A low tech way to estimate airflows in a building

Greetings from a Brit in Germany inspired by this site. I live a few hours from Krameterhof in Austria and plan to visit this summer. Anyone need a little help understanding the German? It's a rather difficult dialect of German which I also have problems with but if I can help I'd love to.

Anyway here's my idea. while I'd love to build such a Simon Dale "hobbit" house - I'm in the middle of renovating an older bigger one, and doing things like having new windows fitted and insulating the roof space - we still face the problems of air escaping the building. I definitely feel draughts moving air round the place and was thinking today about the use of lit candles to estimate air directions and perhaps by the angle of the flame, the strength.

Anyone got any refinements on this idea? Just putting it out there...

Perhaps temporarily introducing a bit of smoke into the house, just long enough to watch how it flows?

If you don't want to use actual smoke, magic shops sell little tubes of rosin to be mashed between one's fingers until little threads of it fly off into the air. That control might be useful.  Down (and similar bits of fluff) also come to mind.

Spider webs are an elegant way. Spiders are very sensitive to airflow, and build webs where insects seem likely to blow through. I learned that strategy from the following blog post, which I recommend:

http://livingthefrugallife.blogspot.com/2009/11/take-away-lessons-from-our-energy-audit.html

Cobwebs! that's genius! We have a conservatory and I've just been to look at where there are cobwebs growing and indeed as there's a strom outside the webs are moving around in the breeze!

In her blog she recommends silicon sealant which is also clever.