For architects and building designers, the phrases ‘zero carbon’, ‘net zero’, ‘fabric first’ and ‘Passivhaus’ might be very familiar. But there’s work to be done to stop these from becoming nothing more than sound bites.

Read the full piece Mhairi wrote for RIAS about meaningfully contributing to mitigating the climate crisis.

Figures from the Scottish Energy Statistics Hub show that in 2017 the share of total final energy consumption by sector for Domestic was approximately 30% (compared to Industry & Commercial and Transport). Clearly housing has an important part to play.

It is now well documented that operational energy use is still considerably higher than currently predicted at the design stage. This performance gap can be as high as 60% and is a real threat to our ability as designers of a low energy, truly sustainable, built environment, which inhibits our ambitions for an operational and embodied zero carbon future.

One issue we are often faced with as designers of new homes is that of prioritising the client’s budget: would the available funds be better spent on technology to generate energy on site, or on making the building fabric more energy efficient. Rarely are the funds available to do everything and so some compromise is inevitable.

Comparing building typologies quickly exposes the fact that less dense development, such as detached dwellings, lends itself well to on-site energy generation, but that more dense housing, such as high-rise, does not as the roof and wall area ratios per m2 of accommodation is low. If on-site generation is considered the primary driving factor in energy efficiency this can lead to a favouring of less efficient building forms.

Reducing the heating demand of dwellings, no matter what their form, is a critical component of a sustainable future. A ‘fabric first’ approach better protects all future home occupants by reducing energy demand to the minimum possible before consideration is given to adding any appropriate Low and Zero Carbon Generating Technologies (LZCGT’s).

As a small Chapter with a predominantly rural and semi-rural character Stirling has much to offer when it comes to sustainable housing. With many properties being situated in open countryside or small conurbations the opportunities to maximise orientation and aspect, and thus reduce energy demand by some passive means, are probably more prevalent than in other, more dense, urban areas.

My own journey towards low energy architecture was sparked by the desire in 2013 to move out of the city and build a new home / home office with my husband, which we chose to do in Kippen, a small village near Stirling, notably off the gas-grid. During the design process the inevitable questions arose: should we be focusing investment in high levels of renewable technologies, such as photovoltaic or solar thermal panels, to generate energy or hot water at source, or is there an alternative way to diminish our reliance on the grid? Much research led me to the discovery of the fabric first Passivhaus Standard, which, at this time, was firmly established in Continental Europe but still relatively unknown in the UK, particularly in Scotland.

There still aren’t many Certified Passivhaus homes within Scotland, although there are a growing number of high-quality low energy buildings constructed either to the Standards, or very close. A 6 year self-build, our house and home office has been a labour of love and discovery, which we have used to develop our ideas as a small practice about many aspects of low energy design. We have learnt that it is more strategic and cost effective to carefully control the percentages of glazing on each elevation in order to reduce the risk of overheating rather than adding complex shading devices; how to detail an airtight building shell in as simple a way as possible; and the benefit of thick walls to create depth and interest on an elevation rather than adding projections and overhangs.

This experience has led me to believe wholeheartedly in a ‘fabric first’ approach, irrespective of whether a building is taken to the Passivhaus Standard or renewable technologies are added. The fundamentals of Passivhaus and low energy design – improved thermal comfort and excellent indoor air quality – illustrate that comfort is of primary importance, whilst simultaneously reducing energy demand. If we apply to our buildings the design principles of high levels of insulation, excellent levels of airtightness in combination with a robust ventilation strategy, and control over the orientation and quantity of glazing, we make better homes for our clients as well as the environment.

The ambitions of low energy development, and use of materials with a low environmental impact, have been taken up by many practitioners keen to create reduced environmental impact and more thermally comfortable homes for their clients.

One such project in our region is the Dunblane self-build collective, which is a beautiful example of friends who got together to realise their dream of building truly sustainable homes for their families. Designed by architect Chris Morgan (now at John Gilbert Architects) this collaborative scheme exemplifies a fabric first approach.

The houses were constructed using prefabricated timber frame panels and have natural materials and finishes throughout. Externally these 3 houses have been designed to complement adjacent properties, and feature pale green timber cladding, with stonework to the lower storey, and a zinc roof.

The homes have spacious, open-plan ground floors; rather than favouring renewable energy generation the buildings reduce heating demand by being highly insulated and airtight with triple glazing. High performance MVHR ventilation systems mean the houses need very little heat input.

Another exemplar fabric first house in Stirling region is in Sauchieburn by the architect Grigor Mitchell. The project aims to create a ‘place’, forming a special environment on the secluded site. The client brief was for a small, low cost, low maintenance, low demand dwelling, within a sheltered unobtrusive area, well screened from public view and informed by the principles of the Passivhaus standard.

The compact linear single storey form with an asymmetrical pitched roof house is a discrete presence on the site and is articulated by recesses on the east and west ends which provide external covered areas. The main feature at ground floor is the open plan living/ dining and kitchen area at the south-west end of the house. The kitchen, utility, two bedrooms and sanitary accommodation are grouped along the northern edge of the floor plan. An additional bedroom/ home office is located on the south east corner adjacent to the entrance.

The palette of new external materials has been selected to be high quality, maintenance free and in keeping with the rural setting. The walls are finished in Scotch larch cladding with the pitched roof finished in coated standing seam metal.

Irrespective of the renewable technologies that can be added to a building, or linked to a development, an investment in a fabric first approach is a sensible and future proofing manoeuvre by designer and client alike, and which can only lead to an improved quality of life for the building occupants as the years progress no matter what happens to energy costs or resources. Reducing the levels of energy required for space heating, hot water production and any unregulated loads by reducing the demand for these loads in the first place leaves the role of site specific renewable technologies to be one of support in a zero carbon future – effectively a ‘top-up’ rather than a way of covering all of the demand. National investment can then be more efficiently utilised for large scale renewable schemes and a focus on the decarbonisation of the grid which has beneficial impacts on all building typologies.

At the heart of a low operational and embodied energy building approach is the ambition to reduce, reduce, reduce. To quote a phrase I have heard recently: the most energy efficient kW/hr is the one which isn’t expended at all.