ᐅ How to Achieve KfW40 Standard? Energy Systems and Cost Efficiency
Created on: 29 Dec 2020 22:25
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Sascha1977S
Sascha197729 Dec 2020 22:25Dear experts,
We have just been very lucky and managed to buy the last available plot in the town of some friends. Now we are building a small house for our parents with a trusted general contractor who built our house 10 years ago. Unfortunately, we are still laypersons and would therefore like to ask for your opinion, especially regarding energy technology, at this early stage of our planning.
A brief overview of the house, plot, and occupants:
Our questions:
Please excuse the many questions and our lack of knowledge. We would be very grateful for your answers so that we at least avoid major mistakes.
Kind regards
We have just been very lucky and managed to buy the last available plot in the town of some friends. Now we are building a small house for our parents with a trusted general contractor who built our house 10 years ago. Unfortunately, we are still laypersons and would therefore like to ask for your opinion, especially regarding energy technology, at this early stage of our planning.
A brief overview of the house, plot, and occupants:
- New build, 11 x 7.25 m (36 x 24 ft)
- 2 full stories
- Gable roof with 25 to max. 30 degrees pitch (approx. 91 m2 (980 ft2) roof area)
- Gable roof oriented east/west
- No bay windows, maximum one double casement window, shading otherwise only by satellite dish
- Ground source heat pump with deep drilling
- The Tecalor TTC 07, which does not seem popular in this forum, is decided on (funding applied for at the last minute; the general contractor installs it regularly)
- Decentralized ventilation system
- Underfloor heating
- Aerated concrete with external thermal insulation composite system (ETICS)
- Utility room will be max. 8 m2 (86 ft2)
- 3-person household
- Energy consumption spread throughout the day (retired occupants)
Our questions:
- We would like to achieve KfW40 standard. Which measures do you suggest or consider essential?
- We have read very positive reports on the economic efficiency of photovoltaic systems with east-west orientation on flat roofs. How do you assess this in relation to our gable roof with a maximum 30-degree pitch? Is 25 or 30 degrees better?
- Does adding a storage system make sense?
- Are there any module manufacturers you would particularly recommend?
- Can you recommend an energy consultant and/or an expert for photovoltaic system installation in the Ruhr area/Sauerland?
Please excuse the many questions and our lack of knowledge. We would be very grateful for your answers so that we at least avoid major mistakes.
Kind regards
P
pagoni202029 Dec 2020 22:41Ultimately, any form of insulation helps—whether it’s insulating the foundation slab, roof insulation, window quality, or especially addressing thermal bridges.
In general, no one can give you a definitive answer. I would start by specifying what you definitely want anyway (for example, foundation slab insulation, partially creditable photovoltaic system, controlled mechanical ventilation, or whatever it is that you want for comfort reasons).
I have just been through this myself, so I believe you should carefully consider your choice of energy consultant because there are significant differences between them.
You could begin, for instance, with a consultation at a consumer advice center—I was genuinely surprised by their expertise even in specialized areas, although luck or misfortune also plays a role in who you get assigned to.
I would definitely choose a consultant who can perform all the necessary services themselves, including calculating thermal bridges. My impression was that some consultants only do this on a basic level.
Once the calculations are done, the consultant can "adjust" things a bit—like using slightly less insulation here and different windows there, etc.
For me, the priority would always be what I want from the start. The building envelope, meaning the type of masonry or material used, is also a significant factor in these calculations.
When it comes to photovoltaic modules, it’s like with cars—there are many options. Initially, I would ask an electrician what they can offer. The usefulness or necessity of a storage system is a never-ending story and also partly depends on the lifestyle of the occupants. For KfW 40 Plus standard, you need one anyway.
Overall, I would not only look at the calculation but also at what I want included—such as a storage system.
In general, no one can give you a definitive answer. I would start by specifying what you definitely want anyway (for example, foundation slab insulation, partially creditable photovoltaic system, controlled mechanical ventilation, or whatever it is that you want for comfort reasons).
I have just been through this myself, so I believe you should carefully consider your choice of energy consultant because there are significant differences between them.
You could begin, for instance, with a consultation at a consumer advice center—I was genuinely surprised by their expertise even in specialized areas, although luck or misfortune also plays a role in who you get assigned to.
I would definitely choose a consultant who can perform all the necessary services themselves, including calculating thermal bridges. My impression was that some consultants only do this on a basic level.
Once the calculations are done, the consultant can "adjust" things a bit—like using slightly less insulation here and different windows there, etc.
For me, the priority would always be what I want from the start. The building envelope, meaning the type of masonry or material used, is also a significant factor in these calculations.
When it comes to photovoltaic modules, it’s like with cars—there are many options. Initially, I would ask an electrician what they can offer. The usefulness or necessity of a storage system is a never-ending story and also partly depends on the lifestyle of the occupants. For KfW 40 Plus standard, you need one anyway.
Overall, I would not only look at the calculation but also at what I want included—such as a storage system.
N
nordanney29 Dec 2020 22:42Sascha1977 schrieb:
We would like to achieve the KfW40 standard. What measures do you recommend or consider essential?ETICS made of Resol.Sascha1977 schrieb:
Any experts for photovoltaic system installation in the Ruhr area/Sauerland to recommend?Clensolar. However, they are based in eastern Germany. Great company with good prices.Sascha1977 schrieb:
Does a battery storage system make sense?If you want to reach KfW40 anyway, then go for 40+. Otherwise, a battery storage system is generally not worthwhile. But consider taking the subsidy already for a wallbox.S
Sascha197729 Dec 2020 22:55pagoni2020 schrieb:
Ultimately, any type of insulation helps—insulating the slab, roof insulation, window quality, especially regarding thermal bridges.
In general, no one can tell you exactly what to do. I would first decide on what you want anyway (e.g., slab insulation, partially creditable photovoltaics, controlled mechanical ventilation… or whatever is important for your comfort.
I just went through this myself and believe you should carefully choose the right energy consultant, as there are significant differences between them.
You could start, for example, with a consultation appointment at the consumer advice center—I was actually impressed by their expertise, even in specific areas, although it can be a matter of luck or bad luck who you end up with.
I would definitely choose someone who can perform all services themselves, including calculating thermal bridges. My impression was that some consultants do this rather superficially.
Once the calculations are done, they can “play” around with it a bit—less insulation here, different windows there, etc.
For me, the priority would always be what I want from the start. The building envelope, meaning the type of brick or block used, is also a significant factor in this calculation.
Photovoltaic modules are like cars—there is everything out there. At first, I would just ask the electrician what they offer. The usefulness or nonsense of a battery storage system… never-ending story. This also partly depends on the residents’ lifestyle; if you build to the KfW 40 Plus standard, you need one anyway.
Overall, I wouldn’t look at just the calculations but also at what I want, such as a storage system. S
Sascha197729 Dec 2020 22:56Thank you all for the quick responses. Wow, that was fast. It really helps a lot!
But Resol-WDVS is very expensive, isn’t it?
But Resol-WDVS is very expensive, isn’t it?
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nordanney29 Dec 2020 23:27Sascha1977 schrieb:
Resol-WDVS is quite expensive, isn’t it?That depends. You can achieve “thin” walls with it while still having excellent insulation. For example, my 1960s building only needs 12 cm (5 inches) of insulation to meet KFW 55 standards. This saves me from having to enlarge the roof overhang. Overall, it ends up being cheaper than using standard insulation materials and hiring a roofer at the same time.
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