Thermal Comfort and Heat Recovery: ASHRAE 55 and IEQ

ASHRAE 55 and Thermal Comfort

ASHRAE 55 defines acceptable thermal environments through the PMV or PPD model, balancing air temperature, mean radiant temperature, humidity, air speed and clothing. Heat recovery changes supply-air conditions, so it must be designed without degrading comfort.

Humidity and IEQ

Enthalpy recovery transfers moisture as well as heat, helping hold indoor relative humidity in the 30 to 60 percent comfort band and limiting mould and virus survival. Sensible-only plates keep moisture separate, which is useful where winter humidity is already low.

Ventilation, Energy and Comfort Together

Recovery lets designers meet ASHRAE 62.1 ventilation rates without a severe energy penalty, so comfort and indoor air quality no longer trade off against the utility bill. 26YC exchangers are selected to hold supply temperatures within ASHRAE 55 comfort limits across the heating and cooling seasons.

Design Checks for Comfort

• Confirm supply-air temperature stays within ASHRAE 55 limits in both heating and cooling seasons after recovery is applied.
• Hold indoor relative humidity near 30-60%; enthalpy recovery helps in humid zones, sensible plate helps where winter humidity is low.
• Keep ventilation at ASHRAE 62.1 rates; recovery removes the energy excuse for cutting fresh air.
• Verify the recovery core does not raise supply-air speed beyond draught limits.

Frequently Asked Questions

Does heat recovery hurt thermal comfort?
Done right it improves comfort by holding stable supply temperatures and humidity instead of dumping cold or hot untreated air.

What indoor humidity should I target?
Roughly 30-60% RH; enthalpy wheels help in humid climates, sensible plates suit dry winter conditions.

Which standard governs ventilation rates?
ASHRAE 62.1 for ventilation, ASHRAE 55 for thermal comfort; recovery lets you meet both without a large energy penalty.

Frequently Asked Questions

Does heat recovery hurt thermal comfort?

Done right it improves comfort by holding stable supply temperatures and humidity instead of dumping cold or hot untreated air.

What indoor humidity should I target?

Roughly 30-60% RH; enthalpy wheels help in humid climates, sensible plates suit dry winter conditions.

Which standard governs ventilation rates?

ASHRAE 62.1 for ventilation, ASHRAE 55 for thermal comfort; recovery lets you meet both without a large energy penalty.