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Identifying and Air Sealing the Building Envelope

Learn how to identify, locate, and seal air leaks in the building envelope for comfort, safety, and energy efficiency. Understand key principles and common sites of breaks in thermal and pressure boundaries.

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Identifying and Air Sealing the Building Envelope

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  1. Identifying and Air Sealing the Building Envelope WEATHERIZATION INSTALLER/TECHNICAN FUNDAMENTALS WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – July 2012

  2. Learning Objectives IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE By attending this session, participants will be able to: • Differentiate between the thermal and pressure boundaries and describe the behavior and function of each. • Summarize basic principles of air leakage. • Identify the proper location of the pressure and thermal boundaries. • Identify common sites and signals of breaks in the pressure and thermal boundaries. • Identify common air sealing materials and their characteristics. (continued on next slide)

  3. Learning Objectives IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE By attending this session, participants will be able to: • Explain what is meant by “inside” and “outside” in terms of air barrier and how a blower door is used to determine that. • Identify typical construction details that lead to gaps in pressure and thermal boundaries and know how to treat them. • Describe treatment options for walk-up attics.

  4. Comfort, Safety and Efficiency IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE A comfortable, safe, and energy-efficient home requires: • A fully insulated thermal envelope or thermal boundary. • A well-sealed air barrier. • Continuous thermal boundaries and air barriers that are in contact with one another. • Efficient, properly sized equipment to condition the living space and heat water. • A well-designed and balanced air distribution system. • Healthy indoor air quality.

  5. Typical Air-Leakage IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE Image courtesy of ENERGY STAR

  6. Primary Air Infiltration Sites IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE 5% Fans and vents 12% Windows Floors, walls, and ceilings 36% 13% Doors 15% Plumbing penetrations Electrical outlets 2% Fireplaces 16% Data courtesy of the California Energy Commission

  7. Finding Air Leaks IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE Check typical hot spots • Flues and plumbing vents • Wire pathways • Recessed fixtures (lights and fans) • Chimney penetrations Signals • Blower door, smoke • Dirty or discolored insulation Photos courtesy of the US Department of Energy

  8. Thermal Boundaries & Air Barriers IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE For maximum efficiency and comfort, the thermal boundaries and air barriers must be continuous and in contact with each other. Graphic developed for the US DOE WAP Standardized Curricula

  9. The Thermal Boundary IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE The Thermal Boundary • Limits heat flow between inside and outside. • Is easily identifiable by presence of insulation. The location of insulation in relation to other building components is critical to its effectiveness. • Even small areas of missing insulation are very important. • Voids of 7% can reduce effective R-value by almost 50%. Graphic courtesy of Dr. Energy Savers

  10. Thermal Boundaries are Obvious IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE Photo courtesy of the US Department of Energy

  11. Air Barrier IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE Air Barrier • Limits air flow between inside and outside. • Is more difficult to identify. • Is not always where you think it is. A blower door is used to locate the air barrier. Graphic developed for the US DOE WAP Standardized Curricula

  12. Thermal Boundaries & Air Barriers IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE An uninsulated attic hatch is a gap in the attic’s thermal boundary. Air Barrier Thermal Boundary Graphic developed for the US DOE WAP Standardized Curricula

  13. PRESSURE & THERMAL BOUNDARIES Photo courtesy of NRCERT

  14. Air Barrier IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE A mechanical chase containing ducts can break the attic’s air barrier. Air Barrier Thermal Boundary Graphic developed for the US DOE WAP Standardized Curricula

  15. Moisture IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE Moisture flows with warm air through breaks in the air barrier, causing damage when it condenses on cool surfaces. Air Barrier Thermal Boundary Graphic developed for the US DOE WAP Standardized Curricula

  16. PRESSURE & THERMAL BOUNDARIES Photo courtesy of NRCERT

  17. PRESSURE & THERMAL BOUNDARIES Photo courtesy of NRCERT

  18. PRESSURE & THERMAL BOUNDARIES Photo courtesy of NRCERT

  19. PRESSURE & THERMAL BOUNDARIES Photo courtesy of NRCERT

  20. Construction Details IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE Other construction details can result in gaps in pressure and thermal barriers. • Changes in ceiling height • Knee-wall attics • Walk-up attics • Dropped soffits • Above kitchen cabinets • In bathrooms • Above vanities • Above built-ins • At duct chases/bulkheads

  21. Changes in Ceiling Height IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE Attic Not only is the top of the wall uninsulated... Conditioned Space Conditioned Space Graphic courtesy of Anthony Cox

  22. Changes in Ceiling Height IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE The interior wall cavities act as a chimney that robs the house of heat and conditioned air. Graphics courtesy of Anthony Cox

  23. Changes in Ceiling Height IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE Open Wall Cavity Photo courtesy of the US Department of Energy

  24. Knee-Wall Attics IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE Main Attic Open Wall Cavities Knee-wall Attic Graphic courtesy of Anthony Cox

  25. Dropped Soffits IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE Kitchen wall cabinets mounted under soffit or valance Graphic courtesy of Anthony Cox

  26. Dropped Soffits IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE Attic insulation can hide dropped soffits. Graphic courtesy of Anthony Cox

  27. Photo courtesy of NRCERT

  28. Dropped Soffits IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE If you see soffit-mounted cabinets, remember to investigate during attic inspection. Graphic courtesy of Anthony Cox

  29. Vent pipe for kitchen exhaust fan helps locate area over kitchen cabinets. Photo courtesy of the US Department of Energy

  30. A closer look reveals a dropped soffit and misaligned pressure and thermal boundaries. Open Wall Cavities Photo Source: US Department of Energy

  31. Where Is the Air Barrier? IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE Cape Cod1½ Story House Graphic developed for the US DOE WAP Standardized Curricula

  32. Where Is the Air Barrier? IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE Targeted air sealing defines air barrier Graphic developed for the US DOE WAP Standardized Curricula

  33. Where Is the Air Barrier? IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE Pressure and thermalboundaries now aligned Graphic developed for the US DOE WAP Standardized Curricula

  34. Plumbing pipe and dirty insulation are clues… …that an attic bypass is allowing air flow through the insulation. Photos courtesy of the US Department of Energy

  35. An innocent looking fireplace and built-inchina cabinet… Photo courtesy of the US Department of Energy

  36. …hides an attic bypass you can park a car in. The client wondered why her silverware got cold in the winter. Photo courtesy of the US Department of Energy

  37. General Guidelines IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE Gaps ≤ 1/4”Caulk Energy Blast Services US Dept. of Energy The Daily Green Gaps 1/4” – 3”Spray foam OtherFoam board, fiberglass in plastic bags, etc.

  38. Drywall Repair IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE Sometimes sealing air leaks requires repairing damaged drywall. Photos courtesy of the US Department of Energy

  39. Shielding prevents blown-in cellulose insulation from touching the chimney. The hole is capped at the level of the attic floor and sealed with the two-part foam. Photo courtesy of the US Department of Energy

  40. Photo courtesy of the US Department of Energy

  41. Changes in Ceiling Height IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE In older homes the ceiling level changes in closets, causing gaps in the pressure and thermal boundaries. The uninsulated bedroom and bathroom walls are exposed to outdoor temperatures. Photo courtesy of the US Department of Energy

  42. Changes in Ceiling Height IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE The pressure boundary is re-established by capping the hole with foam board at the same level as the rest of the attic and air sealing. New insulation will be blown over the repaired pressure boundary and the existing insulation. Photo courtesy of the US Department of Energy

  43. The pressure and thermal boundaries are now continuous and in contact with each other. Photo courtesy of the US Department of Energy

  44. Walk-Up Attics IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE Where Is the Pressure Boundary? Where Should It Be? Graphic developed for the US DOE WAP Standardized Curricula

  45. Walk-Up Attics IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE If the client does not use the attic often: • An insulated, airtight cover can be installed on top of the stairwell. • The pressure and thermal boundaries are aligned at the level of the attic floor. • This approach brings the stairwell into the conditioned space. • It is also cheaper and faster than the alternative. Graphic developed for the US DOE WAP Standardized Curricula

  46. Walk-Up Attics IDENTIFYING & AIR SEALING THE BUILDING ENVELOPE If the client uses the attic fairly often: • The pressure and thermal boundaries must be established at the stairs, stairwell walls, and door to the attic stairs. • This approach leaves the stairwell open to the attic and outside the conditioned space. Graphic developed for the US DOE WAP Standardized Curricula

  47. Since these attic stairs were used often, it was better for the client to keep the stairwell “outside,” which means dense-packing the stairwell walls with insulation. Photo courtesy of the US Department of Energy

  48. Photo courtesy of the US Department of Energy

  49. The door is insulated and weather-stripped. Photo courtesy of the US Department of Energy

  50. The final step in aligning the pressure and thermal boundaries is to insulate and air seal the stairs. Photo courtesy of the US Department of Energy

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