Energy efficiency is a key requirement for homeowners and tenants. Basements benefit from the surrounding ground improving their energy efficiency. As a consequence, the amount of insulation needed to reduce heat loss through a basement wall can be less than that required on upper floor levels.
The saving is around 35-40% when the same type of insulation is used above and below ground. Alternatively, if the same thickness of insulation is continued below ground, the U-value for the basement walls will be enhanced by around 25%.
For information on insulation, see the Basements for Dwellings guidance document published by The Basement Information Centre.
The simple construction methods and minimum wall penetrations associated with basement construction also lead to minimal heat loss through cold bridging.
The heavyweight nature of basement construction can be utilised to naturally regulate the internal temperature of a home and can be part of an energy efficient strategy for controlling the temperature of the whole house. The Met Office has projected average daily temperature rises throughout the UK, indicating the increasing need for passive methods to cool homes, which heavyweight construction – including basements – is well placed to provide.
For further information refer to The Concrete Centre publications Thermal Mass Explained and Thermal Mass for Housing. The risk of overheating is recognised as a growing problem and the creation of naturally cool spaces in homes is becoming increasingly essential.
Typically the walls of a basement will be externally insulated, this means the thermal mass may be fully optimised as the concrete structure can absorb and release heat within the space. This requires a suitable surface finish that will conduct heat freely, such as wet plaster, paint, or visual concrete.
Waterproofing strategies involving internal membranes or cavity drain systems may reduce the effectiveness of thermal mass in the concrete structure. However, in projects where the inner leaf is made of masonry or concrete, the thermal mass of this may be used, providing it has a suitable surface finish. The use of visual concrete offers potential cost, carbon, and programming benefits, by omitting the need for subsequent use of finishing materials and trades, along with the associated waste produced on site.
Please refer to Part L1 (conservation of fuel and power) of our building regulations guide for further information. All information correct as of 2016 amendments.