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Community and Q&A

Are 48″ Baseboard Diffusers necessary?

MollyV | Posted in Energy Efficiency and Durability on

Doing flooring and have pulled out the baseboard diffusers from 1959 house. They are 48″ long but the hole in the floor is only 2″ x 12″. Can I replace with a smaller size or is the 48″ length helping to spread the warm air around the room? Note that there are 2 of the 48″ diffusers along the same wall in the 14′ x 17.5′ living room.

Thanks in advance!

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  1. Expert Member
    Dana Dorsett | | #1

    Are you talking about baseboards, or trench heaters with fin-tube? What are you calling "diffusers"? Is that the fin-tube?

    Trench heaters look like this, and are usually at least 3" wide, often 6-12" wide:

    Can you post a picture of what you're talking about (or find a web-picture and link to it)?

  2. GBA Editor
    Martin Holladay | | #2

    If it is a register for a forced hot air system like the one in the photo below, you can probably get away with a smaller unit.


  3. Jon_R | | #3

    Such a diffuser will reduce air velocity, causing the hot air to rise upward (useful under windows). Other designs move the air horizontally, increasing mixing and reducing stratification.

  4. MollyV | | #4

    The diffusers are what Martin posted a picture of. Everything i can find says to buy them based on the cut out in the floor. The floor opening is 2" x 12" so I bought ones that fit that. No idea why a 48" long one would be necessary.

    Thanks all for your responses!

  5. Jon_R | | #5

    A 48" long one would be a good choice under a 48" window. Or get one with louvers that spread the discharge air.

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