Decrement delay
The term ‘decrement delay’ refers to the time it takes for heat to pass through an element of a building (such as an external wall or roof). Typically this is taken to be the delay in hours between the peak temperature of the outer surface of the element on a summer day and the resulting peak temperature of the internal surface.
This concept reflects increasing awareness that the thermal behaviour of buildings is dynamic, rather than static, and that thermal mass, as well as thermal insulation, has a significant impact on the energy efficiency of a building. For example, two buildings with identical U-values may perform very differently depending on their decrement delay, with a longer delay likely to reduce peak loads on building services systems.
Materials with a low lambda value (sometimes referred to as thermal conductivity or k-value), high specific heat capacity and high density will tend to have a high decrement delay.
The term ‘decrement factor’ refers to the amount by which conditions are moderated by an element of a building. So in the case of the peak temperature on the outer surface of a building on a summer day, this would be the amount by which the peak is reduced by the time it reaches the inner surface. It is expressed as the ratio between the internal surface cyclic temperature variation compared to the external surface.
To reduce summer overheating, a low decrement factor is required, and a decrement delay of 6 to 12 hours.
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
CIOB and CORBON combine forces
To elevate professional standards in Nigeria’s construction industry.
Amendment to the GB Energy Bill welcomed by ECA
Move prevents nationally-owned energy company from investing in solar panels produced by modern slavery.
Gregor Harvie argues that AI is state-sanctioned theft of IP.
Heat pumps, vehicle chargers and heating appliances must be sold with smart functionality.
Experimental AI housing target help for councils
Experimental AI could help councils meet housing targets by digitising records.
New-style degrees set for reformed ARB accreditation
Following the ARB Tomorrow's Architects competency outcomes for Architects.
BSRIA Occupant Wellbeing survey BOW
Occupant satisfaction and wellbeing tool inc. physical environment, indoor facilities, functionality and accessibility.
Preserving, waterproofing and decorating buildings.
Many resources for visitors aswell as new features for members.
Using technology to empower communities
The Community data platform; capturing the DNA of a place and fostering participation, for better design.
Heat pump and wind turbine sound calculations for PDRs
MCS publish updated sound calculation standards for permitted development installations.
Homes England creates largest housing-led site in the North
Successful, 34 hectare land acquisition with the residential allocation now completed.
Scottish apprenticeship training proposals
General support although better accountability and transparency is sought.
The history of building regulations
A story of belated action in response to crisis.
Moisture, fire safety and emerging trends in living walls
How wet is your wall?
Current policy explained and newly published consultation by the UK and Welsh Governments.
British architecture 1919–39. Book review.
Conservation of listed prefabs in Moseley.
Energy industry calls for urgent reform.