a natural materials fabric first approach to retrofit - by fran bradshaw, anne thorne architects

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