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--- efficiency_now:building_envelope:straw_as_insulation_material [2023/08/07 15:11] – yaling.hsiao@passiv.de
+++ efficiency_now:building_envelope:straw_as_insulation_material [2023/08/07 16:11] (current) – yaling.hsiao@passiv.de
@@ Line 10: / Line 10: @@
-Best: Bales on edge or upright. Here, the thermal flux is perpendicular to the direction of the straw stalks, called ‘on edge’ or ‘upright’, see figure 2; the thickness of insulation is in this case 36 cm. Taking into account a wooden frame construction with 6 cm posts at 1 m centres, with clay plaster on the inside and lime plaster on the outside, the U-value of the wall will be 0.15 W/(m²K) at an overall thickness of 42 cm. With bales laid flat, resulting in 48 cm insulation thickness and 54 cm overall thickness (λR = 0.080 W/(mK)), the Uvalue is 0.17 W/(m²K). So, bales on edge are preferable regarding the Uvalue, as well as the space required for construction.
+**Best: Bales on edge or upright.** Here, the thermal flux is perpendicular to the direction of the straw stalks, called ‘on edge’ or ‘upright’, see figure 2; the thickness of insulation is in this case 36 cm. Taking into account a wooden frame construction with 6 cm posts at 1 m centres, with clay plaster on the inside and lime plaster on the outside, the U-value of the wall will be 0.15 W/(m²K) at an overall thickness of 42 cm. With bales laid flat, resulting in 48 cm insulation thickness and 54 cm overall thickness (λR = 0.080 W/(mK)), the Uvalue is 0.17 W/(m²K). So, bales on edge are preferable regarding the Uvalue, as well as the space required for construction.
-[{{.:stroh_als_waermedaemmung_.png?200 |**Figure 2**: Bale orientation © PHI }}]
+[{{:picopen:stroh_als_waermedaemmung_.png?200 |**Figure 2**: Bale orientation © PHI }}]
 **Checklist for straw bales.** The following characteristics should be assessed for construction bales:
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-**Blow-in insulation.** Straw is also available as blow-in insulation. The ETA-18/0305 for the company “Sonnenklee” gives a λD = 0.055 W/(mK), resulting in a λR of approx. 0.057 W/(mK) at a density of between 105 and 140 kg/(m²). Taking into account a wooden frame construction with 6 cm posts at 62.5 cm centers, with OSB-board on the inside and 4 cm wood-fiber board on the outside, the use of 35 cm of blow-in insulation will achieve a U-value of 0.15 W/(m²K). This corresponds also to a wall thickness of 42 cm.
+**Blow-in insulation:** Straw is also available as blow-in insulation. The ETA-18/0305 for the company “Sonnenklee” gives a λD = 0.055 W/(mK), resulting in a λR of approx. 0.057 W/(mK) at a density of between 105 and 140 kg/(m²). Taking into account a wooden frame construction with 6 cm posts at 62.5 cm centers, with OSB-board on the inside and 4 cm wood-fiber board on the outside, the use of 35 cm of blow-in insulation will achieve a U-value of 0.15 W/(m²K). This corresponds also to a wall thickness of 42 cm.
 **Further notes**: Both straw bales and straw blown-in insulation is an untreated organic material. Because of that, it is of highest importance that the construction is airtight in order to prevent warm and humid air from getting through gaps into the wall, where condensation followed by mould growth would accour. This can be achieved by covering the straw from the inside with plaster, OSB-boards or membranes, in combination with proper sealing of the junctions(see PHI recommendations for “airtight construction”). Furthermore, it is favourable to have a higher vapour resistance inside than outside. For examplary straw bale building systems see [[https://database.passivehouse.com/en/components/|https://database.passivehouse.com/en/components/]]