Case Study - Wilmcote House

As part of the EuroPHit project, a selection of residential and non-residential buildings across Europe are being retrofitted according to Passive House principles.

BRE's case study project is Wilmcote House in Portsmouth, owned by Portsmouth City Council.

Existing situation: 

Wilmcote house provides over 100 homes largely in the form of 3 bedroom maisonettes, which are arranged across 3 blocks linked via two main stair cores.  It is located in the central Portsea Island area of Portsmouth. The building is owned and managed by Portsmouth City Council.  Wilmcote House was built in 1968 using a prefabricated reinforced concrete sandwich panel system; it is in need of significant repairs, including some structural work, without which the remaining life of the building is likely to be around 30 years. The concrete sandwich panels incorporate only around 25mm of insulation, which combined with all electric heating means staying warm in the building is expensive; many residents experience fuel poverty.

Improving the building to the demanding EnerPHit standard involves a number of challenges; how to insulate the rear façade which features integral but exposed walkways without introduction thermal bridges, how to provide appropriate and effective ventilation and how to provide cost effective heating in a building with limited space for communal services and whose structural characteristics proscribe the use of gas.

Modernisation proposal: 

Wilmcote House will be split into three thermal envelopes with the two stair cores remaining outside the thermal envelopes in order to simplify the detailing required. External walk ways will be enclosed within the thermal envelopes of the blocks in order to improve the area / volume ratio, make the detailing simpler and thusmore cost effective.  Internal balconies that exist on alternate stories, those between the walkways, will also be enclosed, increasing the size of the maisonettes and again and simplify detailing.  The three blocks will be made airtight using an external membrane before an external insulation system is applied to each block.

Each dwelling will be provided with individual MVHR systems. Existing heating systems will be retained for the time being due to resident familiarity and budgetary constraints.  Heating could be addressed as and when the current systems reach the end of their lives, in accordance with the step-by-step approach taken by EuroPHit.  Ground floors will also not be insulated at this stage but could be considered in a future ‘step’.