With good modern sealed double-glazing fitted, insect pests tend to be less of a pest simply because it is impossible for them to worm their way in through gaps and cracks. In addition, a temperature controlled low-humidity, low condensation environment such as you get with central heating and double glazing is not attractive to insects.
Although, with double glazing, you tend to keep doors and windows shut and sealed during cold weather, you’ll want to throw them open on fine summer days. This of course can allow pests in. This year – 2011 – with the warm early spring, wasps have been a real pest, and big wasps too. You can buy products for spot-killing or slow-release pest control, but this works best with windows closed and many people don’t want to be exposed to chemicals in the home so these measures are less popular today. Useful tips to discourage insect pests include crushed mint, bay leaves, garlic, clove oil, cayenne, lemon juice and coffee grounds, judiciously placed to be most effective, perhaps hanging in small sachets. Cleanliness, of course, is a first line of defence, especially where food and sugary substances are concerned which can attract ants and cockroaches.
One thing you can do, especially with a conservatory or a kitchen, is fit a fly screen door. These are commonly used in warmer climates to deter pests getting into homes; indeed, where mosquitoes and small flying insects are generally a pest, many properties have screens fitted to all windows and doors so that they can be left open without fear of admitting a houseful of pests. With double-glazed units you can buy screens that will fit without causing interference, sometimes with a roller mechanism to lift them clear when not in use or when you come to open and close the windows.
An effective tip if you seem to get too many spiders’ webs is to clear them away and then wash over the area with a dilute vinegar solution. This lifts any debris dropped by spiders and serves to discourage them for several weeks.