HVAC (Heating, Ventilation, and Air Conditioning)

HVAC (Heating, Ventilation, and Air Conditioning) encompasses all the systems and controls that ensure thermal comfort, indoor air quality (IAQ), and hygiene in a building, while managing energy consumption. It covers production (boilers, heat pumps, chillers), distribution (hydraulic/air distribution systems), emission (radiators, underfloor heating, fan coil units, air handling units/mechanical ventilation), control/building management systems (BMS), as well as maintenance and commissioning. A well-designed and properly adjusted HVAC system delivers comfortable, quiet, and energy-efficient spaces.

HVAC: Operational definition and components

An HVAC system is organized into four links:

- Production : air/water heat pumps, water/water heat pumps, boilers (gas/biomass), chillers, recovery systems (free-cooling, heat recovery), tanks and heat exchangers.

- Distribution : hydraulic networks (VFD pumps, 2/3 way valves, balancing, thermal insulation) and aerodynamic networks (AHU/MVHR, ducts, filtration, acoustic attenuation).

- Emission : low temperature radiators, underfloor heating/cooling, fan convectors, cassettes, chilled beams, diffusers.

- Regulation & control : heating curve, external/ambient/CO₂ probes, BMS/EMS (times, scenarios, alarms), remote reading and dashboards.

The entire process relies on data (heating/cooling/electricity metering), measurable criteria (ΔT, flow rates, COP/EER/SCOP/SEER, fan SFP) , and a quality assurance approach (completion, sludge removal, filters, seasonal reviews). In the RE2020 regulations, HVAC systems are combined with architectural features (Ubat, g/TL, solar shading, thermal inertia) to meet Bbio, Cep/Cep,nr, DH, and Ic requirements.

HVAC: Benefits, limitations, and points to consider

Benefits

• Controlled comfort: stable temperatures, filtered IAQ, humidity under control.
• Energy: variable flow rate (VFD), fine regulation, recoveries → kWh and OPEX down.
• Resilience: redundant/sequenced equipment, anti-peak BMS scenarios.
• Traceability: measurement, remote reading, indicators (COP/ΔT/SFP) for control.

Boundaries

• High CAPEX and multi-lot coordination (HVAC/electrical/architectural).
• Complexity: without commission, the calculated performance does not translate into reality.
• Essential maintenance (filters, balancing, adjustments, water testing).

Points to consider

• Logical order: sobriety & envelope → system efficiency → RES.
• Hydraulics: balancing, PICV, ΔP controlled, ΔT targets respected.
• Aerodynamics: adapted filtration, high recovery, bypass for free/night-cooling.
• Regulation: heating curve correctly calibrated, sensors well placed, pressure/setpoints reset via BMS.
• Water quality: descaling, inhibitors, purging/degassing, monitored conductivity.
• Commissioning: functional tests, in-situ measurements, live DOE + seasonal reviews.

Anecdote — “A CVC brought back to life with music in Aix-en-Provence”

In Aix-en-Provence, an office building was experiencing alternating periods of extreme heat and chilly office temperatures. The audit revealed oversized valves, fixed-speed pumps, excessive pressure drop at peak times, an air handling unit (AHU) without CO₂ control, and an overly steep heating curve. The solution was implemented in three steps (without replacing everything): VFDs on the pumps with pressure reset, PICV and balancing, and conversion of the AHU to variable flow controlled by CO₂ with a bypass for night cooling. The result over one season: a 32% reduction in fan/pump usage, maintained temperature drop, and a dramatic decrease in complaints. The manager smiled: "Even the air conditioning is working smoothly now."