ᐅ Indoor heat pump in the basement not possible due to groundwater?
Created on: 10 Jan 2023 19:40
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Baskervile
Hello,
I am currently planning the construction of a detached single-family house. When signing the contract, the general contractor promised an indoor heat pump in the basement, which is also specified in the contract. After receiving the soil survey report, which states a design groundwater level of -1.75m (-5.7 feet), I was told that an indoor heat pump is not possible because the air ducts cannot be sealed according to the relevant standards (DIN).
Is this really impossible or just too risky?
Furthermore, I received an offer for an outdoor installation along with a discount of just under €1000. During the planning discussions, I was told there would be an additional cost of about €5000 for the indoor heat pump. Overall, this feels a bit strange to me.
I would appreciate your experiences and any information on this topic.
A second question about civil engineering work: My general contractor insists on having the excavation supervised by an unexploded ordnance clearance service due to a note in the soil report, without any prior survey. He claims this is now a regulation by the BG-Bau (German Social Accident Insurance for the construction industry). Is this correct?
I am happy to provide further information or pictures if helpful. I hope I have posted this in the appropriate subforum.
Thank you very much for your responses!
I am currently planning the construction of a detached single-family house. When signing the contract, the general contractor promised an indoor heat pump in the basement, which is also specified in the contract. After receiving the soil survey report, which states a design groundwater level of -1.75m (-5.7 feet), I was told that an indoor heat pump is not possible because the air ducts cannot be sealed according to the relevant standards (DIN).
Is this really impossible or just too risky?
Furthermore, I received an offer for an outdoor installation along with a discount of just under €1000. During the planning discussions, I was told there would be an additional cost of about €5000 for the indoor heat pump. Overall, this feels a bit strange to me.
I would appreciate your experiences and any information on this topic.
A second question about civil engineering work: My general contractor insists on having the excavation supervised by an unexploded ordnance clearance service due to a note in the soil report, without any prior survey. He claims this is now a regulation by the BG-Bau (German Social Accident Insurance for the construction industry). Is this correct?
I am happy to provide further information or pictures if helpful. I hope I have posted this in the appropriate subforum.
Thank you very much for your responses!
B
Baskervile14 Jan 2023 17:04Excerpts from the building description:
Ground slab made of waterproof concrete, thickness 25cm (10 inches)
Basement exterior walls made of waterproof concrete, 25cm (10 inches) thick, with 12cm (5 inches) thick perimeter insulation
At the junction between the ground slab and the rising basement exterior wall, a joint flashing is installed.
No further details about the concrete are provided.
Ground slab made of waterproof concrete, thickness 25cm (10 inches)
Basement exterior walls made of waterproof concrete, 25cm (10 inches) thick, with 12cm (5 inches) thick perimeter insulation
At the junction between the ground slab and the rising basement exterior wall, a joint flashing is installed.
No further details about the concrete are provided.
A
Allthewayup14 Jan 2023 18:20Baskervile schrieb:
Don’t worry, the general contractor (GC) also raised enough concerns about the windows and the staircase. However, all issues have been resolved. The windows will be made with waterproof basement windows, obviously not in the sizes shown on the plan (I don’t have the revised plan yet). And there will be a waterproof roof over the basement staircase. How do you explain or interpret the fact that the GC is uncritical about that, but raises objections regarding the heat pump? With the basement staircase, your issue is not the roof but the waterproofing.
Baskervile schrieb:
I do expect that it will be fine. In this region, all basements have to be waterproof against pressing water, and it’s a local supplier. From previous projects, I’m not aware of any problems. I fell for the same misconception: “local supplier, impeccable reputation, mostly buildings below the groundwater level so far”... and ended up disappointed. I don’t want to cause alarm, but where do you get the confidence that your situation will be the same later on? Hopefully, you’re not leaving it to chance—see my previous post.
Baskervile schrieb:
Excerpts from the construction specification:
Base slab made of waterproof concrete, thickness 25cm (10 inches)
Basement exterior walls made of waterproof concrete, 25cm (10 inches) thick, with a 12 cm (5 inches) thick perimeter insulation applied
A joint sheet is installed at the transition from the base slab to the rising basement wall.
There are no more detailed descriptions of the concrete. Okay, no exposure classes or consistency class are specified so far, although the latter is of secondary importance. Was the groundwater classified as “aggressive to concrete” according to the soil report? The thickness of the slab and walls is ultimately part of the structural engineering calculations and without detailed data it’s hardly assessable. The joint sheet can be Pentaflex or an equivalent product. It’s a specially coated “tape” that swells after concreting and creates the seal.
Try searching online for “WU concrete crack width limitation” and read the PDF in the first result. You’ll find a lot of valuable information about waterproof concrete (WU concrete) for basements and what to pay attention to.
Returning to your issue with the heat pump: if you insist on installing it inside the house, you will have to have a solution developed by a specialist and discuss it with the GC directly. What surprises me here is that the GC is relaxed about the basement staircase but raises concerns about the ventilation opening, which is located about 1.5m (5 feet) higher.
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