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Embodied Energy Reduction

As a practice we welcome the introduction of enhanced regulation of building construction and performance such as the RIBA 2030 Challenge, SAP 10 and the new Building Regulations. Our work has had its sights set beyond such targets for over a decade so it’s encouraging to be leading the industry in our drive to address matters of climate change, energy conservation and the drive to reduce domestic energy bills.

Hawkes Architecture are uniquely placed to ensure that the very highest standards of architecture can be delivered to exceptionally high levels of construction excellence whilst ensuring stringent embodied energy standards are assured and exemplary low energy in use is achieved.

Exterior detail of Echo Barn, a Para 55 energy efficient passive house. Another grand design by Hawkes Architecture.

As a practice we welcome the introduction of enhanced regulation of building construction and performance such as the RIBA 2030 Challenge, SAP 10 and the new Building Regulations. Our work has had its sights set beyond such targets for over a decade so it’s encouraging to be leading the industry in our drive to address matters of climate change, energy conservation and the drive to reduce domestic energy bills.

Hawkes Architecture are uniquely placed to ensure that the very highest standards of architecture can be delivered to exceptionally high levels of construction excellence whilst ensuring stringent embodied energy standards are assured and exemplary low energy in use is achieved.

Crossway Passive House

Embodied Energy Study

The embodied energy study of the Crossway Passive House which was undertaken by Cambridge University back in 2009 provided an invaluable insight into the energy expended to build a uniquely designed house. This knowledge has underpinned the practice’s work ever since and has enabled all Hawkes projects to be exceptional in their energy conservation both in construction and in use.

For example, the embodied energy assessment revealed just how significant the transportation component of a project is. The fuel energy expended to just get tradesmen to & from site actually is a significant consideration when designing low energy low carbon buildings.

This knowledge has led the practice to develop construction techniques that aim to reduce time and labour on site thus expending less fuel to complete a building.

Of course such efficiencies in transport & construction time on site also need to be balanced against the idiosyncrasies of each project. Some projects suit more pre-fabrication than others. It’s important to understand where to adopt certain techniques.

It’s a complex balance of technical performance, embodied energy, cost, speed and quality.

One of the revealing facts that came from this study was how significant the transport energy footprint was in comparison to the materials used to build the house. The embodied energy of travel as a component part of the construction of a building led us to developing low embodied energy construction techniques which aim to reduce labour processes and in turn fewer visits to site and thus less fuel energy is expended to complete the build.

Crossway

Crossway Success

Carbon footprint results

The total estimated embodied energy for the entire build, was calculated to be approximately 900 GJ, equivalent to 250,000 kWh and given the project floorspace covered 285m2, this worked out to be 877 kWh/m2. This estimate was based on material components, (I) the solar PV-T panels and (II) the transportation of the construction team.

From the results, it was clear to see that the vast majority of the embodied energy came from just 5 key materials.

EPS (which is expanded polystyrene foam, a rigid insulation material), the PV-T solar panels, concrete, clay tiles and cement, which constituted to over 80% of the total embodied energy. However the other 20% of the entire carbon footprint, was made up of transportation costs, which is often overlooked but makes up a huge percentage of the overall footprint.

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We simplify detail and minimise heat loss

Detailing

Cold bridging & airtightness

We have recognised the importance of air tightness in reducing heat leakage from the building envelope and so we have been adapting and innovating various construction details to make building airtight easier and more attainable to contractors less familiar with airtight passive house construction techniques. Here are examples of some of these innovations which collectively make a significant contribution to reducing operational energy in our buildings.


We favour specifying the highest quality, breathable membrane possible as they are more airtight, vapour transparent and reflect radiant heat away, helping to keep our buildings cool during the summer. To retain heat during the winter, we specify that membrane joints are taped, including to any structural timbers, to maintain the buildings airtightness.

Vertical loads from steel beams get transferred into our buildings structural timbers. Which avoids the use of unnecessary steelwork and the need to compromise the buildings thermal integrity.

Perimeter block work is specified under our timber sole plates, giving the timber frames above “a good pair of boots”, which keeps exterior ground water away. However we substitute the inner block work with an insulated timber ladder, that significantly improves the buildings thermal efficiency and aids the speed of internal construction on-site.

Taping beams to achieve airtightness.

We have recognised the importance of air tightness in reducing heat leakage from the building envelope and so we have been adapting and innovating various construction details to make building airtight easier and more attainable to contractors less familiar with airtight passive house construction techniques. Here are examples of some of these innovations which collectively make a significant contribution to reducing operational energy in our buildings.


We favour specifying the highest quality, breathable membrane possible as they are more airtight, vapour transparent and reflect radiant heat away, helping to keep our buildings cool during the summer. To retain heat during the winter, we specify that membrane joints are taped, including to any structural timbers, to maintain the buildings airtightness.

Vertical loads from steel beams get transferred into our buildings structural timbers. Which avoids the use of unnecessary steelwork and the need to compromise the buildings thermal integrity.

Perimeter block work is specified under our timber sole plates, giving the timber frames above “a good pair of boots”, which keeps exterior ground water away. However we substitute the inner block work with an insulated timber ladder, that significantly improves the buildings thermal efficiency and aids the speed of internal construction on-site.

Glass

Triple & quadruple glazing

We always specify triple, or even quadruple, glazing on our projects, as this is one of the most significant investments a client can make into the fabric of their building. The benefits are multifaceted, not only are the U-values significantly better, saving energy through lower heat loss, triple glazed casement units reduce noise, reflect heat and are generally better sealed which reduces draughts.

This image below illustrates just how well triple glazed windows perform. As you can see, during the harshest of winters ice will form on the exterior of the window, demonstrating just how little heat is lost through the glass. This simply wouldn’t happen with single or double glazed units as the outer pane would be warmer as more heat is lost through it.

To read more about how material choices impact the sustainability of our projects, click the link below!

Conscious Materials

Passive solar gain

Most UK houses don’t wear enough clothes. Houses with ‘T-Shirts’ need lots more energy to stay warm in Winter as they have little mass to store the daytime solar gains. With limited heat storage the internal space will cool down quickly.

Our houses wear ‘Ski Jackets’ are air tight and are built from insulated timber frames. Houses with ski jackets are easier to keep warm in Winter.

The sleeping bag analogy represents a continuous uninterrupted insulation layer around the floor, walls and roof. This keeps the heat in and the cold out. Sun warms air, and the mass inside the sleeping bag stays warm during the day.

Visualisation

Construction Efficiency

So many techniques have improved over recent years and we continue to develop these innovative concepts today. Benefiting from VR and 3D computer modelling, we can now visualise the construction process, with both the client and main contractor to increase the speed of our developments and the productivity on-site.

3D model of the frame of Echo Barn, a Para 55 energy efficient passive house. Another grand design by Hawkes Architecture.

Operational Energy

Energy Use & Efficiency

An average 3 bedroom house consumes around 15,000kWh per year. 80% of this energy is consumed for heating and hot water. Electricity only accounts for 20% of a house’s energy use. This is why we spend the majority of our time designing to reduce the need for heat! Design decisions we make to maximise insulation, enhance airtightness and minimise cold bridging, help to reduce a building’s need for heat. These also tend to be decisions that are difficult to change later!


Ensuring that a building’s walls, roof, floor and windows have all been designed to minimise the need for heating will have the greatest impact on reducing running costs.

With the largest slice of a home’s annual energy load minimised, our focus can turn to optimising the efficiency of hot water and electricity consumption. Modern heat stores with smart controls that learn how to optimise energy consumption to reduce consumption and costs are helping to reduce bills and consumption.

Use of efficient appliances and LED lighting have also helped to reduce electricity bills enormously. Battery storage and the adoption of EVs & home charging are revolutionising the way we travel and how we manage our dependance on the National Grid.

Richard has continued to monitor and evolve the energy systems at his own certified Passive House since 2009. Hawkes Architecture’s experience and pedigree in delivering homes of exceptional quality and unparalleled efficiency is unique in the architectural world.

Generating electricity with solar panels.

An average 3 bedroom house consumes around 15,000kWh per year. 80% of this energy is consumed for heating and hot water. Electricity only accounts for 20% of a house’s energy use. This is why we spend the majority of our time designing to reduce the need for heat! Design decisions we make to maximise insulation, enhance airtightness and minimise cold bridging, help to reduce a building’s need for heat. These also tend to be decisions that are difficult to change later!


Ensuring that a building’s walls, roof, floor and windows have all been designed to minimise the need for heating will have the greatest impact on reducing running costs.

With the largest slice of a home’s annual energy load minimised, our focus can turn to optimising the efficiency of hot water and electricity consumption. Modern heat stores with smart controls that learn how to optimise energy consumption to reduce consumption and costs are helping to reduce bills and consumption.

Use of efficient appliances and LED lighting have also helped to reduce electricity bills enormously. Battery storage and the adoption of EVs & home charging are revolutionising the way we travel and how we manage our dependance on the National Grid.

Richard has continued to monitor and evolve the energy systems at his own certified Passive House since 2009. Hawkes Architecture’s experience and pedigree in delivering homes of exceptional quality and unparalleled efficiency is unique in the architectural world.