March 14, 2017

New Mold Growth Index and Safe Double-Stud Walls: WUFI Pro Shows INTELLO Plus is Key

Double-stud walls have been regarded as a simple to build, low-cost, high-performance solution since the energy crisis in the 1970’s.  (See our blog post The Double-Stud Wall Simplified: Low-Cost High Performance, and free CAD details)  Pack them right, meaning 3.8 to 4.2 lbs/cubic foot of cellulose, 2.5 lbs/cf for fiberglass or wood fiber – and as Jesse Thompson of Kaplan […]

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March 28, 2016

JLC Reports on Success of Foam-Free Unvented Flat Roof Assembly

475 enables more robust assemblies that are less toxic. Such was the case with the Whitchurch home in northern Vermont – working with the owners and their dedicated Passive House team at Montpelier Construction. The walls were a variation on the I-Joist outrigger configuration with dense pack cellulose between DB+ membrane inboard and SOLITEX Mento Plus […]

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October 8, 2015

Yes, Unvented Roof Assemblies Can Be Insulated With Fiberglass – A WUFI Post

And Not Just In Climate Zones 2B & 3B: Cold Climates Too A post on August 21st, 2015 on, Martin Holladay asked the question, Can Unvented Roof Assemlies Be Insulated With Fiberglass?  Martin’s post focuses on the marketing of Owens Corning’s ProPink Unvented Attic Insulation System.   The Owens Corning system is only allowed by code in zones 2B […]

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July 14, 2015

Why The Vapor Curve Matters

How vapor variable materials stack up when it comes to mileage and protection Intelligent membranes, or smart vapor retarders, can help prevent condensation in enclosure assemblies (walls and roofs) in winter, while allowing inward diffusion in summer. This transformation is important to assure the safety of an insulated assembly, by increasing its drying reserves so it can cope with (unforeseen) moisture — both into […]

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January 13, 2015

Insulating Historic Masonry Buildings Safely: How WUFI Can Help

With the rising popularity of Passive House and EnerPHit renovation in brownstone and brick masonry renovations in the US and Canada, the question comes up time and time again: What insulation levels are needed to create an efficient structure and how far should and can we push interior insulation levels without running into issues? One […]

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September 18, 2014

Middlesex VT: Foam-free, WUFI-verified, and OSB-free high performance

The town of Middlesex, Vermont, located just north of Montpelier, has put itself on the high performance building map. Leading the way is the new “Whitchurch Passive House Cottage” – not only in terms of energy efficiency (Passive House certification is in the works), but also as a unique and adventurous example of “form follows function”. The project […]

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February 19, 2014

475 Does WUFI®: Mold Potential and Historic Masonry Retrofits in Climate Zone 6 (Burlington, VT)

A key piece of the puzzle as we decarbonize our building stock is successfully retrofitting historic masonry buildings to high performance standards that provide energy efficient operation and comfort while preserving the structural integrity of these timeless buildings for future generations. We have written often that preservationists and energy efficiency advocates need not be in opposition, […]

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January 13, 2014

Keeping Sheathing Dry in High-R Double-Stud Walls – a WUFI study

(The is the second installment in the 475 blog series 475 Does WUFI. ) Double-stud walls have become a popular and cost efficient way to build well-insulated envelopes: two 2×4’s spaced apart easily makes a R-40+/10.5″ thick wall. Such walls also include a thermal break and can be insulated with densepacked cellulose or fiberglass, both […]

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July 18, 2013

475 Does WUFI®: A Series Introduction

Traditional buildings leak air and are poorly insulated, allowing the enclosure assembly to essentially bake- or air-dry.  In doing so it maintains a resilient and robust construction but is inefficient and uncomfortable. Today, as we evolve to achieve greater levels of comfort and efficiency the enclosures are more insulated and airtight, become colder, and are […]

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