December 14, 2018

By: Doug McCleery, MaGrann Associates

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If this issue kept you up at night, you are not alone.  Discussions about water and moisture were commonplace on construction sites throughout the region.  There are many factors and variables that play a role in this issue, some are under our control and others are not. We know that the standards and conditions we are building in have changed. Increased energy code standards, wetter weather and health and safety requirements all change how moisture moves and is managed in homes.  Let’s look at some of the underlying conditions and building science principals that can help us understand and address this concern going forward.

 

• New codes and the desire to save energy for our customers have pushed insulation levels higher. More stringent air sealing is also required, not only to reduce operating costs, but to protect our more highly insulated buildings from moisture that can get trapped on the “wrong” side of insulation.  The ways that fresh air is introduced into our homes has also changed.

• Naturally ventilated homes used to introduce more fresh air in the winter months during colder, windier conditions and less fresh air during the summer when temperature differences and wind speeds are typically lower.  With building codes now requiring mechanical ventilation in low-rise residential construction, ventilation rates are more constant.  For most homes, this means less fresh air during the winter and more during the summer.  Residents will benefit from lower heating bills and less dry air in the winter.  During the summer, more ventilation often means more moisture entering the homes.

• How we heat our homes and heat our water has changed.  Atmospheric furnaces and water heaters we used to use were inefficient by today’s standards and relied on air from inside the home to send up the flue.  They are certainly less compatible with tighter homes.  What we sometimes forget is that they also removed a lot of moisture.  In the long run, this could be problematic, but in a new home, those natural vent systems contributed to the drying of building materials. 

 

Some things about home building have not changed. 

 

• We still build most of our homes in an uncontrolled environment at the mercy of the weather. A rainy year interferes with construction schedules, fills foundations with water, and increases the moisture content of every building material on site.

• Construction schedules still rule.  Homes need to be completed on time and on budget, rain or no rain.

 

So what do we do to build homes that our customers want, at prices they can afford, while reducing the impact of unusually rainy years like 2018?  Here are a few thoughts to help start productive conversations with key stakeholders in your building projects.

 

• Minimize the introduction of moisture into our buildings during construction.  Solutions should include the grading of the site to improve drainage during construction, and finding ways to protect materials during delivery and storage.

• Protecting buildings from rain and moisture during construction. Drain water away from the foundation. Once the roof is on and the windows are in, keep it dry.  The weather can sometimes be your best ally.  The weather can also be your biggest enemy, as evidenced in 2018, when rain-free days were hard to come by. 

• Removal of bulk water from your buildings under construction is a top priority.  This will likely depend on generator power and temporary pumps.

• Dry, dry, dry.  When things are wet and your building is buttoned up, actively dry your buildings.  Much like providing temporary heat in the winter, you can provide temporary dehumidification. 

• Don’t cover wet building materials with insulation and sheetrock.  Moisture experts say that the moisture content of a material must be below 19% before it gets covered up to reduce the risk of long term material damage.  Giving trades the responsibility and authority to determine when it is appropriate to do their work can prevent damage and the need for remediation down the road.

• Once the home is complete, right-sized and variable capacity cooling systems are critical to moisture removal.  A system that is too large will not run long enough to dehumidify.  Right-sized equipment costs less money and works better.

• Consider new ways to condition and ventilate your homes that reduce moisture during the first year of occupancy (when moisture levels are at their peak) and during extreme weather down the road. All ventilation methods are not alike and supplemental dehumidification may be a good investment.  Ductless HVAC systems eliminate the risk of condensation and moisture problems associated with sweating ducts.

 

Many of this summer’s symptoms have disappeared with cold weather, but don’t assume that they are gone forever.  Be prepared for the return of warm, humid weather in the spring.  None of this is easy or free, but considering the alternatives, is prevention less expensive and less risky than remediation.  If you are done dealing with these issues, but find the list of remedies daunting, let’s talk - while the weather is cool and dry.