This one is simpler. Once you have chosen the type of insulation board you need, then you need to work out the total area of your room. The general rule of thumb is to choose coated insulation board for timber substrates and uncoated insulation board for concrete substrates.
To do this, multiply the width of the room by the length of the room to give a square metre area. We recommend adding 10% to this figure to allow for any wastage when installing the insulation as it comes in boards. This will give you the total amount you need, which will be able to be quoted by your chosen supplier.
How much electric underfloor heating do I need?
Right, this is the crunch point… so some context first.
Each individual heating mat/cable that has its own unique fixed resistance per linear metre. This means that the cable cannot be altered in length at all without affecting the heat output of the system.
So, you’ve probably figured out that this means that you need to always make sure you haven’t got too much heating cable. Correct! It’s really important that you under-quote, rather than over-quote.
However, there is a bit more to this as well.
With underfloor heating, it’s also important to work out something we call the ‘available heating space’. This is the total area of the floor, minus any floor area that is taken up by fixtures like baths, vanity units, wardrobes etc.
You can imagine what happens if this step isn’t thoroughly done… here’s an example:
The customer has a bathroom project with an area of 5m2. The supplier provides a 5m2 mat.
Hang on. There’s a bath. Inevitably the question asked is ‘can I cut the cable?’
NO…. please don’t!