Creating Energy Saving Homes Using Thermal Mass

The energy used to heat a building accounts for up to 50% of its entire energy consumption and around 37% of the carbon emissions from all buildings in the UK. However, the use of thermal mass can massively improve energy efficiency in houses and cut heating costs by reducing the daily fluctuations in temperature.

Thermal mass can provide a number of benefits to a building including:
• Increased energy efficiency in houses and reduced carbon emissions
• More natural light and improved ventilation and air quality
• Reduced heat gains in the summer with increased heat storage and dissipation in the winter
• Reduction in demand for expensive low carbon technologies
• Increased property value

What is thermal mass?

Thermal mass refers to a material's ability to absorb heat and slowly dissipate it, helping to reduce temperature fluctuations within a house. For a material to have high effective thermal mass it must have a high specific heat capacity and high density, so it can absorb more heat, and a moderate thermal conductivity so it is able to dissipate this heat in time with natural daily heating and cooling cycles (see graph below). This gives materials like concrete, brick and sandstone high effective thermal mass making them very important for energy efficient house design.

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Energy Saving House Design in the Summer

On a warm summer day walls built with materials with high thermal mass will slowly absorb heat inward from the surface and store it until the temperature drops at night, at which point heat will dissipate back out to the surface and be released into the room.

This wave-like fluctuation in temperate works to stabilise the internal temperature of a room, providing a largely self-regulating environment. This reduces the cost on mechanical cooling, giving you a more energy efficient house design.

Energy Saving House Design in the Winter

Using thermal mass for energy efficiency in houses requires a more whole-building approach with considerations to orientation, glazing and thermal mass together to provide an energy saving house design.

Passive solar design can be used with thermal mass to cut the cost of heating bills and energy consumption. This aims to maximise solar heat gain in the winter using thermal mass to absorb gains from south-facing windows and heat from internal appliances which is then slowly dissipated at night when the temperature drops, keeping the house warm. Implementing passive solar techniques in energy saving house design can reduce energy use by up to 30%.

Energy Efficiency in Houses All Year Round

To maximise the benefit of thermal mass, energy efficient house design that optimises the house's form, fabric orientation and ventilation, can maximise energy savings and comfort inside the house.

The basic characteristics needed to maximise thermal mass include:
• House spacing to avoid overshadowing
• A high standard of insulation
• South facing windows to maximise solar gains in the winter
• Minimal north-facing windows
• Medium to high level of thermal mass exposed to sunlight
• Adequate ventilation for during the summer
• Adequate shading for south facing windows to prevent overheating in the summer

The Importance of Thermal Mass for Energy Efficiency in Houses

As performance requirements for building materials increase and efforts are made to reduce energy consumption, thermal mass can prove to be highly effective and may become increasingly important in the future. As our climate continues to change and we experience more extreme weather conditions, adapting to temperature fluctuations in your home is essential to create a comfortable living space and help you save money.