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2 Roxburgh Street (1st Floor) Edinburgh

2 Roxburgh Street (1st Floor), Edinburgh

Energy-efficiency upgrade project carried out in a traditional tenement flat

Overview

This case study is part of a new Historic Scotland publication series which presents examples of refurbishment projects of pre-1919 buildings designed to improve their energy efficiency.

This case study refers to a north east facing first floor apartment accessed off a common stair, within four-storey plus basement tenement c. 1800. Upgrading works were carried out to the front wall and two windows to a single room (living room).

Approach

Existing Fabric 

  • Wall to front (north east elevation) of the apartment comprises broached ashlar, with droved margins to window surrounds. Overall masonry thickness is approximately 650 mm.
  • Wall lining in plasterboard, on inadequate timber framing, with the plasterboard largely nailed into the edges of the window shutters, which were, in turn, permanently fixed back into the pockets. Decorative cornice, with sections over the window heads missing, and ogee skirting.
  • 2 no. 6 over 6 pane sash and case windows with fixed shutters with panelled elbows soffit and back. Moulded architraves with skirting blocks
  • Living room – 2 no. windows to north east side
  • Wall lining plasterboard, with 40 – 50 mm cavity

  

Wall upgrades

  • Architraves, skirting blocks, soffit panels and window elbows and backs were removed.
  • The entire wall lining was structurally unsound, and came away as the shutters were carefully opened up, leaving the original stonework fully exposed.
  • The entire wall lining directly below the existing cornice was re-built in 50 x 25 mm timber framing, held clear from the masonry, with 25 mm rigid insulation, and 12.5 mm plasterboard, taped and filled.

 

Window improvements

  • The windows were fitted with single glazed, timber, side hung secondary glazed units with removable handles, to accommodate the shutters in the closed position. 
  • The window reveals, elbows and back and shutter pockets were framed out with timber battens. 
  • All timbers were held clear from the stonework, and the framing to the shutter pockets was sized to ensure adequate depth for pockets to accommodate shutters. 
  • New timber packers were fitted to the window soffits.
  • Rigid insulation was cut and tightly fitted in between the timbers to the new framing and soffit packers as follows: 75 mm thick to window elbows, 100 mm thick to window back, 35 mm thick to shutter pockets, 35 mm thick to soffit.
  • Window linings were then reinstated.

 

Additional Improvements

Insulation works were carried out to the shutters to one of the windows, involving upgrading works to the existing shutters and the manufacture of new shutter flaps, as these were missing, as follows:

  • 10 mm Spacetherm blanket insulation packed into the existing shutter panels, with 3 mm ply cover plate pinned to shutter frame.
  • 10 mm Spacetherm blanket sandwiched between 3 mm ply panels pinned and glued to 16 x 18 / 40 mm re-bated frames, to form each new shutter flap.
  • Schlegel weather seal QWS 77 re-bated into leading edges of shutters, at hinged joint with flaps

Performance

Pre- and Post-intervention U-value testing

U-value tests were carried out before and after the improvements were made. Testing the Sash & Single Glazed Window (which received a new Single Glazed-Secondary glazing unit with timber frame) gave U-value results of 5.2W/m²K before and 1.5 after.

In the shutter, which had a 10mm Spacetherm blanket added, the U-value dropped from  2.2W/m²K to 0.4W/m²K.

 

Thermographic Testing

Following completion of the thermal improvement works, the first floor property at 2 Roxburgh Street was surveyed using an infra-red camera. This can show up areas of heat loss by measuring surface temperatures. The higher the temperature on the surface, the more heat is escaping.

Pre and post-intervention infra-red images were taken, with the shutters shut. The image below shows the improvement in thermal performance, post-intervention (the property is the first floor windows on the left, compared to the rest of the tenement which had not been upgraded).

2 Roxburgh Street (1st Floor)

Image: © Scottish Energy Centre, Edinburgh Napier University

Lessons

The pilot demonstrated that the solution for installing secondary glazing where shutters are present can deliver a substantial thermal and acoustic improvement to the windows without impacting on the appearance or functionality of the existing window features. In addition, the thermal performance of walls and external doors was also improved considerably while retaining existing elements.

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