ᐅ Controlled residential ventilation with heat recovery or exhaust air heat pump

Hello,

we are building a KfW70 house with insulation achieving a U-value of 0.15.
The living area is 180m² (1,938 sq ft) including a separate apartment. The ventilation system is planned only for the 140m² (1,507 sq ft) main house without the separate apartment.
We want to use the Mitsubishi AlphaTherm Zero + Sunhybrid buffer tank for the underfloor heating and hot water preparation.

We have now been offered the Nibe Fighter 120 exhaust air heat pump, which is supposed to heat the water using a small heat pump from the exhaust air. This costs 8,200 EUR.

Looking at another offer, I received a Vaillant recoAir 275 with a cross-flow heat exchanger and 95% heat recovery for 7,780 EUR.

Which option is better, and which one uses less electricity?
Because with the exhaust air heat pump, a heat pump that consumes electricity runs continuously. With the Vaillant system, I assume the cross-flow heat exchanger does not use electricity. So, the incoming air is nearly as warm as the outgoing air at 95% efficiency. However, with the exhaust air heat pump, I wouldn’t need supply air ducts, and hygiene would be better...

Can you help me here? I’m facing a tough decision.
I definitely want to avoid high electricity costs later on.
What are your experiences with Nibe?

Thanks a lot

Best regards,
philipp1983

philipp1983 schrieb:
....we are building a KFW70 house with insulation achieving a U-value of 0.15.

Actually, achieving KFW 55 should be possible.

philipp1983 schrieb:
.... Mitsubishi AlphaTherm Zero + Sunhybrid buffer to handle the underfloor heating and domestic hot water preparation.

The Mitsubishi unit does not have full modulation. Below -15°C (5°F) it stops operating, so neither heating nor hot water will be available. For operational limits, the site-specific minimum temperature matters, not the design heating temperature! No one really knows what lowest temperatures can be expected here.
When using an air source heat pump, a location-specific climate analysis (heating degree days) is indispensable.

philipp1983 schrieb:
.... For this, we were now offered the exhaust air heat pump ...

Exhaust air heat pumps might become a money pit in a KFW 70 house.

philipp1983 schrieb:
.... What is better now, what uses less electricity?.... Can you help me here? I’m facing a tough decision. I definitely don’t want high electricity costs later.

Save yourself the trouble of pointless searching and first have a reliable and precise baseline assessment carried out. Once the actual demand (capacity, energy) for heating and hot water is known, and site-specific conditions are taken into account, the appropriate solution can be found.
Anything else is guessing in the dark, speculation – certainly not a suitable basis for a major investment decision.

Best regards.

The Mitsu indoor unit also has a heating element installed for temperatures below -15°C (5°F)... but that’s not really the main point. Of course, you need to calculate the exact values once I have them.

But can’t we say which is better? How much electricity does the controlled residential ventilation system use compared to the air source heat pump (AWP)? That’s what’s important to me right now and what I want to prepare for in the heating planning phase... because I don’t want to just blindly trust my heating engineer simply because they prefer the AWP...

philipp1983 schrieb:
Of course, you need to calculate it precisely once I have the values. But can’t we say which is better, how much electricity does the controlled residential ventilation use compared to the air-to-water heat pump (AWP)?

Apparently not understood? Also, you can’t compare apples to oranges. The AWP provides heating and ventilation, while the controlled residential ventilation only provides ventilation!

philipp1983 schrieb:
...That’s what’s important to me for now and what I can first prepare for in the heating system planning....

For this, the actual demand must be known! This is the first step that everything else depends on.

Regards

Hello Philipp,

this is a risky construction idea — take €uro’s advice seriously and have a proper HVAC design prepared!

By the way, I always wonder why potential homeowners—basically complete novices when it comes to housebuilding and especially new technologies—seek advice in a forum like this, but then remain resistant to learning.

philipp1983 schrieb:

I definitely don’t want to have high electricity costs afterward

That’s understandable—but in my opinion, you shouldn’t forget that there is no heating system that operates without an electrical connection! However, this

philipp1983 schrieb:

... exhaust air heat pump NIBE Fighter 120 ...

will make your utility company happy at the beginning of the year. Even as a layperson, it should be clear to you that

philipp1983 schrieb:

using exhaust air to heat water

is not possible “without” an additional power source. Where do you have “usable” exhaust air besides the bathroom and kitchen?

philipp1983 schrieb:

can you help me here? Facing a difficult decision?

Search the main forum or Google and read up!

There is a highly reputable competitor, whom I respect overall; they often advertise with those funny tents. What I still don’t understand is that they heat their houses mostly not Passive House standard but using exhaust air heat pumps.

Use Google for this matter, and you will find plenty of posts about "fun with the utility company"…

Best regards

Hello construction expert,

Bauexperte schrieb:
.... What I still don’t understand is that he heats his houses using exhaust air heat pumps, even though he mainly doesn’t build passive houses at the moment

The answer is probably simple: consumption is not part of the contract!

Best regards