Comprehensive Guide to Attic Ventilation for Weatherization Energy Auditors

Explore the purpose, principles, and misconceptions surrounding attic ventilation in single-family homes as part of a weatherization assistance program. Learn about common misconceptions, post-weatherization moisture problems, and passive attic venting techniques using informative visuals provided by the US Department of Energy.

• Attic Ventilation
• Energy Auditors
• Weatherization Assistance Program
• Single-Family Homes
• Ventilation Techniques

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1. WEATHERIZATION ENERGY AUDITOR SINGLE FAMILY Attic Ventilation WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 1 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

2. Learning Objectives ATTIC VENTILATION By attending this session, participants will be able to: Explain the purpose and principles of attic ventilation. Summarize misconceptions about attic ventilation. Determine ventilation needs by code and practical alternatives. List ventilation options. Propose specific attic ventilation. Describe safeguards for ensuring that attic ventilation does not cause problems. 2 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

3. Purpose of Attic Ventilation ATTIC VENTILATION Photo courtesy of US Department of Energy Removes solar heat during hot weather Removes moisture vapor during cold weather 3 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

4. Common Misconceptions ATTIC VENTILATION Attic ventilation always removes moisture vapor during cold weather. Attic ventilation will cure an attic moisture problem. The more attic ventilation, the better. Attic ventilation is not necessary. 4 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

5. Post Wx Attic Moisture Problems ATTIC VENTILATION Mold on Sheathing Frost on Sheathing Photo courtesy of US Department of Energy Both conditions occurred after attics were insulated and vented, not before. 5 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

6. Passive Attic Venting: Convection ATTIC VENTILATION Ridge vent How does it work? Outlet (Heated Air) Natural Convection Hot air rises, escapes high vents Inlet Cooler air pulled through soffit vents (Cool Air) Heat rises, escapes ridge vents Graphic developed for the US Department of Energy 6 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

7. Passive Attic Venting: Wind ATTIC VENTILATION WIND How does it work? Bernoulli Principle Positive pressure on windward side Negative pressure on leeward (protected) side Air sucked out leeward vents Graphic developed for the US Department of Energy 7 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

8. Power Venting ATTIC VENTILATION Fan-powered roof vent How does it work? Attic fan mounted in central hallway used in non-air conditioned homes. Roof vent (pictured) used in air conditioned homes. Neither is recommended as weatherization measure. Potential for moisture condensation is high. Graphic developed for the US Department of Energy 8 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

9. Code Issues ATTIC VENTILATION Requirements are based on presence of ceiling vapor retarder, climate zone, and vent location. Options: Thermal boundary - Ceiling 1/150 One square foot of net free vent area per 150 square feet of attic 1/300 One square foot of net free vent area per 300 square feet of attic Graphic developed for the US Department of Energy 9 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

10. Code Issues ATTIC VENTILATION Thermal boundary Roof deck Attic ventilation not required when the roof assembly is the thermal and pressure boundary. Graphic developed for the US Department of Energy 10 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

11. Applied Ventilation Formula ATTIC VENTILATION How many roof vents does it take? Calculate the number of roof vents required. Climate is Zone 7. Ceiling is air sealed and insulated. Ceiling has vapor retarder. Ceiling area is 60 x 30 . Each vent has a net free area of 60 square inches. Photo courtesy of the US Department of Energy 11 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

12. Applied Ventilation Formula ATTIC VENTILATION Ceiling = 60 x 30 = 1,800 square feet. Formula for attic with vapor retarder = 1/300 1,800 300 = 6 sq. ft. required NFA ventilation Convert to inches: 6 sq. ft. x 144 sq. in./sq. ft. = 864 square inches 864 60 square inches NFA/vent = 14.4 15 vents! 12 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

13. Ground Rules and Specifications ATTIC VENTILATION Vented attics should not communicate with the conditioned space. The ceiling air barrier must be continuous with no leakage. Specify appropriate attic sealing as part of the work scope. Specify that vents be placed low and high on roof. Specify eave chutes when soffit vents are present and loose fill insulation is needed. Specify that all mechanical ventilation ducts and plumbing stacks are vented directly to the outside. 13 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

14. Venting Configurations ATTIC VENTILATION In a perfect world... Continuous ridge vent Continuous eave vent (soffit vents) Graphic developed for the US Department of Energy 14 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

15. Vent Types ATTIC VENTILATION Gable vent Roof vent Eave vent Images courtesy of J&R Products Inc. 15 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

16. Vent Types ATTIC VENTILATION Turbine vent R-144 mushroom roof vent Images courtesy of J&R Products Inc. 16 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

17. Vent Placement ATTIC VENTILATION Roof vents placed high on roof Continuous soffit vent Photo courtesy of PA WTC 17 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

18. Vent Installation ATTIC VENTILATION Cut hole to fit; test fit vent. Caulk edges of hole where flange will sit. Slide vent into place under shingles. Seal and nail. Photo courtesy of the US Department of Energy 18 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

19. Vent Placement ATTIC VENTILATION Gable vents are attached similarly to roof vents. Photos courtesy of the U.S. Department of Energy 19 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

20. Attic Window Vent ATTIC VENTILATION Photo courtesy of the US Department of Energy 20 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

21. Eave Chutes ATTIC VENTILATION Eave Chute Photo courtesy of PA WTC; Product photo by J&R Products, Inc. 21 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

22. Mechanical Vent Terminations ATTIC VENTILATION Photo courtesy of PA WTC 22 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov

23. Summary ATTIC VENTILATION Vent attics where possible and practical. Follow 1/150 and 1/300 code guidelines. Don t specify vents to solve an attic moisture problem. Keep moisture out of the attic by air sealing. Use the right vent for the job. Place vents high and low. Avoid turbine or power vents. 23 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM December 2012 eere.energy.gov