Ireland's only dedicated building services engineering journal
Ireland's only dedicated building services engineering journal

Technical Guidance Document TGD-030 — update and changes summary (Part 1 of two articles)

David Doherty, Vice-Chairman CIBSE Ireland and Projects Manager, Hevac
David Doherty, Vice-Chairman CIBSE Ireland and Projects Manager, Hevac

TGD-030 Mechanical and Electrical Building Services Engineering Guidelines covers primary and post-primary schools and its scope is to offer better guidance to school authorities, and to aid mechanical/electrical engineers in design. TGD – 030 should be of interest to building services consultants, contractors and suppliers involved in schools works and, in particular, the current summer works scheme underway at schools throughout the country.

The document covers various design features including natural ventilation, boiler plant and rainwater harvesting. This publication of the latest revision follows consultation and communication between the department and building professionals, designers and suppliers/manufacturers. It has been widely welcomed and endeavors to future-proof the

M&E services provided in schools. Key changes include:

Daylight Distribution — Average daylight factor for rooms remains at a minimum of 4.5%. The document notes that: “Higher levels just lead to unnecessary heat gains and losses”;

Ventilation — Natural ventilation is to be considered where possible via permanent wall vents and windows. The guideline notes that: “good quality ventilation is critical to the functioning of a teaching space”. The latest revision highlights thermal comfort levels. The maximum time a room can exceed 25°C is 51.85 hours. However, this is an absolute maximum and design team members should endeavour to maximise the thermal comfort potential;

Blinds — The specification on blinds now includes light transmission values 9 – 12%; solar absorption 17-20%; openness factor 3 – 5%, depending on elevation. All blinds to be light and identical in  colour. Instructions on operation to be included to try reduce energy costs;

Access — The document draws attention to Part M Access & Use. It highlights sensible and thought-out locations for light switches, sockets and lift equipment. This is something every project tries to achieve through coordination and layout drawings;

Boiler House — Maximum plant room sizes are now detailed and linked to number of classrooms;

Boilers — Where natural gas supply is available, suitably-sized aluminum or stainless steel modulating boilers shall be provided. This allows for a more efficient selection, and the inclusion of modulating allows for better turn-down ratios on boilers. Weather compensation and three-port mixing valve arrangement with an outside sensor brings the specification up to date with modern wall-hung and floor-standing boilers;

Radiators — Radiator metal thickness, minimum 1.5mm. No fan assisted radiators allowed;

Controls — Clear instructions on heating controls now required;

Water Supply — Test point in boiler house now to be allowed for water sampling, in addition to a dosing point for commissioning and disinfection. The document highlights the requirement for drinking points as per TGD002 and mains water should not be piped to wash hand basins;

Rain Water Harvesting — A new sizing guide is now included for underground storage tanks. No mains water connection should be made to a tank. Anti-legionella requirements are highlighted along with rainwater tap labelling;

Water Services — Attention is drawn to national and international standards that minimise the risk of legionella;

Water Tank Ventilation — Cold water tanks are to be stored below 20°C. Consideration is drawn to stagnate water and calls on both architects and building services engineers to ensure risk of legionella is minimised. If passive ventilation is needed a duct to outside can be considered;

Sanitary Ventilation — All sanitary facilities, including en-suite classroom toilets, to be provided with background ventilation. Shower areas 15 l/s per shower. Toilets 6l/s per WC. En-suite bathrooms must contain an external window, in addition to a mechanical fan, with run-on timer controlled by light switch. Floor grilles and door transfer grilles should not be used with undercut doors and high level transfer grilles are preferred. All systems to be tested and commissioned in accordance with CIBSE commissioning codes;

Dampers — All dampers to shut off when fan not in use. A non-return damper to be provided on ducts of 150mm or less. Motorised dampers are required on larger duct sizes;

Power Distribution — Residual current breaker and overloads need to allow for heavyduty floor cleaning equipment. Lightning protection to be considered. Electronic surge protection required on incoming mains supply at mains switchboard;

Lighting — LED type fittings are to be considered for external, car park and security lighting. Payback of 10 years is required. On internal spaces, LEDs can only be used in corridor and toilet areas. Elsewhere, lighting power consumption levels of 2.5w/m2 per 100 lux shall be the maximum in all areas. Lighting detectors, plus operation instructions, also required.

Also, corridor lighting zones need to consider daylight influences and have local PIR controls alongside local switches. The document looks for commissioning and a re-visit 12 months after handover to ensure levels maintained;

Emergency Lighting — Installations are to comply with IS3217:Dec.2013. Economical solutions are to be considered with ceiling-mounted LED fittings rather than inverter driven packs. The DoES takes the view that a classroom is not a large assembly room. A single fitting will comply, allowing 0.5lux at floor level. Siting of lighting to consider routes and location of emergency equipment;

Communications — In public address systems, local volume control required in classrooms with special education needs. Regarding induction loop systems, the loop cable is not to be run in steel conduit or in the floor;

Fire Alarm Systems — Systems to comply with IS3218: Dec.2013. Open protocol type fire alarm systems only shall be provided in schools.

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The document concludes by outlining handover documentation and requirements for labelling in the control and operation of the equipment. For further information on all the DoE documentation – and to download the entire file – visit their website: Technical-Guidance-Documents/

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