BPE Case study of Pippin Close and Barnlea Close

Transcription

1 BPE Case study of Pippin Close and Barnlea Close Building Performance Evaluation conference 14 th July 2015 Woking Professor Rajat Gupta and Mariam Kapsali Low Carbon Building Group, Oxford Institute for Sustainable Development, Oxford Brookes University

2 Structure of presentation Overview of BPE programme Key findings from BPE study elements Wider Lessons

3 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

4 BPE methodology for our study 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

5 BPE methodology for our study Energy monitoring and assessment Smart metering and sub-metering DomEarm & benchmarking Monitoring of environmental conditions Temperature Relative Humidity CO 2 Levels Window opening Occupant studies Occupant satisfaction survey using BUS Interviews and walkthroughs with occupants Activity logging and thermal comfort diaries

6 Overview Location: Feltham, London Pippin Close Social housing development Scheme comprises of 10 new houses: Eight terraced houses Two detached Barnlea Close Code level 4 development Fabric first approach Timber frame and masonry Construction completed in March 2012

7 Two case study dwellings Pippin Close and Barnlea Close Similar construction Similar occupancy pattern Pippin Close Pippin Close Barnlea Close Area m² Typology Four bed Mid-terrace Five bed Detached Floors 3 2 Barnlea Close Orientation South South West Occupancy patterns Occupants Weekdays: 13:00-8:00 Weekend:24h 2 adults, 3 children Weekdays: 13:00-8:00 Weekend:24h 1 adult, 5 children

8 Two case study dwellings Case study Target design rating CSH Level 4 Main construction elements (as designed) U-values W/m 2 K Space heating and hot water system Target air tightness (m 3 /hm Ventilation strategy Renewables 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 Efficient gas condensing boilers and radiators 3 MVHR system with summer bypass mode and thermal sensors. Photovoltaics 1.65kWp & 1.88kWp

9 Key findings

10 Air permeability tests Measured air-permeability rate is 2x design target. MVHR systems essentially redundant as measured air-permeability rate is above the threshold (3m 3 /h.m 2 ) for installing MVHR systems. Air-permeability rate slightly increased during the 2 year monitoring period

11 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 Barnlea Close Pippin Close Barnlea Close

12 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.

13 Commissioning review and MVHR test 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

14 MVHR testing 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. Pippin Close Barnlea Close Measured air flow low rate (l/s) Test A Test B Test A Test B Total extract Total supply

15 Energy & environmental monitoring & occupant studies

16 Annual energy use (01/09/13-31/08/14) Energy use (kwh/m 2 /annum) Pippin Close Barnlea Close CSH Part L Average UK stock Actual Gas Actual Electricity import Actual PV export Actual PV use Gas (SAP) Electricity import (SAP) PV use (SAP) Figures for CSH 4, Average UK stock, Part L compliant taken from DomEarm analysis

17 Annual CO 2 emissions (01/09/13-31/08/14) Carbon emissions (kgco 2 /m 2 /annum) 8 1 Pippin Close Barnlea Close CSH Carbon factors Gas Electricity Part L Average UK stock Actual Gas Actual Electricity import Gas (SAP) Electricity import (SAP) Figures for CSH 4, Average UK stock, Part L compliant taken from DomEarm analysis

18 Living room temperatures Monthly mean temperatures close to the upper level of comfort band. Mean temperatures in July and August around 25 o C and maximum temperatures reach 31 o C Maximum winter temperatures are also high as compared to UK average. Monthly mean temperatures range from 20 o C in May to 25 o C in July. Summer maximum temperatures reach 32 o C. Winter mean monthly temperatures range between o C but maximum temperatures exceed 26 o C.

19 Internal temperature distribution Temperatures in the living room and bedroom are between o C for 44-46% of the time and between o C for 24-31% of the time. Kitchen temperatures are high, remaining between o C for 46% of the time and above 26 o C for almost 37% of the time. Temperatures in the living room and kitchen are between o C for 31% of the time, o C for 15-21% of the time and above 26 o C for 4% of the time. Bedroom temperatures are higher, remaining between o C for 38% of the time.

20 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.

21 CO 2 levels CO 2 concentration in the living room remains between ppm for 55% of the time. Bedroom CO 2 levels remain between ppm for 60% of the time and above 1500ppm for 7% of the time. CO 2 concentration in the living room remains between ppm for 60% of the time. Bedroom CO 2 levels remain between ppm for 60% of the time and above 1500ppm for 7% of the time.

22 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. Response rate of 80%. Better than benchmark Similar to benchmark Worse than benchmark Utilities Heating

23 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 30 o C. (Pippin Close) High energy use explained by daily heating, cooking and washing patterns and occupant window opening habits

24 Wider lessons for the industry 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.

25 Thank you!