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Decrement Delay Decrement Factor Jargon Buster

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Decrement Delay Decrement Factor Jargon Buster
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Definitions:

Decrement Delay

Refers to the time it takes for heat generated by the sun, to transfer from the outside to the inside of the building envelope and affect the internal conditions. (EESC ’11)

Taking into account Decrement Delay is essential in the design of lightweight (non-masonry) timber or metal frame building’s walls and roofs.
See: Thermal Lag, Decrement Factor
(GBE BRM ’12 – ’16)

Decrement Factor

The time taken (measured in hours) for heat to transfer between opposite surfaces of a material.

Insulation with a high decrement factor can be used to limit solar over-heating in particularly warm climate conditions.
For example, installing cellulose as a roofing insulation will likely slow-down the heat transfer from a sun-heated roof surface, through to the inside by around 7 hours – or by evening time by which time the sun has set and its heat source is removed.

(GreenSpec AEP ’09 & NGS BRM ’12 & GBE BRM ’16)
See: Decrement Delay, Thermal lag,
(GBE BRM ’12)

Numbers:

Editor:

The following refers to a definition on GreenSpec website.
For the benefit of any doubt I automatically assumes the following is based in providing sufficient insulation to meet U value requirements.
With the added bonus of decrement delay.

Insulation materials offering a high decrement ‘factor’ include:

Wood fibre insulation board (11.3 hr);
Cork
Cellulose fibre (7.3 hr),
Cellular glass

whereas materials with a low decrement factor would include:

Low-density mineral fibre (3.7 hr)
Low density foamed/extruded/expanded plastics polyurethane/ polystyrene (2 hr).

the very lowest include:

Vacuum Insulated Panels (VIPs) (0 hr)

(GreenSpec AEP ’09 & NGS BRM ’12 & GBE BRM ’19)

GBE Slogans:

Build-Light, Insulate-Right, Solar-Tight (Slogan) G#2272 ©GBE
Build-Tight, Ventilate-Right (Slogan) G#
Don’t Cook Your Client G#12200
Fabric-First
Fabric First Materials First Performance First (Slogan) G#17243
Lift Your Loft ©GBE G#13957
Lift Your Loft Stuff ©GBE G#13957
Stuffed-Loft, Squashed-Insulation, Lift-Your-Loft-Stuff (Slogan) G#13957 ©GBE

GBE #Hashtags:

#Knowledge>Skills>Care>PerformanceGap
#BuildLightInsulateRightSolarTight G#2272 ©GBE
#BuildTightVentilateRight
#DontCookYourClient G#12200
#LiftYourLoftStuff G#13957 ©GBE

Information sources:

EESC ’11
GreenSpec AEP ’09
NGS BRM ’12
GBE BRM ’16

Relevance to Environmental Construction

Healthy
Environmental
Resourceful
Appropriate
Competent
Effective
Yardstick

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