ᐅ Adding insulation to a concrete slab foundation afterwards despite low ceiling height?

Hello everyone!

I’m currently trying to buy a house built in 1958, without a basement. Some of the windows were replaced in 2005, and the structure is in good condition. It only has electric heating and no insulation. Since there is no gas connection available in the town, I don’t want oil, and a gas tank is not really my preference, I would like to install a pellet heating system with a silo if possible (in case that’s relevant). Originally, I wanted tiles and underfloor heating, but the rooms only have a clear ceiling height of 2.30m (7 ft 7 in) -_-

Upstairs, that wouldn’t be a problem (just leaving out the insulation and accepting heating the rooms below), but on the ground floor with a concrete slab, it’s an issue because of energy efficiency regulations. Insulation plus underfloor heating would reduce the height by at least 10cm (4 inches). Tiles without underfloor heating and without insulation will be cold underfoot, and laminate, hardwood, or vinyl are not really an option because of my cats. Is there “anything” that can be done to reduce the build-up height (e.g., removing the old screed and starting over, a special insulation material that is less than 80mm (3 inches) thick...)? Any other ideas regarding my problem? The ground floor area is about 55sqm (590 sq ft).

I’m completely new to all of this, the potential purchase came up very spontaneously, but I’m fairly handy and a quick learner, so please be kind and patient ;-)

Best regards
Kanjuga

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

How thick is the existing screed? Usually, it is removed when underfloor heating is installed afterward.

There are also underfloor heating systems with a lower build-up height than the traditional type. Just try searching for them online.

Both options, combined with so-called vacuum insulation panels (which are thinner but effective), are possible.

Without endorsing any products

While standard floors typically add up to about 140 mm (5.5 inches) in total height including thermal and impact sound insulation, underfloor heating, cement screed, and floor covering, for example, the new panel "Variotec-NORIT dry/underfloor heating VIP" achieves only 63 mm (2.5 inches):

Kanjuga schrieb:
Pellet heating system with silo installed (if that is important

Where will the silo be located?

Kanjuga schrieb:
Insulation including underfloor heating would reduce the height by at least 10cm (4 inches). Tiles without underfloor heating and insulation feel cold underfoot, and laminate, parquet, or vinyl are not really suitable because of my cats. Is there "anything" that can be done to achieve a lower build-up height?

Definitely remove the old screed and insulation first. There are probably about 2 cm (0.8 inches) of mineral wool insulation and 5-6 cm (2-2.5 inches) of screed.

If you want tiles anyway, it makes sense to skip the screed and apply rigid XPS insulation boards (such as WEDI, Jackodur, etc.) directly onto the raw floor (after possibly leveling with self-leveling compound) and tile directly on top. This way you get 7-8 cm (3-3.1 inches) of insulation. According to WEDI, you can also install an underfloor heating system directly in the upper centimeters of the boards, cover it with leveling compound, and tile over it. We did this in our bathroom with 5 m² (54 ft²) of tiles. It works well, including heat distribution with 10 cm (4 inches) spacing between pipes (16 mm (0.63 inch) pipe). Wedi’s website has more information on this. For additional insulation below, you could first lay 5 cm (2 inches) of PUR or resol rigid foam with a thermal conductivity of 0.028 W/m·K, then stick 30 mm (1.2 inches) of XPS with 0.035 W/m·K on top.

Keep in mind, underfloor heating alone can usually deliver no more than about 50 W/m² (5 W/ft²) heating output. If the walls and roof are not properly insulated, that will not be enough to keep the house warm.

Caspar2020 schrieb:
Both together, combined with so-called vacuum insulation panels (which are thinner but effective).

... and they are quite expensive. Another option is to install 20 mm (0.8 inches) of aerogel mat with a thermal conductivity of 0.007 W/m·K underneath—but don’t ask about the price 🙂

Alternatively to a wood pellet heating system, if you use a surface heating system (underfloor or wall heating), you could also use an electric heat pump. Without underfloor heating, this isn’t really worthwhile due to the high supply temperatures required. Additionally, a water-heated stove connected to a buffer tank can help on very cold days, and/or solar thermal for heating and domestic hot water on the roof. The buffer tank is usually already there, and in major renovation projects all of this is well supported by subsidies (e.g., KfW, BAFA).