Caulking not only protects a house from water and drafts, it saves fuel dollars. But this triple payoff doesn't last forever. Old caulk can crumble, leaving chinks in the siding, open seams between the house and foundation, or crevices around door and window frames.

Stripping out the old caulk and replacing it with a new compound -- often while teetering on a ladder -- is tedious work, and not a chore you'll want to undertake more often than necessary. So when choosing a caulk, look for one that adheres well and applies easily.

The 48 exterior caulks tested recently by the chemists at Consumer Reports were of the three most popular types: latex-based, silicone-based and latex-silicone hybrid. They tested both white and clear (actually translucent) formulations.

All cure to a rubbery solid that expands and contracts with changes in temperature. The elasticity helps them maintain their seal through seasonal changes. Most of the products tested adhered very well -- whether the surfaces bonded were wood, painted or aluminum.

Among the caulks tested, the DAP Acrylic Latex/Silicone, $2.54, and the white HWI Do-It Best Siliconized Acrylic Latex, $2.19, were top-rated. Both are among the hybrids that use silicone only as a minor component.

If a caulk doesn't cure with a dry skin, it may pick up dirt and wind-blown grit. Most clear caulks resisted dirt very well, and their neutral color tended to mask the dirt they did pick up. Most of the white caulks, if left untreated, looked at least a little worse for wear, and some got filthy.

Painting a caulk also helps it shed dirt, but you need one that is compatible with the paint. Most of the tested caulks resisted dirt quite well when painted.

Latex caulks generally hold a coat of paint well and are paintable soon after they're applied. With some, you can caulk and paint almost immediately -- a real plus if you'll be spending a lot of time on a ladder. And the latex-based products clean up with water -- a marked convenience when cleaning up and putting away tools.

Silicone caulks are not normally paintable; paint just beads on them. Some "paintable" silicone products are available, but they didn't paint as well as the latexes.

There are colored, or pigmented, caulks, which are tinted to match popular colors of siding. The chemists have found that the pigmented version of a given brand and type is apt to adhere and weather as well as its white or clear counterpart, and it might be more unobtrusive when in place.

While silicone caulks are touted as more durable than other types, they are the most expensive, and some tested no better than many cheaper latex products. In addition, some silicone caulks were hard to work with. They were stringy, sticky or so stiff to gun or apply that working with them was extremely fatiguing.