ᐅ Single-family house, 140 m², KfW Efficiency House 55 achievable through insulation and air-to-water heat pump?

First of all, it has to be YOUR house, in terms of floor plan, location, features, etc. Once all of that is clear, you can have a proper energy consultant check if, based on your desired specifications, you might already meet a certain standard. Installing something just to qualify for a subsidy is like wasting money to save a little on taxes.

A general contractor will most likely choose the easiest way to meet that standard. But you might prefer less roof insulation or no mechanical ventilation system, and instead want this or that. There are a thousand ways to reach that standard, and you should choose the options that suit you best. In fact, you might even get the house you want without meeting KFW (a German energy standard), but in that case, I’d carefully consider whether you want to chase a KFW standard that is ultimately just a calculated value. You can be happy or completely dissatisfied living in a KFW-rated house...

hanse987 schrieb:

Even if you have entrusted your build to a general contractor, get involved in the design of the air-to-water heat pump yourself to ensure you end up with an efficient heating system.

Isn’t it the energy consultant or the heating engineer who calculates how the air-to-water heat pump should be sized to fit my house? What input can I provide as a layperson?

pagoni2020 schrieb:

First and foremost, it has to be YOUR house in terms of floor plan, location, features, etc. Once that's clear, you can have a proper energy consultant tell you whether you might already meet that standard based on your desired features. Installing something just to get a subsidy is like wasting money to save a little on taxes.
A general contractor will build to whatever standard is easiest for them to achieve. But maybe you want less roof insulation or no mechanical ventilation with heat recovery, and instead prefer this or that. There are a thousand ways to meet the standard—you should pick the options that suit you best. You might even get the house you want without the KFW subsidy, so I would really think carefully before chasing a KFW standard that is ultimately just a calculated value. You can be happy or completely unhappy in a home calculated to the KFW standard...

Our general contractor only mentioned that they build to the KFW55 standard after we told them what kind of house we want and what our preferences are.
I just wanted to check here whether such a standard can really be achieved with such "simple" measures. That seems to be the case, so I am satisfied.
We don’t want any additional gadgets that require maintenance or that might need to be replaced if they fail over the years.

hanse987 schrieb:

Even if you have entrusted your construction to a general contractor, make sure to get involved in the design of the air-to-water heat pump yourself, so that you end up with an efficient heating system.

Keyword: hydraulic balancing and room-specific temperature settings.

SamSamSam schrieb:

Isn't it the energy consultant or the heating engineer who calculates how the air-to-water heat pump needs to be sized to fit my house? What can I, as a layperson, contribute here?

Standard heating engineers usually use a rough estimate, like “we’ve always done it this way.” For example, underfloor heating pipe spacing of 15cm (6 inches), and less spacing in the bathroom—that works too, but it may require a flow temperature of around 38°C (100°F) and higher electricity costs.
If properly calculated and planned—with room-by-room design and specifying a lower flow temperature—you can use closer pipe spacing, achieve a flow temperature of about 28°C (82°F), and have much lower electricity costs.

Both approaches result in warm rooms—one less efficient (ask [USER=20319]@Bookstar) and one more efficient.

nordanney schrieb:

Well calculated and planned = room-by-room design with a target of low supply temperature = shorter pipe lengths = 28°C (82°F) supply and hardly any electricity costs

Is 28°C (82°F) a typical target value or just an example?
I understand that the same spacing shouldn’t be applied as a standard everywhere, but rather the spacing should be determined individually for each room. And it should be kept as small as possible to save heating costs (due to lower supply temperature), right?
Doesn’t an energy consultant look into this?

Acof1978 schrieb:

Keyword: hydraulic balancing and precise temperature control per room

Isn’t that only important once the heating system is commissioned? What influence does this have during construction?
Who should I hire to ensure the heating system is optimally adjusted, if not the heating engineer?