Insulate basement floor

Dear community We recently purchased a terrace house whose basement is above the open underground garage The concrete ceiling between the garage and the basement is about 30 cm thick and quite cold in winter. We would now like to move our office to the basement floor. Therefore, we would like to insulate the floor, install underfloor heating, and put a linoleum covering over it. Unfortunately, we cannot give up more than 6 cm of room height. We have now considered installing underfloor heating which already has a thin insulation layer. Now to my question. How should I design the entire structure? Where do I need a vapor barrier or vapor retarder? Does anyone here have experience with this? Widder says you have to install the supplied PE foil above the heating.... Thank you very much for your answers. Regards Patrick

Hello Patrick, Your project will hardly be feasible. 6 cm build-up height is too little for a warm water underfloor heating system. Even if these 6 cm are sufficient for pipes, screed, and linoleum, there would be no space left for the necessary thermal insulation, which would mainly heat the ceiling between the garage and the basement - that wouldn't help. The floor would probably be warm underfoot; but it would hardly be suitable for heating the room - and if so, then at exorbitant heating costs.

Hello Patrick, Your project will hardly be feasible. 6cm construction height is too little for a warm water underfloor heating system.

Hello Hertweck.. I may correct you a bit.. add to that... such things are definitely possible in Switzerland... there are several companies offering such systems. I have already had such cases several times in my practice.

@Patrick The vapor barrier... bitumen membrane... you have to apply it on the raw concrete, or screed. Then the insulation with integrated heating system... special screed compound... and then the covering.

Hello BauLine, What is this overlay made of and what thickness is it applied with in Switzerland? I mean: If I take the bitumen vapor barrier (approx. 1cm) + linoleum (0.5cm) we still have 4.5cm left for the underfloor heating system and overlay. Let’s put aside Germany’s strict energy saving regulations, but for sufficient thermal insulation these 4.5cm hardly suffice in Switzerland either – or how do you see it? And now add the thickness of the overlay. I am very interested in how a thermally insulated underfloor heating system with heated screed/overlay and floor covering can be accommodated in a 6cm build-up height – Switzerland or not, this is a constructive matter.

Hello Hertweck

What the compound consists of will probably not be revealed by the manufacturer Sika. It was specially developed for, or with, the system manufacturer to meet the requirement.
The system with possible supply temperatures of 25-35°C requires only 10mm installation height itself. Thus, about 4.0 cm remain for good PUR insulation.. that is definitely better than nothing if the user already wants a floor heating system. It is an office after all.. or perhaps just a personal study, so probably not comparable to the usual living area. For tax reasons, he will probably carry it out internally anyway and not report the expansion to the municipal building authority.

I hope I was able to at least partially answer your question.
Since otherwise, when I write contributions, I at most advertise for myself, but not for an IR heating system, which unfortunately appears compulsorily under my signature, I will therefore leave it at this contribution for now.
I wish you continued fun and success with the Swiss construction world.

These 6 cm are simply too little and make no sense. It was similar for us, and the company explained to us that this doesn't work that way. So we installed radiators.