On my bathroom floor I can feel a ton of cold air coming through right behind my steam radiator when it is off. Here is a picture of the radiator with the cover on.

Steam Radiator with Cover

Below is a picture with the radiator cover off. I can feel a ton of cold air coming through the vertical gap that you can see in the picture. How can I insulate the gap while making sure that any insulation is heat resistant due to the proximity of the steam radiator? For any solutions proffered, should the metal grate be removed first? It is held in place with nails which I would rather leave in place if at all possible.

Would insulating foam in a can work here? If so, any specific brands I should use? enter image description here

  • 1
    It wouldn't hurt to clean the debris out of the radiator fins while you're in there...
    – DJohnM
    Commented Jan 2, 2018 at 19:37

2 Answers 2


The "metal grate" you refer to appears to be a metal mesh to reinforce and support plaster trowelled onto/into it to form a finished wall. Perhaps the plasterers missed it.

In some jurisdictions the missing plaster may be required for fire/fumes blockage. For example: if there is a garage on the other side of the brick wall.

enter image description here

One type is here: http://tianmaiwiremesh.en.made-in-china.com/product/qyPEcSAlYThr/China-Wall-Plaster-Mesh-Metal-Rib-Lath.html

In any event the simplest approach may be to trowel the plaster into the grill as intended...


Check and measure the gap between the metal mesh and the radiator coil in the back and around the sides. Go to a hardware store or a Home Depot or Lowes store and buy foil covered polyisocyanurate insulating board. This board can be used in applications up to 300 degrees F. Cut the insulation to fit in the gap area, foil side toward the radiator coil. Glue in place with a construction adhesive and also seal all edges. Or you could have a plasterer come in and plaster the area to seal out the drafts.

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