By brightshark on Skatehive
Heat pumps are excellent—but only when they’re sized for the actual load of your home. Oversize it and you’ll spend more upfront, cycle inefficiently, and risk noisy short bursts of heat. Undersize it and February feels like an apology. The cure is a heat loss and system sizing study grounded in your building’s measured performance. Why “rules of thumb” fail in winter Contractors often default to nameplate square-meter rules or copy the old boiler size. That ignores airtightness, insulation quality, window upgrades, and occupancy patterns. A blower door result or recent envelope upgrade can change the load by 20–40%. What a proper sizing study includes • Room-by-room heat loss at a defined outdoor design temperature (e.g., −15°C), accounting for ventilation and infiltration. • Supply temperature targets for emitters (radiators, underfloor). Lower temps (35–45°C) maximize heat pump efficiency (COP). • Flow rates & delta-T to ensure quiet, stable operation. • Domestic hot water strategy