# Building management systems and why they under-deliver > What a BMS can and cannot do for a commercial EPC rating, why an unmaintained one silently reverses other savings, and the cheap fixes before a replacement. Source: https://commercialepcupgrades.co.uk/measures/building-management-systems --- # Building management systems and why they under-deliver A building management system is the thing deciding when the heating runs, how hard the ventilation works and what the building does overnight. When it is set up properly it is the cheapest energy measure in the building. When it is not, it quietly undoes the savings everything else delivered, and nobody notices because it is a cupboard with a screen in it. Cheap to fix, expensive to replace, and routinely neglected ## Before you replace it, find out what it is doing Most BMS problems are not hardware problems. They are a schedule left in place after a tenant moved out, a sensor that has failed and is reading a constant, a manual override somebody applied in 2019 to fix a cold complaint, or heating and cooling fighting each other in the same zone. None of those cost anything to find and little to fix, and they are extremely common. A day of a competent controls engineer interrogating an existing system is routinely the highest-return spend available in a building that has one. - Time schedules that match how the building is actually occupied now. - Set points that are not fighting: a dead band between heating and cooling, not an overlap. - Sensors that are reading reality, calibrated and in sensible positions. - Overrides and holds reviewed and cleared, with a record of why each remaining one exists. - Optimum start, so the building reaches temperature at opening rather than at four in the morning. ## Why it under-delivers so often A BMS is commissioned once, by somebody who then leaves, for a building that then changes. Occupancy changes, tenants change, plant gets replaced, and the control strategy stays as it was on handover. Within a few years it is managing a building that no longer exists. There is also rarely anyone whose job it is. The system sits between facilities, the maintenance contractor and the original installer, and the gap between them is where it stops being looked after. ## What it does to a rating Controls are credited in the assessment, so a building with proper zoning, scheduling and control is modelled more favourably than the same building without. The larger effect, though, is on what you actually spend, which is a different question from the certificate and frequently the one that gets the budget approved. ## When replacement is genuinely the answer When the hardware is obsolete and parts are no longer available, when the system cannot be interrogated or reported on, or when it is so fragmented that nobody can see the building as a whole. Those are real situations and they justify the capital. What does not justify it is a working system nobody has tuned. Tune it first and then decide. ## Questions we get asked ### Is a new BMS worth the money? ### How do I know if ours is set up badly? ### Does a BMS improve the EPC rating? Sources - A non-domestic EPC is an asset rating: it is based on the fabric of the building and its services rather than on metered consumption. [A guide to energy performance certificates for the construction, sale and let of non-dwellings, DCLG, 2014](https://www.gov.uk/government/publications/energy-performance-certificates-for-the-construction-sale-and-let-of-non-dwellings) Last updated 8 October 2026 . - [Ventilation The plant a BMS is usually mismanaging](https://commercialepcupgrades.co.uk/measures/air-conditioning-and-ventilation) - [Metering How you find out what it is doing](https://commercialepcupgrades.co.uk/measures/metering-and-monitoring) Next step ## Get building management systems priced for your building Tell us the building type, the floor area and the rating you are on now. One commercial contractor comes back to you with a quote off a survey. Or call [07367 293494](tel:+447367293494). Monday to Friday, 9am to 5.30pm.