Will I get damp problems if I install underfloor heating?

[struggling100]

Hi everyone

I am currently doing up a knockthrough lounge/dining room in my 1920s semi. I live in the north, where it's cold and wet, and would love to make the house a bit warmer and do my bit for the environment by having underfloor insulation put in (using boards e.g. Kingspan between the joists) under the suspended wood floor. However, I'm worried about the potential for damp problems caused by condensation accumulating under the floor where the warm air from the room meets the cool air underneath.

There was a minor problem with damp problems under the floor in the hall when we moved in, but this was sorted with the addition of several new airbricks at the front, sides, and back of the house. My house is on a slope so the space beneath the boards is quite large in the dining room (about 4-5 foot), and smaller towards the front of the house.

Would appreciate any advice people can give.

sorry, thread title should say underfloor INSULATION, not underfloor HEATING! I don't know how to edit it.

no

warm air does not travel downwards.

however it is very important to ventilate the underfloor void well. Look at your airbricks and clean out the cobwebs and dirt. If anyone has blocked the passage of air, e.g. by building a too-high path, it os possible, but wearisime, to put in Z vents. An airbrick every two metres, on all sides of the house, is usually adequate for good airflow. When you take the boards up you will see if it seems damp. Clear away all rubbish, especially wood and other organic material. If you are very lucky there will be oversite concrete, otherwise just earth.

Thank you PigletJohn! That is really helpful. You are a marvel!