Building Codes and Building Science are Beginning to Better Align

This post first appeared on the Green Building Advisor website.

I’ve heard Mike Guertin mention that every home built is a building science experiment.  It can take some time for problems in buildings to be known.  For instance, a bad detail on a window installation, like shown in this photo, could take more than 20 years to present as a problem.  If the problem is being repeated, building science might identify the issue and propose a change.  Eventually, the change may end up in the building codes, but this whole process is slow.

That being said, there are many building science principles that we have figured out, with several already added to the codes.  Some have been known about for decades but are still slow to be adopted.  Let’s discuss a few of each.

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Why Knowing Your Climate Zone is Important

Figure N1101.7 (R301.1) Climate Zones-2021 International Residential Code (IRC)

This climate zone map is published by the American Society of Heating and Air-Conditioning Engineers (ASHRAE) and is included in the International Residential Code, chapter 11, Energy Efficiency.  ASHRAE’s purpose is to create standards of how an engineer or HVAC professional calculates and designs heating, air conditioning and ventilations systems to match the insulation, air sealing, and moisture profile of a building.  When designing these often-complicated systems, where the structure is located becomes key, this is the reason the map was created.

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Vapor Control in Walls with Continuous Insulation-IRC Chapter 7 vs Chapter 11

This article first appeared in the January/February 2024 issue of the Journal of Light Construction.

The International Residential Building Code is supposed to provide clarity into how builders construct homes.  In the IRC’s own words, The IRC was created to serve as a complete, comprehensive code regulating the construction of single-family houses, two-family houses (duplexes) and buildings consisting of three or more townhouse units.”  Usually, the codes do a decent job giving us options on how we should build homes with the occupant’s safety and health as our number one priority.  Codes also address energy efficiency and building durability.  Sometimes though, codes can be quite confusing.  How we handle vapor retarders when using continuous insulation is one of those areas.

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A 2021 IRC Code Oversight Could Lead to a Risky Roof Assembly

This post first appeared on the Green Building Advisor Website.

I’ve been working on a future article for Green Building Advisor that has a working title of “Problems with Attic Trusses”.  During research for the piece, I found myself reviewing the ratio rules for hybrid roof insulation strategies.  GBA has two really good articles on the topic:

Combining Exterior Rigid Foam With Fluffy Insulation – GreenBuildingAdvisor by Martin Holiday

The Ratio Rule for Hybrid Roof Insulation – GreenBuildingAdvisor by Allison Bailes

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Code-Blower Door Testing a Small Home

This post originally appeared on the Green Building Advisor website.

Code compliant blower door testing of a small home can be very frustrating for both the person performing the test and the homeowner or contractor who are required to have the test.  A few months ago, I tested a 952 square foot, newly constructed home with a volume of 7616 cubic feet, one of the smallest I’ve tested.  The house had a leakage rate of 416 cfm which resulted in a 3.28 ACH50 number.  A failed blower door test (my climate requires 3 ACH50 or less).  If we take that same CFM rate but increase the ceiling height to 9 feet, which changes the volume to 8568 cubic feet, 2.91 ACH50, a passing test.  Either way, 416 CFM of air moving through the blower door isn’t much, some kitchen exhaust hoods can move more air than that.  Seems unfair to punish smaller homes when blower door testing, especially when the blower door test is testing the surface of a structure, not it’s volume.

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Building Science-“Breathe”

In this blog, I’m going to discuss building tightness and the code dealing with air leakage.  The 2012 International Residential Code for One and Two-Family Dwellings is the current code in force for the state of Minnesota at the time of this blog.  Chapter 11 deals with energy conservation, what most in the building industry call the energy code.  The code on building air leakage states: Continue reading “Building Science-“Breathe””