Natural Fibre Insulation Materials for Retrofit Applications

Student thesis: Doctoral ThesisPhD


Improving the thermal performance of existing domestic buildings can have multiple benefits: reducing greenhouse gas emissions, reducing the cost of heating and therefore fuel poverty, improving comfort and health. Solid wall buildings constitute around 30% of UK housing stock, and are among the least efficient. However, the installation of solid wall insulation, while improving thermal performance can significantly affect the moisture balance of the building. This can result in mould growth, which can cause structural damage and lead to health problems for the occupants.This thesis explores the use of Natural Fibre Insulation (NFI) materials for internal solid wall insulation. The hygrothermal properties of a range of NFI materials are characterised in order to assess their potential for retrofit applications. This is followed by large-scale testing, which compares three solid wall insulation systems in controlled conditions, the results of which are used to validate a heat and moisture transfer model to further assess performance. Experimental results showed that the risk of interstitial condensation is significantly reduced by the application of natural fibre insulation in comparison to a conventional rigid foam system. Simulation of a solid wall exposed to climatic conditions for the UK revealed that the relative humidity at the interface between the masonry and insulation layers remained at 69% when internally insulated with hemp-lime and 96% with rigid foam insulation, while average moisture content of the masonry was 48% lower when hemp-lime was used. Field tests were also conducted to determine the thermal performance of two solid walls internally insulated with 80 mm of hemp-lime when exposed to real weather conditions. The thermal conductivity of the hemp-lime was found to be 30% higher than when measured in dry stead-state laboratory conditions due to the high moisture content of the masonry. However, its application still resulted in 66% and 68% reductions in the U-value compared to the uninsulated wall from 2.73 and 2.65 W/m2K to 0.93 and 0.86 W/m2K.
Date of Award23 Nov 2016
Original languageEnglish
Awarding Institution
  • University of Bath
SupervisorAndrew Shea (Supervisor) & Pete Walker (Supervisor)

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