North carolina 2 jan 2009

Thermal performanceand building codes

Thermal performance

• λ wall mix is 0.0697W/m.k

• R-value of 12” wall is 24

• R-value of 20” wall is 40

• Depending on finishes/framing

Hygro-thermal properties

• Hemcrete® does not behave like a lightweight insulation material

• The latent heat of water phase changes within the material contribute to its performance

Thermal mass

• Hemcrete® has the lowest diffusivity of any material

• It is slow to change temperature

• This gives it a thermal inertia like a high thermal mass material

Diffusivity (λ/ρc)• Expanded polystyrene ≈ 18.4 x 10-7 m2/s• Mineral fibre ≈ 14.4 x 10-7 m2/s• Polyisocyanurate ≈ 5.7 x 10-7 m2/s• Polyurethane ≈ 5.6 x 10-7 m2/s• Brick ≈ 4.1 x 10-7 m2/s• AAC ≈ 3.0 x 10-7 m2/s• Insulating aerated blocks ≈ 2.3 x 10-7 m2/s• Timber ≈ 1.6 x 10-7 m2/s• Hemcrete® ≈ 1.4 x 10-7 m2/s• Water (10oC) ≈ 1.4 x 10-7 m2/s

Dynamic thermal performance

→ 187

Q24h [kJ/m2]

→ 146

→ 410

→ 229

( Cement concrete → 3163 )

Effective U-value of 250mm Hemcrete®

• 187,000 J/m2 lost in 24 hours• 1W = 1J/s• There are 86,400 seconds in 24 hours• The temperature difference was 20oC• Real heat loss was 0.11W/m2k• Theoretical U-value is 0.29W/m2k

Amplitude suppressionand phase displacement

Dampening factor Time shiftat 25 cm at 25 cm

25cm= 1-(25cm/ init) 25cm= tmax,25cm- tmax,init

[-] [h]Material______________________________________________

LHC – “Wall” mixture 98,5 15

Wood 98,8 16

Cellular concrete 95 10,5

Mineral wool 77,5 6

CEM concrete 89,5 7

Air-tightness

• The monlithic nature of Hemcrete® makes it inherently air tight

• There are no complicated details/junctions

• Figures below 2m3/m2/hr at 50 pascals are achievable

Comfort and Health

• High vapour permeability and absorption coefficicient allow Hemcrete® to buffer high humidity, combat condensation and improve air quality

• Low effusivity makes Hemcrete® walls feel wall and make the internal environment feel comfortable

Thermal bridging

• The timbers within a Hemcrete® wall do not behave as thermal bridges.

• This gives Hemcrete® a significant advantage over most other construction materials

Thermal bridging• U-value of a 500mm Hemcrete® wall

(ignoring the timber frame) is 0.134 W/m2.K

• Including 15% timber framing reduces the U-value to 0.137 W/m2.K

• Difference is 0.003 W/m2.K

• Rounding error is bigger than this difference

The Lime Technology Office

Before

Sprayed Hemcrete®

Spray Limetec® render

The finished office

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External Temperature

External recorded temperature – April to September 2007

Addition of 24hourly average external temperature trend line

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External Temperature 24Hr Average (External)

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Existing Office External Temperature

24Hr Average (External)

Existing offices (monitored June onward) showing high internal temperature swing

By comparison, the Hemcrete offices show a low internal temperature swing, which is characteristic of heavyweight structures.

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Tradical Hemcrete Office Existing Office

External Temperature 24Hr Average (External)

The finished office

Tradical® Hemcrete®

• Good thermal conductivity – 0.07 W/m.K

• No thermal bridging

• Low diffusivity

• Low effusivity

Structure

• Tradical® Hemcrete® is not a structural material. The structural requirements are performed by the frame.

• The Hemcrete® stiffens the frame

Tradical®Hemcrete® is nonstructural

ModCell Hemp

Modular panelTypically 3m x 2m

Fast-track constructionOff-site construction

Can be structural

Fire Safety

• Tests have been carried out at the CSTB in France

• 250mm thick wall constructed of blocks made from Tradical® Hemcrete®

• The mortar joints failed after 1hr 40 mins• UK tests on a solid panel have run for 3hrs

45 mins• Full testing to run in February 2009

The best way to predict the future, is to create it !