Our basement boiler-room (steam-heat, water-heater, other heater,
all gas) has, up high, a window looking out into a grate-covered
pit. (Grate at ground-level.)

For safety from CO, we keep the window open a few inches,
always, allowing boiler-updraft to drag in fresh air.

Problem: leaves (southern Westchester county) and then
snow, potentially 100% covering the grate, dangerously.

What to put over the grate to keep leaves and snow
away from it.

Used to have ugly office-chair rug-protector draped over
it. Recently the boss (of this house) tossed it out,
calling it UGLY. (Well, yes, it was -- but it added
safety.)

Happens that six months ago I (surrepticiously) retrieved from our garbage
some old half-inch pieces of plywood.

My idea is to use one of them to lay one of them across near-grate concrete-blocks,
to return the room to a "safe" condition.

To avoid instant UGLY!-judgement, maybe painting it dark-green
would help.

QUESTION: how to weatherproof it?

What kind of paint, primer, brands, number of coats,
etc?


THANKS!


David