ᐅ As for the planning and design of the energy standard and heating concept, beforehand

Hello everyone,

For days (or rather weeks) now, I have been researching the topic of house construction.
First of all, it will be a semi-detached house, and a friend who is an architect is designing it. He will handle all the necessary tasks to submit the plans. Heating concepts, ventilation concepts, etc., are not included here.

The plot is on a slight slope, which is why we are planning a 50 m² (540 sq ft) ground-level granny flat, and the area behind the flat, which connects to the earth, will be used as a basement for heating systems, etc.

Overall, the house will have about 250 m² (2,700 sq ft) of gross floor area and a roof pitch of 45 degrees.

I have already read a lot here in the forum, which has been very helpful, but I think that for the topic of house building, each issue requires its own discussion. 😉

My questions are surely the classic ones:

• Building a house according to the 2016 Energy Saving Ordinance or aiming for KfW 55 standard?
I am currently unsure whether the house will be built according to the 2016 Energy Saving Ordinance or to KfW 55 standard.
Ultimately, this is a question of economic efficiency. But how can I find out exactly?
Do I take my plans to an energy consultant who then calculates this for me?
What costs can be expected for such an energy consultant’s assessment?

I am currently planning to build with Poroton T9 36.5 blocks. As far as I know, it is difficult to achieve KfW 55 with these blocks since the U-value is around 0.23 W/(m²K)?


• Ventilation system
From when is a mechanical ventilation system actually mandatory?


• KfW subsidies
I do not intend to take out a KfW loan. Can I still apply for individual KfW subsidies? Can I apply for individual subsidies myself, or does every subsidy have to be obtained through the bank?

As far as I know, all subsidies must be applied for before starting construction. So, building first and then applying is not possible, right?


• How to heat?
I want to design my heating system primarily for economic efficiency. Being as green or self-sufficient as possible is generally not the top priority. It should simply be the “most economical” system from today’s perspective, with a 15-year outlook (assuming current prices for all necessary resources). A gas connection has already been installed up to the plot. Currently, the new development area is promoting fuel cells (up to €10,000 subsidy). Are there any experiences with this? The system sounds great in theory, with high efficiency, etc.

After much reading here in the forum, I have come to the conclusion that an air source heat pump combined with a small photovoltaic system is currently probably the most economical option?

This is very important to me because I am desperately trying to find the best energy concept for my project and do not know the best way to proceed. For me, the standard according to the 2016 Energy Saving Ordinance is already decent. Maybe one can just save all the effort and simply build with a gas condensing boiler?


Best regards!

Take a look here:

https://www.hausbau-forum.de/threads/leidiges-thema-gas-oder-Wärmepumpe.30849/

This should be very interesting for you.

quattro123 schrieb:

I’m really concerned because I’m desperately trying to find the most suitable energy concept for my project and don’t know the best way to proceed. For me, the standard according to the 2016 Energy Saving Ordinance (EnEV) is already quite good. Maybe all the extra effort isn’t necessary and it would be enough to simply build with a gas condensing boiler?

In the end, it depends on the prices you get for each type of heating system. With heat pumps, more in-house or DIY work might be possible, but otherwise, I think the prices for heat pumps are often set too high. Heat pumps are more efficient the better the house is insulated and the larger and better planned the heating surfaces are. That doesn’t mean, however, that a heat pump doesn’t also make sense under the Energy Saving Ordinance.

Where insulation is affordable, I wouldn’t save on it.

The only thing that can be said almost universally is that photovoltaic systems are almost always cost-effective with current subsidies—provided you don’t wait too long.

Energy Saving Regulation standard. That is sufficient.
Gas heating with a heat meter for both the main apartment and the secondary apartment. This allows for fair billing.
The renewable energy portion is provided by a controlled ventilation system with heat recovery, which also helps prevent mold in the secondary apartment if the tenant does not ventilate properly. Advertise this feature for the secondary apartment and charge an extra $1 per square meter (10.8 sq ft) in rent for fresh air and reduced heating costs. I have rented properties for decades; this is a different level—nothing sophisticated matters here, just simple, rugged, and reliable. And it’s also useful for your living area.

Oh, part of the property will be rented out?

Decentralized ventilation for the rental unit, allow tenants to test it beforehand so they won’t turn it off if it bothers them.

Separate or shared gas boiler for heating the rental unit. A heat pump would generally have low capacity and no buffer tank, which doesn’t work well with tenant behavior and room thermostats. Domestic hot water quality must be 100% safe for drinking and hot water should always be available. While this is possible with a heat pump (e.g., high hot water temperature in the storage tank plus a solar-compatible tankless water heater at the tank outlet, or a fresh water station with tankless heater), it would be more expensive and complex. Also, the local heating technician should be able to repair the tenant’s heating system.

A heat pump can be considered for the owner’s own living unit. It’s worth calculating the costs, especially regarding additional expenses for the landlord if the heating systems are separate.

For complying with the energy-saving regulations, ventilation instead of solar thermal only works with a good energy consultant and possibly not with the minimum level of insulation.

Is it still possible to receive KfW funding twice for two residential units (a secondary apartment plus a separate main unit) under current regulations?

If so, you should double-check this... We went for it, not because of the "great" conditions, but to stay flexible. In our case, unlimited special repayments were still allowed, and the loan ends after just 10 years, which significantly reduces our monthly burden.

Think carefully about using 36.5 (°C) if you have tenants; it’s better to use something insulated or filled! The tenant won’t want to hear the noise you make downstairs... And if you choose insulated materials, you’re basically back to KfW 55 standard. You have to apply for the funding in advance… and be careful with impact sound insulation.

Go with gas. See the other thread and the comment from BoxandProof.

For decentralized heating, I would only consider it in the bathroom for comfort reasons. Otherwise, the units are too noisy to run constantly in living spaces. But maybe there are better models available now.