What pipes for underfloor heating - tips and tricks

If you're planning to implement underfloor heating in your home, apartment, or business and you're not sure which pipes to choose, be sure to read the article below. You will learn how proper pipe layout in underfloor heating should look like to achieve maximum efficiency. You'll also find out where pipes should not be placed, what types of pipes are available on the market, and which ones are the best. Check also what to pay special attention to when choosing pipes for underfloor heating. Welcome to read and get acquainted with our offer.

What are underfloor heating pipes?

Underfloor heating pipes are durable, lightweight, and flexible elements used in underfloor heating systems. They are made of various polymers (e.g., polypropylene - PP, polyethylene - PE-X), which have good thermal conductivity for plastics. This means that the pipes can evenly distribute heat throughout the floor surface, which is an extremely effective way of heating rooms.

In addition, their high flexibility facilitates installation and laying even in hard-to-reach places. They are characterized by high resistance to mechanical damage and aging, which translates into their long-term use. Thanks to their advantages, these pipes enable easy implementation and an economical way to ensure thermal comfort in rooms.

What else is needed in underfloor heating besides pipes?

In addition to underfloor heating pipes, this heating system requires the following elements for correct operation:

• heat source - e.g., heat pump, condensing boiler,
• heat transfer medium - usually water,
• insulation - prevents heat loss (the cold concrete under the pipes is not heated; the heat is directed in the right direction - to the floor),
• fixing elements for pipes to the substrate - guarantee easier laying of the pipes; allow creating the correct shape of the entire underfloor heating system,
• mortar (screed) - used to permanently set the heating elements in the correct position and distances from each other,
• underfloor heating manifold - this is the point where hot water from the heat source is divided and directed to different sections of the underfloor heating to heat different rooms.

Layout of pipes in underfloor heating

In the case of water underfloor heating, pipes are laid in a spiral manner or in the form of a "serpentine" on the floor surface. These pipes are placed on thermal insulation and then covered with mortar, which aims to fix the location where the underfloor heating pipes were placed. Thanks to this, we can be sure that the pipes are still in the same place years later. Typically, the pipes are laid about 10-20 cm apart.

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Where it's not worth placing underfloor heating pipes?

If you're wondering where it's not worth placing underfloor heating pipes, be sure to read the list below.

1. Under heavy furniture permanently placed in one spot: We do not recommend laying pipes under furniture such as beds, heavy cabinets without legs, or kitchen units. Such furniture can restrict heat flow and significantly reduce the efficiency of the entire underfloor heating system.
2. Under walls with a large number of windows / large glazed areas: Windows are often a source of heat loss, so it may be better to install wall radiators directly next to them.
3. In hard-to-reach areas: If an area is difficult to access, such as a floor located under large slopes or directly under stairs, installing underfloor heating pipes can be costly and complicated.
4. In areas with a high risk of damage: Underfloor heating pipes must be as protected as possible from mechanical damage, so they should not be laid in areas where there is a risk of damage, such as garages, basements (not to mention that these are places where underfloor heating is often insufficiently applied, if at all).
5. Outside the building: This seems quite obvious, but just to be sure, placing underfloor heating outside the building makes no sense.
6. In places where rapid heating or cooling of the space is necessary: Underfloor heating systems have thermal inertia. This means they need time to heat up or cool down (this process takes longer compared to standard radiators). Therefore, underfloor heating is not recommended in places where rapid temperature adjustments are required, such as in laboratories.
7. Where it's not possible to add the required insulation to the substrate: Proper insulation under underfloor heating pipes is crucial for the overall efficiency of the system. If we cannot provide adequate insulation, then as a consequence, we may not achieve the temperatures we desire or the underfloor heating may consume much more energy compared to a well-prepared substrate.

Types of underfloor heating pipes

Underfloor heating pipes are typically categorized based on the material they are made of. Below are the most popular types of underfloor heating pipes.

PEX Pipes

The most popular type of pipes for this type of heating are PEX pipes, which are cross-linked polyethylene. They are flexible, easy to install, and have high resistance to temperature variations and chemicals. Their thermal conductivity ranges from 0.35 W/(K*m) to 0.41 W/(K*m).

Copper Pipes

Another material used for manufacturing underfloor heating pipes is copper. Copper pipes have high heat conductivity (up to 400 W/(K*m)) and resistance to corrosion. They are also durable and resistant to mechanical damage. However, they are currently less commonly used due to higher production costs.

However, it is worth noting that due to the much better thermal conductivity of copper compared to plastics, covering the same area with PEX pipes requires about twice as many pipes compared to covering the floor with copper pipes. This is because copper pipes can have much larger spacing between them in underfloor heating construction compared to constructions made of polymer pipes.

The choice of suitable underfloor heating pipes depends on individual preferences and the properties of the specific room, so it is worth consulting with a specialist before making a choice.

Other Popular Types of Underfloor Heating Pipes

• PE-RT pipes, which are polyethylene pipes adapted to work at high temperatures, have thermal conductivity comparable to PEX, i.e., about 0.4 W/(K*m).
• PP pipes - their thermal conductivity is lower than that of PEX pipes and is about 0.22 W/(K*m).
• PB pipes - in this case, the thermal conductivity is about 0.19 W/(K*m).

There are also more advanced multi-layer underfloor heating pipes available on the market (a combination of polymer and metal), such as:

• PEX/Al/PEX - a pipe in which both the outer and inner layers are made of polyethylene, while the middle layer is made of thermally conductive aluminum (about 235 W/(K*m)).
• PEX/Al/PE - a pipe consisting of layers: cross-linked polyethylene, aluminum, and regular polyethylene.
• PE-RT/Al/PE-RT - a pipe made of high-temperature-resistant polyethylene layers and aluminum.
   

What to consider when choosing underfloor heating pipes?

When choosing underfloor heating pipes, there are several important factors to consider. Firstly, the flexibility of the pipes is crucial because they need to be easily bent and laid along the floor. It is also important for the pipes to be thick enough to ensure uniform heat distribution (usually around 2 mm).

The diameter of the pipes also matters because too small a diameter can result in limited flow of hot water, which will affect the efficiency of the heating system (this parameter should fall within the range of 10 to 20 mm - the most commonly used underfloor heating pipes are 16x2 mm, 17x2 mm, and 18x2 mm).

It is also necessary to carry out calculations regarding the amount of material needed. For this purpose, it is worth measuring the floor area precisely and taking into account any corners or obstacles. Then you can calculate how many pipes will be needed to cover the entire surface. Well-chosen and properly installed pipe network is a key element of an effective underfloor heating system.