(Image credit: Apartment Therapy )

As I get older, math increasingly becomes a private affair. Once considered to be good at it, I can now be found hiding out in the bathroom, counting on my fingers, when it comes time to divvy up a restaurant bill. Or quietly tapping on my calculator under my desk just to make sure that 60 inches is still 5 feet. (You never know when these things might change.)

The fun part of design for me — I daresay, for most of us — is in the colors, the shapes, and the textures. But when it comes to going green, good design is (at least partly) in the numbers.

Comparing the benefits and costs of different options is an important part of making good decisions. Unfortunately, many of the benefits and costs associated with green design are not easily quantifiable and, thus, not easily comparable.

Exactly how much better will your health be if you choose a low-VOC paint for your bedroom? $10 better? 100 breaths? 1,000 days?

And how much damage to the local ecosystem will there be if you choose to go with those new mahogany floors? $10 worth? 100 endangered species? 1,000 tons of CO2?

There’s no easy way to answer these questions. Indeed, there are countless academics out there right now, earning their doctorates by trying. But while we cannot quantify and compare every benefit and every cost of our design decisions, there are some that are more straightforward than others. And, luckily for us, there are some new tools available to help us out with the math.

At the beginning of the new year, Wattbot is expected to launch its public beta. The young start-up will offer a free online tool for homeowners and renters to use in determining which home improvements will result in the biggest energy savings per investment dollar.

Start by entering some basic information about your home, such as its location, type, size, and age, and answer some simple questions about your priorities as a homeowner or renter, and Wattbot will provide you with a list of the most appropriate energy-efficiency upgrades for you and your home. The more information you enter, the more accurate your results will be.

The tool will let you know exactly how much the upfront investment cost for each upgrade will be, along with your expected monthly energy savings, the length of time that the upgrade will take to pay itself off, and any related financial incentives that are being offered by the government or other organizations.

Whether it's all new insulation, a handful of new windows, or some combination of the two, Wattbot runs the numbers to help you make good, green design decisions from the comfort and privacy of your own home.

And you won't even need that calculator.

Can't wait to get started? Check out a similar tool: the Home Energy Saver, brought to you by the US Department of Energy.

(Image: Wattbot)