I like to study houses that are still here after 100 years.

What makes them work? What is unique about them? And what can we learn from them?

I used to think basements were a waste of materials, because you can build above-ground spaces for so much less money. The basement, however, gets the wooden part of your house up in the air, away from the problem of rainwater and wet soils. If you look around for old houses that have survived, they are usually higher off the ground than the 8-inch height that code demands. The ones that aren’t off the ground that high have surely had sills replaced at least once, and probably more than once.

Of course, a poorly done basement can be a nightmare. Basements need good drainage around them. That means drainage materials against the basements walls, crushed stone and drainage pipe covered with geotextiles to remove any water away from the building.

The basement slab should be installed the way a slab foundation would be done, with insulation and excellent water barriers.

When a house is insulated, it is usually the basement that gets ignored. The average house (say a 1,500-square-foot ranch house) can lose about 250 gallons of oil a year through an uninsulated basement. That will certainly perk up the tulips for an early spring – and cost you about $1,000 next winter.

I like to install 2 inches of Styrofoam on the exterior of a basement wall from the footing up to grade level. This way, we have no exposed foam susceptible to damage from the sun or lawnmowers.

Then we need to install insulation on the inside of the basement from the sill down a couple feet below grade. Here we can use fiberglass or foam, since it is out of the weather. This leaves us with a well-insulated basement that is frost-protected.

There is another reason to install insulation this way: ants and termites.

We do have termites in some parts of Maine, and ants and termites like to nest in foam. The logic behind not running foam all the way up the outside of the house is that it creates a pathway for insects to move up into the house undetected.

It might never happen, but let’s not tempt fate. In fact, building codes in the South will not allow exterior foam insulation on foundation walls for this reason.

There are some foam insulations that are supposed to be treated to prevent insect infestation, but there is no clear consensus on what works well. Not yet, anyway.

Until that time, we can practice prudent design that also simplifies the process.

Basements are also called into duty as living space. Here another problem comes into play: condensation in the summer. When hot, humid summertime air hits those nice cool basement surfaces, the humid summer air condenses water onto the concrete. Anything with cellulose – wood, plasterboard and gypsum board or cardboard – will mold and mildew. But that is for next week, when we will make a basement into real living space that does not stink.

Questions for Tom Gocze should be sent to homefront@bangordailynews.net or mailed to The Home Page, Bangor Daily News, P.O. Box 1329, Bangor 04402-1329. A library of his practical home-improvement videos, reference material and a home-project blog are at www.bangordailynews.com/thehomepage.