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Look For and Install Attic Vent Baffles

Materials Cost: 1
Difficulty Level: 2

Introduction

Look at the attic to make sure there are baffles in place at soffit vents to keep wind from blowing insulation; if they are missing install them. 

Why

Effective attic ventilation is important to prevent ice dams from forming on the roof in the winter and to keep the attic cool during the summer. Attic baffles are foam or cardboard channels that extend from the floor of the attic along the eaves up along the underside of the roof deck to provide a path for ventilation air coming in the soffit vents to flow up the underside of the roof past the insulation. Baffles keep insulation from blocking the soffit vents and keep air from blowing through the attic insulation (Figure 1). If the attic baffles have fallen down or if there are no baffles, baffles should be properly installed.

The soffit dam and baffle allow air to flow through the vents without disturbing the insulation covering the top plates
The soffit dam and baffle allow air to flow through the vents without disturbing the insulation covering the top plates
The soffit dam and baffle allow air to flow through the vents without disturbing the insulation covering the top plates
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Figure 1. Baffles provide a path for ventilation air to flow up from the soffit vents along the underside of the roof deck and out of the attic through ridge vents near the top of the roof to cool the underside of the attic without disturbing the insulation along the eaves (Source: PNNL).

What You'll Need

  • A ladder 
  • A headlamp or flashlight
  • A camera or camera phone to take pictures
  • An N95 or better mask
  • A disposable coverall suit
  • Work gloves
  • Baffles
  • A heavy stapler and staples

1. See if you have a vented attic.

Look under the roof eaves, on the long sides of your roof, not the pointed gable ends. Do you see vents in the soffits (the wood panel covering the underside of the eaves) as shown in Figure 2? They may be nearly continuous or spaced every couple of feet. They may be visible through the windows from inside, as in Figure 3. If your attic has soffit vents, it is a vented attic - there should be insulation on the attic floor and everywhere you have a soffit vent, you should have a baffle installed in the attic to keep wind that comes up through the vent from blowing the attic insulation away from the eaves. If your home does not have soffit vents, it likely has an unvented attic and does not need baffles. Some attics on new homes are vented with a new type of -low-profile vent that is installed just above the insulation in the roof, instead of in the soffit (see Figure 4). Roofs with these vents do not need soffits because the vent is installed above the insulation. This guide is for homeowners who have vented attics with soffit vents like those shown in Figures 2 and 3. 

Figure 2. This is a soffit vent; it provides ventilation for a vented attic (Source: PNNL)
Figure 3. In this photo, the soffit vents are visible through the window (Source: PNNL).
Figure 4. The dark horizontal lines indicated by blue circles on this roof are actually low-profile roof vents that take the place of soffit vents and are installed above the insulation level so no baffles are needed (Source: PNNL).

2. Go into the attic.

Gain access into the attic. If access is through a hatch in the ceiling, make sure items below are moved well away from the access hole and lay a tarp on the floor to catch falling insulation before setting up the ladder and pushing open the hatch. Wear gloves and a mask when entering an attic insulated with blown insulation (Figure 5). Eye protection and disposable coveralls are also recommended to protect your skin and eyes from loose fiberglass or cellulose insulation.

Figure 5. This attic access hatch is in the master bedroom closet ceiling - be prepared for falling insulation when you lift the hatch (Source: PNNL).

3. Find the baffles.

Once in the attic, look for the eaves, the edges of the roof where the roof slopes down to meet the attic floor. Using a flashlight or headlight, look for baffles tacked to the ceiling of the attic between the rafters or roof trusses. There are several products on the market in various colors and materials– black, grey, white, yellow, and pink plastic or molded foam are common, as is brown cardboard (Figure 6 and 7). If your home has continuous soffit vents, there should be a baffle in every rafter bay. If the vents are spaced out along the soffits, there should be a baffle at every vent location. 

Baffles provide an air space over the insulation to guide ventilation air from the soffit vents up along the underside of the roof deck
Baffles provide an air space over the insulation to guide ventilation air from the soffit vents up along the underside of the roof deck
Baffles provide an air space over the insulation to guide ventilation air from the soffit vents up along the underside of the roof deck
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Figure 6. Baffles made of molded plastic are installed in this new home under construction before the ceiling drywall and insulation are installed (Source: PNNL)
Baffles allow ventilation under roof decking while keeping wind from blowing insulation back from the edges of an attic.
Baffles allow ventilation under roof decking while keeping wind from blowing insulation back from the edges of an attic.
Baffles allow ventilation under roof decking while keeping wind from blowing insulation back from the edges of an attic.
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Figure 7. Baffles made of cardboard will direct ventilation wind past the insulation that will be installed above the ceiling of this new home (Source: PNNL).

4. Install Baffles.

Sometimes you will find baffles in the attic but many of them may have fallen down. These can usually be reattached using a heavy-duty staple gun to staple the edges of the baffles to the underside of the roof deck. Bringing two pieces of plywood with you, cut to about 24 inches wide and long enough to cover at least two bays can make this job easier and safer. You can sit or lay on one piece while you work and move the next piece to the next two bays as you work your way across the attic. 

If there are no baffles present, you can purchase new baffles and install them at each rafter bay that has a soffit vent, using a heavy-duty stapler or staple gun (Figure 8). Pull back any insulation that is in the way. Use a hand broom or shop vac to remove debris. Depending on the configuration of your eaves, when purchasing baffles, you may want to look for products that include the wind dam or flap at the lower edge that bends down floor of the attic at the inside edge of the top plate (the 2x4 or 2x6 running along the top of the exterior wall) providing a backstop for the insulation as shown in Figure 9. If the eaves are low, the straight baffles may come down to the attic floor at the inside edge of the top plate. Seal the bottom edge of the baffle to the top plate with spray foam as shown in Figures 9 and 10. While you are there, you can use spray foam to air seal the top plates of any bay that do not have baffles, as shown in Figure 10.

Figure 8. New baffles are stapled in the eaves of this attic prior to installing insulation (Source: PNNL).
Figure 9. These baffles have a wind dam at the back which drops down into the rafter bay to serve as a backstop for insulation (Source: PNNL).
Figure 10. The baffle is air sealed in place with spray foam before installing fiberglass or cellulose insulation (Source: PNNL).

5. Call a contractor.

Working in the attic can be hot, dangerous work. If you don’t feel safe doing this, call a contractor.

Additional Info

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Disclaimer

This content is a work created with funding provided by the United States Department of Energy under Contract no DE-AC05-076RL01830 for the operation of Pacific Northwest National Laboratory. The information and guidance provided by Pacific Northwest National Laboratory (PNNL) in the content are intended solely for educational purposes only and do not constitute formal training or certification. It is provided with the explicit understanding that neither the United States Government nor the United States Department of Energy, nor the Contractor, nor any or their employees, nor any jurisdiction or organization that has cooperated in the development of these materials, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness or any information, apparatus, product, software, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Viewers assumes full responsibility for all actions that they may take from information provided in this content including ensuring the safety, code compliance, and proper functionality of any products they choose to install. Installation and use of such products should be performed in accordance with local regulations and manufacturer instructions.