May 21, 2019 Last Updated 8:31 AM, Apr 10, 2019

Conlon Construction talks PSBJ through the fabrication of the BREEAM-rated ‘Excellent’ One Hatfield Hospital

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Sean Conlon from Conlon Construction discusses the design and construction of the BREEAM-rated ‘Excellent’ One Hatfield Hospital in Hertfordshire, highlighting the elements of best practice that could be rolled out to other healthcare environments.


While lots of commercial environments attain BREEAM ‘Excellent’ ratings, achieving the required standard of energy efficiency and environmental performance is notoriously difficult in the healthcare sector. There are multiple reasons for this, including the high electrical loading requirements of a 24/7 operation, the need for extensive heating and cooling, the use of advanced equipment and high levels of water consumption.

At One Hatfield Hospital in Hertfordshire, the £40m design and build project delivered by Conlon Construction has incorporated measures to enhance energy efficiency and environmental performance to help drive down running costs while ensuring high standards of patient comfort.

The hospital may be relatively small compared to many NHS Trust hospitals, but there are elements of best practice that can be shared and scaled up to benefit any UK healthcare environment.

Innovative approach

One Healthcare works with the NHS, private medical insurers and communities to innovate in the way care is delivered, utilising advances in technology to facilitate a smoother patient journey with reduced hospital stays.

The same focus on innovation has also led the healthcare provider to push standards of specification in order to reduce energy consumption, utilise renewable energy technologies effectively, conserve water and ensure that sustainability was built into the fabric of One Hatfield Hospital.

To achieve these goals, early engagement with the delivery partners was essential as this was integral to both the energy strategy and building comfort. For example, consideration was given to natural light at the earliest design stages as this influences both patient comfort and energy demand for electrical lighting. The result is a hospital that is permeated by ample natural light, with a ‘Zen Garden’ to provide a relaxing patient environment in the heart of the building. LED lighting throughout is controlled by a DALI-based system with absence detection and daylight linking to ensure electric lighting is only operational on an as-needed basis.

The Conlon Construction team worked with architect practice, Manning Elliot, BREEAM consultant, Aegis, and M&E consultant, Walmsley Associates, from the outset, appointing the company’s own sustainability champion to the project to ensure the scheme met its low-carbon and high comfort goals.

Energy strategy

At the heart of the hospital’s low-carbon strategy is a combined heat and power (CHP) unit, which has a 37kW thermal output to provide the low temperature hot water (LTHW) for the domestic hot water system and the radiators, radiant heating panels and air conditioning coils. Thanks to the constant LTHW load in the 24/7-occupied building, the CHP also provides 19kW of electrical output to contribute to the hospital’s energy requirements.

In addition to the energy generated by the CHP, the hospital has also been fitted with a 32kW solar PV installation on the roof and air source heat pumps have been installed as the energy source for the heat exchangers in the air handling units, with all consulting rooms and en-suite patient bedrooms heated and cooled by VRF (variant refrigerant flow) HVAC systems with heat recovery.

Water management

In addition to energy management, the building’s design and construction have also focused on minimising water consumption and waste as this is another area where healthcare environments tend to be heavy users. Rainwater harvesting provides the water for toilet flushing throughout the building with a 40m3 capacity water butt buried in the grounds. This water is pumped back into the building and filtered before being used in the plumbing system.

The hospital’s sustainable drainage system also includes attenuation of all surface outfalls, minimising the discharge of water into public sewers to reduce the risk of localised flooding.

All incoming mains water supplies are also treated with carbon filtering and UV treatment to safeguard against waterborne infections and bacteria. PIR no-touch taps throughout the building also aid infection control and ensure water is not wasted by taps being allowed to continue running when not in use.

Building fabric

Alongside the BREEAM points scored by the mechanical and electrical installation at One Hatfield Hospital, the building fabric and construction integrity of the building also boosted the score and the hospital’s long-term thermal performance. Insulated beyond mandatory building regulations requirements, the hospital has been specified with BRE Green Guide A+-rated materials throughout – including the cladding, glazing, roofing and flooring. This not only ensures that embedded carbon in the structure is reduced but also supports long-term sustainability in terms of lifecycle, recyclability and responsible material sourcing.

To ensure that the designed thermal performance of the specified building fabric was realised in the completed building, a clear focus was also placed on achieving high standards of airtightness. The building design was tested using robust design and heat loss calculations and, following completion, thermographic and air quality checks were carried out prior to client handover. The building passed these tests with flying colours demonstrating the building’s success in minimising heat loss to support improved energy efficiency.

Considerate constructors

While the building design and specification were pivotal to the building’s low carbon credentials, the BREEAM assessment also takes into account the social value of the build process and the impact of the construction project on local residents.

The Conlon Construction team scored highly on the Considerate Constructors Scheme (CCS) inspections, with scores of 41/50 and 43/50 on the two site visits and commendations on actions taken to reduce disruption for the local community.

Measures taken included provision of an acoustic wall around the outside plant deck and consultation with residents to design an attractive landscape that would encourage biodiversity.

Setting high standards

With 10 consulting rooms, a combination of in-patient and day care patient bedrooms, three next-generation integrated theatre suites and three treatment suites, including endoscopy, One Hatfield creates a benchmark for contemporary healthcare. Thanks to the focus on driving a progressive, low-carbon energy management strategy, the building also raises the bar for hospital construction.

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