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White paper

Measuring waste heat in buildings

Buildings release large amounts of thermal energy they have already paid for. This paper explains what waste heat is, why measurement is the necessary first step toward recovering it, and how low-cost wireless sensors can provide the real-time data needed.

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Buildings release large amounts of thermal energy they have already paid for — through process heat, exhaust air, wastewater, flue gas and many other pathways. Recovering it before adding new energy can lower costs and emissions, reduce the size of new systems and ease pressure on electricity grids. Yet most buildings cannot say how much energy they lose, where it is lost, or when.

Why measurement comes first

Heating and cooling systems are sized for design conditions — assumed occupancy, weather and schedules — which rarely match day-to-day operation. Conventional sources of information fall short:

  • Meters and utility bills show how much energy is consumed, not where it is lost.
  • Building management systems maintain set temperatures but don’t reveal inefficiencies such as simultaneous heating and cooling.
  • Energy audits capture a single point in time and often rely on simulations that are only as accurate as their assumptions.

Measuring with wireless sensors

  • Non-invasive installation — sensors clamp onto existing pipes, ducts and equipment, with no new cabling or system shutdowns.
  • Long battery life — sensors typically run 8–10 years on a single battery.
  • Frequent readings — data every 5–15 minutes shows how waste heat varies across the day and the seasons.
  • Scalable networks — one gateway can serve several buildings.

What this means

Measured data turns an invisible loss into a quantified opportunity — in energy and in money. It lets owners prioritise the opportunities with the strongest return, lets engineers size new systems on measured conditions rather than design assumptions, and gives operators visibility into true operating conditions. Across districts and cities, the same data shows where surplus heat and heat demand sit close together, informing heat sharing and thermal energy networks. Within its limits, LoRaWAN sensing is often the step that justifies more detailed metering — or a recovery investment — later.

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