Venting Glass Block

Venting Glass Block is a not a good idea.  As a masonry product, it’s not really made to have a plastic vent inserted into it.  Some of the glass block windows you may have seen that are close to 100 years old do not have them in them and if you really think about it, when was the last time you actually opened, or even wanted to open your basement windows?

Before considering venting, consider this — many homeowners run a dehumidifier in their basements.  For the most part, a basement is cooler than the outside air in the summer.  Outside summer air in Wisconsin tends to be humid.  A cool basement that has run a dehumidifier can be dry.  If you open a basement window, when that dry cool air comes in contact with the warm moist air, it is going to condensate and cause additional moisture in your basement.  That’s not a good thing.  So let’s break down some of the pros and cons.


  • You get a small amount of air into the basement.  After the size of the frame of the vent and the openable (sash) of the vent, the amount of net air is very limited.  Usually a window vent takes the place of two blocks of glass.


  • Vents are plastic.  Vents used to be made out of metal.  The metal vents were durable, but leaky and they conducted cold which is a big problem in northern climates.
  • Plastic breaks and cracks.  They reduce the durability of a glass block window.
  • Hinges attached to plastic are weak points.
  • Actual ventilation (air) from the outside is limited.
  • Light can be limited as part of the vent is a frame and part is a sash.
  • Before making the decision to add a vent, ask yourself when was the last time you actually opened your basement windows.  If the answer is never, then skip the vents.
  • If the humidity and heat outside meet a basement window in a cooler basement, it will condensate and basements that otherwise may not have had moisture, can start to have problems.

So why do companies even offer vents?  It’s because people request them and companies need to be able to offer what their customers demand, even if the customer took bad advice.



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