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Building Performance
Building Science
Ventilation IAQ
Sustainable Building

Unvented Roofs without Spray Foam: The Rest of the Story

Kohta Ueno • Last updated 08/2021

4.6/5 (view ratings)
405 students
1 module
1:02 hours
4 assignments

Course description

This course was originally presented at BuildingEnergy Boston 2020, a conference presented by the Northeast Sustainable Energy Association (NESEA)

Back in 2016, our team started a multiyear experiment, sponsored by Building America, on unvented roofs without spray foam or exterior rigid insulation, using an instrumented test hut with multiple test bays. The experiment examined cellulose vs. fiberglass insulation, interior vapor control membranes, diffusion vents at the ridge, interior humidification, inward vapor drive issues, and the effect of air barrier imperfections. Some preliminary results were presented at BuildingEnergy Boston in early 2018. After three winters of experimentation, this is the rest of the story. We will give our take on what works, what is too risky, and what you might be able to get away with some of the time.

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Learning Objectives

Participants in this course will upon completion of this course, be able to:

  • Explain the moisture risks inherent in unvented/compact roof assemblies with fibrous (air‐permeable) insulation
  • Define the roles that vapor diffusion and air leakage have on moisture levels in roofs
  • Explain the role that a vapor diffusion vent can have in ameliorating roof moisture risks
  • Describe the risks of inward vapor drive in unvented roof assemblies

Full course outline

Module 1 - Unvented Roofs without Spray Foam: The Rest of the Story

  • Unvented Roofs without Spray Foam: The Rest of the Story (01:02:57 hours)
  • OPTIONAL: Subscribe to NESEA Communications


Kohta Ueno

Building Science Corporation, Senior Associate

Kohta Ueno is a senior associate at Building Science Corporation, a building science consulting and architecture firm with offices in Boston, Massachusetts and Waterloo, Ontario. His responsibilities at Building Science Corporation include forensic field investigations, energy and hygrothermal modeling, building science research, and field testing. His undergraduate... Learn more


53 reviews

405 students have taken this course

by Dave Mitchell 01/27/2023

See above

by Jeremiah Sommer 06/17/2022

As a builder, I found this easy to understand and an excellent way to continue the education process. Building is a constantly evolving discipline and the more tools we can add to our arsenal the better.



by David Cudney 04/14/2021

Good presentation regarding roof venting.

by Stephen Funnell, Home Owner 12/28/2020

I am a home owner of a century home about to embark on a whole house renovation (gut job) and wanted information about the types of un-vented roof/attic. Based on this presentation, I will be doing using closed foam spray insulation.

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Frequently asked questions

How does this course work?

This is a free course. Enroll today and get access to all of the materials instantly. The lecture video and other materials are available any time.

How long do I have access to the materials?

For free courses there is no guarantee for how long the course materials will be available.

Is there a certificate of completion?

Certificates of completion are only provided to HeatSpring Membership subscribers. This course has not been approved by any credentialing organizations (NABCEP, AIA, USGBC etc) for Continuing Education Credits (CEUs). This course is for self education purposes only and completion does not indicate a level of professional expertise or credential.

Can I register multiple people?

Yes, this is a free course so you can share this page with other people from your group.

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