I have an awful time with these bees every year. They are slowly destroying my western red cedar home.
What to use? Spray?
My house is 3 levels—and raised off ground 3 feet.
I suggest you read our CARPENTER BEE CONTROL ARTICLE. There you will learn all you need to know including how to dust existing holes and spray to stop new ones from happening. The article pretty much covers it all and there are links to our product catalog which has details on each product needed including how to use them, packaging and pricing.
Carpenter Bee Control: www.carpenterbees.com/carpenter-bee-control