I have a study that normally has the door closed and all the windows are very tight, modern windows, yet I keep finding insects, especially flying insects like lady bugs and wasps in the room.

Can insects get into ducting from the outside? Is there some kind of external vent in an HVAC ducting system?


They can come in with you, on your clothes in or on bags etc.

Unless you have an airlock entry system with strip and new clothes etc.

They will also come in through any gaps and there are few constructions that are 100% sealed. There are tests that can be done to check this.

As for vents they are easy routes for insects, unless there are grilles or filters on each vent which have to be fitted properly - any gap and they get through.

As for HVAc, that depends on the system, if there is a heat exchanger to prevent outside air and inside air from mixing then insects cannot cross but if the outside air is heated or cooled and there is no filter or the filter is damaged or poorly fitted then insects can get through.


Code requires makeup air vents to have screens so the hvac system should not be the source, back draft dampers in range hoods commonly get stuck open but normally have grease grills the silver foil mesh that you have to clean if that is gone it could be a path or the bathroom exhaust fan. My last home we had 1 wall on the lower level that had thousands of ladybugs and they found cracks and small openings, our local plant nursery would come and collect them (they might pay if you have enough or collect them yourself) we just wanted them gone because they could find ways into the house dozens if not hundreds a day collecting them did help and finding / sealing the very small cracks they were using to get inside many were at the fireplace and around 1 window. That house only had electric base boards so no central air or make up air until I converted to gas and a ac unit. If the screens at your soffit vents are damaged that is another possibility for entry but the hvac system would not be a normal entry point.


There are quite a few ways insects can get in thought an ac system. There are electrical connections that run through conduit that insects can fit along side wires, ive had many insects trapped in bathroom light fittings. They can also get in through condensate piping that is meant to take water out of the building but can sometimes provide a way in. As said in another answer on clothes and bags is the usual route.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.