ᐅ Construction of a Two-Family House / Choosing the Heating System for the Ground Floor Apartment

Dear Sir or Madam,

We are currently in the process of coordinating/selecting the heating system for our condominium unit in a two-family house. We are purchasing the apartment from a developer, who is building the second unit for their own use (essentially: a shared building project). Therefore, we have complete freedom regarding the equipment and selection.

The condominium will be owner-occupied for about 15 years and then sold.

Here are the facts about the building:

1 residential unit on the ground floor (this is the one we are buying).
Building volume: approx. 620 cubic meters
Living area: 172 square meters
Living area + usable area (excluding garage): 235 square meters
Constructed to KfW 70 standard or better
Active residential ventilation with heat recovery – details below (an offer is available!)
Windows: triple glazing with a U-value of 1.1; few load-bearing walls; total window area approx. 15 meters
If further details are needed, please just ask briefly.

2 residential units on the 1st and 2nd floors
Occupied by the developer.
Living area: approx. 380 square meters + 70 square meters usable area in the basement

Total building volume: approx. 2000 cubic meters

On-site facts:

The apartment faces north; the (main) terrace faces west, the second terrace faces east.
The building is located on a slope.
The basement, which also contains the garages, is the lowest level.
Here, 35 cm (14 inches) reinforced concrete walls are planned, with 22 cm (9 inches) of insulation applied on top.
The walls above ground level will be masonry, consisting of 22 cm (9 inches) stone plus 18 cm (7 inches) insulation.

Questions:

1.) Which heating system is recommended?
2.) What U-value should be selected for the windows?
3.) Which ventilation system is advisable?
4.) Are there any specific recommendations for suppliers or specialists in the Stuttgart area we could contact?

Regarding 1.)
Option 1:

A shared heating system could be possible – the current status is: installation of a gas combined heat and power system (CHP) for both residential units together. Details are not yet finalized.
Note: If a CHP system makes sense, it might be worth considering whether the neighboring building (a six-family house with 1700 cubic meters) could also be supplied from our CHP system.

Option 2:

Each residential unit is supplied separately – currently our preferred option!
After thorough research and considering the total cost situation, we are convinced that we will install a gas condensing boiler (for example, Buderus Logamax Plus) supplemented by vacuum tube collectors for heating support and domestic hot water production.

Alternatives to option 2:

- Air-to-air heat pump
- Mini-CHP unit
- Other system (fuel cell, etc.)

Regarding 2.)

According to the building specifications, triple glazing with a U-value of 1.1 is planned. There is an option to upgrade to a U-value of 0.7 for an additional cost, which is currently unknown. Is this upgrade advisable?

Regarding 3.)

The building specifications did not include a ventilation system in the price. However, we would like to have one installed. We have received an offer from the company LANGE Lüftungstechnik.
For our apartment, the following system is proposed:
SCHRAG Recoverysmart EC with summer bypass (what exactly is a summer bypass?) including 7 supply air and 7 exhaust air outlets.
Material cost net: 7,350.00 Euro
Labor cost net: 2,250.00 Euro
Total including VAT: 11,424 Euro

So far, we have no alternatives.
What is important to us is that the entire house will be equipped with KNX automation, so it would be ideal if the ventilation system has a KNX/EIB interface as well.

Regarding 4.)

Could someone recommend a supplier or specialist regarding HEATING and VENTILATION SYSTEMS in the Stuttgart area? The windows will be provided by the developer.

Thank you very much for reading this detailed description to the end. I look forward to your suggestions and advice.

Thank you, André

derKillesberger schrieb:
....Thank you very much for reading this detailed description all the way through; I look forward to your suggestions and tips.

A thorough initial assessment and planning are essential here! Who is willing to take on this topic reliably and for free ? 😕 There probably won’t be a free miracle worker here, and if there is, the advice is unlikely to be economically viable ;-)

best regards

€uro schrieb:
A detailed basic assessment and planning are necessary here! Who is willing to deal with this topic reliably for free? 😕 There probably won’t be a free savior here, and if there is, the answer is likely not economically useful ;-)

best regards

Thank you very much for your comment. I consider this housebuilding forum to be an expert community where professionals, if they wish, can offer advice and tips to those seeking help. Of course, I also use other resources such as an on-site energy consultation. Nevertheless, I strongly believe that there are people who are willing to thoroughly answer detailed posts from time to time. I have made a great effort to be as precise as possible. I think the questions I raised can be well answered based on my data. Or is this a purely commercial forum?

Hello,

derKillesberger schrieb:
Or is this purely a commercial forum?

Definitely not!

Now comes the implied BUT. On this forum, you will receive "advice" – "guidelines" – "tips," but under no circumstances free HVAC engineering planning.

Since you are using an on-site energy consultation, you will surely receive verifiable answers to your post soon 🙄

Kind regards

Bauexperte schrieb:
Hello,


Clearly: no!

Now comes the implied BUT. On this forum, you will receive "hints" – "guidelines" – "tips," but definitely not a free HVAC design.

Since you are using an on-site energy consultation, you will surely receive verifiable answers to your post soon 🙄

Kind regards

Thank you for your advice. I will wait and see. Perhaps I have overestimated the abilities and knowledge of the forum members. Basically, I expected solid answers to four questions, and to get the most qualified responses, I described the project.

Obviously, however, that was a bit too much to ask. We will of course do the planning ourselves, but it is better to approach such planning with prior knowledge than to have contractors talk you into something.

Instead of answers, I only received hints that the case is too complex.

derKillesberger schrieb:
..... Maybe I overestimated the capabilities and knowledge of the forum members a bit.

If you had put a little effort into using the search function, the essentials should have become clear when reviewing similar questions. Without adequate preliminary investigation, no reliable or actionable answer is possible.

derKillesberger schrieb:
..... In principle, I expected solid answers to four questions, and to get those as accurately as possible, I described the project.

This expectation is somewhat presumptuous. 😡

derKillesberger schrieb:
..... Obviously, that was a bit too much to ask.

That’s right; otherwise, you’d have to consult a clairvoyant.

derKillesberger schrieb:
..... Of course we are doing the planning ourselves, but it’s better to approach such planning with prior knowledge than to let craftsmen “sell you something.”

Well then, have the planning done—starting with the preliminary investigation. That is completely independent of any tradesperson. Based on the result parameters, the appropriate system builder can be chosen. “Selling you something” is therefore ruled out ;-)

Best regards.