Transfer Grilles

Scope

Installing transfer grilles is one way to balance pressures from room to room
Installing transfer grilles is one way to balance pressures from room to room

Provide for pressure balancing between bedrooms and the rest of the house.

  • Install ducted returns or a combination of ducted returns, transfer grilles, jump ducts, and/or door undercuts in bedrooms to allow pressure balancing between bedrooms and the rest of the house in homes with ducted heating and cooling systems by providing a path for room air to return to a central air handler thereby increasing the volume of conditioned air circulating in the room.
  • ENERGY STAR Certified Homes requires that the dedicated return ducts, transfer grilles, jump ducts, and/or door undercuts together achieve a rater-measured pressure differential of ≤3 Pascals (0.012 inch water column) with respect to the main body of the house when bedroom doors are closed and the air handler is operating on the highest design fan speed. A rater-measured pressure differential of ≤5 Pascals (0.020 inch water column) is acceptable for rooms with a design airflow ≥150 cfm.
  • If transfer grilles or jump ducts are used, refer to the balancing report provided by the HVAC contractor for the bedroom air flows to size the grilles or ducts. If a balancing report was not provided, the flow of the supply register when the air handler is on high speed may need to be measured using a flow hood, anemometer, or other flow measurement tool. Ensure that both openings have the required free area. Seal all seams, gaps, and holes in the ducts and connections.
  • Test the pressure differential with the bedroom doors closed.

See the Compliance Tab for related codes and standards requirements and criteria to meet national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR Certified Homes, and Indoor airPLUS.

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. 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. Pressure imbalances can also cause the furnace and air conditioning equipment to work harder than necessary. A well-designed return air strategy is critical for the performance of the HVAC system in an energy-efficient house, which may have lower airflow requirements to meet the lower heating and cooling loads (Burdick 2011). The return air must have a clear path back to the air handler from every room that has a supply outlet, with the exception of bathrooms or kitchens due to the potential for spreading odors through the house (Burdick 2011).

Most forced air systems use central return registers consisting of one more centrally located return registers that are ducted to the return side of the air handler. To provide a pathway for air from rooms with closed doors to these central return registers, builders can use door undercuts or install transfer grilles or jump ducts.  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

  1. 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.

Installing transfer grilles is one way to balance pressures from room to room

Figure 1 - Installing transfer grilles is one way to balance pressures from room to room  Reference

  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.

Transfer grilles allow air flow between rooms

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.  Reference

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.

Hidden sheet metal baffles prevent the transmission of light and sound through the grille

Figure 3 - Hidden sheet metal baffles prevent the transmission of light and sound through the grille  Reference

The baffles are made of sheet metal

Figure 4 - The baffles are made of sheet metal  Reference

The baffles are offset to allow the transmission of air but not light or sound

Figure 5 - The baffles are offset to allow the transmission of air but not light or sound  Reference

Ensuring Success

To determine if an adequate pathway exists for air to return to centrally located returns, the following room-to-room pressure measurement can be used:

  1. Turn on the air handler to high.
  2. Close all interior doors.
  3. Using a manometer, connect tubing to the input port. The reference port for the differential pressure measurement can remain open.
  4. While standing in the center of the house or hallway, place the tubing from the manometer under each door and record the pressure difference from each room with respect to the main body of the house (note the presence of a negative or positive sign). The bedroom will typically be pressurized (positive) when the doors are closed.
  5. ENERGY STAR requires that rooms should not be pressurized or depressurized by more than 3 Pascals for any room being supplied with less than 150 cfm of conditioned air. If the supplied airflow to a room exceeds 150 cfm, a threshold of ≤5 Pascals is required. These are good metrics to strive for regardless of whether or not pursuing ENERGY STAR certification. 

Climate

No climate specific information applies.

Training

Right and Wrong Images

Presentations

None Available

Videos

  1. Transfer Grilles (1)
    Publication Date: July, 2015
    Courtesy Of: Tamarak

    Video describing how to install transfer grilles.

  2. Transfer Grilles (2)
    Publication Date: July, 2015
    Courtesy Of: Tamarak

    Video describing how to install transfer grilles.

CAD Images

None Available

Compliance

The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

ENERGY STAR Certified Homes

ENERGY STAR Certified Homes (Version 3/3.1, Revision 08), Rater Field Checklist:

6. Duct Quality Installation 

6.2 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 with respect to the main body of the house when all bedroom doors are closed and all air handlers are operating. See Footnote 34 for alternative.34

Footnote:

(34) Item 6.2 does not apply to ventilation or exhaust ducts. For an HVAC system with a multi-speed fan, the highest design fan speed shall be used when verifying this requirement. As an alternative to the 3 Pa limit, a Rater-measured pressure differential ≤ 5 Pa is permitted to be used for bedrooms with a design airflow ≥ 150 CFM. The Rater-measured pressure shall be rounded to the nearest whole number to assess compliance.

ENERGY STAR Revision 08 requirements are required for homes permitted starting 07/01/2016.

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.

2009 IECC

This topic is not specifically addressed in the 2009 IECC.

2009 IRC

This topic is not specifically addressed in the 2009 IRC.

2012 IECC

This topic is not specifically addressed in the 2012 IECC.

2012 IRC

This topic is not specifically addressed in the 2012 IRC.

2015 IECC

2015 IRC

 

This Retrofit tab provides information that helps installers apply this “new home” guide to improvement projects for existing homes. This tab is organized with headings that mirror the new home tabs, such as “Scope,” “Description,” “Success,” etc. If there is no retrofit-specific information for a section, that heading is not included.

In existing homes, transfer grilles will typically be installed as direct through-the-wall transfers. High-low transfer grille configurations are better able to minimize sound and light transfer but they require a more destructive/intrusive installation. However, there are some grille insert options for through-wall transfers that minimize sound and light transfer. A good rule of thumb is to provide a grille-free area (this is not the grille size, but the available opening area of the grille) of ≥1 square inch for each cubic feet per minute of supply air to a room.

How to Install a Transfer Grille in an Existing Wall:

  1. Verify location of studs over the door or other area where a transfer grille is to be placed. A stud finder can be useful for this task.
  2. Measure the transfer grille frame dimensions and transfer this onto the wall surface. Use a bubble level to properly align the frame outline.
  3. Cut through the wall board. You will need to be careful not to cut or disturb wiring or pipes in the wall assembly. This may require careful exploration into the wall cavity before cutting the full opening required for the transfer grille. If you have an attic above the interior wall or a basement below the wall, one way to confirm the existence of wiring and piping in the stud bay in which a transfer grille is to be installed is to check the top plate or sill plate to see if any wires or plumbing pipes are entering the framed bay. Still, be aware that electrical wires typically run around a room parallel with the floor, so be mindful of the location of electrical outlets and fixtures for potential clues to the location of the wiring. It is also a good idea to shut off the electrical circuit in the area in which you are working as an additional precaution. Also be aware of where the water line shut-off is prior to beginning any work in the walls.
  4. Set the frame in place and trace the outline on the backside of the adjoining wall.
  5. Cut through the opposite wall.
  6. Depending on the transfer grille unit, you may have another frame to slide into the opening from the opposite side.
  7. Secure the grille faces using screws.

See the Training tab for videos showing how to install transfer grilles.

If cutting through painted surfaces, check for lead paint and mitigate as required. If cutting through plaster and wood lath walls, additional care will be required to minimize crumbling of the plaster. High-speed cutting tools, such as powered multi-tools or an angle grinder with a diamond blade, can assist in making clean cuts through the plaster and lath (but will create a considerable amount of dust, so you may want to have a vacuum operating next to the tool while cutting. Another trick is to apply painter’s tape on the wall prior to marking off the area to cut on the tape. This can help control crumbling of the plaster during the cut.   

More Info.

Access to some references may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

Case Studies

  1. Author(s): PNNL
    Organization(s): PNNL
    Publication Date: September, 2010

    Case study about new home construction in the hot-humid climate, part of a project building 100 new homes after hurricane Katrina.

References and Resources*

  1. Author(s): Associated Air Barrier Council
    Organization(s): Associated Air Barrier Council
    Publication Date: January, 2002
    Standards book discussing changes, additions and enhancements over the 5th edition of the AABC National Standards for Total System Balance.
  2. Author(s): Air Conditioning Contractors of America
    Organization(s): Air Conditioning Contractors of America
    Publication Date: June, 2009

    Standard providing guidance on how to select, size, and locate the supply air diffusers, grilles and registers, and the return grilles.

  3. Author(s): DOE
    Organization(s): DOE
    Publication Date: April, 2017

    Standard requirements for DOE's Zero Energy Ready Home national program certification.

  4. Author(s): EPA
    Organization(s): EPA
    Publication Date: December, 2015

    Document outlining the program requirements for ENERGY STAR Certified Homes, Version 3 (Rev. 08).

  5. Author(s): National Environmental Balancing Bureau
    Organization(s): National Environmental Balancing Bureau
    Publication Date: January, 2005
    Standard that includes testing, adjusting and balancing (TAB) to produce design flows for air and hydronic systems.

Contributors to this Guide

The following authors and organizations contributed to the content in this Guide.

Building Science Corporation, lead for the Building Science Consortium (BSC), Steven Winter Associates, Inc., lead for the Consortium for Advanced Residential Buildings (CARB), both DOE Building America Research Teams, and the Pacific Northwest National Laboratory

 

Last Updated: 04/26/2017

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