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Air Seal Floor Penetrations

Materials Cost: 1
Difficulty Level: 1

Introduction

Air seal penetrations in the floor to prevent air leakage and reduce energy losses.

Why

Generous holes are often cut through subflooring for plumbing pipes, vent stacks, gas pipes, electrical wiring, and ducts. These gaps are often hidden from view within walls, in under-sink cabinets, beneath tubs, behind shower enclosures, or behind washing machines and dishwashers. If not properly sealed, large amounts of air can pass through these gaps, encouraged by pressure and temperature differences between conditioned and unconditioned spaces. These air leaks create energy losses. Additionally, they could potentially allow warm, moisture-laden air into wall cavities or attics where it can condense on cold surfaces, creating moisture problems.

What You'll Need

  • Expanding spray foam
  • Caulk and caulk gun
  • Dust mask 
  • Gloves
  • Protective coverall suit

1. Locate floors over unconditioned space.

Identify the floors in the home that are over unconditioned space such as a crawlspace, unconditioned basement, or garage. Remember that the ceiling of the unconditioned space is the subfloor for the floor above.

2. Locate floor penetrations

To locate floor penetrations, first walk through the home to identify where floor penetrations are likely to be. Sketch a map of the floor plan and note where each water fixture is, each gas fixture, each HVAC floor register, and each interior and exterior wall. Be sure to include bathtubs, showers, sinks, toilets, clothes washers, dishwashers, ovens, range tops, furnaces, and water heaters. Many floor penetrations for plumbing and electrical are located at the bottom of a wall so that the pipe or wire will be inside the wall cavity.

Go into your crawlspace, unconditioned basement, or other unconditioned space below the floor. Wear a dust mask, gloves, and a coverall suit in the crawlspace to protect yourself from abrasive fiberglass insulation. Use the floor map you created to locate floor penetrations. In addition to using the map, you can also systematically follow the network of water supply pipes, wastewater pipes, wiring, natural gas pipes, and ducts to identify where they intersect with the subfloor. Finally, you can also use the map to trace along the bottom of each wall to find hidden penetrations. Pull back insulation as needed to find penetrations (Figure 1). Look at each penetration to identify gaps which could use air sealing. Figures 1-13 display a variety of different floor penetrations.

You also may find gaps in the subfloor itself, for instance at joints between plywood or boards. A great time to find and fill these types of gaps is during floor replacement after the old flooring has been pulled up.

Figure 1. Pipes and wires in a crawlspace or basement are often concealed by insulation which can be pulled back while wearing gloves, long sleeves, glasses, and a well-fitting dust mask (Source: PNNL).
Figure 2. When looking for plumbing pipes to find floor penetrations, remember that plumbing pipe may consist of several different materials, such as PEX (white pipes on left), copper (right), plastic, or insulated with foam (gray, far right) (Source: PNNL).
Figure 3. Plumbing pipes often penetrate the subfloor close to where the plumbing fixture is located (Source: PNNL).
Figure 4. Electrical wires for outlets often penetrate the subfloor where there is a wall directly above (Source: PNNL).
Figure 5. Large appliances like electric ovens usually have a dedicated wire that penetrates the subfloor close to where the appliance is located (Source: PNNL).
Figure 6. Wastewater pipes are often large and can have large gaps where they penetrate the subfloor (Source: PNNL).
Figure 7. Ductwork, like this insulated flex duct, penetrates the subfloor where there are floor registers on the floor above (Source: PNNL).
Figure 8. The large hole in the subfloor for this sink drain is a source of air leakage and should be sealed using canned spray foam (Source: PNNL).
Figure 9. The gaps in the subfloor around these copper plumbing pipes should be caulked to protect the conditioned space from air infiltration (Source: PNNL).
Figure 10. The gaps in the subfloor around this copper piping should be sealed with caulk or canned spray foam (Source: PNNL).
Figure 11. Fiberglass insulation stuffed into the large hole around this HVAC duct won’t prevent air leakage from the unconditioned basement to the conditioned space above; the large gap should be sealed with a rigid air barrier and caulked or spray foamed. (Source: PNNL).
Figure 12. This gap around the wastewater pipe, located under a toilet on the floor above, should be air sealed with caulk or spray foam (Source: PNNL).
Figure 13. There are large, unsealed gaps where this HVAC duct penetrates the subfloor to supply a floor register; these gaps should be sealed with spray foam (Source: PNNL).

3. Air seal penetrations.

Air seal gaps in the subfloor around pipes and wires using caulk, canned spray foam, or a combination of rigid foam board and spray foam. Caulk can generally be used for gaps that are less than ¼ inch. Gaps up to about 1 inch can be filled using spray foam. For larger gaps, cover the hole with a rigid air barrier like foam board, plywood, or sheet metal, and use spray foam to seal the board in place. 

Use fire-rated caulk and foam for penetrations in walls. If pests are a concern, use pest-blocking foam or caulk, or embed steel wool or metal mesh in the gap and cover it with sealant. When sealing around sheet metal duct boots, consider using a low-expansion spray foam to prevent the foam from deforming the rectangular boot. For larger gaps, sheet metal can be used in place of rigid foam board. 

Figure 14. The gaps around this HVAC boot have been air sealed with spray foam to limit air leakage between the conditioned space and the basement or crawlspace (Source: PNNL).
Figure 15. The holes around these plumbing pipes in the floor slab and in the sink cabinet have been sealed with canned spray foam to stop air leakage (Source: PNNL).
Figure 17. The electrical conduit (metal) on the left has been sealed to the subfloor using fire-rated caulk, while the penetration for the yellow electrical wire on the right has not been air-sealed yet (Source: PNNL).
Figure 18. The large hole that was cut in the subfloor penetration for this HVAC duct has been air-sealed using sheet metal, mastic, and metal tape (Source: PNNL).

Additional Info

References

Thermal Enclosure System Rater Checklist Guidebook

Publication Date
·
Author(s)
U.S. Environmental Protection Agency,
ENERGY STAR
·
Organization(s)
EPA
Description
Guide describing details that serve as a visual reference for each of the line items in the Thermal Enclosure System Rater Checklist.
Last Updated

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Guide:

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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.