HANDYMAN : STEEL GARAGE DOOR CAN GO LONGER WITHOUT A PAINT JOB.

Byline: Peter Hotton

Q: I am replacing my wood garage door that quit after 40 years. I checked 14 dealers and got 14 ideas, including steel, hardboard and plywood. What would be good - the door is flush, not paneled. Steel sounds good (with a baked enamel finish), but I'm afraid it will be dented by all my kids playing in front of it.

A: Steel is good because it is the sturdiest, especially backed with foam insulation. The insulation is unimportant (in an unheated garage), but the foam will help make the steel dent-proof or dent-resistant. Wood is good - it did last you 40 years, but has to be painted regularly. I am not enamored of plywood, no matter how resistant to delaminating it is supposed to be. I feel the same way about hardboard.

Use steel, and let the dents and dings come if they ever do. The baked enamel finish will be good for 10 or more years. After that, you have to keep it painted, but there is little that doesn't need painting, sooner or later.

Q: A part of my vinyl siding behind shrubs developed a green mildew two years ago, which I washed with bleach and water. Now it's back. Is there a any way I can keep it away?

A: It's an old story, this green stuff and black mildew, and this is the season for it, from now until autumn and maybe beyond. That old story is that it occurs on warm, damp surfaces. The shrubs are shading that part of the siding, making it cool; water vapor condenses on that cool surface, encouraging the growth of the green and the black. The green is not mildew but algae (one-celled marine growths), and fortunately can be killed and removed by the bleach. It will not stay away.

So, keep after it with bleach and water.

You could also remove or relocate those shrubs so the siding will stay warm and dry, discouraging regrowth.

One more thing: Pittsburgh Paints has created a product called Mildew Pruf, which it claims keeps away mildew better and longer than plain bleach and water. It is a butyl-like liquid that tends to stick on the siding invisibly, and when mixed with bleach kills the mildew (and algae) and keeps doing its deadly work. The handyman has tried it and thinks its effect is marginal. But it might work for you.

In the meantime, anyone with mildew or algae can use one part liquid chlorine bleach and three parts water for mildew and algae. And, as usual, this warning: Wear skin and eye protection when working with bleach.

When an Indianapolis reader asked if anything dould be done about the fluctuation in room temperature of 3-1/2 to 4 degrees during the course of a heating cycle with his hot-air furnace, the handyman had this answer: Such a fluctuation is not unusual, but perhaps the thermostat can be adjusted to reduce it.

A Massachusetts reader called to say he had the same problem, and was able to correct it by adjusting the temperature control on the plenum, the air chamber on top of the furnace. The temp control controls the heat sensor in the plenum itself, which turns the fan on when the heat comes up and the temperature rises and turns the fan off when the temperature drops after the heat goes off.

There are movable tabs on this temp control, our correspondent noted, set at different temperatures on a dial. The farther apart the tabs are, the greater the difference in temperature extremes.

MEMO: Peter Hotton writes for the Boston Globe.