New residential energy efficiency building codes are trying to tackle the challenge of how the home’s flow of energy, air, and moisture will affect the indoor environment – including attics and crawlspaces. These codes are requiring homes to meet specific air tightness and indoor air quality standards – both are driving the need for dedicated dehumidification and mechanical ventilation.
Build it Tight. Ventilate Right.
The 2015 International Residential Code requires new homes in Maryland to have less than 3 Air Changes per Hour (ACH) and duct leakage testing requires air leakage rates of less than four cubic feet per minute per 100 square foot of conditioned floor area.
Reducing the amount of air that leaks in and out of the home through insulation, air sealing, ductwork, and new windows and doors are some of the first steps when it comes to cutting heating and cooling costs. But such energy saving strategies can result in unintended consequences. If effective mechanical ventilation and moisture control methods are not implemented the result could lead to uncomfortable living conditions, homeowner health issues and in extreme cases – mold, poor indoor air quality, and significant structural damage.
Virtually every new home requires mechanical ventilation, per Maryland’s adoption of the 2015 International Conservation Energy Code (IECC).
Click to open full size. Source: 2015 Edition of the International Energy Conservation Code (IECC)
Bringing in filtered fresh air to a tight air sealed home from a known location to dilute indoor air contaminants is absolutely necessary. With Maryland being a mixed humid climate, you will also need to think about how to remove the humidity that you are bringing into the home from the outside. Dedicated dehumidification will almost certainly be necessary to maintain <50%RH in a house that meets these new building codes in green grass climates (areas where dew points reach above 60 degrees F).
Traditional practice left it up to the A/C system to remove this moisture in an attempt to keep it at an acceptable level. However, tightening houses limits the air conditioner running time and oversized cooling systems can result in poor dehumidification. An A/C system is only removing moisture when it is running. Shoulder seasons and evening times tend to be when the dew points are highest, and temperatures are mild resulting in high interior humidity levels with little to no moisture removal. By adding mechanical ventilation, in order to ensure indoor air quality, there is an even greater challenge to control the moisture in the living space. The AC in HVAC cannot be counted on for dehumidification anymore. Most homes need dedicated dehumidification in green grass climates. It really needs to be HVACD. Including a dedicated dehumidifier as an integral part of the mechanical system protects the physical investment and creates a more comfortable and healthier living environment.
Caption: Ultra-Aire XT 155H Caption: Ultra-Aire70H
An Ultra-Aire Whole House Ventilating Dehumidifier provides the ability to mechanically remove water until a specific relative humidity set-point is reached throughout the home, plus meet mechanical fresh air ventilation codes and standards. This results in an indoor environment that is healthy, comfortable and provides the ideal conditions conducive to protecting and preserving the building and its contents.
While the goal is to prevent moisture issues when the home is being built, the reality is that most dehumidifiers are installed after the home is complete and the homeowners start noticing there are problems. The number one reason Ultra-Aire dehumidifiers are installed is due to comfort. People want to be comfortable in their homes and were sold on the fact that the HVAC system and the thermostat on the wall can do this 100 percent of the time. The reality is homes need dedicated dehumidification now more than ever.