ᐅ Insulation Beneath Screed in Older Home Renovations with Underfloor Heating – Experiences?
Created on: 15 Dec 2018 00:03
A
AndreasBauer
Hello dear home builders,
I live on the outskirts of Munich and am currently renovating my grandparents’ detached house from the 1960s. The entire floor will be redone with screed and underfloor heating. The old screed and insulation have already been removed. The build-up height of the old floor was about 8cm (3 inches). To avoid problems with doors and balcony windows, the new floor should, if possible, not exceed 10-12cm (4-5 inches) in height—that is, only 2-4cm (1-1.5 inches) more than the old one.
I have received a quote from a heating engineer that includes the following insulation materials, which I don’t know how to evaluate. They are supposed to be placed on top of each other below the underfloor heating and seem unusual to me in this combination. This insulation is planned for the ground floor (unheated cellar) as well as the floors above. No additional insulation is included in the offer.
- Rock wool impact sound insulation 5 kN/m², thickness 13-30mm (0.5-1 inch), thermal conductivity 0.63 mK/W
- Mineral fiber impact sound insulation 3.5 kN/m², thickness 20-50mm (0.8-2 inches), thermal conductivity 0.37 mK/W
My online research has not clarified this so far. I am currently stuck here and would really appreciate it if someone could explain what these materials are and whether this combination is common or if there might be better solutions for me. Of course, I will also discuss this with the heating engineer, but I want to gather more information beforehand if possible.
Many thanks in advance!
AndreasBauer
I live on the outskirts of Munich and am currently renovating my grandparents’ detached house from the 1960s. The entire floor will be redone with screed and underfloor heating. The old screed and insulation have already been removed. The build-up height of the old floor was about 8cm (3 inches). To avoid problems with doors and balcony windows, the new floor should, if possible, not exceed 10-12cm (4-5 inches) in height—that is, only 2-4cm (1-1.5 inches) more than the old one.
I have received a quote from a heating engineer that includes the following insulation materials, which I don’t know how to evaluate. They are supposed to be placed on top of each other below the underfloor heating and seem unusual to me in this combination. This insulation is planned for the ground floor (unheated cellar) as well as the floors above. No additional insulation is included in the offer.
- Rock wool impact sound insulation 5 kN/m², thickness 13-30mm (0.5-1 inch), thermal conductivity 0.63 mK/W
- Mineral fiber impact sound insulation 3.5 kN/m², thickness 20-50mm (0.8-2 inches), thermal conductivity 0.37 mK/W
My online research has not clarified this so far. I am currently stuck here and would really appreciate it if someone could explain what these materials are and whether this combination is common or if there might be better solutions for me. Of course, I will also discuss this with the heating engineer, but I want to gather more information beforehand if possible.
Many thanks in advance!
AndreasBauer
A
AndreasBauer16 Dec 2018 19:12The offer has not been signed yet. To be fair, I have not given the heating installer any specific instructions, and I also assume that such details could still be adjusted.
Is it worth using the underfloor heating system board instead of the biofiber perforated board, and perhaps 30mm XPS/EPS instead of the 20–5 mineral wool impact sound insulation on the ground floor?
Dr Hix schrieb:Unfortunately, I feel this way about most energy-saving measures, especially when renovating older buildings. Energy saving is a luxury. Therefore, we will stick with a gas boiler for now.
The monetary effort for vacuum insulation panels is likely disproportionate to the possible energy savings.
Is it worth using the underfloor heating system board instead of the biofiber perforated board, and perhaps 30mm XPS/EPS instead of the 20–5 mineral wool impact sound insulation on the ground floor?
Insulating an uninsulated floor above an unheated basement (from above and/or below) is almost always cost-effective. We are talking about costs of less than 30€/m² (even less if you do it yourself).
Vacuum insulation panels usually cost well over 100€/m². As far as I can tell, this is a very complex solution because you obviously cannot cut the panels. They must be precisely planned and manufactured according to your specific requirements in advance.
Any kind of "special system" for underfloor heating will ultimately be more expensive than the traditional method with wet screed. With about 10cm (4 inches) floor build-up, I personally see no need for that. Around 2cm (0.8 inches) for the pipes, plus 3.5–4.5cm (1.4–1.8 inches) covering screed, and 1.5–2.0cm (0.6–0.8 inches) for the floor covering, leaves you 20–30mm (0.8–1.2 inches) for insulation under the screed. The cost here in rural areas is about 30€/m² for the underfloor heating plus another 15€ for the screed, excluding floor covering.
If you choose 30mm (1.2 inches) PUR insulation and can add another 60mm (2.4 inches) beneath the basement ceiling, you achieve an overall U-value below 0.25 and might even qualify for support through the KFW program.
On the upper floor, use EPS impact sound insulation in the maximum possible thickness; it doesn’t get cheaper than that.
The package offered seems to come from an ecological approach. If you have the budget for it and want to atone for the X5 in the driveway, then by all means go for it. In my opinion, it does not provide added value.
Vacuum insulation panels usually cost well over 100€/m². As far as I can tell, this is a very complex solution because you obviously cannot cut the panels. They must be precisely planned and manufactured according to your specific requirements in advance.
Any kind of "special system" for underfloor heating will ultimately be more expensive than the traditional method with wet screed. With about 10cm (4 inches) floor build-up, I personally see no need for that. Around 2cm (0.8 inches) for the pipes, plus 3.5–4.5cm (1.4–1.8 inches) covering screed, and 1.5–2.0cm (0.6–0.8 inches) for the floor covering, leaves you 20–30mm (0.8–1.2 inches) for insulation under the screed. The cost here in rural areas is about 30€/m² for the underfloor heating plus another 15€ for the screed, excluding floor covering.
If you choose 30mm (1.2 inches) PUR insulation and can add another 60mm (2.4 inches) beneath the basement ceiling, you achieve an overall U-value below 0.25 and might even qualify for support through the KFW program.
On the upper floor, use EPS impact sound insulation in the maximum possible thickness; it doesn’t get cheaper than that.
The package offered seems to come from an ecological approach. If you have the budget for it and want to atone for the X5 in the driveway, then by all means go for it. In my opinion, it does not provide added value.
AndreasBauer schrieb:
Unfortunately, I have that feeling with most energy-saving measures, especially in renovating older buildings. Saving energy is a luxury. So for now, it will stay with a gas boiler.Investing in energy-saving measures is not a luxury but often pays off. The key is always to start with the most efficient measures first. If you try to do everything, of course, the costs add up, but with a building from the 1960s, there is usually a lot of potential for investments that pay for themselves within 3 to 10 years.
Switching from a gas boiler to something else just because it’s trendy right now (heat pump?) will probably hardly, if at all, be cost-effective in your case.
AndreasBauer schrieb:
Is the floor heating system panel worth it instead of the biofiber perforated board, and instead of the 20-5 mineral wool impact sound insulation on the ground floor maybe 30mm XPS/EPS?Dr Hix schrieb:
Any kind of "special" system for underfloor heating will always be more expensive than the classic version with wet screed.As Dr. Hix already mentioned: underfloor heating is not an energy-saving investment but rather increases comfort and also costs more. Without underfloor heating, you can install wooden floorboards on joists with insulation in between, or insulation plus a dry screed and covering.
For underfloor heating, there are different approaches; not all are more expensive, and many are simpler than the new build method with stapler boards and poured screed. A dry system has a lower build-up height than one with poured screed, allowing for better insulation below.
Suggestion for DIY: fully bond construction panels (cement-coated, glass-fiber-reinforced XPS boards from e.g., WEDI or Jackodur), mill channels for the underfloor heating, lay pipes, fill and cover with floor finish (parquet or tiles). 8 cm (3 inches) insulation, inexpensive and quick. There are also dry systems where, for example, wooden floorboards are simply integrated into the top layer of insulation between the joists. Also offers maximum insulation and quick completion.
PS: On the ground floor, if there is only a basement underneath, impact sound insulation is not necessary.
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