Problem addressed

The UK construction and design industries will need to make a crucial adjustment in order to reach the UK Government’s pledge to reduce emissions to net zero by 2050 and the UN’s sustainable development goals. A focus on increasing building energy efficiency, providing onsite renewable energy and reducing embodied and operational carbon emissions in order to meet these ambitious goals is a must.

Solution overview

ZED PODS is a factory-built modular construction system that can be used to assemble residential or commercial buildings and is designed with an approach to holistically reduce carbon emissions and energy use. Developed and tested at the Building Research Establishments (BRE), this award-winning solution is the only product suited to be built on a steel podium above car parks with special considerations for fire, quality, noise, air quality and utilities.

The steel-framed modular construction system has been designed by ZED PODS in-house architectural team with a “fabric first” approach to reduce operational carbon emissions by minimizing thermal losses by conduction and infiltration. ZED PODS reduces the amount of energy lost when heat is transferred from inside to outside through specifying thick insulation build-ups, insulated floor slabs and thermally efficient triple-glazed windows and doors. A significant reduction in heat loss through the envelope by conduction is achieved with U-Values of less than 0.15W/m2.k for all elements and high attention to breaking thermal bridging. This is supported by robust, approved construction details and thermal breaks that reduce thermal bridging and create a more uniform retention of internal heat.

Each module is provided with a dedicated airtightness layer and careful attention is paid around openings by use of taping to prevent warm air from the inside from escaping via infiltration and convection. Furthermore, ZED PODS use mechanical ventilation that recovers more than 80% of the heat from expelled air. This allows a constant supply of fresh air to circulate without the natural heat loss of other ventilation methods and creates improved indoor air quality by reducing particulate matter and CO2 concentrations — while also increasing oxygen supply.

During the design of the projects, ZED PODS utilise simulation software to ensure that adequate daylight factors are created inside the spaces – reducing artificial lighting and increasing solar gains.

ZED PODS uses onsite renewable technologies to meet the energy demands once the build system has been designed and tested. Hot water and heating demand is met via their MVHR unit and a solar assisted heat pump, which have no gas connections. The remainder of the energy need is met by roof-mounted photovoltaic panels, which offsets the remaining carbon emissions and results in a zero operational carbon scheme.

Cost Benefit

The cost to build ZED PODS’ scheme is £2,925 per m2 per build (does not include land value). Hope Rise was built in 23.5 weeks as compared to 56 weeks build program for a similar housing scheme using traditional construction – which means early rental and financial benefits to council i.e. cost of temporary accommodation, early council tax etc.

Case study

Hope Rise, Bristol

The multi-award winning “Hope Rise” project is the first Modern Methods of Construction (MMC) development of its kind to be completed in the UK in 2020, overcoming various restrictions and nationwide lockdown due to COVID-19 . The project presented 11 affordable and low-carbon, modern design apartments which were installed as a permanent living space for young workers and vulnerable households. The environmentally friendly homes were erected on steel frame podium and built above a council-owned car park in Bristol. ZED PODS inhouse design team retained hundred percent of original parking provision for this project.

The super-insulated homes are fitted with low energy heating systems and renewable energy technologies (including rooftop solar panels) to complement a “fabric first” approach. Electric car charging upgrades were used to facilitate the shift away from the carbon-heavy transport use of the historic car park, while connections to local public transport and cycling/walking routes to local amenities help eliminate the need for private car ownership. The use of Cross Laminated Timber (CLT) enables the superstructure to be erected in days, helping to reduce carbon footprints during construction. This also offers the flexibility of adapting individual designs and internal layouts for the end-users. This project demonstrates that zero operational carbon affordable homes are possible to build within current financial models. Several local authorities and other stakeholders visited the scheme and were inspired of what can be achieved on a constrained site which otherwise would be difficult to build using traditional construction.

A year long “Post-Occupancy Study” was undertaken by an independent body using remote sensors and energy tracking. The study found that 104% of the annual energy usage is generated onsite by the roof solar panels which validated the as design energy performance of the building, apart from improved wellbeing and employment rates of the residents.