ᐅ Renovation of an old building from energy rating H to a KfW 55 EE energy-efficient house
Created on: 7 Sep 2025 12:27
T
TeldorF
Hello everyone,
I’m new to the forum and have a question regarding the following topic:
My wife and I want to buy a semi-detached house, renovate it, and then rent it out. Here are the key details about the property:
Current State:
- Semi-detached house, built in 1956. Classified as a Worst Performing Building
- Energy demand according to the energy certificate = 344 kWh/m²*a
- Living area on ground floor and upper floor = 110 m² (1184 ft²). Ground and upper floors are two separate residential units.
- Usable area according to the energy certificate: 208 m² (2240 ft²). Plot area 397 m² (4273 ft²)
- Basement, ground floor, upper floor, and attic— all basic standard
- Basement likely uninsulated but dry
- Ground and upper floors are finished. The exterior walls appear to have no insulation inside or outside. Originally built with pumice stone or hollow concrete blocks. The exterior wall thickness is about 30 cm (12 inches). Plastered on the outside.
- Attic is unfinished. The gable interior shows the bare pumice stones. See attached picture.
- Roof is not insulated. Rafters and tiles are visible. Rafter thickness approx. 13 cm (5 inches).
- Heating is a floor-level gas heating system, built in 1980.
- Windows are wooden, double-glazed. Need to be replaced.
- Basement ceiling is a reinforced ceiling or concrete slab (see attached picture). The ceiling above the ground floor is probably a wooden beam ceiling but it’s not visible and the real estate agent did not know.
That’s the current situation.
Planned State:
The plan is to renovate the house using a KfW loan 261, aiming to achieve KfW 55 EE standard.
The following measures are planned:
- Full thermal insulation system (ETICS/External Thermal Insulation Composite System) using expanded polystyrene (EPS) on the facade. Thickness will be based on the calculation results.
- Replace windows with triple glazing (currently double glazed).
- Roof insulation from inside: cellulose insulation between the rafters and wood fiber insulation on the outside. Thicknesses depend on calculation results.
- Insulate the basement ceiling from below. Thickness according to calculations, but limited due to the basement’s clear head height of only about 1.90 m (6 ft 3 in).
- New heating system: air-to-water heat pump with radiators. Underfloor heating would likely reduce ceiling height too much because of the build-up required.
- The ground and upper floors are separate apartments and will remain so. The attic will only be added to the upper-floor apartment.
- If necessary, a small photovoltaic system may be installed to reach the renewable energy requirements.
That’s all for the planned state. I hope I haven’t left out any important information, but if so, please feel free to ask.
My question is whether, with the conditions above, it is possible to achieve KfW 55 EE standard for this house. I see a potential problem with the shared wall to the neighboring semi-detached house, as I cannot insulate this wall externally with an ETICS. Has anyone here had experience renovating a semi-detached house and can provide their assessment?
That would be great. Thank you very much in advance. If any information is missing, please just ask.
Best regards
Florian
I’m new to the forum and have a question regarding the following topic:
My wife and I want to buy a semi-detached house, renovate it, and then rent it out. Here are the key details about the property:
Current State:
- Semi-detached house, built in 1956. Classified as a Worst Performing Building
- Energy demand according to the energy certificate = 344 kWh/m²*a
- Living area on ground floor and upper floor = 110 m² (1184 ft²). Ground and upper floors are two separate residential units.
- Usable area according to the energy certificate: 208 m² (2240 ft²). Plot area 397 m² (4273 ft²)
- Basement, ground floor, upper floor, and attic— all basic standard
- Basement likely uninsulated but dry
- Ground and upper floors are finished. The exterior walls appear to have no insulation inside or outside. Originally built with pumice stone or hollow concrete blocks. The exterior wall thickness is about 30 cm (12 inches). Plastered on the outside.
- Attic is unfinished. The gable interior shows the bare pumice stones. See attached picture.
- Roof is not insulated. Rafters and tiles are visible. Rafter thickness approx. 13 cm (5 inches).
- Heating is a floor-level gas heating system, built in 1980.
- Windows are wooden, double-glazed. Need to be replaced.
- Basement ceiling is a reinforced ceiling or concrete slab (see attached picture). The ceiling above the ground floor is probably a wooden beam ceiling but it’s not visible and the real estate agent did not know.
That’s the current situation.
Planned State:
The plan is to renovate the house using a KfW loan 261, aiming to achieve KfW 55 EE standard.
The following measures are planned:
- Full thermal insulation system (ETICS/External Thermal Insulation Composite System) using expanded polystyrene (EPS) on the facade. Thickness will be based on the calculation results.
- Replace windows with triple glazing (currently double glazed).
- Roof insulation from inside: cellulose insulation between the rafters and wood fiber insulation on the outside. Thicknesses depend on calculation results.
- Insulate the basement ceiling from below. Thickness according to calculations, but limited due to the basement’s clear head height of only about 1.90 m (6 ft 3 in).
- New heating system: air-to-water heat pump with radiators. Underfloor heating would likely reduce ceiling height too much because of the build-up required.
- The ground and upper floors are separate apartments and will remain so. The attic will only be added to the upper-floor apartment.
- If necessary, a small photovoltaic system may be installed to reach the renewable energy requirements.
That’s all for the planned state. I hope I haven’t left out any important information, but if so, please feel free to ask.
My question is whether, with the conditions above, it is possible to achieve KfW 55 EE standard for this house. I see a potential problem with the shared wall to the neighboring semi-detached house, as I cannot insulate this wall externally with an ETICS. Has anyone here had experience renovating a semi-detached house and can provide their assessment?
That would be great. Thank you very much in advance. If any information is missing, please just ask.
Best regards
Florian
TeldorF schrieb:
No, we actually don’t want to live in one of the apartments. This is intended purely as a kind of retirement provision. No, what I meant with my question was: would you feel comfortable living there?
You should be able to picture how others might receive the apartment. If you say, “It’s not really my thing, too small or oddly shaped,” then others might feel the same and be unwilling to rent it—possibly not for the rent you have in mind.
TeldorF schrieb:
But yes, it might be that I’m trying to make the attic seem better than it is. Exactly. But not just the attic—also everything else. Like the missing balcony, inefficient room layouts, and outdated room sizes, which limit reaching a healthy or large target group.
TeldorF schrieb:
Access is currently via a hatch in the stairwell floor. I would have closed that off and installed a staircase up from the living room on the upper floor. I measured it, and it should work. Unfortunately, there isn’t enough space in the hallway. Then the living room as a separate room is eliminated as well. What remains? Kitchen, bathroom, small room, and a 9sqm (approximately 97sq ft) bedroom. Where would a balcony fit in there?
TeldorF schrieb:
I would change the layout. Swap kitchen and bathroom. Remove the partition wall to the living room so the kitchen is open to the living space. Currently, the living room is a walkthrough room. I haven’t found a clever solution yet to change that. Moving the hallway only makes the “children’s room” smaller. So that leaves about 19sqm (approximately 205sq ft) for kitchen, dining, and living combined. Does that really improve things?
So, I think it’s a lot of effort for uncertain rent around €10-11 per sqm for a maximum of 110sqm (approximately 1,184 sq ft). And you risk temporary vacancies due to constant tenant turnover.
I see the buyer more as an owner-occupier who does some of the work personally and can use both floors for themselves and their small family.
T
Teimo19887 Sep 2025 21:53ypg schrieb:
Now ask yourself, who as a single person pays over 1000€ cold rent?I live about 50 km (30 miles) northeast of Lindenberg, but I would say that this happens quite often here. Anyone looking for an apartment as a single person, who doesn’t want to live like a student, has to deal with such prices.Teimo1988 schrieb:
I live about 50 km (30 miles) northeast of Lindenberg, but I would say this happens quite often here. If you are single and looking for an apartment and don’t want to live like a student, you have to deal with prices like these. Why? There are larger and more suitable apartments available in your area for less money, but bigger. I said it, and you can verify that on the listing platforms.
Whether "quite often" is enough for you to cover your rent, only you can decide.
Take a look, here is a property comparable to your house: Scout-ID: 158594975
From this, you can at least estimate the roof pitch of over 45 degrees, so rather 50 degrees or more. Also, the knee wall is visible inside.
I sketched it out with a tool and was therefore able to roughly estimate the finished attic and the loft.
You have approximately 40 sqm (about 430 sq ft) of living space in the attic, including the hallway, bathroom, and kitchen, where the height in that area is around 150 cm (5 feet). It’s generally safe to say that any area below this height does not count as living space. But this depends on local regulations, which are similar across most regions.
The attic should or could be about 430 cm (14 feet) wide. This means there is hardly any significant standing space. Additionally, the two chimneys are combined here, so behind them there is mainly storage space.
Here is the finished attic, next to it the roof slope is outlined to determine the width.
Here is the loft, with imagined lines showing where you probably can no longer walk. This leaves about 6 sqm (65 sq ft), which includes the stairwell opening.
Something similar is offered near you as well but defined as storage space.
Scout-ID: 133559463. However, here the loft is significantly wider, while the roof pitch is equal to or less than 45 degrees.
I think that at least the effort of finishing the attic will not be worthwhile.
So you’re looking at a ground floor apartment with about 50 sqm (540 sq ft) plus a conservatory (not calculated), and an attic apartment of about 40 sqm (430 sq ft) without a balcony and “room.” You want to add a balcony, okay, but that also costs money.
Whether all this is worth the risk and will result in only two average apartments that justify your expenses is your risk to take.
Teimo1988 schrieb:
Although I live about 50 km (30 miles) northeast of Lindenberg, I would say that this happens quite frequently here. Anyone looking for an apartment as a single person who doesn’t want to live like a student has to deal with prices like these. Sorry, I confused your username with the original poster’s @TeldorF
I don’t really see two attractive apartments for tenants here either. It might be possible to convert the attic so that it becomes at least an acceptable room for children (although I’m not exactly sure where the chimneys are located, which might make that practically impossible). However, since the staircase on the upper floor also takes up space that is already limited, there isn’t really an appealing apartment left there. And if a family were to move in, they would probably want some storage space somewhere or would like to use the garden as well. Due to the layout, the dining table would likely have to go into the smaller room; otherwise, the living room plus kitchen would become very cramped because of the stairs. This setup is actually more suitable for couples who would then look for something else once expecting a child.
Downstairs, small apartments with a large garden and a rent of around €1000 cold (without utilities) would probably be difficult to find tenants for. Not ideal for families, possibly borderline expensive for retirees, and young couples might prefer not to have to take care of a garden.
Difficult situation...
Downstairs, small apartments with a large garden and a rent of around €1000 cold (without utilities) would probably be difficult to find tenants for. Not ideal for families, possibly borderline expensive for retirees, and young couples might prefer not to have to take care of a garden.
Difficult situation...
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nordanney8 Sep 2025 01:20Just something to consider. You mentioned that the house has been on the market for a while and nobody has dared to take it on so far.
Do you really believe that no one has already thought about renovation, extension, or renting it out? What do you think the results were? That was rhetorical…
What are you doing differently that will suddenly make it successful for you (even with an expensive renovation)? There must be a key factor, a business model, that sets you apart from the others.
I would rather think of having connections with the building authority (for remodeling, which no one has considered so far) or a lot of equity (own company, etc.).
Do you really believe that no one has already thought about renovation, extension, or renting it out? What do you think the results were? That was rhetorical…
What are you doing differently that will suddenly make it successful for you (even with an expensive renovation)? There must be a key factor, a business model, that sets you apart from the others.
I would rather think of having connections with the building authority (for remodeling, which no one has considered so far) or a lot of equity (own company, etc.).
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