Soffit cladding has been popular for over 50 years. Originally the idea was just to eliminate having to paint, but that way of thinking has evolved to include a way to provide proper intake ventilation.
To decide what you need, you first need to understand the basics of ventilation. First, think of a chimney which has intake (in your basement down by your furnace) and then it has exhaust which is the part that sticks up through the roof. Air is drawn up from the bottom and exhausts through the top. In the case of chimneys, this is because toxic carbon monoxide needs to be vented out of our living space so that we don’t die.
Roofs work on the same concept without the dire consequences. If your roof isn’t properly ventilated it will not last as long as it could and your energy bills will be higher than they really should be.
Your soffit provides the intake ventilation for your roof. Your roof vents provide the exhaust.
Air flows from the edge of your roof from the underside of your soffit, to your roof vents. Convection allows air to move in such a way as to cool your roof and the attic space above your living space (also referred to as part of the energy envelope) so your summer cooling bills are reasonable.
So what defines whether a soffit should be vented?
If there is an intake hole cut into your soffit, or should be cut into your soffit, you would benefit from a vented soffit product. If the area is not vented and does not require venting, and these areas often include areas such as porch ceilings, then venting may not be needed in that space.
Is there a way to know how much venting I should have?
Yes there is. If you measure the square footage of your roof, you need to follow the 1:300 rule. The 1:300 rule states that for every 300 square feet of roofing, you should have 1 square foot of ventilation.
Must the intake equal the exhaust?
No. Your intake can far exceed your exhaust in order to move the air and create convection, however, the exhaust should be as close to the 1:300 rule as possible to move air.
Is Hidden Vent necessary?
Hidden vent systems rose came into popularity about 20 years ago for discerning homeowners who don’t like the traditional “cheese grater” venting look that is on many aluminum panel soffit vents. Remember that air is sucked up through the intake vents and is drawn up along the roof until it exhausts through the roof vents. This means that there is a constant flow of air, even if it is slight, whenever the sun hits a roof and convection ensues. This constant flow of air tends to collect dust and dirt around intake vents. With hidden vent systems, those vents are hidden, making you unlikely to be able to see dirty vents as you otherwise would with traditional “cheese grater” intake vents.
In short, it is a matter of aesthetics. If you don’t mind it looking messy, then choose hidden vent.
Are there other areas that don’t require soffit venting?
That’s a loaded question I sometimes get, but it comes from a genuine place so I’m comfortable answering it. The answer is yes and no.
Yes, there are areas that you could simply not cut soffit vents in and therefore you don’t need a vented soffit cladding. Some houses have very small soffit or non existent soffit. Optimally there would always be an intake for exhaust for the roof but it is not always practical, even if best practices dictate that you should make it work so that there is intake. If those cavities that flow from the soffit up to the exhaust venting are clogged and there is no way that they can be unclogged, then cutting in soffit vents is an exercise in futility.
However, sometimes when those areas were insulated, through the passage of time, the insulation in those cavities sometimes settles, allowing for a small amount of air to pass from the soffit, to the exhaust vents, any intake ventilation you can provide would be beneficial to move out both heat and moisture from the home.