What length of convector do I need for a floor-to-ceiling window?

As a rule, the convector covers 70-90% of the glazing length, so the warm stream runs evenly along the whole pane and prevents condensation. The exact length is set by the heat loss of the room.

What trench depth is needed for a convector?

Depth depends on the chosen model and the output required, and the trench is set into the screed ahead of time, at the renovation stage. We give the exact trench dimensions once the model is chosen.

Can I order a non-standard size?

Yes. Novaterm convectors are made to order, so the length can be matched to a specific window rather than forcing the room to fit a standard unit.

How do I work out the output needed?

Output is calculated from the heat loss of the room and the heating-water inlet and outlet temperatures (if known) and the air. We do this calculation free of charge; just send the room and glazing dimensions.

How to Choose the Size of an In-Floor Convector

Updated May 24, 20263 min read

For an in-floor convector to heat efficiently and sit neatly in the floor, its size has to be chosen correctly. The size of an in-floor convector is set by three things: the heat loss of the room, the length of the glazing, and the trench dimensions (width and depth). Let's go through them.

What the size depends on

Room heat loss: how much heat is needed for comfort. The larger the room, the higher the ceilings, and the more glazing, the more output the unit needs: more length, a fan, or both.
Glazing length: the convector runs along the window, and its length is tied to the width of the glass.
The trench: its width and depth are fixed before construction to suit the chosen model.

The window-length rule

A useful guide: the convector covers 70-90% of the glazing length. This matters not just for output and appearance, but for the unit to work as a thermal curtain: the warm stream runs along the whole pane and keeps the window from fogging up. For wide glazed spans, place several convectors in a row.

Width and depth

Casing width affects output and how the grille looks in the floor.
Depth sets the trench height in the screed, which must be planned before the final flooring goes down.

If the installation space is tight but high output is needed, a fan-equipped model is the answer: forced convection gives more output for the same length.

Natural or forced: by output

At the same length, a convector with a fan gives off more heat. So sizing and convection type go hand in hand: sometimes it pays to go a little shorter but with a fan, rather than longer without one. The details are in With or Without a Fan.

How we size it

To get it right, we work from the room's heat loss. Just send us:

the room dimensions and ceiling height;
the length and type of glazing;
the heating-water inlet and outlet temperatures (if known).

From this we choose the length, width, depth, and convector type, and give you the trench dimensions for the builders right away. Novaterm convectors are made to order, so the size is matched to your window.

In short

Sizing a convector is not guesswork; it's a calculation: length to the window, output to the heat loss, trench to the model. It's easy to get wrong and expensive to fix once the screed is down. Send us your room dimensions and we'll choose the convector and work it all out for free. If you're still deciding between units, start by reading Convector or Radiator: Which to Choose.