New Home Builders Care about Moisture
Energy-efficient homes are very airtight
By Dan Welklin
Precision Comfort Systems in Westfield, Indiana designs and installs the Comfort Systems for some of the finest new homes in the Indianapolis area. If you happen to attend one of the highly advertised open home events in Central Indiana, (you know… the home overlooking the lake with 4 geothermal heating systems) chances are, the comfort systems were installed by us. My point in bragging a bit is to simply point out that we work for some of the most discriminating home builders and homeowners in Indiana.
So, what do Central Indiana’s leading builders and their home buyers have on their minds?
Near the top of the list is getting accurate information on the best products for comfort and health. The topics include home air quality, air filtration, fresh air ventilation, and humidity control. Sometimes, their questions are in disguise but we recognize it’s really about air quality; Why do my wood floors cup or separate? Why do my Energy Star windows have condensation? Should I build my new home airtight? Should I ventilate my energy-efficient home and if so, how much? What is an Energy Recovery Ventilator (ERV) and do I need one? Who needs a whole-house dehumidifier? Could mold grow in an energy-efficient new home that passed inspections with flying colors?
Builders should be more interested in these topics today than at any time in the past.
Here’s why. New, energy-efficient homes are very airtight, so in many cities and states, builders are being encouraged to ventilate their homes with outside air. Those who are starting to install outside air ventilation devices feel this feature should be one they can brag about to improve the health and life of the new homebuyer. They want to stand out from other builders by providing the most up to date, healthy, fresh air technology. But “fresh” air is difficult to find in Indiana in the summer and it’s not uncommon for a poorly designed setup to cause more harm than good.
Indiscriminate ventilation during Indiana summers can cause serious humidity problems inside.
Some builders ask me if an energy recovery ventilator (ERV) is the answer but this is not my first-choice solution. True, an ERV is a ventilation machine, but it is a bit overrated and frequently misunderstood. At best, an ERV only removes about one part of the incoming water for every three parts sucked in during the summer. This performance results in a net gain in moisture so the more you use an ERV in the summer, the more humidity you are loading into the home.
Most builders we work for would love to better understand the invisible demon we call humidity.
But typically, they rely on us for guidance on this topic. Briefly, here’s what we know and what we tell the best builders in Indiana.
An energy efficient home does not run the air conditioner as much as a home from the past.
New energy-efficient windows, airtight construction, better insulation products, lighting with low heat output and other improvements lessen the AC run time. In many applications, an energy-efficient home will not dehumidify properly since the AC does not run enough. Additional mechanical ventilation during the summer with humid Indiana air only complicates this issue. And yes, with enough moisture you can grow mold in the best-built home. If the indoor humidity gets high enough and a homeowner cools any interior surfaces low enough, condensation occurs and you get the two most important ingredients for mold growth; moist surfaces on materials that nourish mold!
Some “experts” might blame moisture problems on the size of the air conditioner, but even a perfectly sized AC will not fix many of our new moisture problems.
Instead of relying on the air conditioning, we promote a ventilating whole-house dehumidifier. This may be a new investment for some builders and homebuyers, but in some homes, it may be necessary for complete comfort and to mitigate moisture problems. And if a builder adds mechanical ventilation, then I adjust my advice and insist that a whole-house dehumidifier will be a new investment and will be necessary to mitigate moisture problems.
A ventilating whole house dehumidifier will allow outside air ventilation as needed and also work independently of the air conditioner to help control indoor humidity.
Moisture is good for plants, mushrooms, tree frogs, and rainbows. But as a builder of quality, energy-efficient homes, you have the responsibility to understand moisture and manage it, especially if you are deliberately sucking it into your energy-efficient home.
Dan Welklin works for Precision Comfort Systems in Westfield, Indiana. In addition to promoting precise comfort systems for Indiana homes, Dan teaches a class called Moisture Science 101 to Builders, HVAC contractors, energy raters, and homeowners. Dan@PrecisionComfort.com