Whether in one of our factory built commercial buildings, or at home, the occupant's contact with the HVAC system is usually limited to the thermostat and the registers. They are really the only two items of the HVAC systems that the occupants see and feel. So what's the big deal about registers and grills any way? Just put in the cheapest ones available to keep the cost down. I hear what your saying, but let's look at some issues.

The least expensive and previous most widely used supply register is a stamped face, multi-louvered damper type. This is a carry over from the mobile home industry. There are two reasons why this type of supply register will cause unhappy occupants, and Service calls:

1. The face has it's "slots" stamped inward at 30 degrees from perpendicular. This causes the air to blow almost straight down on the neck of the person below, moving papers on the desk, and leaving hot cold spots in the room.
    
2. The damper is a multi-louver (not an opposed blade) damper. This is O.K. for straight heating systems found in mobile homes and residences, but not for an HVAC system. If the factory standard duct system is one size ductboard directly off the Wall Mount, the only way to get equal air distribution to each register is with OBD's (opposed blade damper). Ever had a complaint that the very first room from the unit got no air at all, and the last room in the module got all the air?

Whether your still using the "Modulux" type plank ceiling or a suspended T-Bar type, the register you select makes a difference. More and more the end users are requesting T-Bar type ceilings, which has motivated the Industry to look for registers that have a face size of 24" x 24". This makes a lot of sense, but your selection is still important. Generally, the most cost effective of this style has a perforated face, and no damper of any kind. There are two reasons why this supply register will cause problems for your end user:

1. When the air hits the perforated face, it forms a "pear shaped" air flow pattern directly under it. This occurs no matter what type of directional louvers are behind the perforation. An architect who specifies a $100 register that has a perforated face is wasting the clients money. Once it hits the perforation the air pattern is the same. A perforated register performs best in a 16-20' high ceiling, not an 8' ceiling.
    
2. Dampers are not standard on any inexpensive perforated supply registers. Because of this, dampers rarely get installed, and there is no way to control the volume of air to each one.

THE ONLY PURPOSE OF A SUPPLY REGISTER IS TO MIX THE INCOMING CONDITIONED AIR WITH THE AIR IN THE ROOM IN A QUIET AND DRAFTLESS METHOD.

It does not take an expensive supply register to do this. In fact, some expensive $100 plus registers actually are very poor performers, and $15 ones perform very well.

So here is the suggestion... use a curved blade supply register with either a fixed or adjustable face blade. This will keep the air flow within 12" of the ceiling, and gently mix the air without the occupant ever feeling a draft. The fixed stamped curve blade works just as well as the adjustable curve blade and at half the price. Both of these are available for "Modulux" or T-Bar type ceilings.

Lastly use an OBD damper on the supply registers. This will allow you to control where you want the air to go. Below are two brands and model numbers for you to request that I know are very readily available in the western part of the country, and probably in the East also. Just ask your HVAC supplier to cross reference the brand and model in your area.

Airmate
# T604-0 12 x 12
for cut in type applications

Shoemaker
# 104-0 12 x 12-10
for 24 x 24 T-Bar applications

If you would like some submittal information with which to cross reference to an available brand in your area, simply fax a request into the MBI Home Office and the information will be forwarded to you.