I am wanting to use several courses of insulating bricks to insulate my chimney as it moves through my attic. These are similar to firebrick, except they have trapped air particles and are typically used in furnaces in layers outside of the fire brick. Note that I would be using these to prevent heat from flowing up and down my masonry chimney, not to keep heat from flowing from the air to my chimney. All around these bricks on the outside will be regular insulation(Fiberglass or Rockwool) and towards the inside between the flue and the bricks/blocks will be filled with perlite rocks.

Has anyone used a similar system? Comments?

I can't exactly tell what you are trying to accomplish by doing all that extra work, but

Why not just build a 'chase' around the chimnney with 2x lumber? Keep at least 2" away from the masonry. Wrap the exterior wiith sheetrock. Meets code here in Oregon.

Mark

The top of my chimney is directly exposed to the outside air. The bottom of my chimney is directly exposed to my inside air, and is acting as my thermal mass. I am trying to get a thermal break in between the top and bottom.

Impossible! You will not be able to accomplish what you have described if you are planning to meet code. The thermal mass ( the fireplace and chimney) must be kept at least two inches away from anything. NO insulation 'wrap' No nothin'! Just airspace!

My recomendation would be to build your 'thermal mass' fireplace, then convert to a class "A" mfg chimney. That will meet code, and there are parts available to do it just fine. It may be better to use class "A" all the way down to the firebox and build a 'chase' around the chimney. Your finished fireplace will look terrific, and perform much better than an all masonry fireplace.

That way you get your thermal mass on the interior, and a superior "factory built" chimney to go up thru the attic to the outside. (Class "A" chimney is insulated pipe, lots of different mfg's) Go with somethig like ICC if it is available in your area.

This will likely accomplish your goal with the added benefit of preventing moisture intrusion, a problem we deal with here in the northwest... lots of rain here, over 100 inches annually.

Good luck on your project, sounds like you're doing an awesome home!

HTH,
Mark