Air vent recommends 1 square foot of ventilation for every 150 square feet of attic floor space with half the ventilation represented by intake vents and half by exhaust vents such as ridge vents.
Attic ventilation requirements ontario.
However in canada the largest contributor to infiltration is the temperature difference between the inside of the house and the outside causing in a phenomenon called stack effect.
For minimum building code requirements use the 1 300 ratio instead of the 1 150 ratio.
Vents are rated by their net free area or the amount of space for air to flow in or out.
Ridge static attic vents 384 00 minimum sq.
How to correct inadequate attic venting to stop attic condensation ice dam leaks attic mold roof structure damage advice on omitting gable end vents when soffit and ridge venting are installed how to detect roof venting deficiencies attic insulation defects and attic condensation problems best construction practices.
You can calculate attic ventilation requirements by determining the square footage of your attic floor its width times its length and compare that to the total required net free area nfa.
Allows cool dry air to enter the attic.
How to correct improper or inadequate attic or under roof ventilation.
This helps make it easy to calculate how many vents you.
Where the roof space is fairly larger for example cold uninhabited attic spaces with roof slopes of greater than 1 6 the total net vent area should be at least 1 300th of the area of insulated ceiling.
These types of roofs therefore require more ventilation than common attic type roofs.
As ventilation rates vary with wind speed and direction the magnitude of natural ventilation is difficult to predict.
Intake vents located at the lowest part of the roof under the eaves allow cool.
The following product options will allow you to achieve an intake nfva of 528 square inches.
Self contained mechanical ventilation systems serving only one dwelling unit shall conform to note.
Live work units shall be mechanically ventilated in accordance with the requirements of sentence 1.
Of net free area of intake needed at or near the soffit.
The ontario building code required ventilation.
For the 1 150 attic ventilation requirement simply double the amount of exhaust and intake calculated.
The ontario building code vent requirements 9 19 1 2.
Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents.
Vent requirements 1 except as provided in sentence 2 the unobstructed vent area shall be not less than 1 300 of the insulated ceiling area.
2 where the roof slope is less than 1 in 6 or in roofs that are constructed with roof joists the unobstructed vent area shall be not less than 1 150 of the insulated ceiling area.
