Ventilation is one of the key ways to prevent condensation and ensure airflow is consistent throughout a roof. In this short guide, we’ll look at roof vents and we’ll figure out the number of vents needed for a roof by using simple formulas of multiplication and division.
Calculating the total airflow required
Firstly, you want to find out the length of the roof in millimetres (mm). After doing this, multiply the length in millimetres (mm) required by the continuous airflow needed.
Length of roof x continuous airflow = total airflow
For example, for a 20m roof requiring 10mm in continuous airflow, you’ll want to first multiply 20m by 1,000 to get to 20,000mm to s. Then multiply 20,000mm by 10mm, and you’ll get 200,000m2 airflow meaning this is the amount of airflow required for your home.
20,000 (length of roof) x 10 (continuous airflow) = 200,000 (total airflow)
Figuring out the number of vents
Depending on the vents you are using, the amount needed for your roof will differ on the type of vent you require to suit your tile and the requirement of continuous airflow. For example, if you’re using a single pantile Klober roof vent which has a ventilation area of 10000 mm2, then you’ll need 20 vents for your roof. However, if you’re using a uni-slate tile vent which has a ventilation area of 6500mm2 meaning, you’ll need 30 vents.
To calculate this, you’ll need to use the formula below by dividing the total airflow by the ventilation area of the vent.
Total airflow ÷ ventilation area of the vent = vents required
Working out the centres for vents
Lastly, you need to work out the distance between each vent. To do this, you have to divide the length of the roof, for example, in our case, 20,000mm by 10 (vents). You should get 2,000mm as your result, meaning this is the distance you need to separate your vents.
Length of roof ÷ ventilation area = distance between vents
Examples of ventilation areas by vent
To find out the correct ventilation area for a roof vent, we highly recommend reading up on the manufacturer’s technical datasheet. This way, you’ll get information that’s reliable and easy to cross-reference for your roofing project.
Here are some examples of ventilation areas by vent:
| Roof Tile Vent | Ventilation Area |
|---|---|
| Klober Uni-line Vent | 6500 mm2 |
| Klober Single Pantile Vent | 10000 mm2 |
| Klober Double Pantile Vent | 10000 mm2 |
| Klober Double Roman Tile Vent | 10000 mm2 |
| Klober Uni-Plain Tile Vent | 6000 mm2 |
| HD TV10/5 Tile Vent | 2,000 mm2 |
| HD TV10/8 Tile Vent | 10,000 mm2 |
| HD TV15/2 Tile Vent | 15,000 mm2 |
| HD TV15/7 Tile Vent | 15,000 mm2 |
