Archive for the ‘Installing tips’ Category

Duct tape, ductboard tape, flex duct tape-what is the difference?

April 25, 2011

Duct tape, ductboard tape, flex duct tape-what is the difference?

You might have heard the joke that all a DIY person needs is duct tape and WD40.  If something is supposed to move and doesn’t, use the WD40.  If it moves and isn’t supposed to, use the duct tape!

Before the advent of fiberglass ductboard and insulated flex duct, gray cloth duct tape was pretty much all we needed for tin ductwork and a million other uses around the home, and it is still great stuff to have on hand.  Today there is also ductboard tape, sometimes called aluminum foil tape, as well as flex duct tape.

As the name implies, ductboard tape was designed to construct and seal fiberglass duct work.  This tape is pressure sensitive which means you must go over it with a small squeegee to make a good seal.  Ductboard tape is available with or without the UL 181 approvals.  The UL 181 is clearly marked on the outside of the tape and must be used when the ductwork will be inspected.  Surprisingly, the non-UL 181 tape has a higher adhesion rating than the UL 181 approved tape.  Most of our local contractors prefer the nonlisted tape unless a job must be inspected.  Our flex duct tape is a very sticky, black tape designed to bond, protect, hold and patch flexible duct pipe.  Flex duct tape is not recommended for metal duct.

Now you can get the right tape for the right job.  We will discuss the WD40 later!

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Height of Chimney?

March 24, 2011

How high above the roof does my chimney have to be?

The following information is for the typical chimney installation.  Always check your local codes.

Table from Metal-Fab, Inc.

Roof Pitch Minimum Height for gas chimneys, B-vent

Flat to 7/12 (305 mm) 1.0 feet

Over 7/12 to 8/12 (451 mm) 1.5 feet

Over 8/12 to 9/12 (610 mm) 2.0 feet

Over 9/12 to 10/12 (762 mm) 2.5 feet

Over 10/12 to 11/12 (991 mm) 3.25 feet

Over 11/12 to 12/12 (1218 mm) 4.0 feet

Over 12/12 to 14/12 (1524 mm) 5.0 feet

Over 14/12 to 16/12 (1829 mm) 6.0 feet

Over 16/12 to 18/12 (2134 mm) 7.0 feet

Over 18/12 to 20/12 (2286 mm) 7.5 feet

Over 20/12 to 21/12 (2438 mm) 8.0 feet

Metal-Fab B-vent (gas vent) instructions

For oil, wood or coal chimneys the top of the chimney must be at least 3 feet above the highest point of contact with the roof and at least 2 feet above the highest roof surface or other obstruction within 10 feet horizontally from the top of the chimney.

For more detailed installation instructions visit:

Metal-Fab Temp/Guard all-fuel chimneys

Metal-Fab L-vent for oil chimneys

We stock Metal-Fab B-vent for gas and Metal-Fab Temp/Guard for oil, coal and wood.  Temp/Guard is rated for 2100F intermittent and 1000F continuous temperatures.