Sensitive low energy retrofit
Phase 2 of the HLNSC (Herefordshire, Ludlow and North Shropshire College) Low Carbon Technology Centre project involved the retrofit of a former stable building in the curtilage of a listed manor house, to create new a new teaching workshop and classrooms intended to help train new plumbers and electricians in the design and installation of renewable and low carbon energy technologies.
Strategy
The original brick and steel structure was retained. Internal wall insulation (IWI) was applied, consisting of a layer of insulating plaster (Diathonite) to improve insulation and provide a continuous airtightness line, with an additional layer of wood fibre insulation applied to the inside. The structural slab was broken out and replaced with a new insulated slab and the roof was internally insulated with further wood fibre insulation applied.
High efficiency mechanical ventilation systems with heat recovery (MVHR), with demand control, were installed to ensure adequate ventilation whilst minimising associated heat losses. An air source heat pump (ASHP) provides heating and cooling to the building via a combination of underfloor heating and fan boost radiators.
A solar thermal water heating system provides domestic hot water to taps and hand basins (also used as a teaching resource in the workshop) and the remainder of the useful roof area is covered with solar PV to offset electricity used in the heat pumps etc. A battery system was installed to help better match times of peak generation to times of peak load.
Project team
Client: Hereford, Ludlow and North Shropshire College
Contractor: GP Thomas
AECB Consultant: Greengauge
M&E Design: Greengauge
Architect: YNGR
AECB Certifier: Greengauge
Key data
“It was a pleasure to help deliver an AECB retrofit and sustainable services strategy on a building which is to be used for Low Carbon Technologies training. We applaud the College for retrofitting its building to these high standards and for setting a great example for a new generation of engineers to follow! “
Gerard Thacker, Associate Director, Greengauge
Challenges & solutions
- The listed curtilage status meant that a less risky external wall insulation (EWI) strategy was not an option, requiring internal wall insulation to be applied. This could potentially cause problems with condensation and mould growth on the existing fabric on the cold side, hence calculations had to be undertaken to check the proposed build-ups and detailing.
- Window frames in the east façade were also required to match those in the manor house opposite, which reduced their thermal performance. Thermal bridging calculations had to be undertaken for these to ensure that they would not cause condensation problems in the otherwise well-insulated wall.
- The interaction between the existing steel roof trusses and the new roof insulation created additional thermal bridging issues, which also needed to be carefully modelled.
- The floor to ceiling height on the ground floor was very constrained resulting in significant challenges in routing ductwork, which needed to be relatively large to cater for the high peak occupancies expected in College classrooms/ workshops. The ductwork had to be carefully coordinated with the existing steel structure, once ceiling finishes had been removed to reveal the size and locations of the down-stand steels.
