A UL-Listed Insulation That Doesn’t Work


This article is not directed at anyone or any company, but rather at the process, and in the name of doing quality work.

Being in the chimney business for over 20 years has allowed me to witness most kinds of installations and repairs. As in any construction, there are right ways to do things, and there are shortcuts in which some choose to take.

What has been brought to my attention is the improper use of poured insulation around stainless steel liners. From my experience, correctly installing insulation mix around stainless steel liners (to get a zero clearance rating) is next to impossible. Aside from the fact that this installation is widely and incorrectly used, manufactures seem to be pushing installers towards this method.

In the December 2011 Issue of The Chimney Sweep News there is a 5-page article on “Copperfield’s Relining Workshop”. In it, Russ Dimmitt states, “I lean more and more toward poured insulations” (meaning poured mix around stainless liners).

The Copperfield Pro Book states that “HomeSavers Insulation Mix” and “TherMix” are to be mixed to “the consistency of damp potting soil”. The same consistency is common with other manufactures like “Best Mix” from New England Chimney Supply, “Everguard” from Olympia, and “Premier Mix” from National. The installation instructions state that a minimum of 1″ of mix is required around the entire liner to obtain the zero-clearance rating.

When installing a liner using this mix, how do you center the liner in the chimney and ensure that the mix is all the way around the liner and has one inch in thickness?

Let’s say for example that we are lining a basic 8″x12″ flue in a 16″x21″ block chimney and we have removed the tile liner after a chimney fire. There is wood touching the chimney (commonly found in homes) so we need to use zero-clearance insulation around the liner. The stove pipe is 7″, the chimney height is over 25′, and let’s say that the chimney is completely plumb (a rarity). The inside dimensions are 9″x12″ after the tiles are removed. The outside dimensions of a 7″ liner are 7.25″. This leaves less than one inch on either side of the short ends of the block (already not to code, but close so we will continue). Now we need to take into account the fact that when the chimney was built there were mortar joints left between the blocks (it would take countless hours to remove these joints and it is hard to believe that any installers do). These mortar joints can easily protrude out into the opening anywhere from 1/8″ to 1/2″ or more.

I have poured “cast in place” liners for over 15 years. In a “cast in place” liner pour, you use a mix that is a self-leveling slurry. Even with this liquid mix you need a vibrator and centering springs on the liner to ensure that the mix has been centered all the way around the former. (We now install stainless steel liners. We are not pushing for cast in place liners.)

It is impossible to center a stainless steel liner even in a completely straight chimney. There are no centering devices sold with this poured insulation by any manufacturer.Why is this? Because even if you used springs to center this liner, the “damp potting soil” consistency of the mix would not flow consistently, if at all, around the liner.

When asking multiple installers and dealers about how to center a stainless steel liner when pouring this mix and how they know the insulation has made it all the way around the liner, the best answers that I have been given are, “well, you pull up on the liner and that centers the mix”, and “you just know.”

So far we have discussed a chimney that has been completely straight. What if a chimney has a bend as is often found in chimneys with a fireplace? What do you do if a common 8″x8″ brick chimney varies in size? What if the blocks are offset a 1/2″? Most installers would say “close enough”!

Another issue with using this mix is that the removal of a damaged liner with poured insulation around it is a nightmare. The mix jams up on itself as you pull up on the liner. I have removed 5 separate liners and each time I had to uncoil the light wall liner to remove it. What if the mix is poured around a “heavy-wall” liner? Demolition is in order!

As stated by Russ Dimmitt. “in a tight space, the liner can go down without insulation and then you can pour insulation in.” (pg 10, Chimney Sweep News) This statement seems more of a sales pitch than a teacher instructing the correct way to do things. I can only hope that this statement was made about code-complying relines, where the liner didn’t actually require insulation, but was extraordinary to do so.

On page 14 of the same Chimney Sweep News issue, Genevieve Bures states, “In only 30% of the confirmed chimney fire cases I investigated and later reviewed proposed repairs on, have I found that the proposed repairs meet the minimum fire code.” How many of these are improperly poured insulation around stainless steel liners?

It is disturbing to see the leading manufacturers pushing a product that cannot be installed correctly. This mix is an easy way for “fly by night” operations and amateur installers/sweeps to take the easy way out and make a quick buck off of homeowners by doing things the wrong way.

I hope that this article can sway sweeps, installers and manufacturers away from poured insulation around stainless steel liners, and steer them towards quality insulation techniques like 1/2 inch foil-faced insulated blankets or snap wraps which give you a zero clearance rating.

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