Dear forum community,
We are planning the construction of a new single-family house. The house should ideally meet the KfW 70 standard in order to qualify for the corresponding funding. We have decided to equip the house in a way that minimizes the heating demand from the start. So, we want a lot of insulation and limited high-tech solutions.
Now we are wondering whether we can achieve KfW 70 with the following construction method and features:
Solid construction, no basement, 1.5 floors, gable roof, 141 sqm (1,518 sq ft) according to DIN, almost square: 9.14 m x 9.83 m (30 ft x 32 ft)
Wall structure: 17.5 cm (7 inches) Poroton bricks, 14 cm (5.5 inches) insulation, cavity, 12.5 cm (5 inches) facing brick
Windows: 5-chamber frame (70 mm / 3 inches), triple glazing, exterior muntins
Roof: 240 mm (9.5 inches) mineral wool insulation with thermal conductivity class 035 (WLG 035) up to the attic ceiling and in the ceiling to the attic
Floor: 100 mm (4 inches) perimeter insulation under the foundation slab, 110 mm (4.3 inches) polystyrene with WLG 035 under the screed
Heating: gas condensing boiler with underfloor heating throughout the entire house
Ventilation: a total of three decentralized ventilators with heat recovery (Meltem)
The gables face north (small windows) and south (large windows)
Is KfW 70 achievable?
Kind regards
Benjih
We are planning the construction of a new single-family house. The house should ideally meet the KfW 70 standard in order to qualify for the corresponding funding. We have decided to equip the house in a way that minimizes the heating demand from the start. So, we want a lot of insulation and limited high-tech solutions.
Now we are wondering whether we can achieve KfW 70 with the following construction method and features:
Solid construction, no basement, 1.5 floors, gable roof, 141 sqm (1,518 sq ft) according to DIN, almost square: 9.14 m x 9.83 m (30 ft x 32 ft)
Wall structure: 17.5 cm (7 inches) Poroton bricks, 14 cm (5.5 inches) insulation, cavity, 12.5 cm (5 inches) facing brick
Windows: 5-chamber frame (70 mm / 3 inches), triple glazing, exterior muntins
Roof: 240 mm (9.5 inches) mineral wool insulation with thermal conductivity class 035 (WLG 035) up to the attic ceiling and in the ceiling to the attic
Floor: 100 mm (4 inches) perimeter insulation under the foundation slab, 110 mm (4.3 inches) polystyrene with WLG 035 under the screed
Heating: gas condensing boiler with underfloor heating throughout the entire house
Ventilation: a total of three decentralized ventilators with heat recovery (Meltem)
The gables face north (small windows) and south (large windows)
Is KfW 70 achievable?
Kind regards
Benjih
District heating with guaranteed energy from CHP and biomass significantly improves the Qp´´ value.Yes, the energy is guaranteed to come from biomass (gas production from household waste, etc., plus biomass cultivation on landfill sites).
That means the primary energy demand hardly matters to me when considering the KfW standard...
What remains is the transmission heat loss! Can this only be improved through insulation? Controlled mechanical ventilation with heat recovery would only improve the primary energy demand, right?
Therefore, only the chosen insulation and windows would determine whether my house reaches KfW 70/55/40?
Shism schrieb:
Yes, the energy is guaranteed to come from biomass (gas production from household waste, etc., plus biomass cultivation on landfill sites) The guarantee refers to the supply contracts. There have been cases where the renewable share was met by mixing biogas with natural gas. After reviewing the supply contracts, it turned out that this mixing was neither guaranteed nor assured and could be changed by the supplier at any time at their discretion. Therefore, this arrangement was not accepted as valid proof.Shism schrieb:
...so then only the chosen insulation/windows would determine whether my house qualifies as KfW70/55/40? Probably (all exterior components). However, it becomes increasingly difficult to meet the Ht value as the efficiency standard improves. If, for example, a building is just below the respective threshold, there are other options to still achieve the value. I prefer not to specify or comment on those here. In general, it is never a bad idea to achieve a high insulation value for the building envelope because the best energy is the energy you don’t need.
It does not make much sense to primarily or exclusively compensate for high demand through building services. With low demand, it may be possible to afford somewhat less efficient building systems and save on investment costs.
Regards.
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