Environmental assessment of the thermal insulation of

period timber-frame walls

Hans Valkhoff

How to renovate historic

timber-frame buildings in SW

France up to thermal

insulation standards ?

while preserving the

environment,

preserving the building’s

vernacular qualities,

reducing embodied energy

and embodied carbon of the

rehab project

Timber-frame heritage

Mirepoix (09) main square

French context French government programme : 40% cut in GHG

emissions of housing sector by 2020 20 million dwellings to be renovated and

thermally insulated French thermal regulations are not yet applied to

historic and old buildings (built before 1948) Dry lining can do much damage to vernacular

buildings

1.‘Conventional’ interior insulation techniques : glass wool and plaster board

2. ‘Ecological’ interior insulation techniques : wood wool, cork and cellulose

3. Interior insulation with plant fibre and binder : hempcrete, earth&straw, woodchip&lime

4. Exterior insulation : polystyrene, wood fibre board, wood wool and cladding

Impact assessment : 20 wall types

Assesment tool COCONScores for 6 parameters : Embodied energy (kWh) Embodied carbon (kg CO2 eq) Resource depletion (kg Sb eq) Thermal resistance (m2K/W) Decrement delay (h) Thermal inertia (kJ/m2K)

Overall scores per wall type

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11 M12 M13 M14 M15 M16 M17 M18 M19 M20

Ove

rall

scor

e (1

-20)

Wall type number

Overall scores (1-20)

Conventional

Ecological Plant fibre Ext. insulation

Best overall scores for walls with exterior insulation made of wood fibre board

Worst overall scores for ‘conventional’ walls (dry lining)

Bad overall score for ‘ecological’ monomur Plant fibre ‘infill’ is a good alternative if

exterior insulation is not possible Hempcrete wall gets low overall score

Results

0

50

100

150

200

250

300

350

400

M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11 M12 M13 M14 M15 M16 M17 M18 M19 M20

EE

(kW

h/m

2)

Wall type number

Embodied Energy (kWh/m2)

-100

-50

0

50

100

150

M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11 M12 M13 M14 M15 M16 M17 M18 M19 M20

EC

(kg

CO

2eq

/m2)

Wall type number

Embodied Carbon (kgCO2eq/m2)

mono m

ur

wood chip

mono m

ur

woodch

ip

eart

h &

stra

w

Not one optimum solution Earth&straw is very compatible with daub

walls and local economy, but labour intensive Lack of data for ecological building materials Need to take hygrothermal properties into

account Consensus that hygroscopic and breathable

insulation materials are better for buildings

Conclusions

HYGROBA research project : • Insulation solutions for old buildings that

don’t disturb their hygrothermal equilibrium • 5 wall types from existing buildings• Hygroscopic versus non-hygroscopic• ‘Breathable’ versus ‘non-breathable’ • Hygrothermal simulations WUFI 2D

The paper is based on the research for an MSc in Architecture at the University of East London and the Centre for Alternative Technology (UEL/CAT, 2010)

Hans Valkhoff, freelance researcher at LRA-ENSA Laboratoire de Recherche en Architecture

(Toulouse, France)

Link to PDF thesis: http://www.areso.asso.fr/IMG/pdf/ThesisHansValkhoff-r-moyen.pdf

Thanks for your attention

Table overall results