It is highly unlikely that you are going to find a window grille manufactured out of wood. But yes, there are those rare exceptions. Its purposeful design is ingrained into the actual window panes or frame. This design, to all intents and purposes, is usually catering for aesthetic outcomes. It does look rather pretty. There is a natural look and feel and rather old-fashioned charm about it. But strictly speaking, most of your commercial use window grilles will be made from hardcore reinforced steel or metal.
The choice may be yours. It all depends on your current infrastructural requirements. You will need to let a risk management professional or insurance company appointed assessor come and have a look at your premises. Thereafter, he can make a qualified determination as to what type of replacement window grilles are required. But in the first place, why are these replacement grilles. Well, to be quite honest with you, the previous grilles may have done nothing in terms of your necessary security provisions.
Because that, essentially, will be the main reason for installing window grilles in the commercial setting. Its main function, perhaps only function, is to provide your existing windows with an added security feature. It must be extremely difficult for any intruder to break in to your premises via the windows. And in actual fact, the bar needs to be raised still higher. Never mind it being difficult for common or sophisticated burglars to break in to your premises.
It should not be possible to break in at all. There! It has been said. If these are your commercial premises, you should be utilizing your risk management inspector or assessor at scheduled intervals to ensure that all security installations remain intact and unbreakable.