ᐅ Towel warmers with air-to-water heat pumps

micric3 schrieb:

Underfloor heating without towel radiator

- Is this sufficient to maintain 21°C (70°F) in a 10m² (108 sq ft) bathroom with a shower and bathtub?
- Will the bathroom remain cooler than the other rooms due to the smaller heating surface?

According to DIN 12831, the standard temperature in the bathroom is 4°C (7°F) higher than in living rooms. Does this mean that underfloor heating should be designed to reach at least 24°C (75°F)? If it doesn’t, your general contractor or heating engineer might have an issue. So, they will likely do their best out of their own interest. It’s a good idea to politely point out that this is important to you.

In my experience, the bathroom temperature should definitely be at least 23°C (73°F). With a baby (bathing, diaper changes), at least 25°C (77°F) is advisable. If this cannot be achieved because of the room size or heating efficiency, then installing a fan heater or an infrared heater can be worthwhile. The latter is also available in discreet mirror or picture formats.

micric3 schrieb:

1.) Underfloor heating without towel radiator

- is this sufficient to maintain 21°C (70°F) in a 10m² (108ft²) bathroom with shower & bathtub?
- will the bathroom be colder than other rooms due to the smaller heating surface?

This cannot be answered without a room-specific heating load calculation. Opinions and estimates are not appropriate!

In our case, it’s sufficient with close occupancy including the shower area and an adjacent cooler bedroom. We don’t exceed 21°C (70°F) significantly unless we raise the heating curve just for the bathroom and reduce it in all other rooms. We designed for just 21°C (70°F) plus electric heating and therefore skipped using heating surfaces in the walls.

Typically, however, it is not enough—see other threads here about optimizing heat pumps. The heating surface in the bathroom is limited and the heat demand is higher.

micric3 schrieb:

2.) Underfloor heating with towel radiator on the same heating circuit as the bathroom

- increases the heating surface somewhat, but the towel radiator only has a temperature of around 21°C (70°F)
- does the advantage of the "larger" heating surface outweigh this?

The towel radiator receives the supply temperature, which is somewhat higher than 21°C (70°F). This option should be avoided. It barely adds any benefit, and the radiator introduces corrosion (rust) into the system.

micric3 schrieb:

3.) Underfloor heating with towel radiator on a separate heating circuit

- probably the least energy-efficient solution

Like option 2, but it requires heavy throttling or there are thermal short circuits. That means the temperature of the towel radiator would be even lower than in option 2, because in option 2 the towel radiator can be placed at the start of the circuit while the rest of the circuit uses the remaining heat.

micric3 schrieb:

4.) Underfloor heating with electric towel radiator

- can be switched on as needed

Either used for short-term extra heating, or if the floor heating also extends into the walls for permanently warmer conditions than in the rest of the house. More comfortable than an electric towel radiator would be an infrared panel.

To make it explicitly clear once again...

Option 5) Extending the Underfloor Heating into Wall Surfaces
If, after balancing, all rooms in the house reach the desired temperature but the bathroom remains at, for example, 19°C (66°F) with the otherwise appropriate supply temperature, then electric heating alone is not the right solution.

What would underfloor heating look like when installed in the wall?

micric3 schrieb:

What would underfloor heating look like in the wall?

Depending on whether it’s drywall construction or brick. With brick, mounting rails are screwed to the wall, and the underfloor heating pipes are clipped into these. Then the surface is plastered. There are many pictures of this available online.