ᐅ Planning Heating and Ventilation Systems for a KfW 40 Plus Single-Family Home

Hello everyone,

We have a planning meeting with the heating and ventilation engineer scheduled for October/November.

In preparation, I have been wondering what I should pay special attention to and what is important. I hope to receive some valuable planning tips for this very important trade.

Brief key information about the planned new build:
- 2 full floors, clear structural height per floor 2.85 m (9 ft 4 in)
- KfW 40 Plus standard
- Heated living area approximately 190 m² (2045 ft²)
- Additional heat source: fireplace in the living/dining/kitchen area about 60 m² (645 ft²)
- Floor plan: see post #254 in https://www.hausbau-forum.de/threads/efh-neubauvorhaben-von-tag-1-an-und-die-planung-beginnt.33766/page-43

The following information and requirements (in addition to the planning documents) have already been sent to the heating/ventilation engineer:
Heating technology:
- Split air-to-water heat pump or ground-source (brine-to-water) heat pump
- Eligible for BAFA funding
- Underfloor heating in all rooms (except garage with storage room) with a target temperature of 21-22°C (70-72°F) in all rooms and 22-23°C (72-73°F) in the bathrooms
- Smart grid compatible (for using photovoltaic electricity)
- Cooling function if possible
- Hot water storage tank sized for a household of 4 persons

Controlled residential ventilation:
- Cooling function or summer bypass

What should I pay special attention to? What tips do you have?

Shading concept is missing. Although your drawings show external venetian blinds, you don’t mention them here, nor do you specify any planned control options.

A summer bypass in the controlled ventilation system is nice to have but offers almost no benefit. The same applies to floor cooling via the heat pump. Especially considering recent summers, which have been getting warmer. Tropical nights are also increasing, and without active air cooling, there is hardly any effective solution.

Enthalpy heat exchanger in controlled residential ventilation.

Regarding your fireplace: It’s important to understand that it will never be cost-effective unless you operate it very intensively and use free wood. Otherwise, the expenses for purchase, maintenance, cleaning, fuel, etc., will always exceed the electricity costs you would need for the heat pump without the fireplace. This is not a problem; some people appreciate it as a luxury feature. It just should be clear that it is exactly that and offers no financial advantage.

Specki schrieb:

that this is never economical

What is truly economical in house construction anyway?

Mycraft schrieb:

The shading concept is missing. Although shading blinds are shown in your elevations, you don’t mention them here. Nor do you specify the planned control options.

A summer bypass in the mechanical ventilation with heat recovery is nice to have but hardly effective. The same applies to floor cooling via the heat pump. Especially considering the recent summers and the fact that it’s getting warmer. Tropical nights are increasing as well, so without active air cooling, you can hardly achieve any significant effect.

Sorry, I didn’t realize that was relevant.

- On the ground floor (except for the north side = main entrance side), shading blinds are installed all around. The other windows on the ground floor and upper floor will have electric aluminum roller shutters. The shading blinds and roller shutters are controlled manually via Somfy TaHoma or automatically via a sun sensor.
- The roof overhang is 60cm (24 inches) with a 22° roof pitch.

I once read that both together (cooling function of heating and mechanical ventilation with heat recovery) can make a difference of about 2 to 3 degrees. I thought: "Better than nothing..." In your opinion, though, are the costs and benefits not proportional?

Specki schrieb:

Enthalpy heat exchanger in mechanical ventilation with heat recovery.

Regarding your fireplace: You do realize it will never be economical unless you run it intensively with free wood. Otherwise, the costs for purchase, maintenance, sweeping, fuel, etc., will always be higher than the electricity you would need for the heat pump without it. It’s not a problem, some people just like it as a luxury item. It should just be clear that it is a luxury and does not bring any financial benefit.

Understood. For us, it’s also a luxury and decorative element. It’s not installed for economic reasons. I thought the info might still be important.

nordanney schrieb:

What really is economical in home construction

Some people (including me) try to include the economic aspect when building a house.
We have a wood stove that heats about one-third of our apartment during winter. At the same time, we cook on it, which saves electricity. The chimney was already there; we just installed a stainless steel flue pipe for 1,200 € (approximately). Apart from that, we heat with gas but save about one-third of our heating costs thanks to the wood stove. And I can get the wood almost for free.
Of course, heating with wood and cooking on the wood stove is enjoyable, even though it requires a lot of work. However, if it had not been economical for us, we would have skipped it.

DaSch17 schrieb:

Thought this information might still be important.

In this case, it is not relevant because the heating system must work without operating the wood stove and still meet all requirements.