**4. Thermal and environmental performance of insulation materials**

The studied insulation materials and their associated reported embodied carbon values are presented in **Table 2**. The values are extracted from available EPDs for each insulation material.

A box and whisker plot was used to graphically illustrate the locality and spread of GWP/unit weight data extracted from EPD documents as presented in **Table 2**. The interquartile range (IQR) between the 25th and 75th percentiles, median and standard deviation values are represented with the box, the line, and the whiskers respectively.

A clear distinction can be observed between studied insulation materials with MW and GW presenting comparable median values. EPS, XPS, PU, and PF as insulation materials with a hydrocarbon base also form a distinctive group with very similar median points. The PU and MW however are demonstrating greater probability distribution due to the discrepancies in the data compared with PF and GW.

For a more meaningful comparison between the insulation materials, their relative thermal performance needs to be reflected in the analysis. The thermal resistance (R-value) target for this analysis was taken as 6.6 m2 .K/W complying with the UK Building Regulation requirements as explained above. **Figure 6** represents the values in **Table 2** converted into the GWP values associated with the target thermal resistance for each insulation material.

The distinct insulation groups, with similar median points, that were formed in **Figure 5** are not evident in **Figure 6** and the GWP values in relation to the thermal




#### **Table 2.**

*Environmental properties of insulation materials with reference to their thermal conductivities.*

#### **Figure 5.**

*GWP per unit weight of different insulation materials.*

resistance demonstrate smaller variation between the insulation groups. The distribution of GWP values for MW becomes significantly broader when the targeted R-value is considered, whereas these values for GW stays relatively stable.

The median point for XPS insulation material demonstrates 100% higher GWP values compared with EPS. The GWP values for Cellulose-based insulations, cover

**Figure 6.** *GWP per unit area of insulation materials for the target thermal resistance.*

a broad range from 0.7–67 kgCO2−eq/m2 . This is due to the variety of base products used for making cellulose-based insulations. The base products can include refined virgin wood chips and blown recycled cellulosic products, such as wastepaper with requiring their own dedicated processing procedures.

The GWP values for VIPs are significantly higher than the other insulation materials even with factoring their considerably better thermal performance (up to 10 times better) in the analysis. This must be noted however that over 90% of the GWP values associated with VIPs are linked to their core material and specifically in the studied EPD associated with the use pyrogenic silica [50, 51]. The studied EPDs for VIPs are based on a cradle to gate approach and therefore not taking into account the recyclability potential for VIPs. Considering different end-of-life scenarios could change the impact of VIPs and other insulation materials such as cellulose based materials significantly.
