Andre Street exteriorAndre Street

Project Lead
Robert Greene, Head of Development, A2Dominion Group

Building type, sector and stage
Domestic new build, post completion, early occupancy, in-use, South East, Hackney, London.

Efficient building fabric, exhaust air heat pump

Building Performance of High Density Apartments is a detailed BPE of a 23 flat development in East London.  Two flats consisting of a 1 bedroom top floor unit and a 3 bedroom mid-floor unit are being studied in detail by evaluating the performance of the building fabric, systems installed and occupant comfort conditions.
The project team are led by the housing association, A2Dominion with evaluation expertise provided by Kiwa GASTEC at CRE.
The development is a part steel frame design with a brick and block construction for the upper floors.  Design U-values and the as built air tightness are below those required by Part L1A building regulations.  Each apartment is served by an exhaust air heat pump (EAHP) which provides domestic hot water and space heating via an underfloor heating network .  The exhaust air heat pump uses the air extracted from the dwelling as its heat source rather than external air as per a conventional air source heat pump (ASHP). The exhaust air heat pump has a back-up immersion heater to meet additional demand.Andre Street exterior

The project team have carried out multiple evaluation techniques to determine the quality of the building fabric.  A co-heating test, CO2 rate of decay analysis, air tightness tests and infra-red thermography have all been carried out.  The fabric evaluation concluded that in general the building fabric was performing as designed with the design heat loss parameter (HLP) being relatively close to that measures by the co-heating test.  Some areas for improvement were discovered and included; air leakage around service penetrations and around window frames.
Early stage analysis of energy use by the project team found that the dwellings were using more energy than expected.  Initial thoughts on the high energy usage included:
• High use of the immersion heater for heating domestic hot water
• Thermal lag of the underfloor heating system
• Lack of understanding of occupants in terms of optimal use of the EAHP system
Detailed monitoring of the EAHP, energy use and comfort conditions are on-going at the site and the team are already acting on the findings made.  Additional commissioning of the heating system and further handover has been carried out with tenants in order to reduce energy use and utility bills.

Key Performance Indicators
Dwellings: 23
Air tightness: Av of two flats 4.6 m3/hr/m2 @ 50Pa average
Heat loss parameter: Av of two flats  112 W/K +/-8
SAP rating: Av of two flats 75 (C)