ᐅ Exhaust Air vs. Recirculation in a Mechanical Ventilation with Heat Recovery System

Hello,

we are building a KfW 70 semi-detached house with a controlled ventilation system, and now I am facing the decision between exhaust air or recirculating air in the kitchen. Unfortunately, I can’t find clear answers on this in the forum or online in general.

My general contractor said it’s no problem and that they can install an exhaust air system if desired.

In five different kitchen showrooms, I received five different answers and recommendations (definitely no exhaust air, exhaust air is prohibited, recirculating air is fine, exhaust air is better, etc.).

How have you solved this in your homes, and which factors are crucial for making this decision?

Thank you!

Hello Momad,

In 2015, we decided on recirculation ventilation because our construction company considered exhaust ventilation difficult for a KfW-certified house with controlled residential ventilation. In hindsight, we regret this decision a lot, as we are very unhappy with the recirculation hood.

We are currently considering having a core drill made afterwards to switch to exhaust ventilation.

If it is that easy for you to do, I would definitely go with exhaust ventilation.

Hello,
the main question in this situation is whether you still want to have a wood-burning stove. That can make using ducted range hoods somewhat tricky.
In terms of performance, a ducted range hood will generally be better, unless you opt for a very high-end recirculating hood.
However, with a ducted hood, you will experience heat loss during operation and possibly some sound transmission issues. Also, a ducted hood limits your kitchen layout options because you still need to find a way to install the exhaust duct.
It also needs to be clarified whether the ducted hood might negatively affect your KfW subsidy calculations. Your energy consultant should be able to give you a definitive answer on that.

Best regards,

Andreas

@Teyla: Which recirculation hood do you have, and how bad is it?
We really enjoy cooking often, and occasionally we fry or deep-fry something.

@andimann: A chimney is not planned. Is heat loss significant for, say, a maximum of 60 minutes of cooking per day?
I’ll have the KfW invoice checked/confirmed by the general contractor—thanks for the tip!
What about mechanical ventilation with heat recovery and pressure equalization in the house? Any experiences?

Momad schrieb:
@Teyla:
What about the controlled residential ventilation system and pressure balancing in the house, any experiences?

We don’t have a controlled residential ventilation system, but instead a decentralized ventilation unit. As soon as the exhaust hood runs at stage 2 out of 3, the fans start buzzing loudly. We don’t stand a chance against the hood; I think the airflow direction is simply reversed by it.

At least now I know that my house is quite well sealed, since when I turn on the hood, the fan upstairs in the first floor buzzes loudly.

We have a standard recirculation cooker hood, which can also be converted into an exhaust hood. Unfortunately, we had no prior experience with recirculation hoods (we always used exhaust systems before), so we naively chose the recirculation hood that the kitchen planner recommended to us.

In my opinion, the recirculation hood hardly does anything, except that the condensation from cooking does not run down the upper cabinets. In terms of odor, you might as well leave it turned off. In our case, the smell of frying lingers in the kitchen for a long time and can only be removed by keeping the patio door open for an extended period.

We are planning to have an exhaust vent installed to the outside during the summer, which is also blower door certified. It apparently only opens when the exhaust hood applies pressure to it.