Passivhaus extension to Sciennes Primary School
We have recently submitted a planning application for this Passivhaus extension to the B listed Sciennes Primary School in Edinburgh.
Existing School, location, context.
The existing primary school, constructed in 1892, is a grade-B listed building located in the Marchmont conservation area south of the meadows in Edinburgh, Scotland. Sciennes Primary is a three-stream school with over 630 pupils making it one of the largest in the country. The school and local context are a display of traditional materials that celebrate the history of the city.
Design Brief/Planning.
In September 2019 Holmes Miller architects were appointed by City of Edinburgh Council to develop a feasibility study to identify whether 4 new classrooms could be created on the existing school site. The provision of these new spaces allows the demolition of the temporary unit classrooms to the rear playground that have outlived their life span. A Working Group, formed with Council Officers, School Management and Parent representatives, agreed that the feasibility study should explore all opportunities with the favoured outcome being a two-storey pavilion.
Concept, solution, site restrictions, landscaping.
The proposed two-storey pavilion, located in the rear playground, seeks to complement the existing primary school provision within an architecture proposal of simple refined composition in keeping with its local context and historic site. The internal open plan design is beneficial for learning as multiple opportunities for interaction between pupils are created through visual connection across the various teaching spaces. Large windows and roof lights flood the building with plentiful natural light creating an ideal environment for optimal performance. Structural cross laminated timber (CLT) will be exposed within teaching areas as this natural material creates a relaxing atmosphere for the users whilst providing environmental benefits.
On approach to the new extension the surroundings enhance the outdoor provision of the school. Numerous benches, new raised planters, new trees and vegetation encourage the school to use the space as a teaching tool, making use of outdoor learning opportunities beneficial for pupils’ well-being.
PassivHaus Strategy.
Sciennes Primary School extension is designed to PassivHaus standard and CLT, the primary structural material, is essential to achieving this. Whilst CLT minimises cold bridging, and is therefore beneficial for thermal comfort, the structural material also has a positive impact on climate change as it provides carbon storage with every m3 of CLT capturing 1 tonne of CO2. The material is both recyclable and biodegradable.
The strategy to achieve PassivHaus criteria is a fabric first approach with a focus on air tightness and thermal performance of the building envelope. The proposition relies on specification that includes quadruple glazing to all external glazed components and heavily insulated external walls and roof. The proposed mechanical strategy is also key for sustainability as it impacts energy consumption and thermal control. The design incorporates a mechanical ventilation heat recovery system (MVHR) and air source heat pumps.
Key figures.
Form Factor - 2.86
Airtightness <0.6 - 0.3 ACH
Annual heat demand - 15.5 kWh/m2a
Peak heat load - 9.0 W/m2
Average building fabric u-value - 0.85 W/m2K
Thermal Bridging heat loss allowance - 5%
MVHR efficiency - 84%
Sciennes Primary School extension is an exciting yet challenging project for Holmes Miller. Delivering PassivHaus standard is a positive step in helping address climate change. The success of this project sets a precedent to advance sustainability within primary school design which Holmes Miller are eager to continue to promote. The proposal is exemplary of modern construction within a historical setting.
