ᐅ Is Insulation Under the Concrete Slab Beneficial? Experiences and Insights
Created on: 7 May 2019 17:18
L
lesmue79
Hello everyone,
I am currently considering leaving out the insulation under the concrete slab. The house itself will be a bungalow with a floor area of 102 m² (1,098 sq ft), featuring an air source heat pump, underfloor heating, controlled mechanical ventilation, and in terms of plumbing, a circulation line in a timber frame house.
In principle, we ordered a KfW 55 house, but since we have not applied for any KfW 55 subsidies from the banks or government, it would theoretically not matter to me whether the house meets the 2016 Energy Saving Ordinance (EnEV 2016) standards or KfW 55 standards. Because we are not receiving any subsidies, we also do not require a blower door test.
From initial discussions, I have learned that for KfW 55 certification, about 80 mm (3 inches) of Styrodur/Jakodur insulation would need to be installed beneath the slab.
Honestly, I don’t mind if the concrete slab has a U-value of 0.20 W/m²·K (values are estimated) due to insulation, or 0.22 W/m²·K without insulation (also estimated values).
What is more important to me right now is whether I should spend the estimated 2,000 € on the insulation and installation in the ground, which would basically pay off after 20 years by saving around 20 € per year in heating costs.
Or if I should rather invest the 2,000 € in something else for the house that I can use more effectively or benefit from, such as upgrading fixtures or investing in a photovoltaic system (and yes, I know that €2,000 is not enough to cover a full PV system).
Or is every millimeter of insulation really crucial when using an air source heat pump and underfloor heating? (I understand electricity costs won’t get cheaper, so that’s why I’m also considering the photovoltaic system…)
I am currently considering leaving out the insulation under the concrete slab. The house itself will be a bungalow with a floor area of 102 m² (1,098 sq ft), featuring an air source heat pump, underfloor heating, controlled mechanical ventilation, and in terms of plumbing, a circulation line in a timber frame house.
In principle, we ordered a KfW 55 house, but since we have not applied for any KfW 55 subsidies from the banks or government, it would theoretically not matter to me whether the house meets the 2016 Energy Saving Ordinance (EnEV 2016) standards or KfW 55 standards. Because we are not receiving any subsidies, we also do not require a blower door test.
From initial discussions, I have learned that for KfW 55 certification, about 80 mm (3 inches) of Styrodur/Jakodur insulation would need to be installed beneath the slab.
Honestly, I don’t mind if the concrete slab has a U-value of 0.20 W/m²·K (values are estimated) due to insulation, or 0.22 W/m²·K without insulation (also estimated values).
What is more important to me right now is whether I should spend the estimated 2,000 € on the insulation and installation in the ground, which would basically pay off after 20 years by saving around 20 € per year in heating costs.
Or if I should rather invest the 2,000 € in something else for the house that I can use more effectively or benefit from, such as upgrading fixtures or investing in a photovoltaic system (and yes, I know that €2,000 is not enough to cover a full PV system).
Or is every millimeter of insulation really crucial when using an air source heat pump and underfloor heating? (I understand electricity costs won’t get cheaper, so that’s why I’m also considering the photovoltaic system…)
N
nordanney13 Jun 2019 07:33lesmue79 schrieb:
I’m keeping everything as originally planned with the 100 mm (4 inches) Styrodur insulation. This will make the house perform even better than KfW 40 standard, but I will never know exactly by how much (because a new thermal performance certificate would need to be created, which no one does for free). I probably won’t notice any savings on heating costs either, since there’s no comparison. If it doesn’t strain your finances, then leave the insulation as it is. However, the heating cost savings will be so small that you won’t notice a real difference compared to the option without insulation. BUT: you will have a house that is potentially more attractive to future buyers than others.
KfW subsidies can also be a factor. It’s a calculation game (rather subjective).
T
Tom_Säuer6 Oct 2019 19:45I also consider insulation below the base plate essential given the current EEV requirements and the foreseeable developments in Germany.
I plan to insulate beneath the base plate with 30 cm XPS (12 inches) and will not use a low-temperature underfloor heating system. It will be a bungalow constructed with timber frame according to passive house standards, featuring oak parquet flooring throughout. Heating will mainly rely on solar radiation; when needed, a wood stove and/or portable infrared convectors will be used. Domestic hot water will be produced by modern instantaneous water heaters located directly at the points of use.
Result: minimal investment costs, no heat losses in pipework, no heat losses in water storage tanks—neither for heating water nor for domestic hot water. Anyone who can do the math clearly has an advantage here.
I plan to insulate beneath the base plate with 30 cm XPS (12 inches) and will not use a low-temperature underfloor heating system. It will be a bungalow constructed with timber frame according to passive house standards, featuring oak parquet flooring throughout. Heating will mainly rely on solar radiation; when needed, a wood stove and/or portable infrared convectors will be used. Domestic hot water will be produced by modern instantaneous water heaters located directly at the points of use.
Result: minimal investment costs, no heat losses in pipework, no heat losses in water storage tanks—neither for heating water nor for domestic hot water. Anyone who can do the math clearly has an advantage here.
N
nordanney6 Oct 2019 21:54Tom_Säuer schrieb:
Heating is mainly provided by solar radiation; if needed, a wood stove and/or portable infrared convectors are used. So the stove is on from October to March?
H
hampshire6 Oct 2019 23:38Tom_Säuer schrieb:
Result: Minimal investment costs, no heat loss in pipes, no heat loss in water tanks; neither for heating water nor for domestic hot water. Those who can calculate here have a clear advantage.We implemented something similar. I cannot confirm minimal investment. A proper masonry heater also costs a significant amount.T
Tom_Säuer7 Oct 2019 09:03nordanney schrieb:
So the stove is on from October to March?Oh, so there is no sun at all from October to March where you live? Where is that?T
Tom_Säuer7 Oct 2019 09:09hampshire schrieb:
We implemented it similarly. I can’t agree that the investment is minimal. A proper masonry heater also costs a significant amount.In my opinion, a masonry heater is not necessary for a passive house built with a timber frame. On the contrary, the single-story house tends to overheat quite quickly with one. Therefore, I don’t need thermal mass in the wood stove either. Besides, how many masonry heaters could I buy with the money saved by installing a heat pump?Similar topics