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Attic Ventilation Fans

Guide describing the use of attic ventilation fans to mechanically pull outside air through the attic in an attempt to cool the attic, control moisture, and prevent ice dams.

About Attic Ventilation

Author(s)

ENERGY STAR

Organization(s)

U.S. Environmental Protection Agency,

EPA,

ENERGY STAR

Publication Date

August, 2022

Energy Star web page providing guidance on attic ventilation.

Calculating Attic Passive Ventilation

Information guide describing how to calculate attic passive ventilation with example calculations.

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

Publication Date

Sun, 01/01/2012 - 12:00

Balanced ventilation strategy for conditioned attic spaces

Publication Date

Wed, 01/01/2020 - 12:00

Literature Review of the Impact and Need for Attic Ventilation in Florida Homes

Author(s)

Parker Danny S

Organization(s)

Florida Solar Energy Center,

FSEC

Publication Date

March, 2005

PDF literature review of the impact and need for attic ventilation in Florida homes.

Guidelines for Ventilating Attics and Cathedral Ceilings to Avoid Icings at Their Eaves

Author(s)

Tobiasson Wayne N,

Buska James S,

Greatorex Alan R

Organization(s)

Oak Ridge National Laboratory,

ORNL,

U.S. Army Corps of Engineers

Publication Date

January, 2001

Report describing the use of fresh air ventilation systems to eliminate the formation of icicles and ice dams along the eaves of roofs.

Attic Air Sealing, Insulating, and Ventilating for Ice Dam Prevention

Information guide describing proper attic air-sealing, insulation, and ventilation to combat ice dam formation on roofs in cold climate zones.

This HRV, installed in a conditioned attic, provides balanced ventilation to the whole home

Reference

Measure Guideline: Selecting Ventilation Systems for Existing Homes

Author(s)

Aldrich Robb

Organization(s)

Consortium for Advanced Residential Buildings,

CARB,

Steven Winter Associates,

SWA,

U.S. Department of Energy,

DOE

This document addresses adding—or improving—mechanical ventilation systems to existing homes. The purpose of ventilation is to remove contaminants from homes either directly or by dilution. This report discusses where, when, and how much ventilation is appropriate in a home, including some discussion of relevant codes and standards.

Publication Date

Sat, 02/01/2014 - 12:00

Attic ventilation fans exhaust hot air from the attic while replacing it with cooler air from the outside through intake vents

Publication Date

Sun, 01/01/2012 - 12:00

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.

Publication Date

Mon, 09/30/2019 - 12:00

Reexamining Roof Ventilation

Author(s)

Woods Tony

Organization(s)

Home Energy,

National Association for State Community Services Programs,

NASCSP

Publication Date

November, 2000

Article describing moisture and ice dam issues in attics and how to air seal the attic floor.

Ceilings and Attics

Author(s)

Southface Energy Institute,

Oak Ridge National Laboratory

Organization(s)

ORNL,

SEI

Publication Date

February, 2000

Information sheet with information about insulating and ventilating attics.

Venting of Attics & Cathedral Ceilings

Author(s)

TenWolde Anton,

Rose William B

Organization(s)

American Society of Heating Refrigerating and Air-Conditioning Engineers,

ASHRAE

Publication Date

October, 2002

Report describing the use of attic ventilation to control moisture in cathedral roofs and avoid the formation of ice dams.

Blown Insulation for Existing Vented Attic

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

Vented versus Unvented Attic

Guide describing options for designing and locating the thermal boundary at either the attic floor or along the roof line in new and existing homes.

Attic Eave Minimum Insulation

Guide providing guidance on insulating attic eaves in new and existing single-family homes and multifamily buildings.

FORTIFIED Animation: Hurricane - ATTIC VENTS

Publication Date

August, 2015

Video showing the requirements for attic vents in homes to comply with IBHS FORTIFIED Home requirements.

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.

Whole House Ventilation Strategies for Existing Homes

Guide describing how to select and install whole-house ventilation systems for existing homes.

Vented and Sealed Attics in Hot Climates, RR-0981

Author(s)

Rudd Armin,

Lstiburek Joseph W

Organization(s)

Building Science Corporation,

BSC

Publication Date

September, 1998

Building science report describing issues with vented attics in hot-humid climates and how sealed attic construction may be a solution.

Spray Foam Insulation Applied to Existing Attic Floor

Guide describing how to apply spray foam insulation to ceilings in existing homes.

Air Sealing and Insulating Ceilings in Vented Attics

Guide describing how to air-seal and insulate a ceiling where the insulation is installed on top of the ceiling (on the attic floor) in a vented attic.

How to Keep Attic Vent From Freezing Up in Winter

Publication Date

December, 2017

Author(s)

Tinsley

Organization(s)

Cold Climate Housing Research Center,

CCHRC

Video describing techniques to prevent attic plumbing vents from freezing during Alaskan winters.

Field Performance of Unvented Cathedralized (UC) Attics in the USA, PA-0502

Author(s)

Rudd Armin

Organization(s)

Building Science Corporation,

BSC

Publication Date

October, 2005

Journal article reporting on field experience of unvented cathedralized (UC) attics in several environments in the United States.

Right – Spray foam fills the roof joist cavities of this vaulted, unvented attic.

Publication Date

Thu, 09/30/2021 - 12:00

1 inch rigid insulation as attic eave baffle cut around manufactured vent

DWG

PDF

Conceptual insulation practice at attic-style truss system - above unconditioned space

DWG

PDF

Conceptual insulation practice at attic-style truss system - above conditioned space

DWG

PDF

This solar powered attic fan runs when the sun is shining and does not draw any power from the home’s electrical system

Publication Date

Sat, 01/01/2022 - 12:00

The spray foam-insulated attic provides a temperate place for the ERV ducts, which provide filtered fresh air to every room in the house.

A Crash Course in Roof Venting, PA-1101

Author(s)

Lstiburek Joseph W

Organization(s)

Building Science Corporation,

BSC

Publication Date

August, 2011

Article describing methods for venting a vented attic and a roof assembly over an unvented attic.

Wrong - Exhaust fans should not have tight bends in duct work, especially right next to the fan as this can block airflow

Reference

Measure Guideline: Selecting Ventilation Systems for Existing Homes

Author(s)

Aldrich Robb

Organization(s)

Consortium for Advanced Residential Buildings,

CARB,

Steven Winter Associates,

SWA,

U.S. Department of Energy,

DOE

This document addresses adding—or improving—mechanical ventilation systems to existing homes. The purpose of ventilation is to remove contaminants from homes either directly or by dilution. This report discusses where, when, and how much ventilation is appropriate in a home, including some discussion of relevant codes and standards.

Publication Date

Sat, 02/01/2014 - 12:00

Building Science Insights: To Vent or Not to Vent

Publication Date

February, 2014

Author(s)

Lstiburek

Organization(s)

Owens Corning

Video presentation describing proper attic venting design for energy efficiency and weather resistance.

Below Deck Spray Foam Insulation for Existing Roofs

Guide describing how to add spray foam insulation to the underside of the existing roof deck as part of the conversion of a vented attic to an unvented, insulated attic.

Roof Venting in a Wet Climate

Author(s)

Fisette Paul

Organization(s)

Journal of Light Construction,

JLC

Publication Date

February, 2011

Q&A article discussing how to address moisture issues in an attic in a wet and humid coastal climate.

Cold Climate Building Techniques and Concepts: Cathedral Roofs

Publication Date

January, 2014

Author(s)

Cold Climate Housing Research Center

Organization(s)

CCHRC

Video describing roof and attic construction for cold climates, including cathedral roof design and insulation strategies, from Cold Climate Housing Research Center.

Attach a strong permanent cover to gable end vents before a severe storm strikes to prevent moisture intrusion.

Publication Date

Wed, 01/01/2020 - 12:00

The polyethylene ceiling vapor barrier is sealed to form an air barrier around the exhaust fan in this very cold climate location (≥ CZ 6).

Publication Date

Mon, 10/30/2006 - 12:00

Technology Solutions Case Study: Complete and Fully Aligned Air Barrier

Author(s)

Pacific Northwest National Laboratory

Organization(s)

PNNL

Publication Date

August, 2012

Case study describing the elimination of excessive humidity in the attic of a multi-floor, single-family home that was causing condensation and water damage along the roof and eaves.

Builders Challenge High Performance Builder Spotlight: David Weekley Homes, Houston, Texas

Author(s)

Pacific Northwest National Laboratory

Organization(s)

PNNL

Publication Date

December, 2009

Case study describing new home construction in the hot-humid climate, optimizing thermal enclosure, HVAC, water heating and lighting measures.

Cool Solutions: The Whole House Fan

Author(s)

Mott-Smith John

Organization(s)

City of Davis,

State of California

Publication Date

June, 2018

Article describing the use of whole-house fans to provide cooling in the region surrounding Sacramento, CA.

Wrong – The open overhang with exposed timbers and unscreened vent holes make this roof more susceptible to ignition.

Publication Date

Mon, 09/01/2008 - 12:00

Avoiding Moisture Problems

Author(s)

Van der Meer Bill

Organization(s)

National Association for State Community Services Programs,

NASCSP,

Weatherization Training Center at Penn College,

Pennsylvania College of Technology,

PCT

Publication Date

February, 2003

Technical article describing issues and moisture concerns related to weatherization efforts.

Water Managed Roof – Re-roofing and Adding Insulation Over a Sloped Roof

Guide describing how to re-roof an existing home with a sloped and add insulation above the roof deck.

DOE ZERH HIA 2017 Case Study: Thrive Home Builders, Courtyard Rows, Lone Tree, CO

Author(s)

Pacific Northwest National Laboratory,

U.S. Department of Energy

Organization(s)

PNNL,

DOE

Publication Date

September, 2017

Case study describing a DOE Zero Energy Ready Home 2017 Housing Innovation Award winner that scored HERS 41 without PV and 8 with PV.

Air Sealing Bathroom and Kitchen Exhaust Fans

Guide describing how to air-seal bathroom and kitchen exhaust fans.