Case Study - Eastlands in Manchester

The UK’s first large-scale Passive House retrofit



Project Name: Erneley Close

Clients: Eastlands Homes

Main Contractor: The Casey Group

Developer/Lead Designer: R-Gen Developments

Architect: Edelmann and Ebling

Building Type: 32 walk up flats and 6 bungalows

MVHR systems design: Alan Clarke & Green Building Store

Location: Longsight, Manchester

Status: Completed February 2015

Building Use: Affordable rental homes

Construction Time: 40 weeks

Airtightness: 0.75 @ 50pa

MVHR Products Used: Zehnder ComfoAir 160

Eastlands
Eastlands Before Development

Overview

The refurbishment of 32 flats and 6 bungalows at Erneley Close, Longsight, Manchester was part of Eastlands Homes £180 million decent homes programme and is the UK’s first large-scale Passive House retrofit.

Objective

To achieve the PassivHaus EnerPHit Standard of low carbon energy efficiency.

Challenges

Designing the MVHR systems to fit into the maisonettes initially proved challenging for the team. Green Building Store’s MVHR department worked with Passivhaus mechanical & electrical expert Alan Clarke to design a system to fit the space available. The Zehnder ComfoAir 160 unit was chosen because of its compact form and performance characteristics, which enabled it to be located on the bathroom wall behind the bath. Space for the rigid steel ductwork was located by creating a ceiling void space over the bathroom and landing. Green Building Store and Alan Clarke carefully designed and attenuated the system to ensure that the system operates quietly and with maximum efficiency. To ensure extra quality control, Green Building Store’s MVHR Technical Manager Andrew Farr gave a toolbox talk to ventilation installers on the project and he and Steve Clarke (Services Engineer at Green Building Store) commissioned the units after installation.

Phil Summers from R-Gen Developments commented:“As a developer undertaking our first PassivHaus project it was vital we installed the most technically effective MVHR given the constraints of working within an existing building. Fortunately, we had excellent design and production specification from Alan Clarke, our retained M & E Consultant, and subsequently a fantastic on site implementation and practical assistance from Andrew Farr and his colleagues at Green Building Store. Each flat now has a great internal air quality with residents amazed at how quiet the MVHR system actually is in performance.”

Solar gain

Ironically, with this particular development, the issue was not about enhancing solar gain but reducing the size of the glazing in both blocks, which, if left in their original sizes, may have caused an overheating issue on the south facing elevations.


Achieving airtightness

The main problem encountered was leakage into the party walls and onwards to other maisonettes, the roof and underfloor voids. The volumes of air travelling through the party walls was far in excess of original expectations mainly due to the very poor build quality of the brickwork and the use throughout of paramount partitioning, which again was a source of major air leakage into the party walls.

Multiple means were used to address the issues including external parging, airtight taping, airtight foam, stitch drilling, spray foaming and airtight and fireproof composite sealing of vertical and horizontal service ducts through party and communal walls. Ongoing tests and training were carried out under the supervision of a trained Air Tightness Champion.

MVHR solutions

Given the challenges presented by available space the key requirements for the MVHR was for a slim unit. The Zehnder Passivhaus accredited ComfoAir 160 unit was used precisely because of its shallow depth and the constant volume fan control, which maintains airflow rate irrespective of filter resistance. Fortunately, there was an existing riser boxed out at the end of the bath, which had some empty space above the level of the toilet and basin and it was possible to enlarge this slightly to make space for the MVHR.

The basic design for the ductwork involved creating a ceiling void space over the bathroom and landing, plus a small riser in the bathroom directly above a services cupboard in the kitchen.

ComfoAir 160

ENERGY SAVINGS

It had been estimated that the tenants living in the accommodation would have required in excess of 300kWhr/m2 per annum prior to the retrofit. Since completion, the EnerPHit Standard has been applied for and savings are anticipated at a minimum of 80%.

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SAP ratings since 1970

As an indication of how much the energy efficiency of UK homes has already improved, average SAP ratings have increased year on year from just 17.6 in 1970 to 56.7 in 2012.