ᐅ Slab foundation with concrete core activation. What are your thoughts?
Created on: 19 Dec 2017 12:37
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Peter L
Hello everyone,
If everything goes well, we plan to start building our own home next year, in 2018. We want to contract the trades independently and also carry out some parts ourselves. Here are some key details:
Approximately 200m² (2,150 sq ft) of living space without a basement. Underfloor heating with hardwood floors and an air-source heat pump. Ideally, a photovoltaic system will be installed on the roof and an energy storage unit in the utility room (KFW40+ standard). We are planning to use calcium silicate bricks with an external insulation system made of Multipor (cost considerations). This is just for your information and not meant to be part of the discussion.
I have spent quite some time researching ground slabs and have read a lot. It puzzles me that there are so few experience reports on Swedish slabs or similar systems. There are only one or two threads on this topic in this forum. It might be due to the tendency to report online mainly when one is dissatisfied, or perhaps people don’t realize when they are building a prefabricated house. Either way, most of the posts I found are five years or older. Often, people are unfamiliar with the Swedish slab, and what is not well known or regarded as proven tends to be viewed negatively. I was able to clarify many criticisms with some research and therefore we are still leaning towards the Swedish slab, although we are not completely certain, as I have never read a clear recommendation.
1. Costs
A frequently mentioned concern is the cost, so I will keep it brief. If you include the underfloor heating and screed in a conventional slab, the cost difference becomes less significant. The Swedish slab, however, offers significantly better insulation and thus saves money over time.
2. Speed
There was a criticism in this forum that the Futura ground slab reacts very slowly. In a building with Futura on the ground floor and a conventional underfloor heating with screed on the upper floor, the upper floor warms up within about 30 minutes, while it takes around 6 hours on the ground floor. Well, concrete is much more inert and it naturally takes longer for the heat to be noticeable. The advantage, however, is that concrete retains heat longer. Each person must decide how important it is to be able to adjust the temperature quickly. I wouldn’t necessarily consider this a disadvantage.
3. Impact noise
I read briefly that impact sound insulation might be worse. How significant is this on the ground floor? Is this really the case and are there current solutions to reduce it?
4. Maintenance
I keep reading that if something breaks, it’s hopeless. I can imagine it’s easier to break open screed than concrete, but to be honest – why would you want to do that? Isn’t it more of a theoretical problem? Suppose a pipe breaks for some unknown reason, water will continue to flow and the concrete won’t dissolve or degrade because of that, right? I don’t fully understand this criticism.
5. Time savings
No criticism here, but a Swedish slab doesn’t require drying time, which speeds up the construction process and eliminates moisture in the house.
So far, I don’t see any significant negatives, though I am not an expert and can only judge based on the information I have. I would therefore appreciate an expert opinion. Are there any mistakes one can make when pouring a Swedish slab, and are there other disadvantages I might not have considered?
What would be the advantages of a conventional slab? I imagine it can also be insulated to achieve similar benefits in that respect. Then the main difference would be the drying time for the screed. Perhaps there are other considerations when building with calcium silicate bricks plus external insulation.
I look forward to your opinions.
Peter L
If everything goes well, we plan to start building our own home next year, in 2018. We want to contract the trades independently and also carry out some parts ourselves. Here are some key details:
Approximately 200m² (2,150 sq ft) of living space without a basement. Underfloor heating with hardwood floors and an air-source heat pump. Ideally, a photovoltaic system will be installed on the roof and an energy storage unit in the utility room (KFW40+ standard). We are planning to use calcium silicate bricks with an external insulation system made of Multipor (cost considerations). This is just for your information and not meant to be part of the discussion.
I have spent quite some time researching ground slabs and have read a lot. It puzzles me that there are so few experience reports on Swedish slabs or similar systems. There are only one or two threads on this topic in this forum. It might be due to the tendency to report online mainly when one is dissatisfied, or perhaps people don’t realize when they are building a prefabricated house. Either way, most of the posts I found are five years or older. Often, people are unfamiliar with the Swedish slab, and what is not well known or regarded as proven tends to be viewed negatively. I was able to clarify many criticisms with some research and therefore we are still leaning towards the Swedish slab, although we are not completely certain, as I have never read a clear recommendation.
1. Costs
A frequently mentioned concern is the cost, so I will keep it brief. If you include the underfloor heating and screed in a conventional slab, the cost difference becomes less significant. The Swedish slab, however, offers significantly better insulation and thus saves money over time.
2. Speed
There was a criticism in this forum that the Futura ground slab reacts very slowly. In a building with Futura on the ground floor and a conventional underfloor heating with screed on the upper floor, the upper floor warms up within about 30 minutes, while it takes around 6 hours on the ground floor. Well, concrete is much more inert and it naturally takes longer for the heat to be noticeable. The advantage, however, is that concrete retains heat longer. Each person must decide how important it is to be able to adjust the temperature quickly. I wouldn’t necessarily consider this a disadvantage.
3. Impact noise
I read briefly that impact sound insulation might be worse. How significant is this on the ground floor? Is this really the case and are there current solutions to reduce it?
4. Maintenance
I keep reading that if something breaks, it’s hopeless. I can imagine it’s easier to break open screed than concrete, but to be honest – why would you want to do that? Isn’t it more of a theoretical problem? Suppose a pipe breaks for some unknown reason, water will continue to flow and the concrete won’t dissolve or degrade because of that, right? I don’t fully understand this criticism.
5. Time savings
No criticism here, but a Swedish slab doesn’t require drying time, which speeds up the construction process and eliminates moisture in the house.
So far, I don’t see any significant negatives, though I am not an expert and can only judge based on the information I have. I would therefore appreciate an expert opinion. Are there any mistakes one can make when pouring a Swedish slab, and are there other disadvantages I might not have considered?
What would be the advantages of a conventional slab? I imagine it can also be insulated to achieve similar benefits in that respect. Then the main difference would be the drying time for the screed. Perhaps there are other considerations when building with calcium silicate bricks plus external insulation.
I look forward to your opinions.
Peter L
Joedreck schrieb:
But you can’t achieve a U-value of 0.17 with screed, right? What is usual?
8cm (3 inches) insulation? If you layer 20cm (8 inches) of insulation with a thermal conductivity of 0.035 W/(m·K), you can reach that value.
How this is arranged above or below the slab is a matter of cost-effectiveness.
I understand the principle. I just keep reading that the Swedish slab achieves the same with 20cm (8 inches) insulation at WLG 035. That is the standard Swedish slab construction.
As a rough comparison, you could look at the floor structure with screed. What is common there? Waterproof membrane, insulation, impact sound insulation, screed?
And what thickness is typical? Also a total of 20cm (8 inches)? I lack experience in this area. Ideally, would one use aluminum foil-coated PUR with WLG 022?
I think this can be compared, since the client rarely interferes and demands a specific build-up above the floor slab...?
As a rough comparison, you could look at the floor structure with screed. What is common there? Waterproof membrane, insulation, impact sound insulation, screed?
And what thickness is typical? Also a total of 20cm (8 inches)? I lack experience in this area. Ideally, would one use aluminum foil-coated PUR with WLG 022?
I think this can be compared, since the client rarely interferes and demands a specific build-up above the floor slab...?
I’m not quite sure what you’re getting at [emoji4]
You need as much insulation as the thermal protection certificate requires for this building component. Whether it is installed on top of the slab or underneath doesn’t really matter in principle, as long as the required thermal insulation value is achieved.
Traditionally, insulation is primarily installed on top of the slab, below the heated screed. This is cost-effective because it can be produced using EPS, and the heat from the underfloor heating is directed upwards rather than downwards. Insulation is also installed under the screed of the upper floor (usually around 6–8cm (2.5–3 inches), in my experience) so that the underfloor heating there heats the upper floor instead of overheating the floor below through the intermediate ceiling.
You need as much insulation as the thermal protection certificate requires for this building component. Whether it is installed on top of the slab or underneath doesn’t really matter in principle, as long as the required thermal insulation value is achieved.
Traditionally, insulation is primarily installed on top of the slab, below the heated screed. This is cost-effective because it can be produced using EPS, and the heat from the underfloor heating is directed upwards rather than downwards. Insulation is also installed under the screed of the upper floor (usually around 6–8cm (2.5–3 inches), in my experience) so that the underfloor heating there heats the upper floor instead of overheating the floor below through the intermediate ceiling.
B
Bieber081521 Dec 2017 08:08Interesting thread. I’ve been wondering whether the term "concrete core activation" here refers to a traditional underfloor heating system embedded in the ground slab (instead of, as usually done, in the screed above). Or if it means that the structural components of a single-family house are to be thermally "activated" (compare to concrete core activation on Wikipedia).
So, what exactly is this about?
So, what exactly is this about?
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