Integrated Dehumidification Solution

Humidity Issues Impacting Building Health and Comfort

Today's highly energy-efficient homes feature insulated enclosures and airtight construction, often requiring mechanical ventilation for fresh air. While these homes conserve resources and reduce heating/cooling costs, they can suffer from high humidity levels in certain U.S. regions. Increased humidity significantly impacts builders, architects, and homeowners seeking a comfortable, safe indoor environment year-round.

Understanding the Home Energy Rating System (HERS) is key to addressing high humidity. HERS is the industry standard for home energy performance, similar to miles-per-gallon ratings for cars. A lower HERS index indicates a more efficient home. For example, a home built to the 2006 International Energy Conservation Code (IECC) might rate around 100, while a 2015 IECC home could rate closer to 70. Older, inefficient homes might rate 150 or higher. The industry trend is towards net-zero homes, which produce as much energy as they consume through renewables.

While high-performance homes reduce energy use, the National Renewable Energy Laboratory (NREL) and Department of Energy (DOE) note their impact on indoor environments:

• As homes in humid climates become more energy efficient, there is evidence that relative humidity levels are increasing.
• As heating and cooling loads decrease, supplemental dehumidification may become necessary.

Challenge

Relative humidity, the amount of water vapor in the air, is a critical health variable that is often overlooked but easily remedied. Ideal humidity is generally between 40% and 60%. High-humidity indoor environments create significant issues for building health and human comfort. Excessive humidity can lead to odor, mold, mildew, peeling paint, water damage, and in severe cases, loss of structural integrity. Developers, builders, and architects are invested in minimizing these issues, especially in unoccupied homes. For homeowners, high humidity affects not only the interior and furnishings but also health. When indoor relative humidity exceeds 60%, occupants may feel sticky and clammy and are exposed to harmful effects of mold, mildew, bacteria, and dust mites, posing particular hazards for individuals with asthma and allergies.

Geography

During warm seasons in generally high-humidity areas like the Gulf Coast and Southeast U.S., regular heat pump or air conditioning cycles maintain humidity. In cooler, drier seasons, high humidity is not an issue. However, during the shoulder seasons (spring and fall), when temperatures are mild (mid-60s to 70s), heating and cooling loads are lower, but relative humidity can be quite high. Indoor moisture sources and outdoor ventilation air can then cause indoor relative humidity to rise to uncomfortable levels.

Striking a Balance

Addressing excessive relative humidity involves various methods and system types, with no single perfect solution. Some existing options require additional components like high-end whole-home dehumidifiers or portable units. Others rely on over-cooling, which can cause temperature fluctuations of up to 3°F off the thermostat set-point, leading to increased energy use and discomfort. Each moisture-removal solution has pros and cons, requiring a balance of initial cost, payback time, and energy usage against building health, human comfort, and ease of use. This white paper explains how the Trane Integrated Dehumidification Solution (IDS) offers a simple, cost-effective method to meet an unmet need for architects, homebuilders, and homeowners in various U.S. regions. While primarily targeted at energy-efficient homes, Trane IDS can be incorporated into any home where value-oriented humidity control is desired.

How The Trane Integrated Dehumidification Solution Works

The Trane Integrated Dehumidification Solution (IDS) addresses excessive humidity by pairing a specialized Trane thermostat with compatible Trane air conditioning units, heat pumps, and variable-speed air handlers. Home occupants can set the thermostat to three dehumidification levels: low, medium, or high, based on desired comfort. When high humidity is detected, the IDS runs for a defined period each hour. (Note: IDS is available only in cooling mode to comply with code requirements.)

IDS maintains home temperature without over-cooling. A heater within the variable-speed air handler can activate independently when humidity is detected, even if cooling is not needed. This results in more predictable humidity reduction while maintaining home comfort. Essentially, IDS uses the cooling coils' dehumidification function combined with the electric heat's warming function to remove moisture while keeping temperatures neutral and comfortable.

Process Description:

1. Indoor humidity levels increase due to internal sources or moist outdoor air.
2. The thermostat detects that humidity exceeds the user-set preference (low, medium, or high) and commands the HVAC system to activate cooling, electric heat, and the variable-speed air handler.
3. The system automatically senses the need to remove moisture. Cooled air passes over the electric heating element in the air handler, is warmed back to the home's temperature, and circulates throughout the home, providing continuous comfort.
4. The air handler circulates the drier, conditioned air throughout the home while IDS operates.
5. After humidity is reduced, the thermostat monitors levels, and the Smart Continuous Fan feature makes airflow adjustments to prevent re-evaporation from the coil or drain pan.

IDS System Components

The system comprises:

• Unique XL824 or XL1050 Control: The specialized thermostat.
• Outdoor Heat Pump or Air Conditioner: The primary HVAC unit.
• Variable Speed Indoor Air Handler: Facilitates air circulation and conditioning.
• Mechanical Ventilator: Optional, not required in all homes.

Why Trane IDS is Needed and the Benefits It Provides

The market requires technology that provides year-round comfort in energy-efficient homes at a low upfront cost. Trane IDS offers benefits for two key customer groups:

Residential Builders/Architects

The construction industry is aware of high indoor humidity issues affecting homeowner satisfaction and building health. For residential projects, Trane IDS offers a cost-effective basic dehumidification solution with low initial price and simple, fast installation. Builders and architects have requested Trane's assistance, and IDS provides an integrated solution that makes financial and practical sense:

• Lower initial cost: Utilizes existing compatible Trane HVAC units, avoiding the purchase of separate equipment.
• Simplified installation: Familiar product lines reduce labor costs and on-site time.
• Investment protection: Effective humidity removal from vacant homes prevents hazards like mold, mildew, and odors, reducing callback issues.
• Increased satisfaction: More comfortable indoor climates lead to higher homeowner satisfaction.

Homeowners

Occupants of energy-efficient homes need fresh air and comfort, protected from issues like mold, mildew, and odors. While HVAC units manage moisture in winter and summer in humid regions, shoulder seasons can lead to uncomfortable indoor humidity. For value-minded homeowners, Trane IDS offers:

• Low initial cost of ownership.
• Whole-house dehumidification through existing ductwork.
• A more comfortable environment.
• Mitigation of health issues from mold and mildew.
• Ease of use: Interaction via a familiar thermostat interface offers low-medium-high levels, maintaining relative humidity under 60% (down to 45%).
• Low maintenance: Requires only regular servicing of standard equipment.

An Economical Solution for Removing Infrequent High Humidity

Trane IDS is an economical solution for value-conscious consumers seeking whole-house dehumidification at a reasonable cost. Given that extreme high humidity is infrequent, the Trane IDS system offers an efficient approach.

Visual Representation: The system allows users to select IDS comfort settings (Low, Medium, High) to manage indoor humidity levels, aiming for a range between 45% RH and above 60% RH.

Low Initial Cost of Ownership

Trane IDS requires only a specialized thermostat at a nominal incremental cost and compatible variable-speed indoor blower equipment.

Typical Cost of Operation

Trane IDS offers moderate operating costs. For example, electricity costs to operate the IDS function might be around $50-$100 annually for a HERS 50, 2,000-square-foot home in Orlando, Florida, to remove extreme humidity events. When considering initial cost and energy consumption, Trane IDS is an economically sensible upgrade that pays for itself through improved comfort and building health. Compared to portable units, IDS offers higher dehumidification capacity and distributes dehumidified air throughout the house.

Building Code Interpretation and Explanation

Energy codes aim to ensure reasonable energy-saving measures in buildings, dictating requirements for construction materials, methods, and appliances, including heating and cooling systems (SEER, HSPF ratings). Codes also address electric resistance heat sources, typically restricting their use when a heat pump can meet the heating load (e.g., between 35-55°F outdoor temperature). Systems are designed to prevent simultaneous heat pump and electric resistance heating use, allowing the latter only when supplemental heat is needed and the mode selector is set to heat.

Trane IDS aligns with the principles and spirit of energy codes. The IDS feature functions solely as a dehumidifier, not for heating the living space. Its electric resistance heat serves the specific purpose of addressing building health and occupant comfort. The IDS-compatible thermostat restricts dehumidification use to when the system is in cooling mode and indoor humidity levels are high; it is disabled and cannot run when set to heat.

Trane IDS Provides an Answer To an Unmet Need

Maintaining proper humidity levels is crucial for home comfort, health, and the longevity of the home. While energy code changes have improved home efficiency, they can inadvertently lead to high-humidity indoor environments, impacting building health and comfort. Trane addresses these issues with solutions like IDS.

Trane IDS is an innovative solution for homes in U.S. regions experiencing high humidity during moderate temperature seasons. Designed for high-efficiency homes, it can be used in any home seeking value-oriented dehumidification. By integrating familiar heating and cooling equipment with an IDS-enabled thermostat, Trane IDS delivers an effective, affordable, and code-compliant dehumidification solution, ideal for builders and homeowners.

Appendix

1. IDS COMPATIBLE MODELS AND SYSTEM CONFIGURATION

* AH/Heater combination cannot be matched with a HP Outdoor Unit.

** Ventilation solutions are recommended for situations like Spray Foam Insulated Homes or homes built after 2013, as per ASHRAE 62.2.

2. STATE BUILDING CODE REQUIREMENTS

2015 IECC, SECTION R403.1.2
Heat pumps with supplementary electric-resistance heat must have controls that, except during defrost, prevent supplemental heat operation when the heat pump compressor can meet the heating load.

2016 CALIFORNIA TITLE 24, SECTION 110.2(B)
Heat pumps with supplementary electric resistance heaters shall have controls that:

1. Prevent supplementary heater operation when the heating load can be met by the heat pump alone.
2. Ensure the cut-on temperature for compression heating is higher than for supplementary heating, and the cut-off temperature for compression heating is higher than for supplementary heating.

EXCEPTION 1 to Section 110.2(b): Controls may allow supplementary heater operation during:

• Defrost; and
• Transient periods (start-ups, thermostat setpoint advances) if controls provide preferential rate control, intelligent recovery, staging, ramping, or similar mechanisms to prevent unnecessary supplementary heating.

EXCEPTION 2 to Section 110.2(b): Room air-conditioner heat pumps.

2015 WASHINGTON STATE ENERGY CODE, SECTION R403.1.2
Unitary air-cooled heat pumps must include controls that minimize supplemental heat usage during start-up, set-up, and defrost. These controls should anticipate heat needs and use compression heating as the first stage. Visual indicators (e.g., LED) should show when supplemental heating is active. Heat pumps with supplementary heaters must have controls preventing supplemental heater operation above 40°F. At final inspection, the auxiliary heat lockout control must be set to 35°F or less.

2018 NORTH CAROLINA ENERGY CODE, SECTION R403.1.2 (PROPOSED)
Heat pumps with supplementary electric-resistance heat must have controls that, except during defrost, prevent supplemental heat operation when the heat pump compressor can meet the heating load. An outdoor temperature lockout thermostat is required to prevent supplemental heat operation when the thermostat is changed to a warmer setting, set between 35°F and 40°F.

EXCEPTION:

1. Alternatively, a time and temperature electric-resistance control can be used. After six minutes of compressor run time in heat mode, supplemental electric heat energizes only if the leaving air temperature from the indoor coil is below 90°F. If the indoor coil leaving air temperature exceeds 100°F, supplemental heat automatically de-energizes, but the compressor continues to operate until the call is satisfied. No thermostat initiates supplemental electric heat. Thermostat-controlled emergency heat is not limited by outdoor temperature. Electric resistance supplemental heat during defrost operates normally without limitation.
2. Alternatively, a programmable indoor thermostat with an automatic temperature ramp-up control feature to minimize supplementary electrical resistance heat use is acceptable.

2018 GEORGIA ENERGY CODE, SECTION R403.1.2 (APPROVED)
Heat pumps with supplementary electric-resistance heat must have controls that, except during defrost, prevent supplemental heat operation when the heat pump compressor can meet the heating load. Except in Emergency heating mode, supplementary electric-resistance heat may only energize if the outdoor temperature is below 40°F (4°C).