Insulated chimney liners installed in Eagles Nest

What a UL 1777 listing means for a liner

UL 1777 is the standard chimney lining systems are listed to, and the residential code accepts listed and labeled systems that comply with it. The listing covers a system installed as its instructions describe, with the parts named there, not a length of pipe on its own.

That is why we install the liner, top plate, cap, base fitting and any insulation as one assembly instead of mixing components from different makers. Your paperwork records the product, so a later sweep, inspector or buyer can see exactly what was installed and check it against the same instructions we followed.

Three situations where insulation helps

One manufacturer lists three situations where an approved insulation wrap enhances the performance and life of the chimney. We explain which, if any, apply to your chimney before you decide, and whether insulation in your case is a requirement or a recommendation.

Insulation also changes the space the liner needs, so the decision comes before the route is proven, not after.

• An installation that must meet UL 1777 at zero clearance to combustibles
• A chimney located on the outside of the house
• Appliances expected to produce low flue gas temperatures

One run, or two joined correctly

Where a single length will not do, one manufacturer allows two lengths of flexible liner to be joined with its listed connector. Improvised joints are not part of the listing.

We plan the liner as one run where the chimney allows, and use only the connectors the instructions name when it does not. A joint also has to sit where it will not catch the liner on its way down, so its position is planned from the proven route.

Rust streaks below an old liner top

Rust running down the crown or the masonry below a metal liner top can come from a failing cap, corroded clamps or a liner not suited to its appliance. The streak shows where to look, not what failed.

We check the cap, plate, clamps and liner end, and tell you which part needs attention. Sometimes a single part can be replaced, and sometimes the corrosion reaches the liner itself, in which case replacement of the whole system is the honest recommendation.