‘Active’ and ’Passive’ strategies to improve the energy efficiency of listed properties – Sustainability Lead Dr Martina Pacifici featured in Listed Heritage Magazine

July 9, 2024

As seen in Listed Heritage, membership journal of the Listed Property Owners’ Club. 

By Dr Martina Pacific.

SUSTAINABLE LISTED HOMES

The Club looks at ways in which listed property owners can make their homes more environmentally
friendly, contribute to reducing carbon emissions and make the most of new technologies and innovations.

To be the owner of a Listed or historic building is undoubtedly a pleasure and a privilege, but few would deny that it can also be a burden and a worry as well as a drain on the bank account. Age, traditional construction and the constraints of designation can individually - and combined - make these beautiful and iconic properties often less habitable and comfortable than their modern counterpart. Many are family homes, and those who live in them require heat, light and a clean, healthy environment whilst ensuring that the historic character of their property is retained. And that can be a challenge, particularly when it comes to increasing energy efficiency.

R: Natural sheep insulation being installed between the existing rafters. Credit: Englefield Estate

The replacement, repair or upgrading of old systems, or the introduction of new systems to improve safety, standards of living and energy performance all have implications for the whole building’s carbon footprint. The whole carbon footprint includes the embodied and operational greenhouse (carbon) emissions generated over the building’s whole life, from cradle to grave.

What we and others like us in the sector advocate are interventions that lock in the existing embodied carbon of the building but also result in the reduction of its operational carbon emissions. Various levels of intervention are possible for Listed properties and really understanding the building is an important first step. This includes how it’s constructed, its fabric, how the structure is able to breathe, and where on the scale its current energy performance lies. Thinking about carbon is key. Much of our built heritage has stood for centuries, with carbon locked up in its timbers and fabric, and that’s where we need to keep it. Historic England rightly said that: “the longer a building and its component parts last, the less embodied carbon is expended over the life of a building”. Therefore, retaining old building elements presents the opportunity to sequester embodied carbon and securely store emissions that would otherwise be released into the atmosphere.

In terms of improving energy efficiency a ‘whole building approach’ will use ‘passive’ and ‘active’ strategies, outlined below, to achieve sustainable renovation and improvement of the building’s energy performance whilst limiting carbon emissions.

Active strategies summarised for a building case study.

Passive strategies summarised for a building case study.

What we term passive strategy makes use of the natural elements such as sunlight and wind patterns to provide heating and cooling of spaces through the different seasons. Many historic buildings have been designed anyway with these factors considered - maximising solar gain and taking account of prevailing wind and weather for example. However, a passive strategy can also involve changes to building fabric by using materials of an improved thermal mass to minimise changes in inside temperature, tackling water ingress, leaks and resolving issues of damp, draught proofing windows, and improving the building’s breathability and natural ventilation. Bringing fireplaces back into use can be good for ambience, attract new buyers and serve as an additional heat source that reduces the use of central heating systems. However, fireplaces emit carbon monoxide, which is dangerous to health, and lose heat through drafts in the chimney’s flue.

An active strategy can be more intrusive and involve the installation of or switching to active technologies for generating or delivering energy and whose adoption can and probably will massively improve the building’s performance.

Active measures can include switching from oil or gas to air source or ground source heat pumps (which may also require an overhaul of internal pipes and ducting and the radiator network), switching to a hybrid boiler/heat pump system, use of biomass or renewables, linking into or creating a district heating network for larger properties with others outlying, or a number of other options. Larger properties may require a dedicated energy centre which can often be sited away from the main house, although heat loss between this and where that heat is needed is also an important consideration.

Both passive and active measures will incur capital costs and an increase of the building’s embodied carbon depending on the materials used, and their manufacture. Active technologies will tend to score higher when compared to passive solutions. However, both favour energy and operational carbon savings which will benefit the economic longevity of the asset, its health and wellbeing.

In reality, improving the energy efficiency, health and carbon footprint of a historic property will lie in a combination of both active and passive solutions with cost also being a determining factor. The most appropriate mix will be asset-dependent. Every property is unique and there isn’t a one size fits all approach although concepts and solutions now are common. The word ‘holistic’ is possibly overused but is the right one in terms of this particular opportunity - or challenge - as there are so many factors that will influence the required work to achieve a suitable level of comfort and efficient energy use while still satisfying the necessary obligations in terms of a Listed property. Heritage is important, and solutions that will last well into the future are important too. Fortunately, we are now much better equipped and able to assess and implement the best approaches, making improved comfort for living and energy efficiency far more achievable with carbon reduction at its core.