BPE Case study of Pippin Close

and Barnlea Close Building Performance Evaluation conference| 14th July 2015 | Woking

Professor Rajat Gupta and Mariam Kapsali Low Carbon Building Group, Oxford Institute for Sustainable Development,

Oxford Brookes University rgupta@brookes.ac.uk

Structure of presentation

• Overview of BPE programme

• Key findings from BPE study elements

• Wider Lessons

BPE competition - TSB programme

Project funded under Technology Strategy

Board’s (now Innovate UK) national ‘Building

Performance Evaluation’ competition

• Performance of buildings in use is highly

variable and does not match predictions

• Case studies investigation of building

performance to understand cause and effects

• Open to domestic new-built, non-domestic

new-built and major refurbishments

• The project included 53 domestic studies: 23

Phase 1 studies and 30 Phase 2 studies

Studies funded under:

• Post completion and early occupation stage

• In-use stage

Design and construction audit

Drawings and SAP calculation review

Interviews and walkthrough with the design team

Review of control interfaces

Fabric testing

Thermographic survey

Air-tightness test

U-value testing

Post construction stage & early occupancy

Commissioning checks of systems and services

MVHR tests

Review of handover process and occupant guidance

BPE methodology for our study

BPE methodology for our study

Energy monitoring and assessment

Smart metering and sub-metering

DomEarm & benchmarking

Monitoring of environmental conditions

Temperature

Relative Humidity

CO2 Levels

Window opening

Occupant studies

Occupant satisfaction survey using BUS

Interviews and walkthroughs with occupants

Activity logging and thermal comfort diaries

Overview

• Location: Feltham, London

• Social housing development

• Scheme comprises of 10 new

houses:

• Eight terraced houses

• Two detached

• Code level 4 development

• Fabric first approach

• Timber frame and masonry

• Construction completed in

March 2012

Barnlea Close

Pippin Close

Pippin Close and Barnlea Close

Similar construction

Similar occupancy pattern

Two case study dwellings

Pippin Close Barnlea Close

Area m² 128 146

Typology Four bed

Mid-terrace

Five bed

Detached

Floors 3 2

Orientation South South West

Occupancy

patterns

Weekdays:

13:00-8:00

Weekend:24h

Weekdays:

13:00-8:00

Weekend:24h

Occupants 2 adults,

3 children

1 adult,

5 children

Barnlea Close

Pippin Close

Two case study dwellings

Case study

Target design rating CSH Level 4

Main construction

elements

(as designed)

U-values W/m2K

Walls: Timber frame and brick, U-value: 0.21

Roof: Slate roofing, U-value: 0.13

Ground floor: Precast concrete with insulation, U-value:

0.25

Windows: Aluminum frame, double glazing, U-value 1.3

Space heating and hot

water system Efficient gas condensing boilers and radiators

Target air tightness

(m3/hm2 @50Pa) 3

Ventilation strategy MVHR system with summer bypass mode and thermal

sensors.

Renewables Photovoltaics 1.65kWp & 1.88kWp

Key findings

Air permeability tests

• Measured air-permeability rate is 2x design target.

• MVHR systems essentially redundant as measured air-permeability rate

is above the threshold (3m3/h.m2) for installing MVHR systems.

• Air-permeability rate slightly increased during the 2 year monitoring period

In-situ U-value tests

Actual wall U-values are better than design U-Values

Location Design

Wall U-value (W/m2K)

Final averaged

U-Value (W/m2K)

Pippin Close 0.21 0.18

Barnlea Close 0.21 0.14

Barnlea Close Pippin Close

Thermal Imaging

• No significant thermal abnormalities evident in

external walls

• Cold bridges from roof beams

• More careful detailing needed in wall/ceiling

joints and junctions.

• Heat loss through thresholds. Air leakage.

• High levels of air ingress evident around some

window frames due to poor fitting.

• All radiator valves set to maximum level (6).

• Heating remains on 24h/day in 16 BC

• Heating thermostat set to 29-30ºC in both houses

• Missing pipe-work insulation in hot water tank cupboard.

• MVHR was found switched off in 2 PC

• In 16 BC, MVHR was on but supply terminals were closed

• MVHR Boost function not working

Commissioning review and MVHR test

MVHR testing

Pippin Close Barnlea Close

Test A Test B Test A Test B

Measured air flow low rate

(l/s)

Total extract

29.7 10.7 27.6 11.5

Total supply

31.1 12.4 0 17.4

• MVHR Tests during commissioning review showed

system imbalances, with supply being higher than

extract and higher than space requirements

• MVHR were re-commissioned and supply and extract

rates were decreased but there was still a discrepancy

between the two with supply being higher.

• Improper commissioning of MVHR system leading to

cold air draughts resulted in mis-use by occupants.

Energy & environmental monitoring & occupant studies

Annual energy use (01/09/13-31/08/14)

Figures for CSH 4, Average UK stock, Part L compliant taken from DomEarm analysis

221

130

83

139

124

26

25

22

29

54

-3

-1

6

6

52

38

3

3

10

8

-50 0 50 100 150 200 250 300

Average UK stock

Part L

CSH 4

Barnlea Close

Pippin Close

Energy use (kWh/m2/annum)

Actual Gas Actual Electricity import Actual PV export

Actual PV use Gas (SAP) Electricity import (SAP)

PV use (SAP)

Annual CO2 emissions (01/09/13-31/08/14)

Figures for CSH 4, Average UK stock, Part L compliant taken from DomEarm analysis

Carbon factors

Gas 0.198

Electricity 0.517

44

26

16

28

25

13

13

11

15

28

10

8

2

1

0 10 20 30 40 50 60 70

Average UK stock

Part L

CSH 4

Barnlea Close

Pippin Close

Carbon emissions (kgCO2/m2/annum)

Actual Gas Actual Electricity import Gas (SAP) Electricity import (SAP)

Living room temperatures

• Monthly mean temperatures close to the

upper level of comfort band.

• Mean temperatures in July and August

around 25oC and maximum temperatures

reach 31oC

• Maximum winter temperatures are also

high as compared to UK average.

• Monthly mean temperatures range from

20oC in May to 25oC in July. Summer

maximum temperatures reach 32oC.

• Winter mean monthly temperatures range

between 20-21oC but maximum

temperatures exceed 26oC.

Internal temperature distribution

• Temperatures in the living room and

bedroom are between 22-24oC for 44-

46% of the time and between 24-26oC

for 24-31% of the time.

• Kitchen temperatures are high,

remaining between 24-26oC for 46% of

the time and above 26oC for almost

37% of the time.

• Temperatures in the living room and

kitchen are between 20-22oC for 31% of

the time, 22-24oC for 15-21% of the time

and above 26oC for 4% of the time.

• Bedroom temperatures are higher,

remaining between 20-22oC for 38% of

the time.

Window opening during winter

• Occupants leave their windows open for long periods leading to temperature variations.

• Pippin Close: Occupants tend to open the living room window and backdoor when indoor

temperatures rise

• Barnlea Close: Occupants leave the living room window open throughout the day.

CO2 levels

• CO2 concentration in the living room

remains between 500-1000ppm for

55% of the time.

• Bedroom CO2 levels remain between

500-1000ppm for 60% of the time and

above 1500ppm for 7% of the time.

• CO2 concentration in the living room

remains between 500-1000ppm for

60% of the time.

• Bedroom CO2 levels remain between

500-1000ppm for 60% of the time and

above 1500ppm for 7% of the time.

Occupant satisfaction survey (BUS)

• Overall positive opinion

towards the houses

• External appearance, layout,

space and storage scored

higher than the benchmark

• Air quality and comfort, most

appreciated elements

• Tenants are not happy with

utility costs.

Better than

benchmark Similar to benchmark

Worse than

benchmark

Response rate of 80%.

Utilities

Heating

Interviews with occupants

• Occupants do not understand the purpose and operation of MVHR. Ventilate

houses by opening windows even when MVHR is on.

• Information passed on during handover about PVs and MVHR not retained

• Occupants do not trust the MVHR system. Noise and draughts coming from the

vents. Several MVHR system breakdowns in Pippin Close

• Heating controls effective and easy to use.

• Windows open throughout the day even when heating is on (Barnlea Close)

• Occupants open windows when spaces get warm but leave heating on.

Thermostat set to 30oC. (Pippin Close)

• High energy use explained by daily heating, cooking and washing patterns and

occupant window opening habits

• It is evident that air-tightness levels <3 m3/h.m2 are not particularly

easy to achieve in mainstream low energy housing, questioning the need

for adding expensive always-on mechanical ventilation systems.

• Ventilation & airtightness strategies should be considered holistically.

• Robust detailing of joints, junctions and thresholds during design and

construction stages. Use rapid diagnostics (thermal imaging, AT tests).

• Accurate ‘as-built’ SAP models (already required under Building

Regulations) should become mandatory and enforced rigorously.

• Arrangements for sub-metering energy use in houses should be

carefully considered as difficult and expensive to retrofit later on.

• Usability of systems, services and controls need to be considered at

the design and specification stages to avoid any potential misuse.

• Maintenance (service) contracts should be set up for unfamiliar low

carbon systems such as heat pumps, MVHR.

• Handover to occupants should involve occupants trying out systems and

controls supplemented by visual home user guides.

• Without the BPE study, the various faults identified with the systems and

services would go unnoticed, and transform into bigger issues at a later

stage requiring expensive and possibly disruptive remedial works.

Wider lessons for the industry

Thank you!