λ(lambda) - value
Otherwise known as ‘thermal conductivity’ or ‘k-value’, the lambda value is a measure of a material to lead or to resist heat transfer. Units are W/mK. When used in reference to insulation, the lower the lambda, the better the insulation.
The lambda value is used to calculate the thermal resistance of a particular material, or ‘R value’ by combining the lambda value and the actual thickness of the material. Hence R=t/λ
Laminated veneer lumber (LVL)
An engineered wood product that uses multiple layers of thin wood assembled with adhesives. It offers several advantages over normal wood: it is stronger, straighter, and more uniform. It is much less likely than conventional lumber to warp, twist, bow, or shrink due to its composite nature.
Latent heat
The heat released or absorbed by a material during a change of state without change of temperature. For example ice to water or water to steam.
Leaking wet systems
Can be identified using infrared thermography. The method is particularly useful where pipework is concealed within walls, ceilings or floors.
Lean Construction
A project management system that maximises value and minimises waste.
Life cycle analysis/assessment (LCA)
A technique that allows the comparison of the environmental impacts of materials and products. LCA analyses the movement of materials and energy from the point of extraction of raw materials, through the manufacture, use in a building, demolition and final disposal. The analysis provides quantitative data to identify the potential environmental impacts of the material or product on the environment. Ideally LCAs encompass the entire life cycle of a material, but it is common for assessments to be made of more limited periods eg ‘cradle-to-gate’.
Life cycle cost analysis (LCCA)
A method for assessing the total cost of facility ownership. It takes into account all costs of acquiring, owning, and disposing of a building or building system.
Lifetime Homes
A design standard that encompasses 16 design features that ensure that a new house or flat will meet the current and future needs of most households.
Light shelf
A horizontal overhanging element located above eye-level and having a reflective upper surface. Daylight is reflected from the upper surface onto the ceiling and deeper into the space.
Locally sourced materials
By sourcing materials in close proximity to a building, embodied energy is saved through reducing transport miles.
Low-E glazing
By coating the face of the inner pane of glass with metal or metal oxide, short wave radiation from the sun is permitted to enter the building, whilst long wave radiation in the form of heat from the inside is reflected back into the room.
Low-grade heat
Normally used to mean heat at a temperature of ≤ 100°C
LPG - Liquid Petroleum Gas
A by-product of oil refining, LPG is used as a fuel for domestic and commercial purposes, often where mains gas is unavailable.
