T05: Radiant Thermal Comfort – Above Green

(2 points)

INTENT

Maximize volume of the space, reduce dust transmission, improve ventilation control and increase thermal comfort by incorporating radiant heat and cooling systems into the building design.

SUMMARY

This WELL feature requires projects to use radiant systems and independently controlled ventilation systems.

ISSUE

Mean radiant temperature is one of the six core thermal comfort parameters. It is influenced by a surface material’s ability to absorb or emit radiant heat, the extent to which the surface area is exposed to the person (view factor) and the temperatures of the surrounding objects. Non-uniform thermal radiation can result from cold windows, uninsulated walls, equipment and improperly sized heating panels, all of which can cause local discomfort. In addition, conventional "all-air" systems have a higher risk of draft discomfort due to elevated indoor air velocity. Furthermore, inadequate humidity control can also impair thermal comfort. Low humidity levels in winter can lead to dryness and irritation of the airways, skin, eyes, throat and mucous membranes and are also linked to the slower inactivation of virus particles.

SOLUTIONS

Radiant heating systems are designed to affect mean radiant temperature, and thus the heat exchange with the people in the space, by supplying heat directly to the surrounding surfaces of the floors, walls and ceilings. With radiant systems, the heat transfer due to radiation increases, while the heat transfer due to convection decreases. There is evidence that radiant systems have potential to provide better comfort than conventional air systems as well as a host of other benefits. For example, radiant heating and cooling systems are known to have lower risk of draught and local discomfort because of lower vertical air temperature gradients. There are also fewer local discomfort complaints in the region of human feet (often under desks) during the heating season, due to reduced temperature fluctuations and vertical temperature gradients. The use of radiant heating and cooling reduces the number of allergens circulated in the air as this type of system does not use forced air to distribute heating or cooling. In addition, buildings with radiant systems have the advantage of quiet operation, low energy consumption and the capability of design integration with an independent ventilation system. The use of radiant systems is also easily scaled to match the area being covered, ensuring proper heating and cooling capacity. With the use of radiant heating, the mean radiant temperature in a space can be kept lower compared to convective heating, providing the benefit of a higher relative humidity in winter time. In addition, by the provision of a radiant system coupled with a dedicated air system, it is possible to separate the twofold role of the mechanical system in controlling both heating/cooling and ventilation, which could result in better control of thermal environment.

IMPACT

Proper design and operation of radiant heating and cooling systems can provide equal or even better thermal comfort compared to all-air systems, which could ultimately be linked to increased human comfort and well-being.

REQUIREMENTS

Part 1

Implement Radiant Systems (1 point)

Verified by MEP

For All Spaces except Commercial Kitchen Spaces

At least 50% of the floor area of regularly occupied spaces within the project boundary is serviced by one of the following systems:

Hydronic radiant heating and/or cooling systems.
Electric radiant systems.

Note: Projects pursuing this part for radiant cooling systems must also meet the condensation management requirements of Part 1: Manage Relative Humidity in Feature T07: Humidity Control.

Part 2

Implement Dedicated Outdoor Air Systems (1 point)

Verified by MEP

For All Spaces

Mechanically ventilated spaces:

In spaces where an independent system is used for heating and/or cooling, dedicated outdoor air systems meet one of the following requirements:

The system complies with ASHRAE Design Guide For Dedicated Outdoor Air Systems (2017).^[59]
A detailed design review of the proposed system is conducted by an independent, qualified and registered professional mechanical engineer demonstrated not to have a conflict of interest. The review addresses thermal comfort (dry-bulb temperature, humidity and air velocity, at a minimum) and ventilation rates, as well as overall serviceability and system reliability. Reports must demonstrate satisfactory compliance with ventilation standards of Part 1: Ensure Adequate Ventilation in Feature A03: Ventilation Effectiveness.