Insights from domestic
BPE studies
Professor Rajat Gupta Oxford Institute for Sustainable Development, Oxford Brookes University
Building better buildings Conference, Oxford Brookes University
26 November 2015
Structure of presentation
• Context: case studies and methodology
• Findings from BPE study elements
• Monitoring of actual energy use
• Assessment of fabric performance and services
• Handover procedures and user guidance
• Usability of controls
• Monitoring of indoor environmental conditions
• Occupant feedback from interviews and surveys
• Wider lessons
Context: case studies
and methodology
Development B
CSH Level 4
Development C
CSH Level 4
Development A
CSH Level 5
Domestic new-build case studies
Mainstream social housing developments in UK
Case A1 Case A2
Weekdays:
24h
Weekend:
24h
Weekdays:
24h
Weekend:
24h
2 adults,
2 children
2 adults,
2 children
Case B1 Case B2
Weekdays:
15:00-8:00
Weekend:
24h
Weekdays:
24h
Weekend:
24h
2 adults,
2 children
4 adults,
1 baby
Case C1 Case C2
Weekdays:
13:00-8:00
Weekend:
24h
Weekdays:
13:00-8:00
Weekend:
24h
2 adults,
3 children
1 adult,
5 children
Development A Development B Development C
Case A1 Case A2 Case B1 Base B2 Case C1 Case C2
Construction type Timber frame with
cast hempcrete
Steel frame with
pre-insulated panels
Timber frame
and brick
U-values W/m2K
Walls: 0.18
Roof: 0.15
Windows: 1.4
Walls: 0.15
Roof: 0.15
Windows< 1.2
Walls: 0.21
Roof: 0.13
Windows: 1.3
Space heating and
hot water system
Exhaust Air Heat
Pump (EAHP),
underfloor heating
Solar thermal
collectors
Air Source Heat Pump
(ASHP), underfloor
heating
Immersion heater
Gas condensing boiler
with radiators
Design air
permeability
(m3/hm2 @50Pa)
2 3 3
Ventilation strategy MVHR through EAHP MVHR MVHR
Renewables 4kWpk Photovoltaics 1.5kWpk Photovoltaics 1.65kWp & 1.88kWp
Photovoltaics
Case studies: physical characteristics
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
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
Energy performance
Annual energy performance
-50 0 50 100 150 200 250 300
Average UK stock CSH 4
Case C2
Case C1
Case B2
Case B1
Case A2
Case A1
kWh/m2/annum
Annual energy consumption (kWh/m2/annum) January - December 2013
Actual Gas Actual Electricity import
Actual PV export Actual PV use
Dwelling energy use (from as designed SAP) Dwelling energy use (from extended as designed SAP)
3x/2x
2x/1.3x
3x/2x
3x/2x
4x/3x
3x/2x
Annual CO2 emissions
0 10 20 30 40 50 60 70
Average UK stock
CSH 4
Case C2
Case C1
Case B2
Case B1
Case A2
Case A1
Annual CO2 emissions (kgCO2/m2/annum)
January - December 2013
Emissions from as designedSAP Emissions from extended as designed SAP
Actual CO2 emissions
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)
Case A2
Case A1
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)
Performance of building
fabric & services
Designed and measured air permeability
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
UK Goodpractice
UK Bestpractice
Case A1 Case A2 Case B1 Case B2 Case C1 Case C2
m3/m
2.h
Air permeability (m3/m2.h)
Measured Design Target
Issues with installation and commissioning A B C
Mechanical ventilation and heat
recovery (MVHR) imbalance between
supply and extract air flow rates
MVHR unit located in loft inaccessible MVHR vents not locked in fixed
positions
MVHR vents shut by occupants Several MVHR system breakdowns Flexible ductwork with unnecessary
bends – adds resistance to air flow.
Scarce insulation
Poorly commissioned heating controls
Challenges for occupants
‘How am I going to
change the filter?
I’ll just leave it there.’
‘I do not like cold air
blowing onto me
when I’m sleeping.
I’ll close the terminal.’
Unintended consequences
Handover procedures, user
guidance and usability of
controls
Evaluation of guidance
Development
A
Development
B
Development
C
Handover and training Handover was clear and simple Heating & PV system were explained Handover would have benefited by
follow-up sessions
No hands-on application
Home User Guide Document was clear and visual
No guidelines on daily operation
of systems
Information was missing Home user was long and confusing Contact information and
troubleshooting guidance
Usability survey of control interfaces Criteria Poor Excellent
Clarity of purpose
Intuitive switching
Usefulness of labelling
Ease of use
Indication of response
Degree of fine control
Accessibility
Development A
Development
B
Development
C
Oversimplified control interfaces
(no labelling or indication of system
response,)
Overcomplicated heating controls
and zoning
No indication of MVHR failure or
maintenance
Usability survey of control interfaces
Environmental conditions
& occupant satisfaction
‘This house is nice
and warm.’
Occupant expectations (or habits)
Internal temperature
• Mean temperatures above 21oC in 5 out of 6 houses.
• Mean above 23oC in 3 out of 6 houses.
• Peak temperatures above 27oC in 5 out of 6 houses.
Internal CO2 levels
• Mean CO2 between 560-640ppm in living rooms and 650-730ppm in bedrooms
• Peak levels are well above 1000ppm in all cases
Window opening - Winter
Occupant feedback: interviews & surveys
Positive feedback
Satisfaction with space and layout Satisfaction with light levels
Temperatures and air quality good
Development
A
Development
B
Development
C
Negative feedback
Poor control over heating & ventilation Dissatisfaction with heating system High energy bills Home User Guide complicated Draughts and/or noise from MVHR
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.
Benefit of BPE: Without the BPE study, many of these problems
would have gone un-noticed and developed into serious issues. It
is vital that feedback loops are embedded for continuous learning
and improvement.
Wider lessons
http://architecture.brookes.ac.uk/research/lowcarbonbuilding/
Thank you!
