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CSA A93-2019 pdf free download

CSA A93-2019 pdf free download.Airflow ventilators for the unoccupied spaces of buildings.
This Annex contains guidelines for the passive ventilating of roof spaces between roof decking and ceiling cladding to minimize moisture and condensation accumulation, which can damage building components and impair insulation efficiency, and to reduce the high levels of heat gain, thereby improving summertime comfort.
The use of mechanically operated ventilators and wind turbine ventilators and the ventilating of flat roofs are beyond the scope of the recommendations given in Annex A. Such ventilating should be engineered to suit specific building designs and prevailing conditions.
A.2 Passive airflow ventilating
The aim of passive airflow ventilating is to create a condition whereby there will be a continuing and total change of air in the ventilated space by natural means, the air entering the lowest regions of the ventilated space and being expelled through the uppermost regions; and to ensure that the rate of air change is sufficient to prevent accumulation of harmful moisture condensation (see Figure A.1).
It is impossible to make recommendations covering all circumstances, and discretion is required to achieve good ventilation while guarding against infiltration of precipitation, short-circuiting airflows, and reverse downward flow.
The potential for achieving the desired upward continuous flow of air is greater if more inward ventilation is provided at the lowest level than outward ventilation at the highest level.
A.3 Amount of ventilation
For normal ceiling-roof spaces, there should be a minimum of 35 cm2 of total vent area for each square metre (1 ft2/300 ft2) of projected ceiling area (see Figure A.2), or the unobstructed vent area should comply with the vent requirements in the applicable building code, whichever is most pertinent for the requirements of the space.
For cathedral ceilings, there should be a minimum of 70 cm2 of total vent area for each square metre
(1 ft2/150 ft2) of projected ceiling area (see Figure A.3).
Of the total vent area, 55% should be in the eave soffits and 45% located near the ridge(s) (see
Figure A3).
A.4 Ventilating capacities of ventilators
Ventilators conforming to this Standard are marked to show their ventilating capacities in terms of net free area or airflow rate. Optionally, the ventilator may be marked with the equivalent net free area, as calculated in Clause 8.3, using the following format:
[Airflow rate) (equivalent to ICalculated net free area))
Note: Example: 2000 ms/h (equivalent to 2600 cm2)
A.5 Location of ventilators
Individual soffit ventilators should be distributed around the building to provide a flow of air to all regions of the ventilated space. They should be spaced uniformly along the soffit and/or be continuous, and should terminate as close as possible to eave ends.
Ridge roof ventilators should be centered over the ridge(s), uniformly spaced, or continuously joined, and positioned equidistant from roof ends.CSA A93-2019 pdf free download.

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