16 Roxburgh Street, Edinburgh
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 Refurbishment Case Study presents an energy-efficiency upgrade project which was carried out in five tenement flats owned and managed by Castle Rock Edinvar Housing Association. 16 Roxburgh Street is a main door, ground floor flat, within a three-storey and basement terrace, built around 1840. This project trialled a way of integrating secondary glazing with insulation behind the wall linings and around the window openings in tenement buildings, to improve the thermal performance of the entire external elevation. External doors were also upgraded.
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Pre- and Post-intervention U-value testing
In order to quantify the energy-efficiency improvements, the thermal performance, or U-value, of all components was tested before and after improvement works. Heat flux sensors were used to measure heat flows through the selected walls and windows. The sensors were mounted on the inner face of the component for 14 days so that an average value could be measured. Sensor locations were chosen to avoid thermal bridging near windows and corners, as well as probable stud locations of plasterboard linings.
U-value measurements results
1. Wall (living room)
Location of measurement: Wall (living room)
Thickness: 590 mm
Improvement type: 40 mm “Warm Fill” poly-bead in cavity
Monitored U-value (pre-intervention): 1.4 W/m²K
Monitored U-value (post-intervention): 0.8 W/m²K
2. Side wall inner window elbows
Location of measurement: Side wall inner window elbows
Thickness: 590 mm
Improvement type: 75 mm “K-span Kooltherm K12”
Monitored U-value (pre-intervention): 1.9 W/m²K
Monitored U-value (post-intervention): 0.4 W/m²K
3. Plaster on hard (hall wall)
Location of measurement: Plaster on hard (hall wall)
Thickness: 590 mm
Improvement type: 10 mm Spacetherm with “Limelite” plaster
Monitored U-value (post-intervention): 0.8 W/m²K
4. Front Door (solid & Spacetherm)
Location of measurement: Front door (solid & Spacetherm)
Thickness: 40 mm
Improvement type: 10 mm Spacetherm + 4 mm ply
Monitored U-value (pre-intervention): 3.0 W/m²K
Monitored U-value (post-intervention): 0.7 W/m²K
Outline costs
Living Room
Improvement type: Secondary glazing (and associated works)
Window type: Aluminium double glazed (approx. 2.2 m high x 1.0 m wide)
Cost: £1,400 per window
Improvement type: Blown insulation
Total area: 4.75 m²
Cost: £50 per m²
Bedroom
Improvement type: Secondary glazing (and associated works)
Window type: Aluminium double glazed (approx. 2.0 m high x 1.0 m wide)
Cost: £1,250 per window
Improvement type: Blown insulation
Total area: 6.00 m²
Cost: £40 per m²
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Prior to improvements, tenants across the five tenement flats rated their windows as ‘poor’ with reference to security, ease of cleaning, thermal performance and acoustic performance. Tenants’ annual energy costs in 2009/10 ranged from £569 to £1597 – all amounting to a little over or substantially more than 10% of the residents’ predicted annual income. This put some of the tenants in ‘fuel poverty’.
Post-completion feedback indicated that the outcome is seen as beneficial by the tenants, although there were a number of issues raised. As the specification was non-standard, and some elements were experimental, the level of site supervision required was beyond that of a normal window replacement contract. The duration of works was a major concern and all tenants would have preferred that the work could have been coordinated more tightly.The work was conducted whilst the homes were still occupied. This presented challenges for all involved and was quite disruptive for residents. Areas which had been previously undisturbed for over a century were opened up, causing issues with dust. The surface insulation that was used caused very fine dust and created problems for both the installer and the tenant. Controlling the spread of dust and the lack of clear areas to work created friction between tenants and contractors.
Some tenants highlighted that the ‘tilt and turn’ timber secondary glazing was heavy and difficult to operate. However, overall feedback from the residents was that the pilot was a good idea. Tenants commented that the properties were much warmer and that aesthetically, the solution ‘was beautiful’.
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Scottish Energy Centre, Edinburgh Napier University