ᐅ Combined heating and ventilation system – looking for opinions on this

Dear forum community,

We are currently planning our house, which we intend to build next year.
Single-family home, approximately 150 m² (1,615 sq ft) of living space, with a desire for controlled ventilation.

At the moment, we are collecting various offers for custom "turnkey solid construction houses" from mid-sized general contractors, not from the large companies like Viebrockhaus or similar.

Important question: How to handle heating and hot water preparation? How to do it well?
Proposal from contractor 1: Gas condensing boiler and solar panels; decentralized ventilation through exterior wall vents with ceramic stone (claimed heat recovery >90%)
Proposal from contractor 2: Heat pump (geothermal) from the company IWS, Celle; central ventilation with heat recovery (about 80%) in bathroom, kitchen, toilet, utility room, and decentralized ventilation through exterior wall vents.

Contractor 1 does not trust heat pumps but otherwise provides the more convincing overall offer; he would install a heat pump for me but is not confident in the technology.
Personally, I want to be independent from gas! That is very important to me!! I would generate electricity (also for the heat pump) with a photovoltaic system on the roof. With a 20-year low-interest loan under the KfW program for an investment of about €14,000 (approximately 15,000 USD), the monthly costs would be lower than paying the electricity provider directly.

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

Best regards
James

Hello,

James schrieb:
...What do you think about 1.) the combined heating and ventilation system and 2.) the idea of photovoltaic panels?

The combination of a heat pump and photovoltaic system is often very effective (annual balance), depending on the actual demand! How high is the demand for heating and hot water? For ventilation, it is better to prioritize a central controlled residential ventilation system!
Often, this leads to a performance step down of the heat generator when combined with analysis of local climate parameters! Real savings with overall higher energy efficiency!

Best regards

Hello €uro,

I don’t have a specific requirement yet; these are initial offers/suggestions. According to a rough preliminary calculation, the company from Celle estimates 35 W/m², which is about 5.3 kW. The annual energy consumption of the heat pump, ventilation system, and "legionella function" is between 4,000 and 5,000 kWh, depending on the installed pump.

The house will be located in northern Germany, with the roof area for photovoltaic panels facing south/southwest (according to an online calculation, the area is approximately 70 m² (750 ft²)).

Regarding the ventilation system, I like this idea: centralized exhaust with heat recovery ("using the warm air to heat water"), and decentralized supply air through valves in the external wall. This way, nothing can accumulate in long ducts—such as germs or similar issues—that you can’t access later.

By the way: in the kitchen, I would like a range hood with external venting; does that contradict anything? Obviously, some heat is lost, but I’m not a fan of recirculating range hoods.

James.

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

Hello,

James schrieb:
....I don’t have a specific demand yet; these are initial offers/suggestions. According to a rough sample calculation, the company from Celle assumes 35 W/m², so 5.3 kW.

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

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

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

James schrieb:
....Regarding the ventilation system, I like this idea: central exhaust with heat recovery ("making warm water with used air"),...

For a passive house, this is quite an interesting option, since a separation of heat generation for heating and domestic hot water is often necessary! Will this be a passive house?

James schrieb:
....Ventilation through valves in the exterior wall decentralized, so nothing can accumulate in long ducts that you never get access to again, like germs or similar.

I would strongly reconsider that!

James schrieb:
...Of course, some heat is lost, but I am not a fan of recirculating range hoods.

Heat recovery systems rely on high exhaust air temperatures!

Best regards

James schrieb:
....But of course, I am thinking about basic things like heating, etc.!

Very sensible, as the heating system correlates with the building’s energy performance!

James schrieb:
....My inquiry to IWS was about the initial investment costs ...

How can investment costs be defined if the actual needs are not known?

James schrieb:
.... and I already mentioned that I don’t want a pipe system.

Then that should be fixed!

James schrieb:
.... I also understand that heat recovery is especially worthwhile with high exhaust air temperatures (which mainly occur in the kitchen). But an extractor hood does not run continuously (only one to two hours during cooking at most and removes odors AND grease).

A certain amount of energy savings in favor of heat recovery is already achieved this way. Why waste it?

James schrieb:
.... Or does the extractor hood “pull” so much air from the kitchen that it creates a slight vacuum (I understand that ventilation causes negative pressure in the house)?

With controlled mechanical ventilation, an air volume plan according to 1946-6 is required, which must also be considered in the heat load calculation (HLB). Part of this is handled in the kitchen by an exhaust hood. A “permanent” negative pressure system only promotes infiltration from outside, which should be avoided.

Best regards

Hello,
have you already had a heating load calculation performed specifically for your house? Because this should definitely be done before making a decision about the heating system. And if you have already decided not to use gas, then the question arises why you are comparing both options.
A combination of the heating and ventilation system can certainly make sense if the overall system fits, as you can also recover heat from the exhaust air.
How cost-effective the photovoltaic system is also depends on its potential output and your electricity consumption. Therefore, it would be necessary to determine the possible energy gains first and then make further considerations.