Daneshill House, Stevenage

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Situation Prior to Refurbishment
Daneshill House is a purpose designed local government office building which was constructed in the 1950’s as part of the Stevenage ‘new town’ developmentThe building has two distinct envelopes, the 1950’s 6 storey (old block) area is a concrete framed building clad with single glazed steel curtain walling. It was refurbished in the 1980’s and 40% of the cladding which was single glazed had its thermal insulation improved with secondary glazing.

The ‘new block’ areas of the building whilst still having a concrete frame and slab, have an insulated brickwork cladding with a relatively high U value of and small areas of windows which are high quality double glazed units with internal solar blinds.

The old block areas have suffered in recent years from severe overheating in summer, which has been made worst by the insulation improvements in the 1980’s

Objectives

• Demonstration of energy efficient refurbishment of an existing office building
• Overall reduction of the CO2 by 50% compared to a similar ‘hypothetical’ existing building with the same use and occupancy levels
• To show that refurbishment is environmentally and economically more efficient than rebuilding

Description of work
The works to Daneshill House relate to three distinct areas of the building, namely the existing 6 storey area constructed in the 1950’s, a two storey relatively modern office area constructed in 1980’s and a public service area also constructed in the 1980’s.

The common theme for all the areas is the use of thermal mass and night ventilation to provide summertime comfort cooling. In the 1950’s part of the building. It is also proposed to use ‘Phase Change Material’ to increase the thermal capacity of the building.In the public service area a new night ventilation passive cooling system incorporating phase change material will be incorporated as part of a new ‘hybrid’ air conditioning system. Low energy lighting with solar and occupancy controls will be include in the 1950’s block as well as the customer service area and a solar collection system will be installed for the existing electric hot water system.

Passive cooling to reduce summertime overheating
The proposals in respect of passive cooling involve two distinct approaches, one for the original 1950’s areas of the building and one for the 1980’s areas where air conditioning was installed as part of the original construction.

For the original areas of the building a passive night cooling system which uses the ‘hidden’ mass of the concrete floor structure, will be incorporated as part of internal refurbishment scheme which will create efficient open plan office areas. The passive cooling installation will use a steel plate system to increase the thermal transfer rate between the air and the concrete structure together with a ‘Phase Change Material’ for additional thermal storage.

In the more modern areas of the building where air conditioning already exists, advanced control strategies will be adopted to enable existing plant to be used for night cooling and to maximise the operation of the system in a simple ventilation mode.

Lighting controls
Day lighting is very effective within the shallow depth of the original office areas and the provision of zoned solar and occupation controls will be employed to significantly reduce the energy consumption of the artificial lighting.

Innovative Technologies

• Passive cooling plate system installed within an existing ceiling void
• Use of phase change material to increase the thermal night cooling capacity of an existing structure
• Use of a ‘Hybrid’ passive cooling system incorporating phase change material within an existing building
• Use of LED lighting system within a public service area
• Advanced control strategies to modify the operation of existing mechanical ventilation plant