Underfloor heating in bathrooms (from 2012)

A bathroom has a higher room temperature requirement, so heat requirements are generally higher, but the floor area available for underfloor heating is reduced due to the area taken up by the bath. I have recently come across a few instances of inadequate heating issues in bathrooms – not surprising. The point of this blog is to discuss the option of continuing the underfloor heating to the floor below the bath. This practice seems to be a no-no, and I’m reticent to suggest it’s a sensible approach. If the floor under the bath has wet underfloor heating, the space under the bath will be warmed, this will add heat to the room by a certain amount simply due to a slightly warmed bath and side-panel surface, and clearly a metal bath would be considerably better here than a plastic one. A roll-top, claw-foot bath even better! I have no idea if the quantity of heat is worthwhile. i.e. if the room temperature in the bathroom would be elevated by a worthwhile amount without the need to increase the underfloor water temperature (Very important when a heat pump is used). Many years ago I took a coil of micro-bore pipe, and wrapped it around the outside of my new plastic bath, and ‘bonded’ it with fibreglass. In this case, I was experimenting to see if the bath could became useful radiator area, and if the bath should stay warm whilst in use. The results seemed worse that expected, and no doubt there was little gain for a lot of effort. Given that bathroom loops are generally some of the shortest loops in the system, it strikes me that putting extra pipe below the bath would be easy, and advantageous. Is it the risk of drilling into a pipe when making a bath fixing? Is it the fear that the under-bath could overheat? Is it a daft idea with little benefit? I suppose I should lay an electric blanket under a bath and monitor some temperatures in various places to see how it performs.