A: The vent flapper opens when air pressure builds inside the house, blowing the air through the fan opening and out through the vent pipe system, just as if the fan itself were pushing the air.
The banging occurs as the flapper opens and slams shut when the pressure is relieved, then builds, and cycles endlessly.
Lowered air pressure on the lee side of the building, just like an airplane wing, also helps pull the flapper open as the wind circles around and over the building. Here are several approaches to this issue that will help:
1. Prevent or balance the air-pressure change. By slightly opening a window or integral window or wall vent on the lee side and closing all openings on the windward side, you eliminate or neutralize the pressure change flowing through the house and fan.
2. Eliminate air movement out of the offending pipe. Remove this column from around the pile of last night's discarded fish bones, or remove it from the bottom of the birdcage, and tape it over the fan opening.
This will prevent air movement into the vent pipe. This is not a permanent solution, as fish oil, newspaper and parakeet droppings are all flammable!
Regardless of the flammability, it should be a dramatic illustration of how the problem is occurring and will help you brainstorm further ideas that are particular to your home.
3. Lessen the symptoms. The flapper is there to keep heat in and animals out. Honestly, they don't work well at either, and the building-supply companies should be ashamed at these chronically shoddy products, but that's another column for another day.
You could remove the flapper and install a mesh screen, but it would allow for unlimited heat loss. A plastic louvered vent is more efficient for heat loss and doesn't rattle, but it is prone to warping and deterioration.
4. And finally, those self-sticking rubber or felt cabinet door/drawer bumpers placed on both edges of the lower side of the flapper will eliminate the noise.
Yes, I realize 19 cents spent on cabinet bumpers and 45 seconds to install, with guaranteed results, seems so much easier than all the other mumbo-jumbo experimentation we just went through — but remember, I get paid by the word!
Q: I, too, had a problem about five years ago with rotted wood separators in a concrete patio (from your Feb. 4 column). My solution was to remove and clean out the old wood. Then a quick trip to a used building-materials outlet furnished me with Roman Bricks.
The bricks fit the slot nicely and with a little mortar they look like they were placed there originally. Besides, they also make a nice contrasting demarcation.
A: Thanks for the great tip. I like the way you think, and also admire the way you recycle! Not just the use of recycled building materials, but also use of the word "demarcation," which I don't believe has been within earshot of the lexicon since World War II.
Q : I've just read your Feb. 18 column. Another potential cause for spontaneous combustion — less well-known — is damp charcoal.
Some years ago, we saw a neighbor's outside deck stairs go up in flames due to a (paper) bag of charcoal briquettes left out in the weather beneath it.
A: Thanks for writing!
Darrell Hay is a local home inspector and manages several rental properties. |
