How does water underfloor heating work?

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Posted on: 2024-05-14
 

Are you about to renovate your apartment or planning to build your dream house and considering installing water underfloor heating system? Are you curious about how water underfloor heating works? Let's explore why heating installed in the floor is generally much better than traditional radiators.

In this article, we will focus on water underfloor heating, as there is also an electric alternative (electric mats under the floor). We are concentrating on the classic version, which is powered by warm water.

Advantages of Water Underfloor Heating

Below, we will quickly outline the advantages of water underfloor heating - for comparison, we will contrast them with traditional radiators.

1️⃣ Water underfloor heating generally incurs lower operating costs than radiators, due to its lower operating temperature. Underfloor systems use a lower temperature (about 30 degrees Celsius) compared to radiators, which require a supply temperature of around 45-65 degrees Celsius to be effective.

2️⃣ Rooms heated with underfloor heating are heated more evenly, whereas with radiators, the areas closest to the radiator are better heated.

3️⃣ The comfort level is incomparably higher, especially in case of the UFH in the bathroom.

4️⃣ Water underfloor heating system does not dry out the air as much as hot radiators do - it's simply healthier, especially for children.

5️⃣ Thanks to the use of manifolds in underfloor heating systems, you gain the ability to regulate the temperature in each room separately, and sometimes even in parts of a room (if we're talking about large halls). While theoretically possible with radiator heating, manifolds are less commonly used.

6️⃣ The pipes used for underfloor heating system can also be used for passive cooling in the summer. This is not possible with radiators; using radiators for passive cooling with a heat pump module would be inefficient.

7️⃣ Again referring to the health of users - water underfloor heating does not stir up dust - it is definitely better than radiators for people with asthma or allergies.

8️⃣ Aesthetics - radiators can disrupt the look of a room, take up space, and make it less practical to arrange furniture (as you can't place furniture close to radiators without blocking the heat) - water underfloor heating offers more freedom in this respect.

Economics of Water Underfloor Heating System

With water underfloor heating system, you are likely to save on heating costs. Water underfloor heating utilizes the entire floor surface to transfer heat to the room, making it very easy and quick to achieve ideal temperature conditions. Additionally, the heat in the room spreads really evenly, no matter where you are located.

If you have doubts - consider why modern heat sources, which are - let's not kid ourselves - energy-intensive (e.g., heat pumps, gas boilers) - work well in homes with water underfloor heating system, while they are very uneconomical in homes with radiators. Of course this is a simplification of the issue, involving thermal inertia, new/old construction, but the low-temperature water underfloor heating plays a huge role here. This is the economics of the UFH system against classic radiators.

You'll Achieve Thermal Comfort More Quickly with Warm Feet

Interestingly with water underfloor heating, you'll heat rooms to lower temperatures and you'll be satisfied. Since the heat comes from the floor, warming feet (for many people the most sensitive part of the body where cold is quickly felt), thermal comfort is perceived differently. People who were accustomed to high temperatures, like 24 degrees Celsius, typically feel comparable comfort at just 21 degrees after installing water underfloor heating system. When your feet are warm, you feel less cold - the air can therefore be cooler, yet you will still feel comfortable.

✅ Cooler temperatures are also better for health.

Pipes Under the Floor - Construction

Water underfloor heating consists of water pipes that distribute heat. These are usually special pipes made from several layers of special material. Their lifespan typically exceeds 45-50 years. So, you can rest assured, they won’t need repairs anytime soon. They are also practically maintenance-free - some people worry about the possibility of a pipe under the floor bursting. What then?
We respond - in practice, this doesn't happen, think about whether you know anyone who has experienced this.

Water underfloor heating pipes need to be properly laid across the entire floor surface, and then covered with an appropriate screed of anhydrite or poured concrete. Anhydrite is a more popular option because it has better properties than concrete. It has a lower weight, better thermal conductivity, and additionally offers easy leveling (easier and faster installation - installation teams therefore prefer it). However, compared to concrete, it is more expensive - by about 20-30% in the UK. It is also possible to lay the pipes in gypsum-fiber boards. The dry version of installation is primarily used in wooden construction.

Dry and Wet Variants

Using concrete or anhydrite is definitely better. Above all, the advantage is the higher load capacity, which is about 60-75 kilograms per square meter. However, every solution, besides its advantages, has its drawbacks - if you ask practitioners, the drying time is certainly a disadvantage - it takes time. The floor is definitely not immediately load-bearing; initially, you have to wait before walking on it (which delays other finishing works). The material must harden to achieve its optimal properties. The floor can be laid no sooner than after 5 weeks.

In the case of the dry option - that is, gypsum-fiber boards - the floor can be laid immediately. However, the load capacity in this case is only up to 20 kilograms per square meter. In both cases, the floor should be laid on adhesive. This makes it adhere much better to the substrate. This will ensure that the heat from the water underfloor heating system is better transferred.

Water underfloor heating system UFH Blog

Temperature in Water Underfloor Heating

In water underfloor heating, heat is distributed via water, which is the primary heat carrier; other heat carriers are generally discouraged for underfloor heating. Additionally the water in underfloor heating is heated to a relatively low level — lower than in traditional radiators, as mentioned above.

✅ While in a traditional heating system, the water temperature can reach up to 60-70 degrees Celsius, in water underfloor heating, the water temperature should never exceed 40-45 degrees Celsius (in extreme cases, because a maximum of 32-35 degrees is usually recommended - in many cases 28 degrees is enough). The temperature of the floor itself is a maximum of 24-28 degrees Celsius. Therefore water underfloor heating system can save energy. This is due to the fact that there is less water in the pipes and it is heated to a lower temperature.

Best Heat Source for Water Underfloor Heating - Furnace? Heat Pump? Fireplace? Woodburner?

What is the best heat source for warming the water in underfloor heating? The answer is simple:
✅ Any heat source is suitable for water underfloor heating.

For underfloor heating, you can use:

Don't worry that some heat sources produce higher temperatures than recommended for water underfloor heating. Today, you can use mixing valves, including thermostatic mixing valves—there will be no problem. In other words, water underfloor heating has no special requirements regarding the heat source.

➡️ On our blog, you can also find an article about combining underfloor heating with a fireplace
and about
➡️ combining underfloor heating with a condensing boiler.

Or Maybe Electric Underfloor Heating?

There is also electric underfloor heating. In this case, instead of water pipes, electric heating mats are placed under the floor.

This makes sense in certain cases—for example, in existing buildings where installing classic (water-based) underfloor heating would require major renovations and significant expense. Electric underfloor heating only requires a minimal elevation of the floor and is much easier to install. The purchase costs for electric underfloor heating are lower. However, the operational costs are significantly higher—unless you have invested heavily in a sizable photovoltaic installation. Also, remember that the pipes of water underfloor heating are long-lasting; you can connect them to a different heat source at any stage of renovation—after 10, 15, or 30 years. Here, the flexibility is less — certainly, you cannot expect such a long lifespan from the system. We advise against it slightly (depending on the specific building), but this is a subjective opinion; electric underfloor heating can have its advantages.

 
Posted in: Underfloor heating and everything about its operation
Author: Adam Bert
Specialist in manifolds and accessories for underfloor heating as well as the selection of heating devices for underfloor heating and conventional radiators, at Nordic Tec since 2017. Planner of heating systems in single-family homes and buildings up to 500 square meters. Privately, a fan of good books.

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Comments

  • Good job guys
    By: Ralf_NI On 2024-05-17

    Hold on to this form, perfectly. Please do a comparison between the radiators and UFH systems.

    Replied by: Adam Bert On 2024-05-25 Thank a lot Ralf. Nordic Tec Team

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