ᐅ Heating Savings: Is up to 95% Heat Recovery Realistically Achievable?

Good evening dear forum members,

We are considering installing a (central) mechanical ventilation system with heat recovery in our new build.

During my research on this topic, I keep coming across the claim:
“...up to 90%-95% heat recovery, resulting in heating energy savings.”

However, I am having trouble fully understanding this.

My understanding of a controlled ventilation system with heat recovery is that it works by retaining as much generated heat as possible (up to 90-95%) inside the building. The warm indoor air is mixed with the colder (winter) / warmer (summer) outdoor air and then brought back inside.

This “heating energy saving” only applies to the winter period, when you would otherwise ventilate by fully opening windows for a short time, correct?

Is it even possible to calculate how much energy you save? I imagine it is quite minimal if you only ventilate twice a day for 5-10 minutes, for example. Also, it is not guaranteed that you actually achieve 90-95% heat recovery, right?

We will not base our decision solely on this, but I am just curious whether it is realistically possible to make such a calculation in advance with certain assumptions or if anyone has practical experience with this?

Best regards

In a modern new building, about 40-50% of heat loss is due to ventilation alone. The rest is lost through heat transmission via walls, windows, the foundation slab, and the roof.

Yes, this is calculated during the creation of the thermal insulation proof and/or the heating load calculation to properly size the heating system.

However, whether the stated 90% is realistic remains questionable. This is tested, among others, by the Passive House Institute. You can find the test results at passiv . de.

My impression is that the OP means a controlled residential ventilation system saves 90% of heating costs? You only recover 90% of the ventilation losses. The amount of ventilation required is standardized.

Aliban2014 schrieb:

Is it even possible to calculate how much that saves? I imagine it’s very little if you, for example, ventilate twice daily for 5-10 minutes.

Hello. Since I ventilate using decentralized ventilation without heat recovery, I can’t provide specific figures.

However, because air is a poor heat conductor, heat loss through ventilation is generally low.

And even if the suggested 40-50% heat loss, with 90% heat recovery, were true, we are talking about saving approximately 15-20 euros per month. The system should therefore have no maintenance costs and ideally run for at least 20 years to make it cost-effective! ;-)

Ventilation systems are not primarily about cost-effectiveness. Either you have one and no longer need to ventilate manually, or you don’t.

The amount of energy loss depends greatly on the building. In a typical house from the 1970s, losses are around 25% of the energy used... in modern energy-efficient buildings, losses can easily reach 50%, simply because the construction (insulation, etc.) requires much less energy to achieve and maintain the same temperatures.

Thank you for the previous responses; this clears up the question regarding the argument about “heating cost savings.”

@Lumpi_LE
This seems to be a misunderstanding—if a mechanical ventilation system with heat recovery saved 90% of heating costs, everyone would have one. That’s not what I meant.

In fact, it’s really only about ventilation heat losses, which was more or less my assumption.

I did not intend to start any fundamental debates.

Thanks to everyone!