Windows can appear more fragile than surrounding walls. However, window professionals are aware of the many stresses they will have to bear, from the dead weight of the sidewalk to the force of the wind that will hit them. That’s why they give PVC windows all necessary reinforcements to offer healthy and sustainable products.
Why do PVC windows need reinforcement?
PVC is a relatively non-rigid material. Physicists and engineers talk about the modulus of elasticity or longitudinal elasticity (symbol E). In short, this parameter determines the ability of a given body to withstand the pressure of an external force trying to deform it. The higher the Jungian modulus, the less plastic the material and the more resistant to deformation.
The value of the longitudinal modulus of elasticity of steel is 21,000 kN / cm2. This means that one cm2 of steel can « withstand » a load of 21,000 kN without deforming. The modulus of elasticity of aluminum is 7000 kN / cm². On the other hand, Young’s PVC modulus is 240 kN / cm². The difference is obvious and results in PVC windows having additional parts, usually steel, that reinforce their structure. This is traditionally referred to as reinforcement.
Steel reinforcement properties
The extension Metals increase the hardness and durability of PVC profiles. However, their effectiveness does not only depend on the type of material they are made of (steel). In order for the reinforcement to perform its function, it must have the correct length, thickness and geometry.
In terms of length, Reinforcement of PVC windows They should have a circumference, that is, fill the entire length of the frame. It is not enough to just reinforce certain elements of the sash, as sections without a metal support will still be weak points where the window can warp.
On the other hand, the thickness and geometry of the reinforcement influence the so-called moment of inertia, which in turn determines the bending strength of the part. If we simplify it a bit, we can say that the greater the moment of inertia, the more a given body – and not just the material that body is made of – has to bend (and thus deform). Calculations and tests prove that the shape (geometry) of the cross-section of the reinforcing steel PVC windows directly affects the degree of rigidity of their profiles. In order for this degree to be optimal, the geometry of the reinforcement must correspond to the static calculations of the loads that the analyzed window will bear. The goal will always be the same: to find a cross-section that increases the moment of inertia of the reinforcement and therefore increases the ability to withstand deformation of the entire frame.
Finally, it should be noted that the steel reinforcements must have a galvanized layer to protect them from corrosion.
Metal reinforcements have two disadvantages. On the one hand, they increase the weight of the leaves. On the other hand, they influence the heat transfer from the window. In contrast to PVC, steel is a good conductor of heat and the fact that it is one of the components of the window increases the thermal transmittance of the sash by approximately 0.2 W / m2k. Some manufacturers are trying to replace it with fiberglass, a combination of steel and synthetic material, or a combination of rigid PVC, expanded PVC, fiberglass and steel cables. However, these innovative materials can significantly increase the price of the end product, namely the window. In terms of quality and price, the metal frames remain unsurpassed. In addition, they are more environmentally friendly as they are much easier to recycle.
As we can see Reinforcement of PVC windowsAlthough invisible to the naked eye, they are extremely important components. Therefore, when ordering glazing, it is advisable to ask about the technical details of these parts. In particular, whether the manufacturer installed them around the perimeter of the frame (or just in some of its sections), and their dimensions and cross-sectional shape are selected based on mathematical calculations that include size and weight. Sheet plus the physical stresses to which the sheet is subjected.