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2017 Oregon Code Amendment for Ductless Range Hood

Policy Profile by Benjamin Wolk and Chris van Daalen
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2017 Oregon Code Amendment for Ductless Range Hood
Image courtesy Green Building Advisor
Building Envelope
Energy
Heating, Ventilation & AC
Passive House
Building Code
State
State of Oregon
Homes in Oregon with Whole House Mechanical Ventilation
Oregon Building Codes Division
Oregon Cities and Counties
Oregon Cities and Counties
In Effect October 2017
2017
6 years
Amendment to Oregon Residential Specialty Code, M1503 Range Hoods

Abstract

This code amendment allows for ductless range hoods to be installed in a residence, provided that there is also a whole house mechanical ventilation system installed that has an outdoor air supply. It also brings the Oregon Residential Specialty Code into complete agreement with the 2015 International Residential Code regarding ductless range hoods.

Origin and purpose

This code amendment addresses the installation of ducted range hoods in homes built to be "air-tight" with a continuous air barrier, such as those built to the Passive House standard. A standard ducted range hood compromises the air barrier as the duct constitutes a large hole in both the insulation layer and allows large amounts of air to move through the duct, thus compromising the energy efficiency goal and purpose of making a house "air-tight". Direct exhaust appliances such as range hoods compromise these energy-efficiency investments and make energy performance objectives more challenging and costly to meet. Additionally, with such a tight envelope, a direct exhaust range hood may require a make-up air duct which would increase thermal losses further.

Policy Title Purpose of Policy
Amendment to Oregon Residential Specialty Code, M1503 Range Hoods Allows for ductless range hoods to be installed in a residence, provided that there is also a whole house mechanical ventilation system installed that has an outdoor air supply.

Development of Code Amendment

The amendment was a proposal to the Oregon Building Codes Division, during the 2016 amendment process.  It was developed and argued for by Benjamin Wolk of Zoetic Architecture.  It arose from Ben talking to many architects and builders that specialize in Passive House and energy efficient construction in Oregon and their input that allowing ductless range hoods would make the design and construction of these types of buildings much easier. Passive Houses are designed with computer based energy modeling programs which can directly show how much energy is wasted when you have a large air leak and thermal bridge from a ducted range hood.

Application and Scope

The 2015 International Residential Code allows for this exception already. However the recent Statewide Alternate Method No. 16-04 issued on April 6, 2016 is not clear on this exception as the Oregon amendments that are applicable have an error. Under section M1503 Range Hoods, the table lists subsection M1503.1 Duct Material and the action is "Amend to delete Exception". Subsection M1503.1 is titled General, not Duct Material. Duct Material is subsection 1503.2, so it is not clear which subsection and exception are affected.

Compliance Path

Before this amendment, the Passive House standard was an Oregon Code accepted building method, however the 2014 Oregon Residential Specialty Code conflicts with this intent by requiring ducted range hoods and not allowing ductless range hoods, which compromise the "air-tight" envelope which is a critical component in a Passive House. This made it much harder to meet the Passive House standard without applying for alternative method appeal, causing delays as builders must wait for officials to return a decision. Several Passive House projects located in Portland applied for alternative methods appeals for ductless range hood installations and have been approved (See Related Case Study:  Kitchen Exhaust with Ventilation by HRV at Ankeny Row).  By accepting this proposal, the Building Codes Division wiil eliminate this hodgepodge of ductless range hood acceptance and allow builders to be confident that they can successfully build a Passive House in any part of the state, without concern for compromising the air-tight envelope of the house.

Additional Resources

Passive House Northwest Website Heriott Watt University Technical Report on Drainage Waste and Vent Systems Green Hammer page on Passive House

Technical Details

Passive House or other "air-tight" buildings always install a Whole house mechanical ventilation systems (HRVs) that supply outdoor air. By allowing ductless range hoods, this proposal eliminates the large gap in the air barrier and increases the ability to meet the Passive House air tightness and energy performance standards. Range hoods that duct to the exterior have the potential to depressurize the house with such a tight envelope, thus requiring a make-up air duct to be installed, which increases thermal and air losses further. Because this proposal specifically only allows ductless hoods to be installed when there is also a whole house mechanical ventilation system installed that has an outdoor air supply, it eliminates the concern of not having combustion gases, cooking odors, steam, or other cooking byproducts able to be vented to the outdoors. It also requires that the mechanical ventilation system meet the current exhaust rates listed in Table M1507.4, which means that the kitchen area will be ventilated at the same rate as it would be with a standard ducted range hood.

Economic Impact

The code amendment will lower the costs of construction and operation of the buildings that are affected. The people who own the home are most directly affected as the proposal will help to lower their energy usage, thus lowering their monthly utility bills. This proposal also reduces the costs of construction as it will not require the installation of extra ductwork and workarounds to prevent thermal losses and air leakage and/or installation of make-up air ductwork to prevent depressurization of the house.

Policy and Program Contacts
Proponent: Benjamin Wolk, Architect Zoetic Architecture 541-497-1164
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