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Abstract
As the quantity of insulation used in wood-frame attics has increased to reduce energy consumption, we have observed a disturbing increase in moisture damage and mold growth on the framing components within those attics. Proposed building codes in some jurisdictions intend to increase minimum insulation values further in the next few years. Code ventilation requirements for attics in North America have not changed in nearly 60 years. However, insufficient ventilation is unlikely to be the sole cause of the observed problems. This research utilizes case studies and computer model simulation to review the contributing factors to the observed attic moisture problems. We also explore parallels between moisture-related problems in wall assemblies that the Pacific Northwest has experienced over the last several decades. This paper will discuss the impact of the following: • Reduced conductive heat loss through the insulation • Uncontrolled air leakage, both through the building enclosure and through mechanical systems • Discharging exhaust vents through soffits • Venting rainscreen cavities into the attic space • Fireplaces and ice damming In conclusion, this paper discusses the above factors as they relate to steps that should be considered when developing remedial solutions. It will also discuss alternate insulating strategies and how those methods may address the currently observed problems.
As the quantity of insulation used in wood-frame attics has increased to reduce energy consumption, we have observed a disturbing increase in moisture damage and mold growth on the framing components within those attics. Proposed building codes in some jurisdictions intend to increase minimum insulation values further in the next few years. Code ventilation requirements for attics in North America have not changed in nearly 60 years. However, insufficient ventilation is unlikely to be the sole cause of the observed problems. This research utilizes case studies and computer model simulation to review the contributing factors to the observed attic moisture problems. We also explore parallels between moisture-related problems in wall assemblies that the Pacific Northwest has experienced over the last several decades. This paper will discuss the impact of the following: • Reduced conductive heat loss through the insulation • Uncontrolled air leakage, both through the building enclosure and through mechanical systems • Discharging exhaust vents through soffits • Venting rainscreen cavities into the attic space • Fireplaces and ice damming In conclusion, this paper discusses the above factors as they relate to steps that should be considered when developing remedial solutions. It will also discuss alternate insulating strategies and how those methods may address the currently observed problems.
Date
10/2011
10/2011
Author(s)
Marcus Dell; Graham Finch; Brian Hubbs; Ariel Levy
Marcus Dell; Graham Finch; Brian Hubbs; Ariel Levy
Page(s)
91- 106
91- 106
Source
Roof Consultants Institute
Roof Consultants Institute
Keyword(s)
attic ventilation; insulation; moisture damage; condensation
attic ventilation; insulation; moisture damage; condensation