Like all sales, HVAC sales are not really about "gimmicks." Sales gimmicks are the mark of an amateur who does not really understand what sales is: assessing a lead's needs and responding to them with a product or service.
Having said that, there are HVAC sales approaches that can help you make more sales and increase your commissions.
Ask your lead questions that relate to his heating and cooling needs. By doing this, you will be making him think about what he likes and doesn't like about his current living situation and, further, start thinking about how he could make changes. By doing this, you're having the lead essentially sell the HVAC system to himself rather than have you push it on him.
First, you need to restate your lead's questions back to him to ensure that you understand what he says. A lead won't think you're stupid--rather, he'll be impressed by the fact that you're making sure you understand.
When it comes to answering your lead's questions, answer them in HVAC terms. If you want, you can phrase them in a good-better-best manner, showing how each solution will fix your lead's problems in different degrees.
Finally, avoid jargon. It's great that you know so much about blower door testing, heating solutions and other HVAC terms--but your lead doesn't really care. He cares what the system can do for him.
So rather than answer his questions with technical HVAC terms, answer them with solutions. You can touch on how the system works, but your focus should be on the benefits to the lead rather than the features it has on its own.