Over the past few decades, big improvements have been made in the art of draught-proofing. Modern windows are airtight, which is great for energy efficiency. But, unfortunately, while we don't want draughts to get into our home, an entirely air-tight interior is bad for moisture and air quality. To maintain a healthy and comfortable living environment, it is essential that your home is well ventilated. For this reason, window manufacturers fit Trickle Vents in the frames of their windows.