ᐅ KfW 40 (plus) standard for a multi-family house cannot be achieved
Created on: 1 Sep 2019 16:57
C
curverbox
Hello everyone,
I am planning to build a five-family house. Since the plot is very narrow but long, the planned house will be 20.415m (67 feet) long and only 7.24m (24 feet) wide, which are the maximum dimensions approved by the building authority / planning permission.
The house will have two full stories and a 45° pitched roof. The gables will face southwest / northeast. The exterior walls will be a cavity wall construction with a thickness of 49cm (19 inches), consisting of 17.5cm (7 inches) Ytong blocks, 12cm (5 inches) PUR insulation with a 0.24 air gap, and 11.5cm (5 inches) facing brickwork. There will be no basement. All technical specifications meet the requirements of a KfW55-standard house, including a ground-source heat pump, underfloor heating, decentralized ventilation systems, photovoltaic panels with battery storage, etc.
Nevertheless, according to calculations by my energy consultant, the house only reaches KfW55 standard because of the unfavorable length-to-width ratio, and she has reached the limits of her expertise.
Is this a calculation error or is it really not possible?
I am really at my wit’s end...
I am planning to build a five-family house. Since the plot is very narrow but long, the planned house will be 20.415m (67 feet) long and only 7.24m (24 feet) wide, which are the maximum dimensions approved by the building authority / planning permission.
The house will have two full stories and a 45° pitched roof. The gables will face southwest / northeast. The exterior walls will be a cavity wall construction with a thickness of 49cm (19 inches), consisting of 17.5cm (7 inches) Ytong blocks, 12cm (5 inches) PUR insulation with a 0.24 air gap, and 11.5cm (5 inches) facing brickwork. There will be no basement. All technical specifications meet the requirements of a KfW55-standard house, including a ground-source heat pump, underfloor heating, decentralized ventilation systems, photovoltaic panels with battery storage, etc.
Nevertheless, according to calculations by my energy consultant, the house only reaches KfW55 standard because of the unfavorable length-to-width ratio, and she has reached the limits of her expertise.
Is this a calculation error or is it really not possible?
I am really at my wit’s end...
C
curverbox1 Sep 2019 18:5180mm (3 inches) perimeter insulation. Overall floor U-value is 0.18, the roof has 0.14.
The basement was definitely not included in the calculation.
The windows are triple-glazed with 0.60 glass.
The basement was definitely not included in the calculation.
The windows are triple-glazed with 0.60 glass.
C
curverbox1 Sep 2019 18:55tomtom79 schrieb:
1m wall, not bad, but what’s the point for peace of mind?
Are the energy consultants changing? They don’t seem to have a clue.
How big are the units that the heating and stuff are for? The calculation with 1m was only to see if it makes any difference...
The units are ground floor and first floor, each 2x 50sqm (538 sq ft), and attic 74sqm (796 sq ft) according to DIN.
curverbox schrieb:
The overall floor U-value is 0.18 There’s still some room for improvement.
curverbox schrieb:
The windows are triple-glazed with 0.60 glass Glass 0.6 but overall only 0.9? Then the frame isn’t good enough. You definitely have more potential there.
tomtom79 schrieb:
1 meter (3.3 feet) wall is not bad, but what is it for, just peace of mind? I would build it differently, especially if it’s an investment property. The construction is way too expensive, both in terms of materials and space usage.
The motivation is probably driven by the KfW subsidy multiplied fivefold.
C
curverbox1 Sep 2019 19:28tomtom79 schrieb:
Well, but the costs for KfW40plus aren't exactly low either.
@curverbox What type of heating? What are you doing for KfW40plus?Ground source heat pump, 10 kW photovoltaic system with a corresponding battery storage and monitoring capability in the residential units. With an investment of 500,000 euros, I would receive about 50,000 euros more in grants for KfW40plus, which roughly matches the additional costs. I’m estimating an extra 10,000 euros myself, but it would be worth it to me.
Similar topics