Fabric-First Energy Efficiency

In today’s dynamic environmental landscape, there is an increasing need for sustainable and energy-efficient building solutions. One such approach making significant strides in the ‘fabric-first’ approach to energy efficiency. A fabric-first method prioritises the enhancement of the building’s envelope as the initial step towards reducing energy consumption.

The fabric-first approach is centred on three primary elements: insulation, airtightness, and thermal bridging. Let’s delve deeper into each to understand how they contribute to the overall efficiency of a structure.

Insulation

Insulation acts as a thermal barrier that resists the flow of heat. In a fabric-first approach, it is therefore essential to utilise high-quality insulating materials. You must also ensure they’re installed correctly in the building’s fabric, including walls, roofs, and floors. This is to create an efficient thermal envelope that minimises heat loss during cold weather and reduces heat gain during warmer months.

Insulation is achieved using various materials. This can come from traditional options like fibreglass and mineral wool to more sustainable choices like cellulose or sheep’s wool. However, the type of insulation selected will depend on the specific requirements of the building, local climate, and budget. For example, Mineral Wool is more expensive but it does provide acoustic as well as thermal insulation. Moreover, it is A1 fire rated. Alternatively, EPS is a cost-effective solution that is very easy to handle. Lastly, Kingspan K5 is a premium space-saving system, composed of phenolic foam, with an extra emphasis on compressive strength.

Airtightness

Airtightness, in the context of a fabric-first approach, means eliminating unintended airflow through the building envelope. It involves sealing all potential points of leakage. This includes windows, doors, joints between building elements and openings for pipes and cables.

Achieving airtightness requires meticulous attention to detail during construction. It often involves using airtight membranes, tapes, or sealants to seal joints and gaps, and high-performance windows and doors. Airtight buildings not only prevent heat loss but also improve indoor air quality. They do so by reducing the ingress of outdoor pollutants and allergens.

However, it’s critical to balance airtightness with adequate ventilation. While the goal is to prevent unintended air leakage, buildings still need to ‘breathe’. This is to ensure a healthy and comfortable indoor environment. An MVHR system provides fresh air and controls humidity while recovering heat from the outgoing air. The mechanical ventilation with heat recovery system supplies and extracts air throughout the property.

Thermal Bridging

Thermal bridges are areas in a building’s envelope where more heat is transferred than in others. This is usually due to either the presence of more conductive materials (like steel or concrete) or breaks in insulation continuity (like at the junction between a wall and roof).

In a fabric-first approach, it’s important to minimise thermal bridging to ensure an even temperature throughout the building and to also reduce overall heat loss. This involves careful design and construction to ensure insulation continuity and the use of thermal breaks – less conductive materials inserted in the structure to reduce heat flow.

Thermal bridging is often assessed with thermal modelling software. This allows architects and engineers to identify potential problem areas and consequently devise solutions in the design stage. By managing thermal bridging effectively, we can further enhance the energy efficiency of buildings and contribute to a more sustainable built environment.

These 3 elements all feed into Passive Solar Design.

Passive Solar Design

Passive solar design is a concept that aligns perfectly with the fabric-first approach to energy efficiency. By integrating the principles of passive solar design, a building can gain additional advantages in energy savings and occupant comfort, complementing the fabric-first strategy’s benefits.

Passive solar design involves the strategic use of a building’s structure, orientation, and materials to harness solar energy for natural heating, cooling, and lighting. It primarily consists of three aspects: direct gain, indirect gain, and isolated gain.

Direct Gain is the simplest form of passive solar design, where sunlight directly enters and heats a space, usually through large, south-facing windows in the northern hemisphere (or north-facing in the southern hemisphere).

Indirect Gain involves absorbing the sun’s heat in thermal mass (e.g., concrete or brick walls, tile floors) during the day and releasing it slowly into the building as temperatures drop.

Isolated Gain includes techniques like sunspaces or greenhouses, which collect heat separately from the main living spaces and transfer it as needed.

Benefits of the fabric-first approach

• Long-term savings – While the initial investment might be higher due to the quality of materials used, the fabric-first method pays for itself in the long run. Reduced energy consumption translates to lower utility bills, leading to significant cost savings over the lifespan of the building.
• Environmental impact – The approach also has considerable environmental benefits; by minimising energy consumption, it significantly reduces carbon emissions, aligning with global efforts to combat climate change.
• Health and comfort – From a human perspective, fabric-first results in a healthier, more comfortable living environment. With better insulation and fewer drafts, indoor temperatures are more consistent, creating a more pleasant living or working space.
• Regulatory compliance – With tightening energy efficiency regulations worldwide, adopting a fabric-first approach can ensure compliance with these laws, future-proofing your building project.