I'm getting a new boiler and 7 new radiators installed. For four of the new radiators I've asked for this columnar type rather than the standard panel radiator type. The heating engineer has said that choice will add an extra day of his time to the estimate because they are "not bi-directional and have to go onto the flow pipe work which would need tracing". I'm not entirely sure what this means and whether the extra time is reasonable, so if you have any insight, please pass it on.