|Location: Plymouth, Devon|
|Completion Status: Completed August 2013||Occupancy: Occupied since August 2013|
|Architect: NA||Consultant: WARM: Low Energy Building Practice, Certifier: BRE|
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Situated on the Stonehouse peninsula, by the banks of the River Tamar, Number 3 Admirals Hard was built in the 1960s and comprises a shop on the ground floor and WARM's office, originally a flat, on the first floor. The extensive retrofit works included external wall insulation, cavity wall fill, floor insulation (between the office and the shop), roof insulation at rafter level, high levels of air tightness and high-performance triple-glazed windows, as well as a self-balancing MVHR system.
The first floor is EnerPHit certified. The shop has triple glazed windows and external insulation, but requires floor insulation and ventilation which will be installed at the next break in the lease.
The initial airtightness test failed to give a result as the standard domestic airtesting fan was unable to reach 50 Pascals! We kept the airtesting equipment on site, with tests carried out each week. This way we were able to closely monitor progress and identify leaks as we went along. This was one of the biggest successes of the project and whilst the airtightness was always a challenge, the process enabled us to keep on top of it.
We improved the heating balance by simplifying the window design & slight reductions in the extent of glazing: this was possible because the MVHR meant we didn’t need as many openings.
We also made significant savings by optimising key junctions using THERM, in particular the window-wall junction where the reveals were splayed to maximise daylight in a way that didn’t compromise the ‘wrapping’ of insulation.
We had previously obtained planning permission for a sizeable balcony which was added to the south side, adding amenity and providing an escape route. The balcony is a separate structure to the building, whilst this is a classic Passivhaus principal it required significant negotiation with the structural engineer and builder to develop a suitable solution (initially the SE wanted to put in piles!!)
The original shop blinds were refurbished, both on the shop front and on the balcony to provide summer shading and an appropriate aesthetic. Attaching these to the building through the 250mm of insulation required a very bespoke solution. We carried out research into fixings through thick (>200mm) external insulation for high loads.
We designed our own electrical distribution system dividing office plug loads into three types: those on each desk, served by an illuminated switch for each desk; those that were common but did not need to be on when the office was not occupied – printers, Ethernet, ventilation, door entry etc etc, served by a heavy duty switch by the exit; and finally those that needed to be on all the time – the server, the fibre router, their UPS. We chose components such as a fan less server allowing us to reduce this continuous load to 40 W.
We undertook all of the design work in-house, and all of the WARM team spent time on site. In this way we have a very strong connection to the building; it has given us fantastic experience of the process.
The WARM team worked closely with the builders – very skilled carpenters – to ensure they understood everything necessary to achieve the target. The builders were paid on a day-rate to ensure they were not tempted to cut corners. Whilst they had never undertook anything like this before (never seen airtesting equipment!) these two aspects made for a low risk project. The building is semi-detached, with the neighbouring property offset slightly which lead to some complicated detailing around the party wall. We added a layer of internal insulation on the whole of the party wall, which was thicker where it was adjacent to the neighbours unheated attic space.
We decided to insulate at roof level to give an attic for storage and possible expansion, but more importantly to give enough space for a decent MVHR installation (always a problem on retrofits) this added significant cost but on reflection was a good decision. We used a specially designed radial ventilation system with orifice plates and a self-balancing ventilation unit (Brink). This means that the flowrate to each terminal is to an extent pre-set, and the supply and extract are always the same. We were very keen to try out this kit ourselves as commissioning has been a major downfall of mechanical ventilation systems. Once installed, the commissioning found that none of the terminals had to be adjusted at all – proving that the type of design had advantages in reducing the difficulty of commissioning.