We currently work from the Food Safety and Hygiene (England) Regulations 2013, made under Regulation (EC) No. 852/2004.  The EU Regs provide the legal requirements and state that food businesses must take reasonable precautions to prevent food pests, namely rats, mice, cockroaches and flying insects gaining entry into food storage and preparation areas. This is to prevent the contamination of foodstuffs.   Regulation (EC) No 852/2004 Annex II Chapter IX para 4


Annex II, Chapter II covers the specific requirements in rooms where foodstuffs are prepared and states at Chapter II, paragraph 1(d): windows and other openings are to be constructed to prevent the accumulation of dirt. Those which can be opened to the outside environment are, where necessary, to be fitted with insect-proof screens which can be easily removed for cleaning. Where open windows would result in contamination, windows are to remain closed and fixed during production;


We would also use this section to require repairs to any damaged screens (or cleaning of the same) and to ensure that windows are kept closed if there are no screens and are being used for ventilation.

Flydor Strip Curtain Insect Screen Door