Windows with a PTAC below.

A PTAC is a packaged heating and cooling unit that sits in a sleeve through the outside wall. On many apartment and hotel facades the sleeve sits directly under the window, and a louver covers it. When the louver is built into the window frame, the glass, the louver and the mullion between them become one opening, made by one supplier and shown on one drawing. That means four things have to be settled before shop drawings are signed: the sleeve, the airflow, the drainage, and the mullion. At Vistaza the louver band is made for the exact unit behind it, so all four start from the same document: the cut sheet for the unit and its sleeve.

Two ways to build it.

• A separate grille in the wall. The window stops at its sill. The sleeve gets its own opening lower down, with its own grille, flashing and sealant joint. That is two openings to frame and flash on every unit.
• A louver in the window line. The window frame continues down, and the lower band holds a louver in place of glass. From the street it reads as one more pane in the grid. Inside, the unit sits behind the louver and blank-off panels close the remainder of the band.

A VTAC, the vertical version that stands in a closet, needs the same coordination.

How Vistaza builds the louver band.

The band under the glass is made of two things: a blade band, and an insulated blank-off panel around it.

• The blade band. An architectural louver with fixed blades of extruded aluminum, set at 42°. It is built into the Vi6 frame line, and its finish is matched to the window frame.
• The blank-off panel. A 1 inch insulated panel, aluminum on both faces, R-4. It closes every part of the band that is not open to air, and it is sealed on all edges. It is the same color as the louver.

We cut the blank-off to the unit. The opening in it matches the model of the sleeve and the PTAC that sits in it: where the unit takes air in, where it throws air out, how much free area it needs, where the sleeve drains and how. Two buildings with the same window can have different louver bands, because the units behind them are different.

It is rated for free area and for air only. It is not water-rated, and we say so in writing on every louver order, so it is not discovered at submittal review. If the specification says drainable or storm-proof, that is a different louver, and the time to raise it is before ordering.

The louver band is drawn for the Vi6. The smallest unit it is made for is 42 by 16 inches. An insect screen over a PTAC louver is not recommended. Ask before adding one.

1. The sleeve.

Most wall sleeves share a common size, but do not design from memory. Get the cut sheet for the exact unit and sleeve, and take these from it:

• The outside dimensions of the sleeve, and how far it projects beyond the wall.
• The clearance the maker requires between the sleeve and the back of the louver.
• Where the outdoor coil takes air in and where it throws air out.
• The slope of the sleeve towards the outside.

The louver band is sized to the sleeve, not the sleeve to the band.

If the HVAC unit changes during buyout, the louver band has to be checked again, because the blank-off was cut for the first unit.

2. Airflow.

Free area is the part of the louver face that is actually open to air, once the blades and the frame are taken out. Two louvers of the same overall size can have very different free areas.

The unit maker states the minimum free area the outdoor coil needs, and often a maximum pressure drop. With too little, the unit cannot get rid of its heat. It loses capacity, runs longer and may trip on high pressure on the hottest days. Recirculation does the same harm: hot discharge air bounces off the blades and is drawn back into the intake. Many unit makers publish rules for blade angle and baffles. Send those rules with the cut sheet.

We size the open part of the band to what the unit asks for, and close the rest with insulated panel. The net free area goes on the louver submittal as a number, for the size that was ordered.

3. Drainage.

Three kinds of water meet at this band:

• Rain through the louver. A louver that is not water-rated will let wind-driven rain through. The sleeve and the pan behind it have to catch that water and send it back outside.
• Condensate. In cooling mode the unit makes water. It leaves through the sleeve, or through a drain kit to an internal drain. Decide which. Water dripping down a facade leaves stains.
• The window above. The window drains through weep holes at its sill, which now sits over the louver band. That path has to stay open and must not empty into the sleeve.

The louver band has its own drainage. Weep holes in the sill of the louver frame let out the water that gets past the blades. They can be on the outside face only, or on the face and the rear. Where the unit drains inward, the band can be made with no rear weeps, or with an emergency overflow for the PTAC. We set the weeps to match where your sleeve drains and the way it drains, which is one more reason the cut sheet comes first.

The whole opening still has to be waterproofed before the unit goes in. The louver does not replace that.

4. The mullion between.

The horizontal member between the glass and the louver works hard. It carries wind load from the glass above and from the band below. The blank-off panels and the sleeve trim land on it too.

• It has to be engineered for the opening, like any other mullion, and shown on the shop drawings with its reinforcement.
• The structural class on a window test report belongs to the window that was tested. A combined window and louver opening is a different assembly. Ask how the rating applies to it.
• The blank-off panels around the sleeve are part of the thermal and air barrier. Ours are 1 inch insulated panels, sealed on all edges. Ask how they are sealed to the sleeve.
• Where the band sits outboard of the wall framing, flush with a metal panel, the wall does not carry it. Clip angles, sleeves and anchors into the structure are by the installing contractor, and the anchor design is by others.

What the louver does to the ratings.

• Energy. The NFRC U-factor covers the glazed window. The louver, the sleeve and the unit are an opening in the wall by design, and the energy model should count them separately from the window.
• Sound. A through-wall unit is the weak point of a quiet facade. The STC and OITC ratings of the window say nothing about the band below it. Tell the acoustic consultant early that PTACs are planned.
• Air. The seal between the sleeve and the louver frame keeps room air in, and it stops discharge air from leaking back around the sleeve.

What we need to price it and draw it.

• The opening size, width by height, verified in the field.
• The PTAC or VTAC model and its sleeve, with the cut sheet.
• The drainage: weeps on the face, on the face and rear, or an internal drain.
• The color, matched to the window and confirmed by the architect.
• Anything other than the standard 1 inch insulated blank-off.

What the louver submittal should carry.

1. The overall size and the cutout height, dimensioned.
2. The unit and sleeve model, coordinated with the approved PTAC size.
3. The blank-off type, insulated both sides, and the frame position, sealed on all edges.
4. The color, and who approved it.
5. The net free area, as a number, for the ordered size.
6. A plain sentence on the water rating.
7. How the band is supported, if it sits outboard of the wall framing.

A checklist before shop drawings.

1. The cut sheet for the exact unit and sleeve is in hand, and it has been sent with the plans.
2. The minimum free area and any blade or baffle rules from the unit maker are written down.
3. The louver specification has been checked for the words drainable or storm-proof.
4. The condensate route is decided: to the outside, or to an internal drain, and the weeps match it.
5. The mullion between glass and louver is engineered, and it is shown with its reinforcement.
6. The acoustic consultant and the energy modeller know the units are there.

The product and its limits are on the PTAC louvers page. To have the louver band sized to your unit, send the plans together with the cut sheet.