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Merkins Avenue, Dumbarton

Refurbishment of 1950s tenements with the aims of enhancing energy efficiency, aesthetics and community cohesion

Overview

This was the second phase of ongoing refurbishment work carried out by Bellsmyre Housing Association, which owns 150 properties in a housing estate on the outskirts of Dumbarton. The housing described in this study was built in 1956 and contains 42 flats entered by seven closes. The Association acquired the properties from Scottish Homes in 1992.

The tenements were gutted to provide 40 high quality units with enhanced energy efficiency, gas central heating and door entry systems. Concrete balconies were cut back and used to support new bay windows. There was full tenant engagement throughout involving weekly meetings, decanting and re-housing on site for some tenants. A difficult-to-let unpopular scheme was transformed into a popular development with low turnover and low vacancy rates.

The construction comprises external walls of no-fines concrete, pitched roofs and solid concrete floors. Heating was by electric fires.

Merkins Avenue

Approach

The original flats were very energy inefficient and reliant on electric fires and storage heaters for heating. Energy efficiency was enhanced by rendered 60mm polystyrene external cladding, 30mm expanded polyurethane insulation to close walls, 150mm mineral fibre to roofs, enclosure of balconies, 100mm ground floor insulation, new timber windows with 12mm double glazing and full gas fired central heating with combination boilers. The concrete construction required ceilings to be lowered and floors raised for services installation. This has produced SAP ratings of 82 for top floor flats and 97 for first floor flats, and reduced heating bills by 80%.

There have been some difficulties: the void behind the bay window has created draughts, the external insulation is not strong enough to hold satellite dishes and is subject to vandalism, and the original boilers have been replaced by cheaper and more reliable and efficient alternatives.

 

Energy efficiency specification

Item

Before refurbishment

After refurbishment

Roof

Uninsulated loft

150mm mineral fibre

External walls

103mm no-fines concrete (250mm on third floor)

Render (6mm) and 60mm expanded polystyrene to existing walls. 50mm cavity and plasterboard (12.5 mm) internally

Close walls

Uninsulated

9.5mm plasterboard and 30mm polyurethane composite board to existing wall

Ground Floor

Uninsulated

18mm chipboard over 100mm insulation

Windows

Single glazing

Replacement timber frame double glazing (12mm gap) and draughtstripping

Ventilation

Uncontrolled

Draughtstripped windows, bathroom and kitchen extract fans (on a time switch)

Heating

electric fires

Gas-fired central heating with combination boiler (fan assisted flue), programmer, room thermostat and TRVs

Hot water

Electric immersion heaters

From combination boiler system

Performance

A SAP analysis was carried out for the flats before and after refurbishment. The Table gives the results for the two flat types estimated to have the highest and lowest SAP ratings after refurbishment. The analysis showed that excellent SAP ratings were achieved, above those which could be typically expected for refurbishment. Annual space and water heating costs were estimated to reduce by 84% for the top floor 1-bed flat and 79% for the first floor 3-bed flat. Corresponding CO2 emissions were estimated to have reduced by 58% and 26% respectively.

Item

Top floor 1 bed flat

First floor 3- bed flat

Before

After

Before

After

SAP rating

1

82

32

97

CO2 emissions (tonnes/year)

6.5

2.7

5.0

3.7

 

U-values

0.25 W/m2K roof

0.45 W/m2K walls

0.45 W/m2K ground floor

Fuel Costs

Estimated 80% reduction

Lessons

At a meeting with the Association’s development committee it was clear that the tenants were very pleased with the refurbished housing, but that the high standard had been achieved not through the Association’s own knowledge but because an architect had been employed who was experienced in refurbishment. However, for future refurbishment projects the Committee is likely to use the SAP energy rating as a design tool. This will include asking the architect to achieve a specified minimum SAP energy rating value.

There have been some difficulties: the void behind the bay window has created draughts, the external insulation is not strong enough to hold satellite dishes and is subject to vandalism, and the original boilers have been replaced by cheaper and more reliable and efficient alternatives.

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