PNNL. 2012. Building America Case Study: Green Coast Enterprises, Project Home Again, New Orleans, LA. PNNL-SA-87332, prepared by the Pacific Northwest National Laboratory for the U.S. Department of Energy Building America Program.
Transfer Grilles
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Scope
Pressure Balancing Bedrooms
Option A.
Bedrooms pressure-balanced using any combination of transfer grills, jump ducts, dedicated return ducts, and/or undercut doors to provide 1 square inch of free area opening per 1 CFM of supply air, as reported on the contractor-provided balancing report:
- Refer to the balancing report provided by the HVAC contractor for the bedroom air flows to size the transfer grills and/or jumper ducts.
- Install and seal properly sized transfer grills during framing. Both openings of the transfer grill must have the required free area.
- If transfer grills are not used, install and seal jumper ducts during framing. Both openings and ducts must have the required free area.
- ENERGY STAR recommends that doors are undercut to approximately 3/4 inch above the finished floor.
Notes:
For homes with a date of final inspection through 12/31/2012: Homes are permitted to be qualified without enforcement of this item to provide architects and designers with additional time to integrate these features into their homes.
For homes with a date of final inspection on or after 01/01/2013: Homes shall meet this item to be qualified.
For HVAC system with multi-speed fans, the highest design fan speed shall be used when verifying this requirement.
Option B.
Bedrooms pressure-balanced using any combination of transfer grills, jump ducts, dedicated return ducts, and/or undercut doors to achieve a Rater-measured pressure differential ≤ 3 Pa (0.012 in. w.c.) with respect to the main body of the house when bedroom doors are closed and the air handler is operating
- ENERGY STAR recommends that transfer grills, jumper ducts or dedicated returns be installed and doors undercut to approximately ¾ inch above the finished floor.
- Test the pressures of each bedroom.
| Rooms supply air flow | Free area opening required | Height required for 10 in. wide transfer grill* | Height required for 12 in. wide transfer grill* | Height required for 14 in. wide transfer grill* | Jumper duct diameter |
| CFM | in2 | in | in | in | in |
| 50 | 50 | 6.7 | 5.6 | 4.8 | 8 |
| 75 | 75 | 10 | 8.3 | 7.1 | 10 |
| 100 | 100 | 13.3 | 11.1 | 9.5 | 12 |
| 125 | 125 | - | 13.8 | 11.9 | 14 |
| 150 | 150 | - | - | 14.3 | 14 |
| 175 | 175 | - | - | - | 16 |
| 200 | 200 | - | - | - | 16 |
* Assumes the net free area of the transfer grill as .75 in.
For homes with a date of final inspection through 12/31/2012: Homes are permitted to be qualified without enforcement of this item to provide architects and designers with additional time to integrate these features into their homes.
For homes with a date of final inspection on or after 01/01/2013: Homes shall meet this item to be qualified.
For HVAC system with multi-speed fans, the highest design fan speed shall be used when verifying this requirement.
Option B.
Bedrooms pressure-balanced using any combination of transfer grills, jump ducts, dedicated return ducts, and/or undercut doors to achieve a Rater-measured pressure differential ≤ 3 Pa (0.012 in. w.c.) with respect to the main body of the house when bedroom doors are closed and the air handler is operating
- ENERGY STAR recommends that transfer grills, jumper ducts or dedicated returns be installed and doors undercut to approximately ¾ inch above the finished floor.
- Test the pressures of each bedroom.
| Rooms | Pressure (PA) with Respect to Main Body |
| Bedroom 1 | |
| Bedroom 2 | |
| Bedroom 3 | |
| Bedroom 4 | |
| Bedroom 5 | |
| Bedroom 6 |
Notes:
For homes with a date of final inspection through 12/31/2012: Homes are permitted to be qualified without enforcement of this item to provide architects and designers with additional time to integrate these features into their homes.
For homes with a date of final inspection on or after 01/01/2013: Homes shall meet this item to be qualified.
For HVAC system with multi-speed fans, the highest design fan speed shall be used when verifying this requirement.
Pressure Relief Tips
- ENERGY STAR recommends that HVAC contractors install transfer grills, jumper ducts, or dedicated returns.
- ENERGY STAR recommends that framers undercut doors to approximately ¾ inch above the finished floor.
- If transfer grills are used, contractors must install and seal properly sized transfer grills according to the load calculation.
- If jumper ducts are installed, contractors must seal all seams, gaps, and holes of the ducts and connections.
- If return ducts are installed, contractors must seal all seams, gaps, and holes of the return duct system with mastic and seal the return box to the floor, wall, or ceiling with mastic, caulk, and/or foam.
Pressure Testing Tips
- Prior to testing pressures:
- Verify all supply and return terminations are unrestricted.
- Turn the HVAC system on to cooling mode. If there is no cooling mode, set it to heating mode.
- Verify air is blowing out of the supply terminations.
- Verify the reference pressure is measuring the outdoor pressure.
- Test all pressures by placing the pressure measuring device in each bedroom with the door shut.
Additional Information
For additional information and specific duct testing protocols please refer to RESNET Chapter 8 (Standard for Performance Testing and Work Scope: Enclosure and Air Distribution Leakage Testing).
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Description
For central “forced air” furnace and air conditioning systems to operate properly, the HVAC distribution system should be designed with adequate supply and return registers to provide conditioned air to all parts of the house and return stale air to the furnace for reconditioning. Most HVAC distribution systems are designed with at least one supply register in each room, but typically only a few larger return registers are installed in a home—usually one on each floor level in a central hallway floor or ceiling. To ensure that “stale” air is able to return to these central returns from rooms that have closeable doors such as bedrooms or offices, builders will often rely on door undercuts. These can be inadequate for providing enough air flow, especially when carpet is installed. Inadequate return air pathways can cause pressure imbalances from room to room, which can cause drafts and temperature differences between rooms or floors, leading to comfort complaints. These imbalances can overly pressurize closed rooms, thereby forcing conditioned air into exterior walls, which can result in condensation issues in wall cavities; pressure imbalances can also cause the furnace and air conditioning equipment to work harder than necessary. One option is to install a return air duct in each room. Other options include installing jump ducts or transfer grilles in these rooms. A transfer grille is a grille or register installed in the wall or above the door to connect the closed room with an open space such as a hallway or living room, thereby providing an additional pathway for stale air to reach the centrally located return.
Transfer grilles may be installed by the framer or drywaller. This task should be included in the contract for the appropriate trade depending on the workflow at a specific job site.
How to Install a Transfer Grille
- Determine a location for the transfer grille on an interior wall between the frequently closed room and an open area; preferably this should be the wall where air would have the most direct path to the central return. Mark a location between two studs. Measure and cut openings in the drywall on both sides of the wall to snuggly fit the duct registers. Install the registers. Sound and light transfer between rooms can be minimized in one of the ways described below.
Figure 1 - Installing transfer grilles is one way to balance pressures from room to room 
2. Offset the openings from each other with the grille on the room side located high on the wall (to avoid being blocked by furniture) and the grille on the hallway side located low on the wall. The registers are offset to minimize sound and light transfer. Air flows through the uninsulated interior wall cavity.
Figure 2 - A transfer grille is installed in the wall to connect a closed room with an open area, thus providing an air pathway to the central return air register. The registers are offset to minimize sound and light transfer. Air flows through the uninsulated interior wall cavity.
Or –
3. Cut the wall openings directly opposite each other and install sheet metal baffles offset from each other inside each opening to allow air passage but prevent light passage and minimize sound transfer.
Figure 3 - Hidden sheet metal baffles prevent the transmission of light and sound through the grille
Figure 4 - The baffles are made of sheet metal
Figure 5 - The baffles are offset to allow the transmission of air but not light or sound
Ensuring Success
Duct blaster testing equipment can be used with a pressure pan as part of HVAC commissioning to determine pressure differences at each supply register and to determine if there are adequate pathways for air to return to centrally located returns.
Climate
No climate specific information applies.
Right and Wrong Images
Presentations
None Available
Videos
None Available
CAD Images
None Available
Compliance
ENERGY STAR Version 3, (Rev. 6)
HVAC System Quality Installation Rater Checklist, Duct Quality Installation. Bedrooms pressure-balanced using any combination of transfer grilles, jump ducts, dedicated return ducts, and/or undercut doors to either: a) provide 1 sq. in. of free area opening per 1 CFM of supply air, as reported on the contractor-provided balancing report; or b) achieve a Rater-measured pressure differential ≤ 3 Pa (0.012 in. w.c.) with respect to the main body of the house when all bedroom doors are closed and all air handlers are operating. For homes with a date of final inspection through 12/31/2012: Homes are permitted to be qualified without enforcement of this item to provide architects and designers with additional time to integrate these features into their homes. For homes with a date of final inspection on or after 01/01/2013: Homes shall meet this item to be qualified.
Air Conditioning Contractors of America
Air Conditioning Contractors of America. 1995. Manual T Air Distribution Basics for Residential and Small Commercial Buildings. Manual T provides details on selecting, sizing, and locating supply air diffusers, grilles and registers, and return grilles.
Associated Air Barrier Council
Associated Air Barrier Council. 2002. AABC National Standards for Total System Balance 2002. The manual details the minimum standards for total system balance.
National Environmental Balancing Bureau
National Environmental Balancing Bureau (NEBB) Section 15990 – Testing, Adjusting, and Balancing. NEBB is a certification association whose members perform testing, adjusting and balancing (TAB) of heating, ventilating, and air-conditioning systems and commission and retro-commission building systems. This document is the TAB procedural standards.
This topic is not specifically addressed in the 2009 IECC.
This topic is not specifically addressed in the 2009 IRC.
This topic is not specifically addressed in the 2012 IECC.
This topic is not specifically addressed in the 2012 IRC.
References
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AABC National Standards for Total System Balance 2002
Associated Air Barrier Council (AABC). 2002. AABC National Standards for Total System Balance 2002.
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ENERGY STAR Qualified Homes, Version 3 (Rev. 06) Inspection Checklist for National Program Requirements
EPA. 2012. ENERGY STAR Qualified Homes, Version 3 (Rev. 06) Inspection Checklist for National Program Requirements. U.S. Environmental Protection Agency, Washington, D.C.
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HVAC System Quality Installation Rater Checklist
EPA. 2011. HVAC System Quality Installation Rater Checklist. U.S. Environmental Protection Agency, Washington, D.C.
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Manual T Air Distribution Basics for Residential and Small Commercial Buildings
Air Conditioning Contractors of America (ACCA). 1995. Manual T Air Distribution Basics for Residential and Small Commercial Buildings.
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NEBB Section 15990 – Testing, Adjusting, and Balancing
National Environmental Balancing Bureau. (NEBB) Section 15990 – Testing, Adjusting, and Balancing. National Environmental Balancing Bureau.
