a natural materials fabric first approach to retrofit - by fran bradshaw, anne thorne architects
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a natural materialsfabric first approachto retrofit
for CoREfabric first and refurbishment excellence:
up-skilling to deliver the green deal and
beyond
may 2012
Hanley 2010
built on clay
a living community
an architectural diversity developed over time
- part of a unified, stepped terrace
- exit directly onto street
- east/west orientation
- uninsulated solid brick walls
- uninsulated solid floor
- tight for space internally
- gas fire heating only
- ‘hard to heat’ home
23 St Lukes StreetSmall window area give minimum solar gain
plan before refurbishmen
t
55m2 internal floor area
before refurbishment
old gas boiler / hot water tank in bedroom – inefficient and noisy
north-east facing glazed roof - loses a lot of heat from house
no entrance lobby - heat loss when front door opened
non airtight construction- major heat loss through loft hatch- existing house drafty
heat loss through chimney stacks
building orientation = minimal solar gain
poor quality thermal elements- no insulation, solid external brick walls, solid ground floors and poor quality glazing
north-east facing rear windows - inadequate sunlight and increased heat loss
energy performance
heat demand* 670 kWh/m2yrPassivhaus Enerphit standardmax. 25 kWh/m2yr
primary energy demand 765 kWh/m2yr
TSB Retrofit for the Future target
Max. 115 kWh/m2yr
air tightness(air changes per
hour) 10.9h-h
CO2 emissions 141 kg/m2yr
TSB Retrofit for the Future target
max. 20 kg/m2yr
SAP rating 47** band ‘E’
energy bills £1170 a year
* to keep house at comfortable temperature of 21oC** standard SAP rating taken from table 7.1, English House Condition Survey 2006
the challenge...
St Luke street existing
energy use
St Luke street retrofit
energy use
90% reduction
natural materials retrofit approach
health non-toxic production /
disposal
no off-gassing
minimise allergies
low embodied energy carbon sequestering
bio-degradable
renewable materials
better indoor air quality naturally balances
humidity
exothermic - ‘phase
change’
protect existing fabric hygroscopic
vapour permeable
(‘breathing’)
prevent trapped moisture
Passivhaus building standard
highly insulated & airtight fabricwall U-value = max. 0.15 W/(m²K)roofs = max. 0.15 W/(m²K)floors = max. 0.15 W/(m²K)
thermal bridge freecontinuous air-tight layer
triple glazed windowswindow U-value = max. 0.8 W/(m²K)
heat recovery ventilationmin. 75% efficient heat recoverysupplies fresh, warm air
low energy solar thermal hot waterAAA+ energy efficient electrical appliances
0
10000
20000
30000
40000
50000
60000
Total Heat Demand (kWh/yr)
Pas
sivh
aus
Sta
ndar
d =
15
kWh
/sq
m/y
r
Existing heat demand of 23 St Lukes Street = 33,000 kWh/yr = 660 kWh/sqm/yr
Insu
late
Nor
th W
all
0.20
W/m
2K
Insu
late
Sou
th W
all
0.15
W/m
2K
Exi
stin
g H
ou
se
Insu
late
Roo
f0.
10 W
/m2K
Insu
late
Flo
or
0.15
W/m
2K
Trip
le-G
laze
dW
indo
ws
Imp
rove
Airt
ight
ness
Hea
t R
ecov
ery
Ven
tila
tion
up to 80% reduction with fabric measures alone...overall 97% reduction in heating demand = 22 kWhr/sqm/yr
Pas
sivh
aus
Ene
rphi
t =
25
kWh
/sq
m/y
r
space heat demand (kWhr/yr)
Passivhaus methodology retrofit
typical variation in occupant use of energy
depth of insulation - design for it!- front & rear elevations of terrace usually shortest width- chimney breasts removed to improve airtightness - compensated for floor area lost to insulation- extend kitchen with rooflight- consider splaying reveals on future projects
Front Elevation
Air-tight layer
Internal wall insulationU-Value =0.20
External wall insulationU-Value =0.15
U-Value = 0.10
New-solid floor U-Value = 0.12
Rear Elevation
continuous insulation & air-tight layer
0.15 W/m2K
fabric first approach - walls
airtight membrane, vapour control layer
sheepswool insulation between cross battens
woodfibre insulation, fixed to battens thru airtight layer
service zone
solid brickwork with external render
avoiding thermal bridges - carefully detailed junctions floor to wall
1. continuous insulation2. thermal bridge free3. continuous airtight layer
eaves detail
windows in the wall - St Luke street
new extension walls
fabric first approach - walls
woodfibre insulation to party walls
monitoring moisture : internal wall insulation
leaking gutter soaking wallconstruction drying out
what is the airtight barrier?walls and roof: air-tight membranefully plastered walldamp proof membrane
carefully detailed airtight junctionstapes, windows, service penetrations
air-tightness buildability communication between designer and site team
careful site installationattention to detailmethodical sequencing
airtight detailing
heat recovery whole house ventilation
fresh, warm, low energy airair supply will never be lower than 16.5℃due to high efficiency of heat exchanger and frost protection to unit.
ventilates the whole housesupply fresh air to living room and bedroomsextract stale moist air from kitchen & bathroom
find space for the unit and ductscareful planning required in existing house for ducts
+ reduction of heat losses+ limit air humidity / avoid mould growth+ avoid build-up of pollutants + limit odours+ cleaning (filters)+ heating & cooling+ manages humidity+ increased comfort
St Luke’s Street - completed retrofit
Existing House(50sqm)
Retrofit House(64sqm)
Heat demand* 670 kWh/m2yr 22 kWh/m2yr 97% Reduction
Hot water demand 27 kWh/m2yr 9 kWh/m2yr 65% Reduction
Electricity demand 38 kWh/m2yr 17 kWh/m2yr 55% Reduction
Air tightness(air changes per
hour)10.9h-1 3.5 h-1*** 78% Reduction
total primary energy demand
788 kWh/m2yr 85 kWh/m2yr 89% Reduction
CO2 emissions 164 CO2/m2yr 16 CO2/m2yr 90% Reduction
SAP Rating 47** 90
predicted energy bills
£1170 a year £121 a year 90% Reduction
St Luke street - results, calculated and measured
“We are delighted to have the opportunity to be involved with this ground breaking project. We feel it is an innovative way of creating an energy efficient and economical home.”
“After our first two months here, we love our eco-house, and enjoy living here, and it’s good to feel environmentally responsible without having to make vast lifestyle changes.“Mr and Mrs Watt
resident experience
• Whole house approach• Educated project team and committed contractor essential• Joint working opportunities between development and asset management teams• Found out more about particular technologies, materials & processes
BUT …limitations• Replicability• Cost• Enthusiasm from residents• Only one particular house type
what did we learn?
where next for Stoke?
be boldwell wrapped upairtightwell ventilated
where next ?
simple measures on a whole terrace scale
create local employment
maximise learning and practising new skills, airtightness building techniques, once learnt never forgotten
part selfbuild by residents providing timebank to reduce rents
• UK Government target to reduce carbon emissions by 80% by 2050
• 85% of all buildings in existence today will still be here in 2050
• how best to cost stock improvements?
• a whole new approach to asset management?
• Sophie Atkinson - Sanctuary HA
the retrofit challenge
thanks to - the project team
Client: Sanctuary Group
Architect: Anne Thorne Architects LLP
Contractor: Seddon Construction Ltd
Quantity Surveyor: McBains Cooper
Services and Structural Engineer: King Shaw Associates
Monitoring: Building Sciences Ltd