Embracing Passivhaus Principles: A Blueprint for Sustainable Architecture
09 January 2024
In the pursuit of sustainable living, Passivhaus has emerged as a beacon of energy-efficient construction, providing a blueprint for homes that are not only environmentally friendly but also economically viable. Through insights gathered from seminars at the National Self-build Centre’s Passivhaus workshop, this article delves into the key principles of Passivhaus design and how they are reshaping the landscape of modern architecture.
Jae Cotterell, a representative from Passivhaus Homes, highlighted a significant shift in the economics of Passivhaus construction. Initially considered 8% more expensive than traditional builds, the extra cost now hovers around 6%. With potential further reductions to 4% or even 3%, this cost dynamic challenges the misconception that sustainable building practices are financially prohibitive.
The major contributors to this extra cost are the Mechanical Ventilation and Heat Recovery (MVHR) system and triple-glazed windows. It's crucial to note, however that there is a perceived "extra cost" that arises from occupants failing to adjust their energy usage in alignment with the enhanced performance of Passivhaus structures. The key objective is to achieve an annual specific space heat demand of 15kWh/m2.a (kilowatt hours per square metre per annum), a goal that not only minimises environmental impact but also significantly reduces operational costs.
Robin Miller of BECO Wallform emphasised the importance of a "fabric first" approach for Passivhaus performance. This involves prioritising the building's envelope to reduce energy loss and demand. BECO Wallform, a robust insulated concrete formwork, exemplifies this principle by addressing three of the five Passivhaus tenets: insulation, air tightness, and thermal bridging.
With 300 millimetres of insulation in walls, 400 millimetres in the roof, and additional features such as air source heat pumps and roof-mounted solar panels, BECO Wallform offers a reliable and stable solution for sustainable construction. Completed with triple glazed windows the system stands as a testament to the notion that technology, when known and proven, can lead to reliable performance and reduced energy bills.
Anna Carton of Passivhaus Homes (PH15) introduced a low carbon approach to Passivhaus design. PH15 derives its name from the remarkable 15-kilowatts per hour per square metre required to heat a Passivhaus, significantly less than the 80 to 160 kilowatts used in a conventional house. The philosophy prioritises reducing risk, providing adequate training, eliminating fear factors, protecting delivery, removing complexity, and limiting cost uplift to achieve its goal.
PH15's commitment to carbon reduction is evident in its construction methods, as compared to traditional alternatives. The embodied carbon of PH15 stands at 21 kg CO2 equivalent per square metre, dwarfing the figures of masonry (75 kg CO2 e/m2) and Structural Insulated Panels (SIPS) (40 kg CO2 e/m2). Through innovative low carbon systems and design practices, PH15 actively works to eliminate waste and contribute to a more sustainable future. As a primarily a timber system the materials also contribute to carbon sequestration during their growth cycles.
Michael Holliday of Palmer & Partners highlighted a counterintuitive approach to saving money in construction. By spending approximately 10% more on the initial build, significant savings can be realised in operational costs. This approach challenges the short-sighted focus on upfront expenses and encourages a broader perspective that considers the long-term financial benefits of energy-efficient design.
He went on to reason that construction methods should be considered carefully in their context, as site dependent rather than purely an aesthetic choice. The emphasis is on creating comfortable living spaces, addressing nuances such as a two-degree temperature difference between the air at head level and that at floor level, a difference that can create discomfort due to air movement. The integration of a Heat Pump Ventilation (HPV) unit, combining a heat pump and MVHR, not only ensures a comfortable fresh indoor environment but also provides hot water, adding another layer of efficiency to Passivhaus design and ticking off its final key principle – ventilation.
In conclusion, the seminars by industry experts provide a comprehensive view of Passivhaus principles, showcasing the evolution of its economics, the importance of a fabric-first approach, low carbon methodologies, and the potential for long-term savings. As architects and builders embrace these principles, Passivhaus is not merely a trend but a transformative force shaping the future of sustainable architecture.