The concept of “Conservation and Efficiency Before Renewables” is an important green building practice.
Lets break it down.
The greenest building is to NOT build in the first place. In any green building it is important to constantly ask, “Is this building step necessary? Do we really need to buy this product? Does it really require is to do that? Can we not do it? What previous step make it so that we had to do this next step and can we eliminate both steps…?”
In terms of Brooklyn brownstones, the first green question is, does the brownstone need to be gutted or simply spruced up? There is not right answer but gutting always consumes more.
And if you have to build then the next question is, “How can we use as little materials as possible? How can we build for maximum building life so we don’t have to build again for a very long time (100 years min for a Brooklyn Brownstone)…”
This applies to energy efficiency. How can you make the existing structure are efficient as possible? Fill holes, file holes and then fill holes. Use spray foam, tape, insulation, caulk, molding, splashing, paint, goop, bubble gum and spit to fill absolutely every hole in the building envelope.
Insulate the hell out of the house. Insulate like you are obsessive compulsive. Insulation is cheap. A couple years of energy bills are not.
Make sure all your toilets and faucets are water smart and low flow.
Then attack the larger things: get energy efficient appliances and heating. Get low E triple pane gas filled windows. Become more intelligent with how you use water, heat, cooling and electricity.
Once you have done all the above THEN, and only then, can you start thinking about renewables, i.e. solar PV, solar hot water, wind, water turbnines etc.
The basic idea is LOWER YOUR ENERGY USAGE THEN MAKE YOUR ENERGY SUPPLY GREEN. NOT THE OTHER WAY AROUND.