Case Study 7 - Energy Saving Rehabilitation, Ecological Specification of Materials
Meadowside and Thornwood Housing Association
589-597 Dumbarton Road, Glasgow
| Type: | Rebabilitation, Victorian Tenement | |||
| Number of units: | 12 | |||
| SAP rating: | 92 | |||
| U-values: | 0.17 Wm2C roof |
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| 0.33 Wm2C walls | ||||
| n/a Wm2C floor |
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| Fuel costs: | £2.75 pw (predicted) |
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| Works costs: | £626,100 |
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| Unit cost: | £52,175 |
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| Completion date: | January 2000 |
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| Contacts | Client: | Meadowside and Thornwood Housing Association | Neil Whitelaw | 0141 357 3200 |
| Architect: | Murray Design Group | Ronnie Murray | 0141 339 3472 | |
| Builder: | Melville Dundas | Roy Paterson | 0141 883 1155 |
The client for this scheme wished to set a replicable 'green template' for rehabilitation schemes and has introduced a variety of measures more usually associated with new build. The existing tenement block has been wholly retained, sustaining a rich and dense urban fabric while at the same time minimising resource use. Car parking is minimal and access to all local facilities is excellent.
Figure 7.1 A number of innovatory techniques have been incorporated into this tenement rehabilitation scheme.
Key Features
Energy
Solar ventilation through tiles, passive stack ventilation, passive solar extensions, high insulation for refurbishment, condensing boilers, low energy lighting
Wall insulation: 100mm cellulose fibre
Roof insulation: 200mm cellulose fibre
Passive solar extensions: these are 1000mm deep and cover almost a third of the rear south facing elevation, providing extra amenity space, protection of the existing fabric and a thermal 'buffer zone'.
Solar ventilation through tiles: air warmed by the sun on the roof tiles is used to ventilate the flats and common staircase using very low wattage fans. The positive pressure generated by the fans minimises draughts.
Passive stack ventilation: this is collected via individual stacks from the bathroom and kitchen and taken out through the roof.
High insulation: the internal dry-lining of the flats is separated from the existing external wall using standard timber framing. The generous size of existing rooms meant that drylining had little impact in terms of lost space. Retrofitting a high level of loft insulation was relatively straightforward.
Condensing boilers: these are probably not necessary and could be deemed an overspecification. Communal heating was not an option for the client, however, as half of the residents are owner occupiers. The radiators have been deliberately sized large to ensure efficient running of the boilers.
Low energy lighting: low energy light bulbs supplied to each room reduce energy consumption from lighting by 80%.
Healthy Dwellings
Ecological specification of materials, 'breathing' insulation strategy
A thorough environmental appraisal and life cycle costing on materials and products has substantially improved the standard specification for tenement rehabilitation.
| Standard specification: | Environmental specification | Rationale |
|---|---|---|
| Polyethelyne insulation | Cellulose loose-fill insulation | Allows building to 'breathe' more, recycles newspaper, low embodied energy |
| 150 mm roof insulation 50 mm wall insulation |
200 mm roof insulation 100 mm wall insulation |
Saves energy Cost-benefit |
| Structurally certified timber | Forest Stewardship Council certified timber | Sustainable forest sourcing |
| UPVC above ground drain pipes |
HDPE (high density polyethylene)
drain pipes LSV (polyethylene) cabling |
Phase out use of uPVC Phase out use of PVC |
| Copper pipework | HDPE pipework | Saves embodied energy |
| MR Chipboard flooring | MR Formaldehyde free chipboard | Avoids offgassing of toxins in formaldehyde |
| Melamine faced kitchen units | Solid timber door and drawer fronts | Avoids pollutant and melamine facing which impedes waste disposal |
| Melamine faced chipboard kitchen worktops | Solid beech worktops | Avoids pollutant and melamine facing worktops which impedes waste disposal |
| CCA timber treatment | Borate timber treatment | Avoids toxins |
| Solvent paints | Natural water based paints | Avoids carcinogens |
| Chemical solvent DPC and timber 'low odour' DPC and
timber Reduces toxins treatment |
'low odour' DPC and timber treatment | Reduces toxins |
Other Relevant Aspects
Costs and maintenance
The funding for this scheme attracted 90% HAG because acquisitions were very high. In addition the two bedroom units were roughly £10,000 over the cost of a normal two bedroom unit (£40,000). The passive solar extensions, hot water heating system and solar tile heating are the biggest on-costs. Extra insulation, borax treatment and the use of HDPE drainage piping instead of uPVC represent the lowest on costs. Predicted simple payback on most energy measures ranges between 8-14 years. The passive solar extensions do not offer a suitable energy payback over the predicted life of the building.
The contractor prices were generally high suggesting that a 'comfort zone' had been built in to deal with the innovative aspects of the specification. The client may consider recovering additional costs by offsetting the rents against the energy savings in future schemes.