Currently Reading

Keeping Your Homes on the Dry Side


Keeping Your Homes on the Dry Side

Why insulation is crucial for managing moisture

June 22, 2016
Moisture is one of the most damaging elements for a building.

Image: T.C. Torres via Pixabay

Moisture is one of the most damaging elements buildings can encounter. It’s also the leading cause of construction litigation. But keeping buildings perfectly dry isn’t entirely practical; instead, buildings must manage water in a balanced way. Effective moisture balance means minimizing opportunities for building systems to get wet, while maximizing opportunities for incidental water to dry out.


Limiting Condensation

Minimizing wetting means keeping the rain out and limiting condensation. Weather resistive barriers, flashings and sealants keep rain out of the building envelope. Air barriers and sealing of air leaks are the primary methods of preventing air leakage, which may lead to condensation. Fortunately, improved sealing against water and air tends to work in tandem with new building energy codes. Drying of building elements is achieved passively, by allowing incidental moisture to dry either to the interior or exterior.  Unfortunately new energy codes, which have resulted in less air leakage and heat flow through the building envelope, may actually reduce the ability of these systems to dry if they get wet. Thus, greater emphasis should be placed on designing for both minimizing wetting and maximizing drying. 


Using Insulation

In combination with water and air barriers, insulation plays a key role in managing moisture in buildings by:

  • Reducing heat flow through the building envelope
  • In cold weather, preventing humid interior air from condensing on exterior walls
  • In hot weather, with proper air sealing, ensuring air-conditioned surfaces aren’t exposed to humid air that could lead to condensation


Most buildings constructed in North America are built with framed construction. The cavities formed by framing elements provide space for insulation—most frequently fiberglass or mineral fiber, chosen for their thermal, fire and acoustical properties, and cost-effectiveness.  When combined with effective air barriers and properly installed, these materials perform as effectively as alternative products, according to Building Science Corporation’s Thermal Metric Report. But thermal bridging through framing elements can interfere with the insulation’s ability to control surface temperatures. Especially in steel framed buildings, thermal bridging through framing can cause cold surfaces at the framing edges, such as corners, around windows, behind furniture, and in closets.  This can lead to condensation and moisture problems. For these situations, continuous insulation is a critical component for preventing thermal bridging and reducing condensation.


Balance Is Key

Because water vapor in the air can condense on cold surfaces, insulation must be paired with good air barriers to prevent leakage, and as well as with vapor retarders to slow moisture permeating surfaces. So, balance between air and water is key.

Preventing or slowing water vapor from reaching cold surfaces where it could condense is critical. But, it’s also important to allow for drying if wetting occurs. In the building envelope some wetting may occur and drying is imperative. This is where fiberglass or mineral fiber, paired with kraft paper or engineered “smart” vapor retarders is highly effective. Kraft paper and smart vapor retarders keep moisture out of the building envelope when humidity levels are moderate to low, but “open up” and allow water vapor to pass through if there is high humidity, such as after liquid water leaks into a wall. 

Combining air barriers with smart vapor retarders and the right combination of cavity and continuous insulation is a great way for insulation to be an effective part of the moisture balance for buildings.

Written By

J.R Babineau is a research engineer and the principal building scientist for Johns Manville. For almost 20 years, he has been involved in research and development of building products, as well as providing education and consulting on building systems, with an emphasis on heat, air, moisture, noise, and energy efficiency. 

Related Stories


The Leading Cause of New Home Structural Failures? Fill Dirt

As the leading cause of new home structural failures, fill dirt is one of the most important structural elements of a home. And when fill dirt…

Quality Matters

A Checklist for Building Party Walls the Right Way

Party wall mistakes can be costly to fix. Use this guide to avoid them

Life of an Architect Podcast

Critical Skills of an Architect

Architects are expected to have a working mastery of building science and technology, construction techniques, and methodologies, all while bringing everything together in a visually pleasing manner. In Episode 76, we discuss the critical skills of an architect. Thanks to our episode sponsor, BQE CORE ARCHITECT.


More in Category


Create an account

By creating an account, you agree to Pro Builder's terms of service and privacy policy.

Daily Feed Newsletter

Get Pro Builder in your inbox

Each day, Pro Builder's editors assemble the latest breaking industry news, hottest trends, and most relevant research, delivered to your inbox.

Save the stories you care about

Lorem ipsum dolor sit amet lorem ipsum dolor sit amet lorem ipsum dolor sit amet.

The bookmark icon allows you to save any story to your account to read it later
Tap it once to save, and tap it again to unsave

It looks like you’re using an ad-blocker!

Pro Builder is an advertisting supported site and we noticed you have ad-blocking enabled in your browser. There are two ways you can keep reading:

Disable your ad-blocker
Disable now
Subscribe to Pro Builder
Already a member? Sign in
Become a Member

Subscribe to Pro Builder for unlimited access

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.