# New in May 2026

<div id="bkmrk-heatpunk-uk-has-been">Heatpunk UK has been updated to enact various MCS changes to operating temperature and air change rates.</div><div id="bkmrk-operating-temps-for-">- [Operating temps for post-2006 buildings have been increased in almost all rooms](https://heatloadcalculator.mcscertified.com/docs/reference-sources/design-conditions#design-room-temperatures).
- [Air change rates now default to 0.5 for all rooms except internal](https://heatloadcalculator.mcscertified.com/docs/reference-sources/ventilation-rates#minimum-room-air-change-rates).
- [Using the standard ventilation method now uses a fixed default air permeability of 12 m³/h.m² @ 50 Pa rather than using an occupancy-based estimator as before](https://heatloadcalculator.mcscertified.com/docs/reference-sources/ventilation-rates#standard-airtightness-method).

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