Search the library databases for trends or products. Put your product or trend into the search box. At the advanced search page, try narrowing by date and to trade publications.
For Canadian trends in the HVAC market try CBCA Complete (including CBCA Business) and Canadian Newsstand (access to Canadian newspapers online)
Plumbing, Heating and Air-Conditioning Contractors (NAICS 23822) from Industry Canada provides statistics on the number of establishments and on financial returns.