Before adding renewable energy to a building it is best to first make energy efficiency improvements. These type of improvements often have the shortest payback period of all energy improvements. Additionally, the size of any subsequent renewable energy system can be reduced providing additional savings. Often there a number of do it yourself (DIY) tasks that can improvement efficiency.
If you are not the DIY type, you can hire a professional to perform a home energy audit. There are different types of audits from a relatively short and inexpensive walk through to a more thorough examination of the entire building insulation and air sealing along with heating system and major appliances. A blower door test is part of a complete energy audit. The US department of energy has a great webpage to get you up to speed on professional energy audits.
The Colorado State University (CSU) Extension provides help with energy efficiency as well as renewables. See their Home Energy Guide download showing how the average homeowner can save money and improve comfort. They offer a DIY energy audit. CSU also provides a number of energy efficiency and renewable energy calculators and fact sheets.