of Buildings Directive (EPBD) requirements

• Existing approaches & the need for a faster SAP

• Developing the dataset and methodology

RDSAP Development

• NHER, Elmhurst & MVM were commissioned in 2002 :-• Phase 1 – Data set, inferences, approach• Phase 2 – Testing• Phase 3 – Revisions• Phase 4 – Energy Report• Phase 5 – Quality Assurance• Phase 6 – Field Trials

Initial Dataset

• Criteria• Accuracy• Repeatability• Length of survey/time

• Existing Methodologies• Elmhurst, MVM and NES systems differed in a

number of areas• Initial dataset contained the best features of

each• Dataset not influenced by commercial

constraints

Sensitivity Testing

• Full SAP data items examined for sensitivity

• Comparison between full SAP and initial dataset

• Initial dataset reassessed

• Inferred or actual data ?- Sensitivity plus surveyor accuracy

• Assumptions, inferences and surveyed items defined

Sensitivity Examples (1)

• Number of external doors :-• High data variation – little variation in result

• Number of doors can be assumed

• Based on dwelling type etc.

• Room Height :-• Potential large variations in SAP

• 2.4 m – 2.2 m = 2 SAP points

• Need to measure room height

• Relatively easy !

Sensitivity Examples (2)

• Window area :-• Potential large variations in area

• Time consuming to measure

• Potential surveyor errors

• Best approach to use set of equations based on age and built form

• 25% in window area = 1 SAP point

Non Standard Dwellings

• Non standard – accurate rating only requires extra data collection• Excess glazing, more than one extension

• Excluded – accurate rating cannot be provided due to limitations of the SAP model• HMOs, sheltered housing

Field Trials

• Dataset consolidation

• Repeatability

• Accuracy

• Time requirements

• Dataset finalised

Field Trials (1)

Field Trials (2)

Field Trials (3)

Field Trials - Conclusions

• Greater consistency achieved with simpler properties

• Larger/more complex properties showed greatest variation

• Definite identifiable need for clear conventions and good training

• Assisted in refining the RDSAP methodology

RDSAP Methodology

• Energy Performance of Buildings Directive (EPBD) requirements

• Existing approaches & the need for a faster SAP

• Developing the dataset and methodology

• Current status

EPC Assessment

• Must be undertaken by Domestic Energy Assessors (DEAs) or Home Inspectors (HIs)

• DEA qualification is a Level 3 Diploma, HI qualification is a Level 4 Diploma

• All must belong to Accreditation or Certification Scheme

• DEA/HIs will be able to work in rental sector – social housing etc.

• EPC Online

Case Study

EPC Online - General

EPC Online - Construction

Secondary Heating

EPC Online - Heating

Windows

EPC Online - Openings

Final EPC – Page 1

Final EPC – Page 2

Final EPC – Page 3

Final EPC – Page 4

Final EPC – Page 5

Final EPC – Page 6

Final EPC – Page 7

Current Status (England & Wales )

• 1 August 2007 EPCs required for the marketed sales of existing dwellings with >=4 bedrooms. For newbuild, Interim and Predicted Energy Assessments.

• 1 October 2007 EPCs required on construction of all new dwellings

• 6 April 2008 EPCs required for sale/rent of non-dwellings of over 500 sqm and EPCs required for the construction of all non-dwellings and 'Display EPCs' required for public buildings of over 1,000 sqm

• 1 October 2008 EPCs required for rental of all dwellings and all remaining sales. EPCs required for the construction, rental or sale of all other non-dwellings.

NHER Web Links and Contact Details

• www.nher.co.uk

• www.dea-training.co.uk

• Mark.Sreeves@nesltd.co.uk

• Lisa.Dores@nesltd.co.uk