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Mold on the sheathing in this attic occurred after attic ventilation was increased

Mold on the sheathing in this attic occurred after attic ventilation was increased
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Balanced ventilation strategy for conditioned attic spaces

Balanced ventilation strategy for conditioned attic spaces
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This is a soffit vent; it provides ventilation for a vented attic

This is a soffit vent; it provides ventilation for a vented attic
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Right – Button vents provide ventilation to a vented attic

Right – Button vents provide ventilation to a vented attic
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This HRV, installed in a conditioned attic, provides balanced ventilation to the whole home

This HRV, installed in a conditioned attic, provides balanced ventilation to the whole home
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Right – A continuous ridge vent provides full ventilation to a vented attic

Right – A continuous ridge vent provides full ventilation to a vented attic
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This finished retrofit installation of radiant barrier in attic shows the air spaces at the soffit and ridge to promote attic ventilation

This finished retrofit installation of radiant barrier in attic shows the air spaces at the soffit and ridge to promote attic ventilation
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Clean the attic floor of debris prior to installing new attic insulation. Use baffles to provide a path for ventilation air entering the attic from the soffit vents

Clean the attic floor of debris prior to installing new attic insulation. Use baffles to provide a path for ventilation air entering the attic from the soffit vents
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Attic ventilation fans exhaust hot air from the attic while replacing it with cooler air from the outside through intake vents

Attic ventilation fans exhaust hot air from the attic while replacing it with cooler air from the outside through intake vents
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Attic ventilation can reduce the likelihood of ice dam formation by cooling the roof deck.

Attic ventilation can reduce the likelihood of ice dam formation by cooling the roof deck.
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Right - Baffles are installed in attic to keep blown insulation from blocking soffit vents and ventilation path

Right - Baffles are installed in attic to keep blown insulation from blocking soffit vents and ventilation path
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Ventilation air comes directly from outdoors, not from adjacent dwelling units, garages, crawlspaces, or attics

Ventilation air comes directly from outdoors, not from adjacent dwelling units, garages, crawlspaces, or attics
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The ventilation space in this vented over-roof keeps the roof cool to prevent ice dams over the unvented attic

The ventilation space in this vented over-roof keeps the roof cool to prevent ice dams over the unvented attic
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Supply-only ventilation with a fresh air intake ducted to the return side of a horizontal air handler unit located in the attic

Supply-only ventilation with a fresh air intake ducted to the return side of a horizontal air handler unit located in the attic
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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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Right – The HVAC unit installed in the insulated attic uses a heat pump to provide heating and cooling while also providing dehumidification and fresh air ventilation.

Right – The HVAC unit installed in the insulated attic uses a heat pump to provide heating and cooling while also providing dehumidification and fresh air ventilation.
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A simple vented attic with good air-sealing of the drywall ceiling air barrier, air flow from soffit vents to ridge vents protected by ventilation baffles, and lots of insulation covering the attic floor is unlikely to encourage ice dams.

A simple vented attic with good air-sealing of the drywall ceiling air barrier, air flow from soffit vents to ridge vents protected by ventilation baffles, and lots of insulation covering the attic floor is unlikely to encourage ice dams.
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Closed-cell spray foam covers the heat recovery ventilator ducts and also seals all top plates and seams in the ceiling drywall of the vented attic.

Closed-cell spray foam covers the heat recovery ventilator ducts and also seals all top plates and seams in the ceiling drywall of the vented attic.
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Right – Open-cell spray foam is installed over closed-cell spray foam in this hybrid approach to achieve adequate attic ventilation while allowing some vapor permeability.

Right – Open-cell spray foam is installed over closed-cell spray foam in this hybrid approach to achieve adequate attic ventilation while allowing some vapor permeability.
Guide:

Obvious Ventilation Controls

Description
Guide describing how to install obvious ventilation controls for continuous and intermittent exhaust fans used for whole-house ventilation.
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Ventilation Air Inlet Locations

Description
Guide describing how to install ventilation air inlets in open locations at a safe distance from potential air contamination sources.
Guide:

Continuously Operating Ventilation and Exhaust Fans

Description
Guide describing how to set controls on an exhaust fan for continuous operation.
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Unvented Attic Insulation

Description
Guide describing methods for insulating an unvented attic along the roof line.
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Blown Insulation for Existing Vented Attic

Description
Guide describing how to insulate a vented attic in an existing home using blown insulation added to the attic floor.
Guide:

Batt Insulation for Existing Vented Attics

Description
Guide describing how to increase insulation in existing homes by installing batt insulation on the ceiling plane of a vented attic.
Guide:

Attic Radiant Barriers

Description
Guide describing application of a radiant barrier layer in the attic to block radiant heat transfer between hot surfaces and heat-absorbing surfaces.
Guide:

Vented versus Unvented Attic

Description
Guide describing options for insulating and air sealing at either the attic floor or along the roof line in new homes.
Guide:

Construct Roofs and Attics for Ice Dam Prevention

Description
Guide describing how ice dams form and how roofs can be constructed to prevent them.
Guide:

Attic Eave Minimum Insulation

Description
Guide providing guidance on insulating attic eaves in new and existing single-family homes and multifamily buildings.
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Right - The energy recovery ventilator ducts supply filtered outside air to multiple locations in the home and continuously exhaust stale air to provide clean, balanced ventilation.

Right - The energy recovery ventilator ducts supply filtered outside air to multiple locations in the home and continuously exhaust stale air to provide clean, balanced ventilation.