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- Proper ventilation fights heat & moisture build up in your attic
- Proper ventilation eliminates mold/mildew which can lead to major health problems!
- Colonizing spores need a food source = heat & moisture. Extreme caution should be exercised if an odor or mold colony is detected!
- All shingle manufacturers void their warranty if shingles roofs are installed over improperly ventilated attics!
- In order to validate the shingles manufacturer warranty you should follow the manufacturers application guide, with ventilation being one of the essential topics to be followed.
- Proper ventilation is not only an important issue for shingles manufacturers, but by building codes, utility companies, HVAC companies, manufacturers of insulation, plasterboard, paint, floors, furniture, doors and windows stress the importance.
3. How to build a ventilated shingles roof/attic?
1. IKO shingles
2. IKO underlay
3. Roof deck
4. Ventilated air gap
5. Insulation
6. Vapour barrier
7. Ceiling
To build a ventilated shingle roof you should create an open space under the roof deck which allows the continuous supply of air through the attic space, air intake at eaves and exhaust as close as possible to the roof peak.
The air gap between the insulation and the roof deck must be 4 to 6 cm. Air should flow in from the bottom of the roof (eaves) and out through the roof peak. Armourvent Multi (Plus) or Ridge Plus are the ideal vents on the roof ridge, Armourvent Standard vents can be positioned close to the ridge.
The continuous air movement follows the laws of physics. Because hot air is less dense it will always rise (getting out through exhaust vents) and once the hot air moves, it also pulls fresh air into the attic (through intake vents). That is how continuous air flow prevents heat & moisture builds up in to the attic. There is no better way to build a roof assembly than to have a ventilated attic!
4. How to properly size a roof/attic ventilation system?
To properly size the ventilation system you must calculate the total required net free area (NFA) of vent opening. To do so you must take into consideration the roof pitch and surface of the “warm” ceiling under the roof/attic (P).
For efficient roof/attic ventilation you should also focus on having an absolute air tight ceiling, which means not to install the HVAC units (Heating, Ventilation, Air Conditioning) inside the attic and to avoid as much as possible the ceiling penetrations. When installing kitchen and bathroom fans, you shouldn’t vent them into the attic space. These heat and moisture sources must be ventilated outside on top of the roof, not under the roof eave because moisture will trap into your attic.
!!! Attention:
For roofs with vapor barriers you can decrease the NFA result with 40% (you need less ventilation).
But in certain regions (coast or mountains) special building regulations may apply! Always follow the local building code!
Note: In hot weather conditions or cathedral roof or insulated roof with pitch between 41° - 85° you should duplicate the ventilation and airflow by using 150 as divisor factor instead of 300!
Example of calculation:
- Roof area (P) = 120 m²
- Roof pitch = 35°
- Total required net free area (NFA) of vent opening = 120m²/300 = 0.4 m² = 4.000 cm²
50% intake & 50% exhaust => 2.000 cm² exhaust and 2.000 cm² intake
Using the technical description of the IKO vents range you can complete the calculation for the exhaust. Following the same algorithm you should complete the calculation for the intake vents (taking in to consideration products technical parameters).
