Beware of mud dauber nests in your furnace vent

By Russ and Tiña De Maris
A friend of ours was having a fluky sort of problem: His RV furnace wasn't quite up to par; didn't want to light, made some odd noises — the last of the odd noises more like a cannon shot. Kaboom! After determining that various muscles in his body hadn't failed him at a critical and embarrassing time, he hustled out doors from whence the noise had come. Sure enough, on the ground around his furnace vent, the tell-tale remains of a mud-dauber nest. The poor creature had built her nest and lain precious eggs in Joe's furnace vent, only to be swiftly evicted.

First, a word about mud daubers: These solitary wasps gather mud, roll it into balls, and form small dirt nests. Into these small but cleverly constructed cells, a stung (and thoroughly stunned) insect is placed, along with a solitary egg. Mama mud dauber flies away, secure in her buggy knowledge that "junior" will have something to eat when hatched.

While this tear-jerking story from nature may cause some to reach for the tissues, the rest of us swear and curse the day that Mama found our RV. The common reaction — head off to RV MegaPart and pick up a set of "mud dauber screens, an essential companion to your RV furnace." Hold onto your bee-veils, fellow wasp warriors — "essential" ain't necessarily so.

RV furnaces and water heaters, like us, are air breathers. And like us, stick a little something extra over our nose (or vent) and you get what? A bit of an obstruction that can cause problems, particularly for RV appliances. Systems can operate in strange ways when not enough precious pneuma is available, and some RV technicians warn that obstructed windage can actually lead to premature appliance death. If you've priced out furnaces lately, you'll want yours to last a long time. Sticking on one of those so-called "essential" screens can actually cause more harm than good.

What's to do? When not using the rig, TAPE over the vent, and post a note over the furnace thermostat or water heater switch warning the user to remove the tape before firing up the appliance. When in use, make checking out appliance vents a regular part of your "walk around" routine. Worried about getting stung? If you spot a wasp nest, take a stick and remove it at night. We don't recommend shooting the nest with wasp killer — can you imagine what might happen if your wasp spray turned out to be flammable and your furnace "lit off" when you sallied forth with your can of "Bug Off!" Ah, the picture it presents.