Ventilation

One of the keys to an efficient and long lasting, worry-free roofing system is ventilation.

It is important to understand the difference between venting the roofing system, and venting the house (attic). To understand the difference, we need to begin with understanding the reasons for, and effective ways to vent a roof. The following diagram illustrates the basic roof structure. With a properly ventilated and insulated attic, the temperature in the attic and the temperature of the exterior air will be the same, or within a few degrees difference. The three main reasons that a roof needs to have ventilation are firstly to create a way to expel the trapped heat in the attic, secondly allowing the air to circulate in the attic will prevent condensation from forming, and thirdly reducing the temperature in the attic.

When warm air escapes through the ceiling into the attic, it brings with it moisture. If this moisture is allowed to accumulate in the attic it creates the possibility for mold to form, it can also increase the risk of wood rot in the structure. In the cooler months, when this warm moist air contacts the cold roof decking, the moisture can then condense and turn into water inside the roof. This causes leaks, rot, and mold. In a house with a properly sealed vapour barrier, and sufficient insulation, the amount of heat escaping into the attic is reduced. Although these factors reduce the amount of heat and moisture getting into the attic, the warm moist air does still get into the attic. By adding soffit (inlet) vents, cooler and drier air from outside is allowed to enter the attic. This air helps to reduce the temperature inside the attic.
By adding dry air into the attic, it also allows the moisture in the air to be dispersed.

A major concern with any steel roofing system is condensation. As the warm, moist air escapes through the old roof, this moisture will "cling" to the steel. When you add a cold exterior, with a warm interior, you are now creating a prime opportunity for moisture to accumulate (condense) between the steel roof and the old roof. If enough moisture condenses on the back of the steel, you can then have water between the roofs. In the winter, this water can then freeze and create ice between the roofs.

With the Hy–Grade strapping process we are creating an air space between the roofs, and more importantly, also creating air flow between the roofs. This is because of a combination of the design and installation of our system. This begins with our 1x3 vertical strapping. By using the vertical strapping, we are raising the horizontal strapping off of the old roof at least ¾ of an inch, creating the opportunity for air to flow from the eaves all the way to the ridge. The installation of our moldings also plays a part.

Our starter sits on the 1x3s at the eaves of the roof, and is positioned about ½ an inch from the fascia allowing air to enter our system. At the top of our system, the ridge cap sits on top of our shakes, with a support/baffle underneath which allows air to exit the system.

In addition, at the end of each row of shakes, the shakes are cut to fit into our moldings. Any place where a shake is fit into a molding, they are cut back ½ an inch to allow for expansion, also creating additional areas for air to enter and exit our system.