Question: I bought a package of 3 pleated air filters from Flanders. I am not sure how to install them. One side is plain white pleated and the other side is plain white pleated with a X of cardboard. Which side goes toward the furnace? What is the proper furnace filter direction?
As discussed in previous articles here at www.furnacefiltercare.com, there are many different types of filters and often it is difficult to determine which way a furnace filter should be installed.
The filter type that generates the most questions regarding which way 
it should be installed, is the pleated air filter. These filters also happen the be the most popular air filters for home owners. Because of this there are many manufacturers competing for market share and therefore many different designs.
To increase the durability of pleated air filters, manufacturers often extend the cardboard frame across the face of the filter in the form of an X or strips. This enables to filter to maintain it’s shape and prevents 
it from collapsing under the strain exerted on it when air is passing through it.
If , as in this case, there is only one side of the filter that has cardboard across the face. That side should be facing the furnace.
More on the subject of furnace air filter direction:
Which Way Do Furnace Filters Go?
Installing an air conditioner filter or furnace filter incorrectly can have a very negative effect on it’s performance. The ability of a high efficiency filter to remove dust from the air can be drastically reduced if it is not installed properly.
1 comment so far ↓
Thanks for answering my email. The cardboard X made me so nervous. I was praying I didn’t install the filter incorrectly. I also called Home Depot around 7 yesterday morning. They, too, told me I was installing the filter correctly. I know I emailed you around 2 a.m., and I was so nervous about the installation. I said Home Depot opens at 7, so their answer will hold me until I hear from you. I love these filter. Plus, they are good for 3 month. They product efficiency and money efficient. Thank you again.
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