Moisture has always posed a challenge in the built environment, whether in your house, your kid’s school or even your van. It creates real problems – poor air quality, mold, structural damage. Moisture was less of a problem back when structures were drafty and therefore able to breath and dry out. However, as buildings have become more efficient (tight) this has created the unintended consequence of excessive moisture build up. Let’s look at how the construction industry has responded and Havelock Wool’s role in developing a sustainable, healthy insulation solution.


The dew point is a popular data point in the construction community… and in case you missed that day in 5th grade science class, the dew point is the temperature, pressure and humidity level that causes water vapour to turn into liquid. Specifically there is the Dew Point Method which measures moisture transport in a building. The industry uses the Dew Point Method in a lot of ways, including assessing the impact building materials have on a structure. For example, the discussion spray foam insulation is often on how much insulation would be needed to ‘push the dew point to the outside’ in a given climate zone.

The problem is that the Dew Point Method is flawed in many ways resulting in an incomplete or inaccurate measure of moisture transfer.

Emu, an organization that helps the construction industry adapt to advanced building science, puts it clearly:

“This method was developed decades ago when computers were scarcely around, and professionals had to crunch numbers by hand.  Among other things, the Dew Point Method fails to account for :

  • any material properties besides perm rating and R/in value,
  • assembly orientation,
  • color and slope,
  • construction moisture,
  • air exfiltration,
  • occupancy,
  • ventilation strategies,
  • wind, rain, sun…”

So, it’s safe to say the dew point method should be left in the rearview mirror, especially given the more holistic methods we now have to properly measure building moisture. These evolved methods account for a key variable that the Dew Point Method does not… moisture from inside a building.

According to ASHRAE, a family of 4 produces an average 2.5 gallons of water vapor every single day – by breathing, cooking, taking showers, etc.

Yikes. Just that quickly the challenge has shifted from moisture infiltration from the outside to what to do with an airtight structure loaded with materials that are not equipped to manage moisture, vapor or condensation from the inside!

And this is where wool comes in as part of a healthy, sustainable insulation solution.

Wool fibers inherently manage moisture, absorbing and releasing it against 65% relative humidity. This allows for condensation to be minimized as wool generates heat from energy, thus making it warm when wet. Equally important, wool is a keratin and therefore will not support the growth of mold. Sheep wool insulation R-value equals often surpasses that of other insulation materials. Aside from technical performance, it is safe and easy to install (no mask needed!), it’s a sustainable and renewable resource and its a compostable carbon reducer.

See our Why Wool Page for more details.

The construction industry had been slow to adapt to new challenges of the built environment but the good news is that building practices and materials are now changing rapidly to allow for both a healthier planet and healthier buildings. A few reasons we see:

  • Consumers are more aware of the negative environmental impact of traditional building methods – both in and outside of their homes
  • Industry leadership from companies like emu, and 475 are gaining momentum with efforts to offer real alternatives
  • Carbon footprint is no longer an ancillary item to the discussion and is making strides to be at the forefront
  • The built environment is a MAJOR contributor to GHGs and climate change, which is no longer being pushed aside
  • Natural, high-quality, high-performance options are increasingly available

Here’s looking forward to a healthier, more sustainable world. As Greta Thunberg succinctly tells us – all we have to do is act.

Thanks for reading and be well,

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