Tips underfloor heating

Thursday, December 15, 2016

The “Do’s and Don’ts” of installing underfloor heating

You can only build it once; otherwise it becomes a very expensive project. We're talking about underfloor heating, of course. There are a lot of factors to take into account – during both the design and installation phases. That’s why Stefan Lenting, product specialist for Ubel (Dutch technical wholesaler), is sharing his top 5 Do's and Don'ts for a hassle-free installation. Thanks Stefan!

These are the Do's
Stefan Lenting , Ubel

1.  Determine the main heat source before you start

Will you go for a heating distributor with or without pump? This choice depends on the size of the floor space. When systems are relatively small, a regular boiler offers sufficient capacity to pump the water around. The tipping point is at a floor heating system with 6 to 7 groups. At 7 groups, you will need at least one distributor with a pump.

2. Check if room control is required

For 30 to 40 percent of underfloor heating systems, people opt for a separate room control, or in other words, the ability to set the temperature in different rooms.  If this is a requirement, then apply an electrical control system, which lets you open and close separate groups. It's best to include this when designing the system. With a wireless control, you have the option to add this at a later stage.

3. Yes/no border zone

In some situations, such as when your house has a glass façade, it is wise to make a border zone in the heating system. This prevents cold traps (when cold air drops alongside a window) and generates extra warmth and comfort. Although you would normally install the system 15 mm from center to center in the border zone, it’s better to opt for 10 mm.

4. Choose a smart place for the manifold

When choosing a location for the manifold, think of the design carefully. Choose a place where you can install it easily, neatly, and where the central heating pipes can be seamlessly passed around. A suitable place for the manifold is often under the stairs, in the storage area or in the wall near the meter. Small hallway? It doesn’t matter because it is simply not convenient to place the manifold in the hallway. If all supply and return lines run through the hallway, the temperature in the hall itself will be poorly regulated. In this case, opt to make a recess in the wall and run the cables directly through the wall itself.

5. Get a heat loss calculation

The making of a heat loss calculation costs money and is therefore often overlooked. Yet my strong advice is that you will do well to make this relatively small investment and incorporate the calculation results into the design. Such a heat loss calculation will clearly show exactly how much heat you’ll need to reach the desired temperatures in the different areas. Who knows? You may learn that your floor heating h.o.h. can lay 20 mm, instead of 15 mm. The result: fewer cables and power will be needed, which is better for your pocketbook and for the environment.

These are the Don'ts
Stefan Lenting , Ubel

1. Floor cooling: temperature flow below the dew point

An absolute no-no for floor cooling: setting the water temperature supply below the dew point. The floor will condense, resulting in moisture on the floor. Wet feet! So always make sure that you keep the temperature flow above the dew point; by 18 degrees, for the supply pipes and by 22 degrees, for the return lines. This works well in most cases. 

2. Drilling underfloor heating in the floor?

Beware of drilling! Even though you have the drawing at hand, there is a risk that you will become a conduit. My advice is to think of everything that needs to be done in/with the floor and incorporate this into the design. Think of baseboards, sills, create a floor chute or confirm the settings. Is drilling still inevitable? If so, drill – but not too deep.

3. Floor temperature > 29 degrees

A floor temperature over 29 degrees Celcius is guaranteed to make your feet too warm. At this juncture, floor heating is really not comfortable anymore. It is the task of the installer to set the maximum temperature.

4. Non-impermeable pipes

When installing a new heating system, always select diffusion-tight pipes. If you don’t, the pipes and/or the distributor can corrode and the boiler or heat pump may be impacted. Not exactly conducive to the life of the system. Until about 20 years ago, non-impermeable pipes were often used in underfloor heating systems. Do you have such a system? Then, place a heat exchanger between the pipes and the heat source. Thus, any rust water will stay in the pipes and keep the central heating area clean.

5. No expansion joints

All floor surfaces expand and contract to some degree, so allowance has to be made for this or you will have ugly cracks. This is what will happen if you do not use expansion joints. My advice: when you work with larger floor surfaces (40 square meters+), always use expansion joints. In large, luxury homes, expansion joints are a must. Most of these homes have marble floors which are subject to cracking if there are no provisions made for underfloor expansion. Expansion joints are often avoided because of aesthetic reasons but let’s be honest, with tears in your expensive marble tile floor, you have much bigger problems!

To learn more about Wavin's underfloor heating solutions, please visit your local Wavin company website.