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Sword Street, Glasgow

Sword Street, Glasgow

Internal wall insulation to six tenement flats

Overview

In this case study, two measures of performance - the improvement in thermal properties and the assessment moisture levels within the tenement walls following the installation of insulation measures. Five different insulation materials were used in the trial in order to provide comparative data to compare relative improvements in thermal performance.

The aim of the project was to examine methods and materials that could be used to improve the thermal performance of traditionally constructed buildings. There was a desire, where possible, to use materials which were natural and vapour permeable to help maintain the performance of mass masonry walls.

Approach

Existing Fabric

The tenement property on Sword Street, where the trial took place is four storeys in height - the ground floor comprises of retail accommodation and each of the upper three floors contains two flats. The building is constructed of sandstone rubble masonry with brick internal partitions, and dates to around 1890.

Due to structural repairs the tenement was empty at the time of the refurbishment. All internal wall linings had been stripped out and replaced with dry lining in a previous extensive refurbishment meaning that there were no conditions regarding the retention of original wall linings or other features.

Improvement measures

Five different insulation types were installed and measured in the Sword Street properties. These are:

  • Blown polystyrene bead
  • Blown cellulose
  • Hemp fibreboard
  • Wood fibreboard
  • Aerogel board (two different thicknesses trialled)

 

Further details of all the insulation materials and the installation techniques can be found by downloading the full case study on the right.

 

Performance

Pre- and post intervention U-value testing was undertaken by Glasgow Caledonian University to measure thermal improvements in the mass masonry walls.

The external walls of all six flats were measured prior to improvement works using standard equipment, and all were found to have an initial U-value of 1.1W/m2K.

The results of the thermal improvement made by each of the insulation materials are summarised in the table below. These show that the thermal performance of traditionally constructed solid wall masonry can be improved substantially by using a range of different types of internal insulation. The greatest improvement was gained by the use of 80 mm thick wood fibreboard, which gave an 81% improvement in U-value.

Insulation Type

Thickness applied

Improved U-value

Wood fibreboard

80 mm

0.19

Hemp board

100 mm

0.22

Aerogel board

50 mm

0.23

Blown cellulose

100 mm

0.29

Injected polystyrene bead

50 mm (approx)

0.32

Aerogel board

40 mm

0.37

 

Considerations of thickness and cost of material are presented in the full case study, available to download on the right.

In addition to measuring the improvement in thermal performance, measurements were taken at the Sword Street properties to identify any changes in moisture levels within the fabric of the masonry walls that may have resulted from the application of the insulation. The results of this testing can also be seen in the full case study.

Lessons

The insulation trials described in this case study show that six different internal insulation measures could significantly improve the thermal performance of mass masonry walls. Four of these measures achieved a U-value of below 0.3.

All of the measures were aimed at maintaining vapour permeability, and monitoring of moisture levels has shown that there are no significant increases in moisture due to the insulation work.

This case study also shows that consideration should be given to the thickness of materials and how this fits with existing cornicing or skirting boards, not just the achievable U-value. The issue of cost was also raised; blown polystyrene bead insulation was the cheapest of the six options, due to material costs and also due to the ease of insulation.

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Case Study

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