BPE Case Study - Lyndhurst Crescent, Swindon Professor Rajat Gupta Oxford Institute for Sustainable Development, Oxford Brookes University [email protected] Building Better Buildings Conference, Bristol 3 rd February 2016
BPE Case Study - Lyndhurst
Crescent, Swindon
Professor Rajat Gupta Oxford Institute for Sustainable Development, Oxford Brookes University
Building Better Buildings Conference, Bristol
3rd February 2016
• BPE studies of domestic, non-domestic,
(new-build and refurbishment) over 15
years.
• Flagship PGT module on POE: 12 years
• Case studies investigation of building
performance to understand cause and
effects.
• Period of investigation: construction
stage through to in-use
• Socio-technical research using mixed-
methods approach.
• Externally-funded research:
• Innovate UK
• Research Councils (EPSRC/ESRC)
• EU Horizon 2020
• Industry
Low Carbon Building GroupBPE research portfolio
http://architecture.brookes.ac.uk/res
earch/lowcarbonbuilding/
Involvement in Innovate UK BPE programme
Appointed by Innovate UK
as building performance
evaluator to provide
technical advice and peer
review at the project and
programme level.
Meta-study on characteristics
and performance of MVHR
systems
(with Glasgow School of Art and
Four Walls Ltd.)
Funded by: Innovate UK Building Performance Evaluation programme
Our new BPE research booklet summarises our research in this area.
http://architecture.brookes.ac.uk/research/lowcarbonbuilding/resources/lcb
g-bpe-booklet-2015.pdf
Structure of presentation
• Context: case studies and methodology
• Findings from BPE study elements
• Assessment of fabric performance and services
• Handover procedures and user guidance
• Usability of controls
• Monitoring of actual energy use
• Monitoring of indoor environmental conditions
• Occupant feedback from interviews and surveys
• Wider lessons
Context: case study and methodology
Phase 1:
Post-construction &Initial occupancy
Nine-month study (2011)
• Capture ‘as built’ performance of
building envelope and compare it to
‘as designed’.
• Evaluate handover process.
• Map initial occupant reaction of
occupants (amenity, comfort levels,
understanding of systems).
Overview of BPE study
To broaden our understanding of actual energy performance of low-carbon homes
and close the feedback loop between design intent and outcome.
Phase 2:
In-use & Post Occupancy evaluation
Two year study (2012-2014)
• Assess overall energy use and
provision of comfort.
• Detailed analysis of usability,
effectiveness and robustness of
micro-generation.
Fabric testing
Thermographic survey
Air-tightness test
Co-heating test
U-value test
Commissioning review of services and systems
Commissioning checks of systems and services
MVHR tests
Review of handover process and occupant guidance
BPE methodology
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
BPE methodology (Phase 2 BPE)
• Completed in March 2011.
• Owned by Swindon Borough Council
• Code Level 5 certification, SAP rating A
• Combination of optimized airtight
building envelope and use of
renewables
• Built in one construction phase by
applying hempcrete cast into a timber
frame.
Case study background
13 Code Level 5 houses
for social rental in Swindon
• 1 end-terrace, 5bed, 9 persons
• 3 end-terrace, 3bed, 6 persons
• 3 mid-terrace, 3bed, 6 persons
• 6 mid terrace, 2bed, 4 persons
Case study development: Lyndhurst Crescent
House 6
Case study homes
House 7
Phase 2:
• House 5: mid-terrace, 2bed
• House 11: mid-terrace, 2bed
House 5
House 11Phase 1:
• House 6: mid-terrace, 3bed
• House 7: end-terrace, 3bed
House 6 House 7
Phase 1 Phase 2
House 6 House 7 House 5 House 11
Area m2 140 140 94 94
Typology3storey, mid
terrace
3storey, end
terrace
two-storey, mid
terrace
two-storey, mid
terrace
No. of
bedrooms3 bed 3 bed
2 bed
(One adult & two
children,
24h
occupancy)
2 bed
(Two adults &
two children,
24h occupancy)
Case study homes
House 5 House 11
Construction details & design performance
Main construction elementsDesign U-value
W/m2K
Ground Floor Screed over insulation on beam and block 0.12
Roof Tile on timber 0.15
Walls Rendered hempcrete cast into timber frame 0.18
Windows Timber frame, double glazing, low-e 1.4
External door Wooden 1.6
Services & specifications
Main heatingNIBE Fighter heat pump air-to-water. Heat pump load or weather
compensation. Underfloor heating coils
Heating
controlsTime and temperature zone control
Hot water From primary heating system. Immersion present
Solar water
heatingNu-Heat solar panel. South oriented
VentilationMechanical extract from kitchen and bathroom, fresh air supply in
other rooms, connected to the ASHP.
Renewables 4kWp photovoltaics
Target air
tightness (m3/hm2 @50Pa)
2
Findings from the BPE study:
Fabric tests, services and systems
Air permeability tests
• Measured AP values were well above the design target of 2m3/h.m2
suggesting heat losses due to air leakage paths.
• Air leakage paths were revealed behind / below various skirting boards,
windows, electrical cupboards.
• House 11: Air-permeability did not meet UK Building Regulation
(10m3/h.m2)
Phase 1(2011)
Phase 2(2013)
Thermal Imaging
• Air leakage through door and
window frames, window sills.
• Heat loss through exposed
wall
• Cold spot identified on wall.
• Air leakage around door
frames.
• Thermal bridging across
threshold.
• Air leakage through window
frame
• At the time of the inspection, the
installed systems remained to be
finally commissioned.
• Exhaust air heat pump (EAHP) and
heating system were not fully
commissioned.
• EAHP fan speed set very high.
• Underfloor heating system out of
operation on the first floor and
related control circuit disconnected.
• Uninsulated primary heating
pipework.
• Use of MVHR system during
sanding activities resulted in highly
contaminated filters with dust
particles.
Review of commissioning
MVHR testing
Methodology
• The airflow of all extract and vents were measured in
both houses.
• Measurements were taken on 2nd July 2013 for House
5 and on 16 April 2013 for House 11.
Findings
• The tests revealed great discrepancy between the
supply and extract rates.
House 5 House 11
Low rate (l/s) High rate (l/s) Low rate (l/s) High rate (l/s)
Extract
rates15.9 16.1 33.9 39.5
Supply rates 28.1 29.9 47.8 51.1
Supply & extract rates
balance ratio-113.21% -70.11%
• Heating room thermostat had
oversimplified arbitrary line scale
without labelling or numbering.
• Red light indicating whole system
operation rather than room
status.
• Masterstat without indication of
system response (no light,
sound, temperature indication).
• Room and master thermostats
had significantly different
displays and approaches.
• Not clear annotation. User
needed to experiment.
Room thermostat
Usability criteria Ranking Poor Excellent
Clarity of purpose
Intuitive switching
Labeling and annotation
Ease of use
Indication of system response
Degree of fine control
Review of control interfaces
Design team interview and handover
• Weak communication between
contractor, and specialists and
poor feedback to design team.
• Hempcrete drying delayed the
handover process and affected
appearance of external walls.
• Inexperience of local
contractor hindered delivery of
the innovative design
expectations.
• Handover was graduated but
home user guide was not ready
during the induction tour,
resulting in inadequate user
knowledge concerning
systems’ operation and control.
Energy monitoring
& assessment
Total electricity use (Sept 2013-Aug 2014)
Total carbon emissions (Sept 2013-Aug 2014)
Carbon factor (kgCO2)
Electricity: 0.517
Gas: 0.198
Annual energy costs (Sept 2013-Aug 2014)
Cost estimated as
£ 0.1146p /kWh
Breakdown of energy by end-use
0 20 40 60 80 100 120 140 160 180 200
Case C2
Design estimate (SAP)
Case C1
Design estimate (SAP)
House 11
House 5
Design estimate (SAP)
Energy by end uses (kWh/m2/annum)
Space Heating Hot Water Fans and Pumps Lighting Cooking
Electronics Refrigeration Wet appliances Small power Other
32% unregulated
35% unregulated
21% unregulated
22% unregulated
SAP tends to
underestimate
heating and hot
water loads
(REGULATED)
& does not take into
account cooking and
appliances use
(UNREGULATED)
Heat pump efficiency: Degree days
• Heat pump electricity use in House 11 follows temperature variations more
closely, resulting in more efficient performance.
• Baseload heat pump electricity use for hot water: House 5 (300kWh),
House 11(200kWh)
Environmental monitoring and
feedback from occupants
Living room temperatures (Min, mean, max)
• House 11 generally 1-2oC cooler than House 5.
• Temperatures in House 11 more variable due to different air-permeability
levels and heating patterns
• Temperatures within comfort levels.
• House 11 cooler in summer due to high air-permeability levels.
Internal temperature distribution
House 5
Living room: 30% of the time
temperatures range between 24-26oC,
and 2% of the time they range
between 26-28oC.
Bedrooms: 75% of the time
temperatures range between 22-24oC,
13% of the time they range between
24-26oC and 2% of the time they
range between 26-28oC.
House 11
Living room: 14% of the time
temperatures range between 24-26oC,
and 3.3% of the time they range
between 26-28oC.
Bedrooms: 27% of the time
temperatures range between 20-22oC,
16% of the time they range between
22-24oC.
Indoor CO2 concentration
House 5
• Living room: 72% of the time
CO2 levels range between 500-
1000ppm, and 2.5% of the time
they range between 1000-
1500ppm.
• South bedroom: 78% of the
time CO2 levels range between
500-1000ppm, 3.8% of the time
they range between 1000-
1500ppm.
House 11
• Living room: 83% of the time
CO2 levels range between 500-
1000ppm, and 1.6% of the time
they range between 1000-
1500ppm.
• North Bedroom: 75% of the
time CO2 levels range between
500-1000ppm, 15.6% of the time
they range between 1000-
1500ppm.
BUS survey• Respondents feel facilities
provided meet their needs
well.
• Lighting level overall is one of
the most appreciated aspects
of the dwellings.
• Temperatures during winter
are generally regarded as
quite comfortable.
• Summer temperatures are
regarded as less comfortable.
• Air quality is considered to be
quite satisfactory during
summer but less so during
winter.
Energy and water consumption
• High electricity bills. Not satisfied with heat pump performance
Occupant satisfaction
• House 5: not pleased with open plan kitchen and appearance
• House 11: very pleased with the design, layout and overall appearance
Ventilation system (mechanical ventilation and heat recovery)
• Not sufficient training on operation of MVHR
• Noise and draughts coming from MVHR.
Heating system
• Confusion about daily/seasonal operation of heat pump.
• House 5: complained for having little control over heating.
• Not sufficient guidance during the induction.
• No direct instructions in Home User Guide about operation of heating
system.
Home User Guide & Induction process
• Home User Guide very long and hard to understand
• Information included in the guide was not always accurate
Feedback from occupants
Wider lessons
Modelling tools: When modelling building energy use at the
design stage, potential issues of underperformance and occupant
behaviour need to be considered, otherwise there is a risk of
under-estimating energy use.
Documentation: ‘As built’ energy models (and commissioning
records) should be enforced to check if dwellings are built as
designed, and any changes in design or procurement are
captured.
Detailing: Careful detailing (robust details) to avoid thermal
bridging and achieve designed air-permeability rates. Rapid
diagnostics onsite and better communication between design
team, builder and sub-contractors is required given the inter-
dependencies in building performance.
Commissioning: Seasonal commissioning needs to be
encouraged for technologies such as heat pumps and MVHR
systems.
Wider lessons
Ventilation strategies: MVHR was adopted for achieving a high
code compliance without considering the expectations and habits
of occupants. Balance between air-tightness and ventilation should
be achieved otherwise indoor air quality may get compromised.
Guidance and training: Simple and clear guidance and handover
procedures on seasonal operation tailored to the needs of
occupants (gender, age, technical ability)
Control interfaces: Usability of control interfaces influence
occupant interaction. Controls to be accessible and clearly labelled
with an indication of system response that is rapid and detectable.
Building monitoring: Retrofitting monitoring kit is neither
particularly easy nor cheap. Building designers should design in
monitoring kit into building space anticipation of BPE studies.
Monitoring kit should be integrated within low carbon technologies.
Benefit of BPE: Without the BPE study, many of these problems
would have gone un-noticed and developed into serious issues.
Feedback loops are vital for continuous learning and improvement.
Wider lessons
http://architecture.brookes.ac.uk/research/lowcarbonbuilding/
Thank you!