Green gingerbread construction.

As I mentioned earlier, the sprogs and I decided to try our hands at building an entry for the contest to build a gingerbread house using sustainable building design practices. We read up on principles of sustainable design and stocked up on unsulfured molasses and powdered sugar.

Here's what we did and what we learned.

Every engineering project involves working within constraints. For starters, there are the contest rules:

1. Everything must be edible.
2. However half-baked (har har), there must be at least FOUR identifiable sustainable building design elements.
3. Your design must include a minimum of a floor, a door, four walls, a roof, and two windows.

There were other constraints I imposed on our design (like being able to use ingredients and materials we already had on hand rather than having to purchase everything, and making the gingerbread dough and royal icing in such a way that the kids could taste them without worries about salmonella).

And of course, there are the limitations of the materials, about which more in just a moment.

In thinking about a sustainable gingerbread house, we decided to try to incorporate the following design elements:

• A plan that minimized surface area to volume -- so rather than a sprawling ranch house with many wings, we aimed for something more like a New England saltbox.
• Making use of recycled materials -- particularly candy from Hallowe'ens and birthday parties of yore.
• Double-paned windows, for better insulation.

The "glass" for those windows came from recycled hard-candy. (It's worth noting, however, that really old hard candy is more gummy than brittle, so we had to stick it in the freezer in order to be able to smash it to do the windows.)

• "Straw bale" construction -- using a light, renewable material to build well-insulated walls.

Yes, those "straw bales" are Shredded Wheat biscuits. If they had been fabricated with their use as a construction material in mind, I suspect the wheat shreds would have been packed more tightly.

We attached the "bales" to the exterior walls of the house with a layer of royal icing plaster (made with pasteurized egg whites, so that licking the batter was OK). We then put another layer of royal icing plaster on the "interior wall" surface of the bales.

The windows were actually pretty easy to do. Rather than trying to make super-big windows that might not have survived verticality, we opted for lots of smaller windows (using cookie cutters to make the openings in the dough). Since the house pieces are rolled out and baked on pieces of aluminum foil, all you have to do to make a "window" is to gently lift out the cut-out (so as not to rip the foil underneath) and fill the cut-out space with pulverized hard candy bits. Better to put more than you think you'll need than less, especially if you're trying to make thick windows that will keep out the cold.

The oven melts the candy into glass. When the glass has cooled (and not a moment before!) you carefully peel the foil off the back. (In order for the gingerbread to cool properly, this means you're peeling foil off the back up to where the window are while the candy glass is still cooling.)

We ended up putting in a total of nine windows.

• Solar panels -- made of nori. You'd figure that seaweed knows a little something about turning sunlight into energy.

And while it's seasonal rather than a permanent design feature, those (recycled candy) holiday lights are LEDs rather than more energy-hungry traditional lights.

Sad to say, however, we were not able to make this house while abiding by the rules of the contest.

Gingerbread is a heavy building material, and it's also a relatively floppy one. Gingerbread walls aren't good at bearing a load.

There was no way we could put a gingerbread roof on this house without bring the whole thing down. We ended up using a (recycled) cardboard roof instead.

It should be noted that most of the plans I've seen for gingerbread houses make heavy use of things like cardboard, foamcore, and even wood to build a stable structure onto which one affixes the gingerbread. The few exceptions I've seen have requires making gingerbread houses that are quite small.

Probably there are ways around this, and perhaps with more lead time next year we might experiment with gingerbread brick construction.

We send our well-seasoned wishes to those inspired to enter the contest -- we're sure some of you will be able to succeed where we fell short. You have until Midnight PST, December 31, 2007 to enter. And even if you don't, you may want to check out the photos of other people's gingerbread houses in the Bake for a Change Flickr group.