Thermal analysis and post construction verification

Purpose

The residential sector in Ireland accounted for 25 per cent of energy related CO₂ emissions in 2016 through burning fossil fuels, a major contributor to climate change. In support of Ireland’s CO₂ reduction targets, the existing housing stock could contribute greatly to the reduction of space-heating energy demand through retrofit. Approximately 50 per cent of Ireland’s 2m dwellings pre-date building regulations and are predominantly of cavity and solid wall construction, the performance of which has not been extensively investigated at present. Although commitment to thermal upgrade/retrofit of existing buildings may increase under future government policies, the poor characterisation of actual thermal performance of external walls may hinder the realisation of these targets. Thermal transmittance (U-values) of exterior walls represents a source of uncertainty when estimating the energy performance of dwellings. It has been noted in research that the standard calculation methodology for thermal transmittance should be improved. Implementing currentU-value calculation methods may result in misguided retrofit strategies due to the considerable discrepancies betweenin situmeasurements and calculated wallU-values as documented in the case studies carried out in this research. If the method of hygrothermal analysis were to be employed as a replacement for the current standard calculation, it could have significant implications for policy and retrofit decision making. The paper aims to discuss this issue.

Design/methodology/approach

This research project analysed a case study situated in Dublin, Ireland. The case studies offer an account of thein situthermal transmittance of exterior walls and link these to hygrothermally simulated comparisons along with more traditional designU-values.

Findings

The findings of this research identify discrepancies betweenin situand designU-values, using measurement, hygrothermal simulation and standard methodU-value calculations. The outcomes of the research serve as an introduction to issues emanating from a larger research project in order to encourage researchers to understand and further explore the topic.

Originality/value

It has previously been highlighted that moisture content is linked to the increase in thermal conductivity of building materials, thus reducing the thermal effectiveness and increasing the elementalU-value. Therefore, it is vital to implement reliable prediction tools to assess potential thermal performance values. This paper presents the findings of a critical instance case study in Dublin, Ireland in which an existing west facing external wall in a semi-detached dwelling was analysed, simulated and measured to verify the elemental wall assembly and quantify thermal transmittance (U-value) incorporating the major criteria required for building performance simulation.