ᐅ Controlled Residential Ventilation with Cooling: Ground Source Heat Pump Using Brine Loop Instead of Air-to-Water Heat Pump?

Hello everyone,

So far, I assumed that cooling with a mechanical ventilation system with heat recovery is done using an additional device that can be retrofitted later. This seems to be only partially true, as it is indeed an additional device, but retrofitting it later is difficult. Or are there systems that operate purely electrically? In our case, a photovoltaic system would be available, so we could technically cool using electricity in the summer.

Cooling with a mechanical ventilation system with heat recovery is done either with an earth-to-air heat exchanger (EWT) or a ground heat exchanger (ground loop). Since we need to raise the ground level by about 1.5m (5 feet), we could save on excavation work. It would be interesting to know what a ground heat exchanger would cost. So far, I haven’t found any concrete information because frequently only ground-source heat pumps are mentioned and not ground heat exchangers for mechanical ventilation systems, or if so, usually together with excavation work.

In my research, I came up with the idea of replacing our planned air-to-water heat pump with a ground-source heat pump. After all, I would have to install a system for cooling the mechanical ventilation anyway, so I could just extend the installation somewhat and switch to a ground-source heat pump, right? Or is it not that simple, and what disadvantages would there be? The costs are, of course, also interesting here, especially considering that we wouldn’t have additional excavation work.

I wasn’t able to find clear answers to these three questions and hope someone here can provide some clarification.

Good luck, CK

Hello Christian, unfortunately I don’t have an answer to your question. Instead, I have a question for you 🙂

Would you completely replace the air-water heat pump with a brine-to-water heat exchanger? Is it possible to effectively heat the house in winter with that, and not just preheat the air? I find that interesting!

You can also effectively heat with an air-to-water heat pump...

Regarding the topic: with a controlled ventilation system, you can't really cool. If you install a heat pump—whether an air-to-water heat pump or a ground-source heat pump—you can use it to cool. The best method is through the ceilings.

And with a brine heat exchanger? Would it be possible to heat properly with that?

The airflow of a mechanical ventilation system with heat recovery is far too low for cooling or heating.

Lucrezia schrieb:
Hello Christian, unfortunately I don’t have an answer to your question. Instead, a counter question 🙂
Would you completely replace the air-to-water heat pump with a ground source heat exchanger? Can you really heat properly in winter with that and not just preheat the air? That would be interesting!

I will stick with an air-to-water heat pump, but as far as I know, it could also be fully replaced by a ground source heat exchanger. With deep drilling, no problem at all. As for a ground collector, I believe it’s possible as well, but probably not feasible. You would need very long pipes, which is not achievable on today’s small plots.

Steffen80 schrieb:
The airflow of a mechanical ventilation with heat recovery might be way too low for cooling or heating..

Who says so? Define cooling. If you mean that it doesn’t replace an air conditioner, then that’s correct. A mechanical ventilation with heat recovery can cool by about 2-3 degrees Celsius (4-5 degrees Fahrenheit) as far as I know, so it can cool. But yes, it’s not comparable to an air conditioning system that reaches a specific temperature (e.g. 18°C (64°F)).

We are currently planning to install a coil before the mechanical ventilation system that slightly cools the air in summer. A 2-3 degree Celsius (4-5 degree Fahrenheit) reduction is perfectly sufficient for us, as there is a difference between 26°C and 24°C (79°F and 75°F) in the room, which is also better for the immune system ;-)