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BEAM P
LUS FOR
N
EW
B
UILDINGS
A
PPENDICES
V
ERSION
1.2
8.8 P
ASSIVE
D
ESIGN
A
SSESSMENT
M
ETHODOLOGY
Copyright © 2012 BEAM Society Limited. All rights reserved.
A - 28
Based on JGJ 75-2003 , the maximum permissible OTTV for residential
buildings with good envelope design will have an equivalent OTTV of less than
or equal to 30 W/m
2
; as such this is taken as the baseline value against which
improvements are calculated.
8.8.1.4 Natural
Ventilation
When outdoor conditions are suitable, natural ventilation, as oppose to
mechanical cooling, can be used to remove heat gains and pollutants from
buildings. This reduces energy consumption.
The wind availability at a window is determined by site massing and
neighbourhood massing which are addressed elsewhere in this guidance. It is
not the intention of this credit to assess the natural ventilation potential in a
specific wind environment, simply to give designers a tool to optimise window
design and spatial to achieve good natural ventilation.
This methodology allows for two methods of compliance, both can receive the
same number of credits - 5.
Prescriptive Approach
The prescriptive approach assesses the quality of natural ventilation within
habitable areas based on a set of requirements. The assessment for the
prescriptive approach shall demonstrate compliance for either the cross
ventilation requirements or the single sided ventilation, but not both.
Note 1: This simplified, prescriptive, approach can only be applied to single
floor units or a single floor of a multi-floor unit.
Note 2: If the building is designed without internal partitions, the designer must
include a reasonable number of partitions to represent typical occupancy.
Cross Ventilation Requirements
Units can be considered to have good cross ventilation when the air flow path
between facade openings if relatively unobstructed. As such, in this
assessment, all windows and internal doors (excluding the main entrance) that
can be opened are assumed to be opened.
Openable windows can be located in different habitable areas, e.g. living
room and bedroom or on differently orientated facades of the same
habitable area. Facades shall be orientated, so that they face, a minimum
of 90
o
difference;
The cross ventilation path between the two shall consist of no more than
two straight lines (one turn only), from the middle of one window to another;
(Figure 8.8.1.4-1)
The angle of turn for the cross ventilation path at the joint of the two lines
shall not be greater than 90
o
; (Figure 8.8.1.4-1)
Cross ventilation path shall not be more than 12m in length for each
habitable area; (Figure 8.8.1.4-1)