How to find where wasps come from?

For the last about 3 weeks, I started finding a wasp or 2 in my office.
Office is on the 2nd floor.
Wasp is either flying or mostly crawling on the window..
They are sort of - lame, not very active. Easy to kill.
But, that makes me very anxious that there's a large nest somewhere in either walls or attic.

So how in the world do I figure, where they are coming from? Attic lid is shut. I see no holes, tracks, nothing. They just - appear.

On the first floor, laundry room, they got into a crack between siding and window trim. Window is not directly down, it's off my office window and maybe 20-25 ft away. I am suspicious, they got into the walls and make their way up into the office somehow.

Any suggestions, how to track this?

 

Not to forget, I got that gap above the laundry window sealed from the outside. Entire gap. I'll probably hire someone to cut that board out, it's just poorly fitted plank, and replace it with tight seal.

 

I've always just started watching where I thought was most likely and started moving around to new areas based on what I learned in the process. Last tracking like this was a yellow jacket nest after I got swarmed. Found a hole in the lawn for them.

 

That's lawn.
I'm talking room, I spend maybe an hour a day in.

 

About a week ago when the weather turned cold I found 4 live and 1 dead wasps in two rooms. I think wasps in the bathroom may have come in through the exhaust fan vent. A couple in the office may have come in via the attic above. Part of a wall in the office is open in anticipation of some renovation construction. I do not think there is a nest, just individual wasps looking for a place to winter over. I have not seen any in the past 10 days or so.

 

Assuming that the wasp ID is correct; that they are the brownish/reddish wasp (smaller nests) as opposed to the yellow jacket (larger nests), what's happening this time of year is that the colony is dying off as they don't over winter. The queen will stay in the nest and will leave in the spring. She is the only one to overwinter. Common places that they enter into living spaces from are bathroom vent fans as the nest could be where the vent exits the side of the house and the paper nest is blocking the flapper open. Maybe go outside with binoculars. Fireplaces and wood stoves are common as they follow them down and can enter through the barometric dampers, if there is one on the stove.
Winter should solve this problem for you this season. Consider that next spring, re-check/apply caulking, sealing, gasketing, etc. Gaps in any wood work, usually up high in the soffits. If wooden soffits, sometimes a knot hole will fall out, for example. Give the place a good inspection; hopefully the heights won't be prohibitive. Sometimes things like this will drive you crazy though. Large nests are easier to find than the small ones, which this sounds like. Keep us posted.

 

Yellowjackets.
I'm pretty sure, I found where they come from.
I re inspected the trim above the laundry room window, looking for gaps etc, and located another entry point. It's few feet away from the "main entrance" above the window - but on the wall, above which the office corner is! So I figured, they must have travelled up the wall space and into the room.
After close inspection in the room, I found that that corner, ABOVE the mentioned entry point, has a gap between floorboard and carpet, large enough for a wasp to get through and, carpet has several inches of dust, debris, along that corner. Like as if it was all dragged out when crawling out the gap.
So lower entry point had hefty shot of wasp killer and was sealed. And, the one in my office got 2nd shot of same this morning. I modified can nozzle so that straw fits in and shot a bunch of it into the gap.

 

Good job! They don't overwinter, either. In fact, the only bees that do overwinter as a complete colony are honey bees.
Next summer and fall, on warm sunny days, slowly walk around the exterior periodically and visually inspect the soffits, corners, etc for yellow jackets exiting/entering as that is when the nests are large enough to notice. Hopefully you won't have this issue again. Thanks for the update!

 

I do this regularly anyway. house has about 2 feet overhang around perimeter, it's their favorite place to nest. I got cought with this one as it's behind large tree growing in front of the laundry room and under the overhang. Not easy to notice and get to. But it's all sealed anyway.