Hello everyone,
We are planning to build a house this year and are currently reviewing offers. However, I have been thinking about it all weekend, and every builder says something different. What should we believe regarding the KFW eligibility?
Maybe you can help us a bit. We have the following offer.
House type Urban villa (2 full floors) with a total living area of 127 m² (1365 sq ft)
Base slab
Reinforced concrete slab C20/25 with a thickness of 20 cm (19 kg of steel reinforcement per m² [4 lbs per sq ft]), constructed as a thermal base slab with 6 cm (2.4 inches) of insulation under the slab.
Floor structure
- approx. 8 cm (3.1 inches) of thermal insulation / leveling layer 040
- Piping (pipe spacing based on heat demand) – does this mean underfloor heating?
- approx. 6.5 cm (2.6 inches) of rapid-drying cement screed
Exterior wall construction
17.5 cm (7 inches) or optionally (additional cost of 5,900 euros) 24 cm (9.5 inches) aerated concrete block PPW4
+ 14 cm (5.5 inches) external thermal insulation composite system (ETICS) made of polystyrene rigid foam insulation with thermal conductivity WLG035
+ organically bound textured render with a grain size of 2 mm (0.08 inches)
Roof
24 cm (9.5 inches) of mineral fiber insulation with thermal conductivity WLG035 between rafters and collar beams
Windows and doors
Triple-glazed with 6-chamber profiles (I still need to clarify what exactly this means).
U-value of 0.7 W/m²K (0.12 Btu/(hr·ft²·°F))
Heating
The house will be heated and supplied with hot water by an air-to-water heat pump from Nibe.
270-liter (71 gallons) buffer storage tank.
Modulating output (inverter technology = continuous operation) from 3.5 kW to 12 kW.
Plus 6 kW additional heating for reheating drinking water and the heating circuit.
Ventilation system
A ventilation unit without heat recovery from the company Lunos will be installed.
Roller shutters
PVC roller shutters will be installed on the ground floor and first floor.
These consist of a room-side closed and thermally insulated PVC roller shutter box with revision opening from below and plastered on the room side.
Chimney
With a heating stove in the living room.
The living-dining area and bedroom are oriented south.
What concerns us most now is whether to build the exterior wall with the 17.5 cm aerated concrete or the 24 cm version, and whether the price is reasonable.
When we asked the builder, the price for 17.5 cm Poroton block instead of 17.5 cm aerated concrete is the same, but the KfW requirements could not be met.
Who can help us with these questions?
Since we are quite young (25), we would like to get some tips and advice from more experienced people.
We hope you can help us a little.
Best regards,
Sonja and Andreas
We are planning to build a house this year and are currently reviewing offers. However, I have been thinking about it all weekend, and every builder says something different. What should we believe regarding the KFW eligibility?
Maybe you can help us a bit. We have the following offer.
House type Urban villa (2 full floors) with a total living area of 127 m² (1365 sq ft)
Base slab
Reinforced concrete slab C20/25 with a thickness of 20 cm (19 kg of steel reinforcement per m² [4 lbs per sq ft]), constructed as a thermal base slab with 6 cm (2.4 inches) of insulation under the slab.
Floor structure
- approx. 8 cm (3.1 inches) of thermal insulation / leveling layer 040
- Piping (pipe spacing based on heat demand) – does this mean underfloor heating?
- approx. 6.5 cm (2.6 inches) of rapid-drying cement screed
Exterior wall construction
17.5 cm (7 inches) or optionally (additional cost of 5,900 euros) 24 cm (9.5 inches) aerated concrete block PPW4
+ 14 cm (5.5 inches) external thermal insulation composite system (ETICS) made of polystyrene rigid foam insulation with thermal conductivity WLG035
+ organically bound textured render with a grain size of 2 mm (0.08 inches)
Roof
24 cm (9.5 inches) of mineral fiber insulation with thermal conductivity WLG035 between rafters and collar beams
Windows and doors
Triple-glazed with 6-chamber profiles (I still need to clarify what exactly this means).
U-value of 0.7 W/m²K (0.12 Btu/(hr·ft²·°F))
Heating
The house will be heated and supplied with hot water by an air-to-water heat pump from Nibe.
270-liter (71 gallons) buffer storage tank.
Modulating output (inverter technology = continuous operation) from 3.5 kW to 12 kW.
Plus 6 kW additional heating for reheating drinking water and the heating circuit.
Ventilation system
A ventilation unit without heat recovery from the company Lunos will be installed.
Roller shutters
PVC roller shutters will be installed on the ground floor and first floor.
These consist of a room-side closed and thermally insulated PVC roller shutter box with revision opening from below and plastered on the room side.
Chimney
With a heating stove in the living room.
The living-dining area and bedroom are oriented south.
What concerns us most now is whether to build the exterior wall with the 17.5 cm aerated concrete or the 24 cm version, and whether the price is reasonable.
When we asked the builder, the price for 17.5 cm Poroton block instead of 17.5 cm aerated concrete is the same, but the KfW requirements could not be met.
Who can help us with these questions?
Since we are quite young (25), we would like to get some tips and advice from more experienced people.
We hope you can help us a little.
Best regards,
Sonja and Andreas
L
luemmelchris21 Feb 2010 20:58First of all, you haven’t mentioned a price yet that we could evaluate.
Secondly, the question: do you plan to finance through the KfW? So, are you even applying for that funding approval?
You can look up what a 6-chamber profile is—it’s related to the frame construction method. However, having many chambers does not necessarily guarantee a high-quality window.
Secondly, the question: do you plan to finance through the KfW? So, are you even applying for that funding approval?
You can look up what a 6-chamber profile is—it’s related to the frame construction method. However, having many chambers does not necessarily guarantee a high-quality window.
Hello,
First, you should find out what a developer or general contractor (GC) is. Most likely, it is a GC.
Uw or Ug?
Whether the air heat pump is the optimum solution cannot be judged without further economic analysis. However, I have serious doubts about the sizing!
Complete nonsense. Both aerated concrete and Poroton have different lambda values!! He is probably mixing apples and oranges and has a large stock of PPW4. Check price differences with building material wholesalers.
I urgently recommend you seek external advice, especially regarding the building services system.
Best regards
Colonius schrieb:
..
We are planning to build a house this year,...and every developer tells a different story, ...
First, you should find out what a developer or general contractor (GC) is. Most likely, it is a GC.
Colonius schrieb:This is not a bad option compared to the more common 1.5-story design.
..
(2 full stories)
Colonius schrieb:The sub-slab insulation only makes sense if it is ensured that neither groundwater nor capillary moisture reaches the insulation layer. Otherwise, it loses its insulative effect. So it depends on your building site conditions.
..
Concrete slab... and designed as a thermal slab with 6 cm sub-slab insulation.
Colonius schrieb:That would be too little for me.
.. Floor construction approx. 8 cm thermal insulation / leveling layer 040..
Colonius schrieb:Yes.
.. -Piping (pipe spacing according to heat demand) does this refer to underfloor heating?
Colonius schrieb:Here I would choose 36.5 cm PPW2 + ETICS + mineral-based plaster.
.. Exterior wall construction
17.5 cm or alternatively (additional cost 5,900 €) 24 cm aerated concrete PPW4... + ETICS with 14 cm polystyrene rigid foam insulation WLG035 + organic bound textured plaster with 2 mm grain
Colonius schrieb:
.. Windows and doors
Triple-glazed in 6-chamber profiles (whatever that means) I still have to ask. With a U-value of 0.7 W/m²K.
Uw or Ug?
Colonius schrieb:
.. Heating
The house will be heated and supplied with hot water by an air-to-water heat pump from Nibe. 270-liter buffer tank.
Modulating capacity (inverter technology = variable operation) from 3.5 kW to 12 kW. ??? plus 6 kW additional heater for reheating domestic hot water and heating circuit.
Whether the air heat pump is the optimum solution cannot be judged without further economic analysis. However, I have serious doubts about the sizing!
Colonius schrieb:I consider controlled residential ventilation without heat recovery to be energy wasteful and therefore impractical.
.. Ventilation system without heat recovery from the company Lunos will be installed.
Colonius schrieb:As I said, 36.5 cm!
..
Our main concern now is whether the exterior wall should be built with the 17.5 cm aerated concrete or the 24 cm version.
and whether the price is reasonable?
Colonius schrieb:
..
On inquiry with the developer, the price for 17.5 Poroton blocks instead of 17.5 cm aerated concrete would be the same, but the KfW energy standards could not be met.
Complete nonsense. Both aerated concrete and Poroton have different lambda values!! He is probably mixing apples and oranges and has a large stock of PPW4. Check price differences with building material wholesalers.
I urgently recommend you seek external advice, especially regarding the building services system.
Best regards
Hello everyone,
First of all, many thanks for all the responses. Since I still have some doubts, I handed over the entire house construction contract today to an expert who will also accompany me during the build. I hope he will be able to help me.
The construction company is a general contractor who assigns the work to local tradespeople.
Foundation slab
For the entire plot, wastewater and rainwater are only allowed to be discharged into the sewer system; nothing is allowed to infiltrate on the property. This might be the reason for the sub-slab insulation? I am not sure about the groundwater situation yet, as there is no soil survey available.
Windows
There is no information on whether the U-value refers to the glass unit or the whole window. For the standard windows, it says double glazing and a glass U-value of 1.1. In the upgrade package, it only mentions triple glazing with a glazing U-value of 0.7 W/m²K.
Regarding the ventilation system, this is not a central ventilation system. According to the contract, exhaust fans will be installed on the external walls in the bathroom, utility room, guest toilet, and kitchen. Four air supply openings will be installed in the dining/living room, bedroom, and children's room. The exhaust fans can be switched with single or double rocker switches (in the bathroom, they are humidity-controlled).
A suggestion from a friend caught my attention—the Inventer ventilation technology. I plan to request a quote for this system sometime this week.
About the air-to-water heat pump, I don’t know much about it. It is supposed to be a fairly new model from Nibe, which can be found on their website. This split system is suitable for both cooling and heating. I have no idea if this results in a capacity of 12 kW or something else. The house contract mentions somewhere between 3.5 kW and 12 kW. I hope the expert can clarify this for me.
Underfloor heating
I know that the loops for the underfloor heating are to be installed closer together. I specifically asked about this, but I was not given an exact measurement in centimeters—only that the company generally lays the pipes closer together when using an air-to-water heat pump compared to a gas boiler.
Exterior walls
Regarding whether the price is reasonable, I was referring to the 24 cm (9.5 inches) wall block. This would mean 17.5 cm (7 inches) blocks without extra cost and 24 cm (9.5 inches) for 5,900 € more.
Regarding the chimney, the contract states that in addition to the chimney, a safety pressure monitor will be installed.
Will I be able to operate only a room air–independent stove in the house, or also a room air–dependent one?
Finally, a question for those who have built with aerated concrete blocks: How is living in a house constructed from this material? I am impressed by the insulation properties of the blocks but a bit worried that the whole thing might collapse someday. I will probably choose the 24 cm (9.5 inches) blocks, even though they cost almost 6,000 € more and reduce the living area.
Best regards,
Andreas & Sonja
First of all, many thanks for all the responses. Since I still have some doubts, I handed over the entire house construction contract today to an expert who will also accompany me during the build. I hope he will be able to help me.
The construction company is a general contractor who assigns the work to local tradespeople.
Foundation slab
For the entire plot, wastewater and rainwater are only allowed to be discharged into the sewer system; nothing is allowed to infiltrate on the property. This might be the reason for the sub-slab insulation? I am not sure about the groundwater situation yet, as there is no soil survey available.
Windows
There is no information on whether the U-value refers to the glass unit or the whole window. For the standard windows, it says double glazing and a glass U-value of 1.1. In the upgrade package, it only mentions triple glazing with a glazing U-value of 0.7 W/m²K.
Regarding the ventilation system, this is not a central ventilation system. According to the contract, exhaust fans will be installed on the external walls in the bathroom, utility room, guest toilet, and kitchen. Four air supply openings will be installed in the dining/living room, bedroom, and children's room. The exhaust fans can be switched with single or double rocker switches (in the bathroom, they are humidity-controlled).
A suggestion from a friend caught my attention—the Inventer ventilation technology. I plan to request a quote for this system sometime this week.
About the air-to-water heat pump, I don’t know much about it. It is supposed to be a fairly new model from Nibe, which can be found on their website. This split system is suitable for both cooling and heating. I have no idea if this results in a capacity of 12 kW or something else. The house contract mentions somewhere between 3.5 kW and 12 kW. I hope the expert can clarify this for me.
Underfloor heating
I know that the loops for the underfloor heating are to be installed closer together. I specifically asked about this, but I was not given an exact measurement in centimeters—only that the company generally lays the pipes closer together when using an air-to-water heat pump compared to a gas boiler.
Exterior walls
Regarding whether the price is reasonable, I was referring to the 24 cm (9.5 inches) wall block. This would mean 17.5 cm (7 inches) blocks without extra cost and 24 cm (9.5 inches) for 5,900 € more.
Regarding the chimney, the contract states that in addition to the chimney, a safety pressure monitor will be installed.
Will I be able to operate only a room air–independent stove in the house, or also a room air–dependent one?
Finally, a question for those who have built with aerated concrete blocks: How is living in a house constructed from this material? I am impressed by the insulation properties of the blocks but a bit worried that the whole thing might collapse someday. I will probably choose the 24 cm (9.5 inches) blocks, even though they cost almost 6,000 € more and reduce the living area.
Best regards,
Andreas & Sonja
L
luemmelchris23 Feb 2010 08:58It is a soil survey, not a building inspection report, and you need to arrange that yourself.
Windows: that’s exactly why you should ask. I assume that it’s “obviously” not the overall value. Make sure to get written confirmation.
Ventilation system: sorry, either do it properly or not at all. (My opinion) therefore, only a controlled ventilation system with heat recovery is acceptable. Above all, this lets you manage the entire house, instead of having four separate devices in different rooms.
Also, get detailed information about the air-to-water heat pump. Especially if it’s supposed to provide cooling, that function must be integrated into the overall system.
Exterior wall: none of the options will crumble on you, whether 17 or 24 (cm) (7 or 9.5 inches), but again my question: why not timber stud framing? It offers the best insulation, minimal loss of living space, and you can still hang everything you want.
Windows: that’s exactly why you should ask. I assume that it’s “obviously” not the overall value. Make sure to get written confirmation.
Ventilation system: sorry, either do it properly or not at all. (My opinion) therefore, only a controlled ventilation system with heat recovery is acceptable. Above all, this lets you manage the entire house, instead of having four separate devices in different rooms.
Also, get detailed information about the air-to-water heat pump. Especially if it’s supposed to provide cooling, that function must be integrated into the overall system.
Exterior wall: none of the options will crumble on you, whether 17 or 24 (cm) (7 or 9.5 inches), but again my question: why not timber stud framing? It offers the best insulation, minimal loss of living space, and you can still hang everything you want.
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