ᐅ Controlled residential ventilation system or photovoltaic system? Looking for decision-making guidance, pros and cons

Hello,

I have been thinking for a while about the following question:
New build single-family house, 220m² (2,370 sq ft) plus basement, not built to KFW standard, gas boiler plus solar thermal system.
The budget still allows for either a mechanical ventilation system with heat recovery or a photovoltaic system.

My current pros and cons are:

If I choose the mechanical ventilation system, I get better indoor air quality and save on heating costs in winter (but electricity costs will increase). I could retrofit the photovoltaic system later, but I don’t expect to do so (due to financing rates, saving around €10,000 just on the photovoltaic system is practically not feasible).

If I choose the photovoltaic system, I also save money in summer (when heating and mechanical ventilation are hardly needed anyway). However, in winter, manual ventilation (obviously without heat recovery) means higher heating costs. Retrofitting a mechanical ventilation system later would definitely not be possible.

At the moment, I see it like this: whatever I choose, it feels like the wrong decision.

Maybe someone can offer me a tip or advice...

Thanks and best regards
cybergnom

The mechanical ventilation system offers increased living comfort (fresh air, heat, automation). The photovoltaic system should be evaluated purely based on its economic efficiency. Therefore, for me, this comparison is somewhat flawed. I do see potential savings on heating through a mechanical ventilation system due to the absence of a KfW standard and a size of 220m² (2368 sq ft), but of course this cannot be substantiated with figures from a distance.

The sentence:

cybergnom schrieb:
Through financing rates, saving about €10,000 just on the photovoltaic system is practically impossible.

might allow for a third option:
Neither of them, and instead put the money into the buffer or later into lower installments. The photovoltaic system can always be added later if, unexpectedly, there is extra money available, and if you currently consider the mechanical ventilation system purely from an economic perspective, you probably wouldn’t miss anything. Neither seems absolutely necessary, and the returns, if any, are likely to be only marginal.

Are you referring to a central or decentralized mechanical ventilation system with heat recovery? It is usually very difficult to retrofit a central system later on. For me, mechanical ventilation with heat recovery is a comfort feature that is definitely worth considering. Photovoltaic systems are more of an investment to save on electricity costs. Regarding the mechanical ventilation, I would definitely install the ductwork now— or is it already too late for that? A small photovoltaic system would probably also be worthwhile due to self-consumption.

Aside from the fact that these two things are not comparable at all...

You will never retrofit a central mechanical ventilation system with heat recovery – it’s far too complex. On the other hand, you can always add photovoltaic panels later.

--> Definitely in favor of the mechanical ventilation system with heat recovery

We are still in the planning phase, so everything is possible.
I am thinking of a central ventilation system. So far, two decentralized ventilation units with heat recovery are planned in the two bathrooms.

I am aware that controlled mechanical ventilation and photovoltaic systems cannot be directly compared. That actually makes it even harder to decide between the two...
I tend to prefer controlled mechanical ventilation because it cannot be retrofitted later.
The problem is that I can’t really grasp the comfort benefit at all. Yes, it is a comfort improvement. But to what extent?

Difficult...

Without a mechanical ventilation system, one of you will need to air out the house by fully opening windows about twice a day. You basically become a slave to your home.
And with 220 sqm (2,370 sq ft)... (who needs 220 sqm (2,370 sq ft)? [emoji848])... that can take a while.

How much do you value your time per hour?