CS14 Wilmcote Multifamily House in Portsmouth

Wilmcote house provides over 100 homes largely in the form of 3 bedroom maisonettes.  The homes are arranged in 5 levels (10 stories) 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.  The existing floor area is 10,233m2.External insulation will be applied to the exposed façades of the building, excluding the stair cores which will fall outside the thermal envelopes created.  A steel frame, resting on new foundations at ground level, will be fixed to the rear elevation, enclosing the existing walkways and balconies and providing a suitable structural plane into which the windows enclosing the walkways can be installed, and the new insulated façade can be fixed to. On the front façade, insulation will be fixed to the existing structure; the proposed wall build up following refurbishment is shown in the following sketch.Existing windows and doors are to be replaced with Passive House certified windows and doors, including insulated doors from the stair cores into each of the newly enclosed walkways that provide access to each dwelling.  Front doors to dwellings will open into communal space that has been enclose within the thermal envelope thus these doors need not be certified or insulated.Pre refurbishment testing has shown that Wilmcote House is reasonably airtight for an existing structure built without regard to a particular airtightness standard.  The refurbishment strategy is to install an air tight layer around the building before the application of the external wall insulation system.  Details will be developed by the design team from April 2014 onwards.Each dwelling will be provided with individual MVHR systems. Existing individual space heating systems in the form of electric storage and panel heaters will be retained for the time being due to resident familiarity and budgetary constraints.  Surveys of residents suggest that they are keen to ensure sufficient provision of heating.Work began on-site in August 2014 and is expected to be completed in September 2015.