Inventory of Carbon & Energy methodology for windows

Contents

Summary

This methodology represents embodied energy, and carbon dioxide (CO2) emissions associated with window units. The data and calculation methodology is sourced from the Inventory of Carbon & Energy (ICE), version 2.0 life cycle dataset, produced in conjunction with the University of Bath.


The methodology

Emissions model

The methodology is based on factors which describe the quantities of energy and CO2 which are 'embodied' within typical window units. By multiplying the number of windows under consideration by these factors, an estimate of the embodied energy and emissions associated with that quantity can be calculated.

In addition, this methodology incorporates embodied energy and emissions associated with the specific type of air space fill used within double glazed windows.

For both window units and air space fills, the factors assume unit sizes of 1.2 m by 1.2 m.

Model data

Embodied energy and CO2 emissions vary between different frame and glazing types. This methodology therefore represents 11 different scenarios, differentiated by their frame (e.g. aluminium, aluminium-clad timber, PVC) and glazing (single, double) types. In addition, a further differentiation is the basis on which the emissions factors are estimated: the upper, lower or average of the range of values provided in the ICE source documentation.

Each scenario is represented by two data values:

  • embodied energy per window unit (MJ/window)
  • embodied CO2 per window unit (kg/window)

In addition, each scenario is described by a life cycle analysis boundary, indicating the stages in the window life cycle which are represented by the energy and CO2 factors, and in most cases author notes on the sourcing of the data.

Activity data required

Embodied energy and emissions are directly proportionate to the number of windows under consideration, which therefore must be available in order to calculate. In addition, the type of glazing air space fill can be specified. The default fill is simply air, which is represented by the base window unit emissions factors alone.

Calculation and results

Embodied energy and emissions are calculated by multiplying the specified number of windows by the appropriate factors. Unit energy and emissions associated with air space fills are referenced from the associated ICE dataset and incorporated into the base window unit calculations.

Two values are calculated, representing the embodied energy and CO2 emissions attributable to the specified number of windows.


Related methodologies

The ICE methodology for window air space fills is available separately, although it is incorporated into calculations in the present methodology.

Several other methodologies sourced from the ICE database are available. The bulk of the ICE database represents several hundred distinct materials, emissions and energy for which can be calculated on the basis of mass or area.

In addition, there exist several methodologies which provide data and calculations specific to particular types of materials: concrete and timber (including biogenic CO2 emissions).

Details of the sources of data for the ICE database are also available.


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