2018 International Residential Code for One- and Two-Family Dwellings

Every 3 years the International Residential building Code (IRC) releases code updates. 2018 is a cycle year. Below is the attic ventilation section. Key notes/changes:


  • The minimum amount of attic ventilation remains 1/150 (1 square foot of Net Free Area for every 150 square feet of attic floor space. Attic floor is defined as length x width FLOOR of the attic).

  • The amount of ventilation can be reduced to 1/300 (in effect 50% less) BUT 2 conditions must be met effective 1.1.18. Previously only 1 condition had to be met. The ARMA Ventilation Task Force pushed the IRC for this change. (See below).

  • Renewed for 2018 is the requirement that “vents must be installed according to the vent manufacturer.” This includes: Don’t Mix Exhaust, give the exhaust vent proper intake, etc.


pdf smallRead the full 2018 Bulletin Here

How Roofing Contractors Can Help Clients with Insurance and Attic Ventilation Upgrades

After the Storm

"After the Storm"

The weather forecast looks poor. Strong winds, heavy rain and the possiblity of hail — golf-ball sized or larger — could hit the area. The storm strikes, and may houses are damaged to the point of roof replacement is necessary. Homeowner's insurance will pay the cost of the new roof and the attic ventilation, but what if the vents that were in place don't meet code requirements? Will homeowner"s insurance pick up the tab? And what if the contractor recommends a better, more efficient way to vent the attic different than the vents that were in place? Will insurance pay for the upgrade? 


Some roofing contractors in storm-prone markets are successfully convincing homeowner's insurance to pay. Here's how....


PDF Read the full article



ARMA Ventilation Task Force

The ARMA Asphalt Roofing Ventilation Task Force acts as the voice of the roof ventilation community to identify the sound theory and scientific data supporting roof ventilation.

Attic Ventilation Best Practices for Steep Slope Asphalt Shingle Roof Systems

This technical bulletin "Attic Ventilation Best Practices for Steep Slope Asphalt Shingle Roof Systems" is the result of the work of the ARMA Ventilation Task Force. It highlights important best practices including:


1. Balance the system with INTAKE and EXHAUST vents.

2. DO NOT mix different types of exhaust vents.

3. When reroofing DO NOT reuse the old vents. Replace them with new vents.


Read the full article:  pdf Attic Ventilation Best Practices for Steep Slope Asphalt Shingle Roof Systems (219 KB)



Attic Ventilation in Accessory Structures

The 2015 International Residential Code and International Building Code, published by the International Code Council, include requirements for attic ventilation to help manage temperature and moisture that could accumulate in attic spaces. Although the code requirements are understood to apply to habitable buildings, not everyone understandes how the code addresses accessory structures, like workshops, storage buildings, detached garages and other buildings. What's the answer? The code treats all attic spaces the same, whether the space below the attic is conditioned or not...


Read the full article:   pdf Attic Ventilation in Accessory Structures (2.54 MB)






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