Insulating the foundation slab afterwards despite low room height?

Hello dear ones!

I am currently trying to buy a house, built in 1958, without a basement, windows partially renewed in 2005, structure is good, it only has electric heating and no insulation. Since there is no gas connection in the village, I don’t want oil, and a gas tank is also not really my favorite, a pellet heating system with a silo should be installed if possible (in case that is important). Originally, I definitely wanted tiles and underfloor heating, but the rooms only have a clear height of 2.30m -_-

in the upper floor that wouldn’t be a problem (simply leave out the insulation and accept heating the lower rooms as well), but on the ground floor on the slab, it is already a problem because of the energy saving regulations. Insulation including underfloor heating would mean a loss of at least 10cm in height. Tiles without underfloor heating and without insulation will be cold underfoot, laminate, parquet, vinyl are actually no alternatives because of my cats. Is there "anything" that can be done to achieve a lower build-up height (e.g. break out the old screed and make it new from scratch, a special insulation material that is not 80mm, ..)? Any other ideas for my problem? The ground floor area is about 55sqm

I am still absolutely ignorant in the whole field, the possible purchase came up very spontaneously, but I am not unskilled in craftsmanship and able to learn, so please be kind and understanding ;-)

Best regards
Kanjuga

Wall heating instead of underfloor heating comes to mind. The principle is similar.

How thick is the current screed? Normally, it is removed when underfloor heating is installed afterwards.

And then there are definitely underfloor heating systems with a lower build-up than the "classic" underfloor heating. Just try googling it.

Both together and then also in combination with so-called vacuum insulation panels (they are thinner but good).

Without advertising now

Where standard floors build up to an average total height of 140 mm due to thermal and impact sound insulation, underfloor heating, and cement screed including covering, for example, the new panel "Variotec-NORIT-Trocken-/Fußbodenheizung VIP" reaches only 63 mm:

Pellet heating system with silo to be installed (in case that is important

Where will the silo be placed?

Insulation including underfloor heating would mean a height loss of at least 10 cm. Tiles without underfloor heating and without insulation will be cold on the feet; laminate, parquet, and vinyl are actually not an alternative because of my cats. Is there "anything" that can be done to achieve a lower build-up height?

Definitely remove the old screed and the old insulation first. Probably there are about 2 cm mineral fiber insulation and 5-6 cm screed in there.

If you want to tile anyway, it makes sense to leave out the screed altogether and glue XPS construction boards (WEDI, Jackodur, etc.) directly onto the raw floor (after possibly pouring leveling compounds) and tile directly on them. This way you can achieve 7-8 cm insulation. According to WEDI, you can also install underfloor heating directly in the top centimeters of the construction boards, skim over, and tile on top. We did that in our bathroom, but only on 5 m² of tiles. It works well, also in terms of heat distribution with 10 cm spacing between the pipes (16 mm pipe). There is information about this on Wedi's website. For even more insulation beneath, you could first use 5 cm PUR or resol rigid foam with a WLG of 028 and then glue 30 mm XPS with a WLG of 035 on top.

However, note that you cannot get much more than 50 W/m² heating power with underfloor heating alone. If the walls and roof are not sufficiently insulated, that is not enough to heat the house adequately.

Both together and then also in combination with so-called vacuum insulation panels (they are thinner but good).

... and they are quite expensive. Otherwise, you could lay 20 mm aerogel mats with a WLG of 007 underneath – but don't ask about the price :)

Alternatively to the wood pellet heating, if you use surface heating (underfloor or wall), you could also use an electric heat pump. Without underfloor heating, however, this is not worthwhile due to the high flow temperatures. Additionally, take a wood stove, water-based with connection to the buffer tank for the really cold days and/or solar thermal on the roof for heating and domestic hot water. The buffer tank is there anyway, and in renovation subsidy programs (KfW, BAFA) all of this is well supported.