How to properly design underfloor heating at home?

How to design water-based underfloor heating? Let's begin

✅ The question of how to design underfloor heating in our specific building (because every building may have its own characteristics) is where we should start the conversation with the installer, as we advise against doing it ourselves if we lack experience in underfloor heating design. Nevertheless, it's good to know the basics so that we can monitor and assess the progress of the work.

It's not without reason that they say, "The Masters Eye Makes the Horse Fat," and it's worth it for the installation team to know that we have basic information about underfloor heating. Surely, this won't hurt the thoroughness of the work, as confirmed by most people who have already gone through building a house.

Designing underfloor heating - the issue of floor insulation and ceiling height

✅ Good floor insulation is essential. In rooms where we plan to install underfloor heating, the ceiling should be high enough to allow us to lay layers of insulation, such as styrofoam, and then install the heating loops plus a layer of screed, which will function as the underfloor heating. If we are purchasing a ready-made house design with underfloor heating planned, it should already be included in the design.

Laying underfloor heating

Laying underfloor heating is crucial for the system to operate correctly. Unfortunately, there are many conflicting opinions on how to do it optimally. Below are a few commonly accepted truths regarding the laying of underfloor heating.

☑️ Underfloor heating pipes should not be laid out arbitrarily and uniformly. The farther away from the boiler room or heat source (such as a boiler, fireplace with a water jacket, heat pump, etc.), the cooler the water in the pipes will be, as it gives off its heat to the concrete screed, heating the floor. Therefore, closer to the boiler room or heat source, we can, and perhaps should, lay the loops less densely than in rooms further away.

Many professionals, not without reason, advocate for starting to lay the loops from the wall most exposed to heat loss. This is the wall with large windows or the wall facing the shaded or northern side. This seems justified and practical.

What should be the spacing between underfloor heating pipes?

✅ It is often mentioned that underfloor heating pipes should be laid at distances ranging from 10 to 35cm from each other. In areas closer to the edges, such as near internal walls, it's worth running them more densely, as the floor potentially cools down faster there. However, loops should run at least 10-15cm away from external walls (a value assumed for insulated buildings).

☑️ If you notice that the team of professionals is laying the underfloor heating pipes in a system that is unclear to you - you observe that in some places the distances between the pipes are different than in other places - everything is likely fine. However, it's worth asking questions and requesting an explanation to ensure that everything is proceeding according to the underfloor heating design.

Where not to lay underfloor heating loops?

It's advisable to sketch out the potential layout of furniture, especially built-in kitchen or bathroom furniture that won't be rearranged, before laying the loops.
✅ Laying underfloor heating loops under furniture is not recommended; efficient underfloor heating does not heat the underside of our cabinets or drawers. This results in inefficient heat distribution, which over time may only distort or warp the shape of our built-in furniture. Moreover, it doesn't positively impact the costs of using underfloor heating because proper loop placement significantly affects the financial aspect over many years.

Underfloor heating in the shower area?

Of course, installing underfloor heating in the shower significantly enhances the comfort of using the shower (assuming no shower tray is used - only a linear drain).

☑️ However, underfloor heating in the shower area should be designed and executed thoughtfully. A common mistake is installing underfloor heating loops in close proximity to the linear shower drain (if applicable). Naturally, laying loops in the shower area, and having a warm floor in that space, is a great comfort-enhancing feature for our bathroom. However, placing the heating pipe directly near the drain may cause it to dry out, resulting in no water in the trap, and we may experience odors from the sewage system. (This applies to so-called "wet" traps).