Is the liner insulation without foil ok to use?

[sodamark]

Hello,

I've noticed that there are fireplace suppliers that sell liner insulation with foil facing and insulation without foil. What is the benefit of the foil? If I've got a cap that is sealed off from moisture and a kaowool blanket(and maybe a mesh sock) around the chimney liner is there a need for foil? The liner is already installed and will need to be pulled out, but the existing clay flue in the external chimney is in very good condition. This would be for a VC Montpelier insert.

If it helps, the specifics on my install: Vermont Castings Montpelier inserted into a fireplace that is on an external wall, the chimney is in good condition. The installer claimed only the chimney liner was necessary with insulation under the cap, then the flue would fill with warm air. The theory made sense at the time, but that open air space seemed to exchange cold air as quick as warm. I am passed the debate of whether or not to insulate and put in a block-off plate in. I am more curious about foil faced vs. non foil faced insulation.

Thanks for any thoughts. I've appreciated the knowledge sharing I've already read, and like many others, wish I would have stopped in at this forum to arm myself with knowledge before the installer came last year.
Mark

 

[mellow]

I do believe the foil helps reflect the heat back towards the liner and acts as a protection for the insulation.

I have foil faced on mine.

The other thing to do if you are not wanting to pull the liner out is look into doing a pourable insulation like thermix.

 

[sodamark]

Thanks for the reply!

It sounds like there is nothing wrong, or dangerous about unfaced insulation. I'd simply lose an unknown percentage of heat being reflected back, and would potentially scuff up the insulation, or possibly tear it if it got snagged on something? Unless there is another benefit like condensation protection? Or perhaps the foil reflects back a measurable amount of heat.

I thought about the pourable insulation, but started to get the impression based on the suggestions here that for the possibility of future removal, replacement, maintenance, the wrapped liner would be less mess. If I get the same insulating value from the thermix, then I may reconsider using it. Seems easier as long as the flue liner is running right down the center of the flue and I have a block-off.