Hygrothermal performance of hemp based thermal insulation materials in the UK

This thesis explores the hygrothermal performance of hemp insulation in the context of the United Kingdom. The key objectives of this investigation were to assess the heat and moisture management capacities of hemp insulations in two constructions typical to the UK, of timber frame and solid brick walls and to put the findings of the assessment into the greater context of conventional insulation materials by comparing hemp insulation’s performance with that of stone wool. The assessments were performed by means of laboratory-based experiments, in situ experimental monitoring and computer based numerical hygrothermal simulations. The most important finding during the laboratory-based experiment is that, in high relative humidity, the likelihood and frequency of interstitial condensation is higher in stone wool insulation than in hemp insulation. In terms of the material properties, one of the key findings during the laboratory-based experiment is the high level of moisture buffering capacities of hemp insulations, and therefore their potential in managing moisture in buildings. The in situ assessment of hygrothermal properties of hemp and stone wool insulations confirms the findings of the laboratory based experiments of the corresponding moisture management capacities of these two insulation materials. Parametric analysis of the in situ data shows that mould spore germination is possible in the insulations in vapour open walls although the visual observation has not confirmed the outcome of this analysis. In terms of thermal conductivity, the important finding is that the equivalent thermal conductivity of hemp and stone wool insulations are always equal or below the manufacturers’ declared thermal conductivity values. Long-term hygrothermal performances of hemp and stone wool insulation in timber frame and solid brick walls have been also assessed using a numerical hygrothermal simulation tool (WUFI). As far as the WUFI predictions are concerned, the application of the hemp or stone wool insulation on solid brick wall does not seem to be feasible with reference to condensation and mould growth in the insulations

Experimental analysis of moisture-dependent thermal conductivity, and hygric properties of novel hemp–shive insulations with numerical assessment of their in-built hygrothermal and energy performance

The use of lime as a binder in hemp–lime considerably increases the drying time of hemp– lime after casting. Furthermore, lime is a non-renewable mineral resource. As such, this paper explores the effectiveness of using an alternative non-mineral binder instead of lime to formulate a novel hemp–shive insulation. The moisture-dependent thermal conductivity, adsorption isotherm, vapour diffusion resistance factor, and in-built hygrothermal performance of four variants of a novel bio-based insulation were investigated. The hygrothermal performance of the novel hemp–shive insulation was compared with that of a previously developed novel hemp–lime insulation. No significant variation in thermal conductivity of hemp–shive insulations between the equilibrium moisture contents (EMC) at 0% and 50% relative humidity (RH) was observed, but there was a substantial increase in thermal conductivity hemp–shive insulations when the material reached the EMC at 98% RH. The average dry thermal conductivity values of hemp–shive and hemp–lime insulations were also similar. The adsorption isotherms of hemp–shive insulations were determined at 0%, 20%, 50%, 70%, 90%, and 98% relative humidity steps. At 98% RH, the moisture adsorption capacity of hemp– shive insulations was 4-to-5-times higher than that of hemp–lime insulation. Hemp–shive insulations’ vapour diffusion resistance factor (μ value) was about double the μ value of hemp–lime insulation. Hemp–shive insulations exhibited 4-to-5-times higher water absorption resistance than that of hemp–lime insulation. Numerically determined porosity values of hemp–shive agree with the values of wood-based insulation materials of similar density. Finally, using all experimentally acquired data as inputs, dynamic whole-building hygrothermal simulations were carried out and the results show that novel hemp–shive insulation materials perform at a similar level to the hemp–lime insulation in terms of heating and cooling energy demand but require 45% less energy for humidification. However, the relative humidity inside the hemp–shive wall remains higher than 70%, which can potentially induce mould growth

A review of low energy thermal insulation materials for building applications

In response to the need for reducing energy demand for heating and cooling in buildings, ‘fabric first’ approach is suggested and prescribed by building regulations and voluntary standards worldwide. The ‘fabric first’ approach focuses on reducing the U-value of building envelope by applying efficient and adequate thermal insulation materials. As operational energy demand of buildings is gradually reducing, the embodied energy of buildings is becoming a major contributor to carbon emissions compared to operational energy. As such it is pertinent to specify building materials with low embodied energy and lessened environmental impact. This paper reviews thermal insulation materials with low embodied energy and lessened environmental impact and compares them with conventional but high-impact insulation materials. Keywords - Embodied Energy, Operational Energy, U-Value, Thermal Insulation, Sustainable Materials

Transient versus steady-state thermal conductivity measurements: A case study of thermal characterisation of a novel biobased insulation material

Abstract. For quick measurement of the thermal conductivity of building mate rials, the transient method is favoured by researchers. However, the steady-state method is recognised as a more reliable method for measuring thermal conductivity. The current work is part of the hygrothermal characterisation of a novel biobased material for building envelope applications. The aim of this part of the research work was to assess the reliability of the transient method in determining the thermal conductivity of the novel biobased material. As such, steady-state thermal conductivity values of the materials were determined using a Fox 600 guarded hotplate. Transient thermal conductivity was determined with an Isomet 2114 Thermal Properties Analyzer. To measure transient thermal conductivity both surface probes and needle probes were used with and without the application of thermal paste between the probes and the surface of the materials. It was observed that, in comparison to a steady-state measurement, transient measurement with needle probe overestimates and with disk probe underestimates thermal conductivity by about 14%. However, the average of the values determined by needle probes and disk probes were close to the values determined by steady-state method. It was further observed that the direct application of thermal paste on the material surface resulted in an increase of thermal conductivity by 52% from the values obtained by steady-state method

Reducing energy use in housing: insulation and retrofit problems in Wales and the UK

There is general agreement that existing and new build houses should achieve higher standards of energy efficiency. Research into different forms of insulation and methods of installation has been carried out for a new book on insulation materials. (ICE Publications later in 2019). There has been an assumption that all insulation materials are much the same and that, providing that thermal performance figures are satisfactory, any material can be used in any form of construction. The evidence shows, however, that inappropriate insulation and installation measures can lead to many unintended consequences and a gap between predicted and actual performance. Far from reducing fuel poverty and carbon emissions, mould and damp can occur, aggravating health problems, which has been confirmed by academic research. Sealing up increasingly airtight buildings with non-breathable, flammable and even hazardous synthetic materials can cause damage to building fabric and occupant health. Furthermore the embodied energy and pollution involved in the production of many commonly produced insulation materials can be bad for the environment. The importance of indoor air quality and ventilation is often overlooked, though recent work by NICE and the Environmental Audit Committee in Westminster has drawn attention to the problems. The paper will review the range of insulation materials available and their differences. It will be illustrated with case study examples of so-called retrofit disasters where cavity wall, external wall and internal insulation have been wrongly applied. Some of these case study examples are in Wales and the assistance of CIVALLI (based in Newport) will be acknowledged

Incorporating circular economy into passive design strategies in tropical Nigeria

The natural environment is in need for an urgent rescue due to dilapidation and recession of resources. Passive design strategies have proven to be one of the effective ways to reduce CO2 emissions and to improve building performance. On the other hand, there is a huge drop in material availability due to poor recycling culture. Consequently, building waste pose environmental hazard due to unrecycled building materials from construction and deconstruction. Buildings are seen to be material banks for a circular economy, therefore incorporating circular economy into passive housing will not only safe guide the climate but also improve resource efficiency. The study focuses on incorporating a circular economy in passive design strategies for an affordable energy and resource efficient residential building in Nigeria. Carbon dioxide (CO2) concentration is still on the increase as buildings are responsible for a significant amount of this emission globally. Therefore, prompt measures need to be taken to combat the effect of global warming and associated threats. Nigeria is rapidly growing in human population, resources on the other hand have receded greatly, and there is an abrupt need for recycling even in the built environment. It is necessary that Nigeria responds to these challenges effectively and efficiently considering building resource and energy. Passive design strategies were assessed using simulations to obtain qualitative and quantitative data which were inferred to case studies as it relates to the Nigeria climate. Building materials were analysed using the ReSOLVE model in order to explore possible recycling phase. This provided relevant information and strategies to illustrate the possibility of circular economy in passive buildings. The study offers an alternative approach, as it is the general principle for the reworking of an economy on ecological lines in passive housing and by closing material loops in circular economy

The comparative in situ hygrothermal performance of Hemp and Stone Wool insulations in vapour open timber frame wall panels

An in situ experiment in a full scale timber frame test building was carried out to compare the hygrothermal performance of Hemp and Stone Wool insulations of identical thermal conductivity. Hemp and Stone Wool insulations were installed in timber frame wall panels without vapour barrier. The comparison was made in terms of heat transfer properties, likelihood of mould growth and condensation. Step changes in internal relative humidity were performed to explore the effect of high and normal internal moisture load on the wall panels. No significant difference between the average equivalent thermal transmittance (U-values) of the panels incorporating Hemp and Stone Wool insulations was observed. The average equivalent U-values of the panels were closer to the calculated U-values of the panels based on the manufacturers’ declared thermal conductivity of Hemp and Stone Wool insulations. It was observed that the placement of heat flux sensor along the depth of the insulation had significant influence on the measured equivalent U-value of the panels during high internal moisture load. The frequency and likelihood of condensation was higher in the interface of Stone Wool and Oriented Strand Board (OSB). In terms of the parametric assessment of mould germination potential, relative humidity, temperature and exposure conditions in the insulation-OSB interfaces were found to be favourable to germination of mould spore. However, when the insulations were dismantled, no mould was visually detected

Moisture buffer potential of experimental wall assemblies incorporating formulated hemp-lime

Experiments were carried out according to the Nordtest protocol to study the moisture buffer potential of hemp-lime walls with a range of different internal linings and surface treatments. It was observed that the moisture buffer value was ‘Excellent’ when the inner surface of hemp-lime was exposed. ‘Excellent’ moisture buffer values were also obtained for hemp-lime with lime plaster. All other assemblies demonstrated ‘Good’ moisture buffer value. Moisture buffer values of the assemblies, after application of paint on the upper surfaces, were also determined. It was observed that application of synthetic pigment based trade paint could reduce the moisture buffer performance of the assembly consisting of hemp-lime and lime-plaster from ‘Excellent’ to ‘Good’ while between 61 and 69% reduction of moisture buffer value was observed for the other assemblies. However, the reduced buffer values of the assemblies are still comparable with other moisture buffering building materials. It was further observed that moisture buffer performance was improved when clay based organic paint was used instead of trade paint

Paving the way to net zero carbon standards: A guide to designing net zero carbon building in a region that lacks carbon assessment framework

This paper presents a provisional pathway for carbon assessment in India, essential for realising net-zero carbon building standards in regions with limited data. It amalgamates various data sources to compute embodied carbon, and utilises dynamic simulation for assessing operational carbon. Importantly, this methodology lays the groundwork for the development of early-stage design tools, empowering architects and engineers to integrate sustainable decisions. The adoption of this framework holds significant potential for transforming the built environment, encouraging greener design practices and enhanced adherence to regulatory standards. This initiative is a crucial step towards environmentally responsible construction practices in India