Combined heating/ventilation system - please share your opinions on this

Dear forum community,
we are currently planning our house, which we want to build (have built) next year.
Single-family house, approx. 150 m² living space, controlled ventilation desired
At the moment we are obtaining various offers for individual "turnkey solid houses" (from medium-sized general contractors, not from the "big players" like Viebrockhaus or similar).

Important question: How to heat & produce hot water? How for good
Suggestion contractor 1: gas condensing boiler and solar modules; decentralized ventilation via exterior wall vents with ceramic stone (heat recovery allegedly >90 %)
Suggestion contractor 2: heat pump (geothermal) from the company IWS, Celle; central ventilation with heat recovery (approx. 80 %) in bathroom, kitchen, WC, utility room and decentralized ventilation via exterior wall vents.

Contractor 1 does not trust heat pumps but otherwise delivers the more convincing overall offer; he would install a heat pump for me but does not stand behind the technology.
Personally, I want to be independent from gas! That is important to me!! I would generate electricity (also for the heat pump) with a photovoltaic system on the roof. With a KfW loan over 20 years at about €14,000 investment sum, the monthly costs are lower than paying the electricity provider directly.

What do you think 1.) about the combined heating/ventilation system and 2.) about the idea with photovoltaics?
Best regards
James

Hello,

...What do you think 1.) about the combined heating/ventilation system and 2.) about the idea with photovoltaics?

The combination of heat pump + photovoltaics is often very effective (annual balance), depending on the actual demand! How high is it for heating and hot water? For ventilation, one should prefer a central controlled residential ventilation system! It is not uncommon that this results, in connection with the evaluation of regional climate parameters, in a performance step of the heat generator one level lower! Real savings with overall higher energy efficiency! Best regards

Hello €uro,

I do not have a concrete need yet; these are first offers/ suggestions. According to a rough sample calculation, the company from Celle assumes 35 W/m², i.e. 5.3 kW. Annual energy consumption of heat pump, ventilation and "Legionella switching" between 4,000 and 5,000 kWh (depending on the installed pump).

The house is supposed to be located in northern Germany, roof area for photovoltaics facing south/ southwest (according to internet calculation with an area of approx. 70 m²).

Regarding the ventilation system, I like the following idea: central exhaust with heat recovery ("making warm water with used air"), ventilation through valves in the outer wall decentralized, so that nothing can accumulate there, like germs etc., in long ducts that you never get access to again.

By the way: In the kitchen I would like a cooker hood with external extraction; does that contradict itself somehow? Of course some heat is lost, but I am not a fan of recirculation hoods.

James.

P.S.: Sorry dear admins, I did not insert the link in the opening post with bad intentions.

Hello,

....I don’t have a concrete demand yet; these are first offers/suggestions. According to a rough sample calculation, the company from Celle assumes 35 W/m², that is 5.3 kW.

That would at best be a standard performance determination, which must be based on DIN EN 12831! If not even the actual air volumes of a controlled residential ventilation system with/without heat recovery have been taken into account here, the result is already very questionable.

....Annual energy consumption of heat pump, ventilation and "legionella control" between 4,000 and 5,000 kWh (depending on the installed pump).

How does one arrive at such statements if the performance is not sufficiently clarified? Which heat pump?

....Regarding the ventilation system, I like the following idea: centralized exhaust with heat recovery ("making warm water with used air"),...

In a PH definitely an interesting alternative, since here a separation of heat generation for heating and hot water is often necessary! Will this be a PH?

....Ventilation through valves in the exterior wall decentralized, so that nothing can accumulate with germs etc. in long ducts which one never gets to again.

I would think about that very carefully once again!

... Of course some heat is lost there, but I’m not fond of recirculating range hoods.

A heat recovery system “lives” from high exhaust air temperatures!

best regards

....But nevertheless, I do think about these basic things like heating, etc.!

Very sensible, since heating technology correlates with the energetic building status!

....My inquiry at IWS was about the amount of acquisition costs ...

How can investment costs be defined if the actual demand is not known?

.... and that I do not want a pipe system, I already wrote.

Then that should be a given!

.... That heat recovery is particularly worthwhile at high exhaust air temperatures (which of course mainly occur in the kitchen) is also clear to me. But an extractor hood does not run continuously (but at most one to two hours while cooking and removes odors AND grease).

A certain energy share in favor of heat recovery is already provided by this. Why waste it?

.... Or does the extractor hood "suck" so much air out of the kitchen and create a slight vacuum (that a negative pressure in the house is created by the ventilation, I understand)?

For controlled residential ventilation, an air volume plan according to 1946-6 is required, which must also be taken into account at the HLB. Part of this is also handled by an exhaust hood in the kitchen. A "permanent" negative pressure system only promotes infiltration from outside, which can be avoided.

Regards

Hello,
do you already have a heating load calculation tailored to your house?
Because that should definitely be done before you make a decision regarding the choice of heating system. And if you have already made the "decision" that you do not want to use gas, the question arises why you are comparing both.
A combination of the heating and ventilation system can definitely make sense if the overall system fits, since you can also recover heat from the exhaust.
To what extent the photovoltaic system pays off is also a question of the possible performance of the photovoltaic and how your electricity consumption looks. Therefore, it would also be necessary here to have the possible energy gains determined and then to make further considerations.