Hello everyone,
We are in the final planning stage of our single-family house. Since this is our first house (probably like for most people), we are, at best, amateurs in this field.
Here are some key details about the house:
Type: Timber frame construction, no basement
Standard: KfW 40plus
Footprint: 106m² (1141 sq ft)
Living area: 165m² (1776 sq ft)
Regarding the insulation, I have the following question:
Under the ground slab, a 140mm (5.5 inches) thick perimeter insulation (thermal conductivity WLG035) is being installed (the ends have 100mm (4 inches)).
The construction company has now told me that the floor inside the house will also get an additional 100mm (4 inches) insulation toward the ground slab, on top of which the underfloor heating will be installed. My question is whether it is really necessary to insulate the floor again with this thickness against the ground slab. After all, the installation costs for the underfloor heating including the mentioned insulation and the subsequent screed add up to a considerable €19,000 for 155m² (1668 sq ft) of heated area.
Thanks for your assessment.
Best regards,
Torsten
We are in the final planning stage of our single-family house. Since this is our first house (probably like for most people), we are, at best, amateurs in this field.
Here are some key details about the house:
Type: Timber frame construction, no basement
Standard: KfW 40plus
Footprint: 106m² (1141 sq ft)
Living area: 165m² (1776 sq ft)
Regarding the insulation, I have the following question:
Under the ground slab, a 140mm (5.5 inches) thick perimeter insulation (thermal conductivity WLG035) is being installed (the ends have 100mm (4 inches)).
The construction company has now told me that the floor inside the house will also get an additional 100mm (4 inches) insulation toward the ground slab, on top of which the underfloor heating will be installed. My question is whether it is really necessary to insulate the floor again with this thickness against the ground slab. After all, the installation costs for the underfloor heating including the mentioned insulation and the subsequent screed add up to a considerable €19,000 for 155m² (1668 sq ft) of heated area.
Thanks for your assessment.
Best regards,
Torsten
T
torsten8026 Nov 2016 21:20But maybe the thread creator will add something The creator says the following:
The purpose and relevance of KfW standards should actually not be the topic of this thread.
My concern was to find out whether a second layer of insulation makes sense or if it is pointless. To me, it’s simply redundant—if the perimeter insulation is not thick enough, then I would just make it thicker instead of applying another insulation layer 20cm (8 inches) higher up.
That’s my way of thinking—though it might be completely wrong—so I would simply like to hear the opinion of an expert.
If the insulation is placed below the vapor barrier (BOPA), it is inside the thermal envelope, so there is no thermal bridge. And you need the insulation on the vapor barrier anyway because of the underfloor heating!
An expert can gladly explain this to you in more detail. Have a nice evening.
An expert can gladly explain this to you in more detail. Have a nice evening.
T
torsten8027 Nov 2016 19:10Okay, thanks for the explanation – it kind of makes sense now – although I’m wondering about the underfloor heating systems that are directly embedded in the concrete slab… they work as well, right?
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