Function — Louvers permit free air passage, controlling
the volume by their size or design. They diffuse or control direction of air flow by blade design.
Insert louvers — Louvers commonly used in standard
steel doors are of the “insert” type designed to be mounted
into a cutout in the door and an overlapping frame. Inverted “V” blade, “Z” blade, inverted “Y” or chevron-type
blade, lightproof, adjustable blade, grille type, and fusible link self-closing fire door type are available in a wide
range of sizes. Also available from some steel door manufacturers is a pierced louver design. Insert louvers intended for exterior doors or other doors where security is
a consideration should have fasteners or materials specified accordingly.
Note: If a louver door is required to provide security, the
steel door manufacturer should be consulted.
Bird or insect screens are available with many of the
standard design louvers. Where specified, consult steel
door manufacturer for availability.
Weatherproof louvers — True weatherproof designs do
not exist. Some louvers are manufactured to provide a
certain degree of rain protection.
Louver construction — Standard louver frames are a
minimum 20 gauge steel with louver blades of a minimum 24 gauge steel. The louver blades can be welded
or tenoned to the frame and the entire assembly is generally fastened to the door with moldings. Generally, one
molding will be an integral part of the louver, while the
other molding will be detachable. When louvers are installed, the detachable moldings should be located on
the room or non-security side of the door.
Inverted “V” blade and “Z” blade types allow maximum
free air flow with minimum static pressure differential.
Inverted “Y” or chevron blade louver, while offering less
free air space, offers a higher strength factor for schools
and other areas where vandalism or hard usage may occur.
Lightproof louvers are used where light transmission
must be avoided. These provide a minimal free air flow.
Adjustable blade louvers are used where air flow is varied in velocity and control of flow must be provided.
Grille type louvers are normally associated with air conditioning, where air must be diffused in random flow, avoiding higher velocity air flow patterns.
Fusible link louvers are used in fire doors where flames
and intense heat passage must be controlled. The link
release temperature recommended is 135°F (57°C).
These louvers must be labeled and may not exceed
24" x 24". Fusible link louvers are allowed only at the bottom of fire doors. Since closing is heat activated, these
louvers are not to be used on smoke control doors.
Pierced louvers, available from some steel door manufacturers, offer a flush condition and may be furnished
with internal insect screens. Louvers are formed by embossing the door face sheets.
Louver size determinations
As a guide, the following approximate percentages of louver size may be used to determine the free area in a
given size louver:
|Pierced louver |
Inverted “V” inserted louver
Inverted “Y” (chevron) inserted louver
“Z” type inserted louver
Adjustable inserted louver
Lightproof inserted louver
Fusible link inserted louver
50 – 60%
40 – 60%
40 – 45%
40 – 50%
The above percentages assume there is no air pressure
drop from one side of the door to the other. On air condition grilles an air pressure drop is normal. An average
70% of the grille size can be used in computing free area
on doors with air condition grilles.
The percentages noted above are approximates. Consult the individual manufacturer’s literature for the specific sizes and ratings normal to their program.
A combination of glass lites and louvers is common in
steel door work. Care should be taken to avoid specifying too long a narrow lite when a louver or grille occurs in
the bottom of the same unit. In addition, handicap codes
may dictate the location of the louver relative to the bottom of the door.
Standard steel doors can be provided with a variety of louver designs and sizes. This publication contains explanations
and details of louver designs that are most commonly available within the standard door industry.
When specified, doors shall be provided with louvers at the bottom and/or top. The choice of which to use must be
determined by the architect on aesthetic, functional, and economic grounds.
Inverted “V” Blade Inverted “Y” Blade Chevron or Hood-Type Blade
Grille “Z” Blade Lightproof
Cross Section Details
Full louver doors
A minimum 5" (127.0mm) rail occurs at the top and at the
vertical edge of this type unit, a 8" (203.2mm) minimum
rail occurs at the bottom. The percentages noted above
on inserted louvers also apply to this type of door. Pierced
louvers are not available on full louvered doors. Consult
with door manufacturer for exact stile/rail dimensions.
The finish is to be prime painted, except when the louver
is used in a factory prefinished door, in which case the
louver will be finish painted with a color to match the door.
For exterior doors, zinc coated louvers are available where