There are a number of types of radiant chilled ceilings on the market. Ensuring good thermal conductivity between the cooling element and the other parts of the radiant chilled ceilings is important to ensure maximum performance. The cooling capacity of chilled ceilings is one of the major selection criteria.
The technical data of different manufacturers are comparable only if the cooling capacity measurements are made to the same testing standard, BS EN 14240: 2004 Ventilation for buildings – Chilled ceilings – Testing and rating. Care should be taken to ensure the same flow and return water temperatures are being compared. The difference between the mean water temperature and the internal air temperature must also be comparable.
The main considerations when selecting radiant chilled ceilings are as follows:
1) Calculation of heat loads within the design space:
- Selection of thermal environment level.
- Range of room temperatures in the summer.
- Range of room temperatures in the winter.
- Calculation of required cooling capacity.
- Internal and external loads.
- Shading of facades (are passive chilled beams needed at the perimeter to offset the solar gain?)
- Effect of primary ventilation: cooling, humidity and fresh air requirement (separate system).
2) Positioning of radiant chilled ceiling for optimum performance:
- Design for system flexibility.
- Consultation with architect and building services consultant.
- Provision for potential space partitioning changes.
3) Selection of suitable radiant chilled ceilings:
- Determining the amount of ‘active’ chilled ceiling area.
- Integrated lighting or not.
- Selection of the inlet water temperature (cooling) to avoid the risk of condensation.
- Selecting a required temperature differential between the room air and mean cooling water temperature.
- Design primary air conditions in summer and winter.
- Selection of flow and return water temperature differential.
- Calculation of maximum water flow rate.
- Maintaining turbulent water flow conditions.
- Minimum water mass flow rates to maintain turbulent flow conditions.
- System pressure loss calculation.
Does the selected radiant chilled ceiling meet all the design criteria?
If not -> go back and consider all parameters.
If yes -> proceed.
