At March Consultants Limited (MCL), we are committed to pioneering sustainable building solutions that not only meet but exceed current performance standards. Our latest project, the refurbishment of the historic former nurses' home on Westmoreland Road, is a prime example of this.
An architectural highlight of the project is the top storey, which is distinctively encased in curtain walling. This feature, while aesthetically pleasing, presented unique challenges due to the potential for high solar heat gain, which could lead to significant overheating, particularly in the warmer months, yes, even on the Isle of Man.
Recent evidence underscores that overheating risk needs to be taken seriously, particularly in the residential sector. Many new or refurbished homes face overheating risks due to factors like high proportions of glazing, inadequate natural ventilation, or mechanical ventilation systems failing to deliver the intended air change rates. The health and well-being impacts of overheating can be profound, resulting in issues like stress, anxiety, sleep deprivation, and even premature deaths during heatwaves. According to the UKHSA, mortality rates from overheating, without adaptation, could rise to 10,000 per year by the 2050s.
To effectively address these challenges, MCL employed TM59: Design methodology for the assessment of overheating risk in homes, a rigorous standard developed by the Chartered Institute of Building Services Engineers (CIBSE).
TM59 is particularly valuable for its robust approach to evaluating these risks by considering a range of factors such as geographic location, climate, building orientation, and a standardised set of internal conditions. It particularly stands out for its compliance criteria, including:
Criterion A: For living rooms, kitchens, and bedrooms; sets a limit of 3% on the number of occupied hours that the operative temperature can exceed the threshold comfort temperature, Tmax, by 1K or more during a typical non-heating season – 1 May to 30 September. Tmax is a function of the outdoor running-mean temperature.
Criterion B: For bedrooms only; to guarantee comfort during the sleeping hours the operative temperature in the bedroom from 10 pm to 7 am shall not exceed 26 °C for more than 1% of annual hours.
As anticipated, the first iteration of the TM59 model showed significant overheating in the living spaces and bedrooms. This initial finding underscored the critical need for a design rethink to ensure thermal comfort.
In response, our team engaged in a focused collaboration with the architect, cost consultant, and window manufacturer to develop a series of targeted design interventions. We chose parallel opening windows which offer a significantly larger openable area compared to other restricted window openings, e.g. top-hung. Carefully positioned to maximise crossflow ventilation, these windows greatly improved the efficiency of our passive cooling strategy. Additionally, we selected high-performance glass engineered to reduce solar gain while maintaining excellent light transmission.
These targeted measures successfully met the rigorous standards of TM59 criteria A & B, confirming our ability to maintain thermal comfort on the top floor without relying on energy-intensive mechanical cooling systems.
The U-value of the glazing was also carefully selected, again, in partnership with with the design team. We undertook a detailed cost-benefit analysis to evaluate the balance between installation costs and anticipated energy savings. This strategic decision ensures that our solutions are not only effective in reducing energy consumption but also economically viable, providing long-term value to our clients.
By combining innovative design strategies with rigorous engineering analysis, MCL continues to lead in the field of MEP engineering, pushing the boundaries of what is possible in the design of contemporary and architecturally striking structures. Our expertise allows architects to embrace ambitious designs, without compromising on environmental sustainability or occupant comfort.
For more insights into our projects or to discuss your own needs for innovative MEP solutions, please call 01624 616300.
Project Info:
Title: Former Nurses' Home
Client: Manx Development Corporation
Architect: Ellis Williams Architects
Structural Engineer: BB Consulting Engineers
Quantity Surveyor: Bell Burton Associates