ᐅ Heat pump or gas with a central ventilation system featuring heat recovery
Created on: 3 Apr 2019 14:33
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Llehsif
Hello everyone,
I am currently planning our new single-family home. I am interested in your experience regarding the choice of heating or an overall heating system concept.
A few key details:
Single-family house
2 stories with a gable roof
Approximately 160-170 sqm (1720-1830 sq ft)
KfW standard: Not planned yet
At first, I favored gas condensing technology combined with solar because air source heat pumps didn’t seem fully developed to me, and the units on the house didn’t look appealing.
In the meantime, a central ventilation system has come into play, which I now definitely want to consider. I was then advised that combining an air source heat pump with heat recovery ventilation would put me in a significantly better position.
What has been your experience? What would you recommend?
Additionally, there seems to be the option of using a combined unit (heat pump and ventilation). Does that make sense, or would it be better to install these two systems separately?
Which manufacturers do you prefer?
Thank you in advance for every response. If you need any more information, I will of course try to provide it.
Best regards,
Fabian
I am currently planning our new single-family home. I am interested in your experience regarding the choice of heating or an overall heating system concept.
A few key details:
Single-family house
2 stories with a gable roof
Approximately 160-170 sqm (1720-1830 sq ft)
KfW standard: Not planned yet
At first, I favored gas condensing technology combined with solar because air source heat pumps didn’t seem fully developed to me, and the units on the house didn’t look appealing.
In the meantime, a central ventilation system has come into play, which I now definitely want to consider. I was then advised that combining an air source heat pump with heat recovery ventilation would put me in a significantly better position.
What has been your experience? What would you recommend?
Additionally, there seems to be the option of using a combined unit (heat pump and ventilation). Does that make sense, or would it be better to install these two systems separately?
Which manufacturers do you prefer?
Thank you in advance for every response. If you need any more information, I will of course try to provide it.
Best regards,
Fabian
B
boxandroof3 Apr 2019 22:21I would never choose a combined unit without a good reason. In this case, the seller benefits, not the buyer. Separate systems are more efficient, less complex, and importantly: easier and cheaper to replace in the long run than any specialized device.
With controlled ventilation, the supply temperature can be lowered, making the heat pump somewhat more efficient.
Personally, for new builds, I would go with:
- Heat pump + controlled ventilation
or
- Gas + controlled ventilation instead of solar thermal
A heat pump is the "better" technology for new buildings but requires careful planning to outperform gas with current costs and avoid becoming a financial risk.
When it comes to insulation, there is no need to overdo it, but it should definitely be somewhat better than the energy saving regulations, which is not expensive in the right areas. The actual insulation value (H't) of the building envelope is what matters.
Photovoltaics are almost always worthwhile regardless of the heating system, but especially with a heat pump.
With controlled ventilation, the supply temperature can be lowered, making the heat pump somewhat more efficient.
Personally, for new builds, I would go with:
- Heat pump + controlled ventilation
or
- Gas + controlled ventilation instead of solar thermal
A heat pump is the "better" technology for new buildings but requires careful planning to outperform gas with current costs and avoid becoming a financial risk.
When it comes to insulation, there is no need to overdo it, but it should definitely be somewhat better than the energy saving regulations, which is not expensive in the right areas. The actual insulation value (H't) of the building envelope is what matters.
Photovoltaics are almost always worthwhile regardless of the heating system, but especially with a heat pump.
Mycraft schrieb:
To put it exaggeratedly, you could hit gas heating systems with a hammer and they would keep running.
Heat pumps, on the other hand, are very sensitive to everything. Even a slightly incorrect setting or too low outdoor temperatures can cause a failure or significantly higher energy consumption.
A dedicated mechanical ventilation with heat recovery unit (MVHR) performs the task better simply because it is designed solely for that purpose, unlike a combined unit.That’s also the impression I have in general. However, I was brought back to the air source heat pump because an architect said that if I choose an MVHR with heat recovery, then an air source heat pump makes much more sense and significantly increases efficiency. Is there any truth to that?
dhd82 schrieb:
If you go with gas, then try to meet the energy saving regulations without solar thermal, but instead with mechanical ventilation with heat recovery.
How many people are or will be living in the house? Take this into account when sizing the hot water storage tank, if you don’t use gas.
If I could choose, I would go for a ground source heat pump from Nibe and mechanical ventilation with heat recovery from Zehnder. These systems are regularly praised here and also in the pink forum. That of course doesn’t mean that Stiebel products are bad.Oh, I thought that gas automatically implies solar thermal as well. What advantages do you see in skipping solar thermal?
We are planning for four people in the future. Unfortunately, my choice of equipment is limited because of a general contractor. I suspect Vaillant will be used.
What should I look out for with mechanical ventilation with heat recovery? I’ve heard of a Swedish company called Östberg. The advantage is said to be that the system uses a rotary heat exchanger, which is better (because of humidity and mold protection?!).
boxandroof schrieb:
I would never choose a combined unit without a strong reason. The seller benefits from this, not the buyer. Separate systems are more efficient, less complex, and importantly: easier and cheaper to replace later on than some special combined device.
With mechanical ventilation with heat recovery, the supply water temperature can be lowered, and the heat pump becomes somewhat more efficient.
Personally, for new builds I would do:
- Heat pump + mechanical ventilation with heat recovery
or
- Gas + mechanical ventilation with heat recovery instead of solar thermal
A heat pump is the “better” technology in a new build but requires good planning to outperform gas at today’s costs and avoid becoming a financial risk.
With insulation, you don’t need to overdo it, but it should be somewhat better than the energy saving regulations require and it’s not expensive at the right spots. The pure thermal transmittance value (H't) of the building envelope matters.
Photovoltaics almost always make sense regardless of heating system, but especially with a heat pump.I hadn’t thought about the future issues with a combined unit either. Thanks a lot! Photovoltaics are critical for us because we don’t always have a lot of sun, and the costs probably won’t be recovered.
Llehsif schrieb:
That’s the overall impression I have as well. However, I was advised to reconsider the air source heat pump because an architect said that if I choose mechanical ventilation with heat recovery, then an air source heat pump makes much more sense and significantly increases efficiency. Is there any truth to that? If you change “significantly” to “slightly” and adjust the supply temperature a bit...
Llehsif schrieb:
Oh, I thought that gas automatically meant solar thermal as well. What advantage do you see in not using solar thermal? Solar thermal isn’t cost-effective, so if it can be avoided, you should do so.
Llehsif schrieb:
What should I pay attention to with mechanical ventilation with heat recovery? I’ve heard about a Swedish company, Östberg. The advantage is supposed to be that their system uses a rotary heat exchanger, which is better (because of moisture and mold?!). For a single-family house, you should make sure the unit is properly sized and has an enthalpy exchanger.
Llehsif schrieb:
I hadn’t considered a combination unit in the future either. Thanks a lot! Photovoltaics are tricky for us because there isn’t consistent strong sunlight and the costs probably cannot be recovered. Do you live in a forested area or on a north-facing slope? Then it does make sense to avoid it. Otherwise, photovoltaics are always worthwhile.
Llehsif schrieb:
That’s also the impression I have overall. However, I was brought back to the topic of the air source heat pump because an architect said that if I choose a mechanical ventilation system with heat recovery (MVHR), then an air source heat pump makes much more sense and significantly increases efficiency. Is there any truth to that?No matter what you decide, the mechanical ventilation system with heat recovery should be considered separately. This system basically “improves” the efficiency of any heating method (if we follow the same logic) because ventilation heat losses are reduced.
However, if one of the positive arguments for an air source heat pump is only that it requires an MVHR system to increase efficiency, then I would think twice. Because, conversely (just thinking aloud), it implies that without an MVHR system, an air source heat pump is not efficient enough.
Llehsif schrieb:
Oh, I thought that gas automatically means solar thermal. What advantages do you see in opting out of solar thermal? No, not really. But you have to calculate carefully, and there are alternative measures that make it possible, with the right house design, to forgo solar thermal and use only gas plus MVHR.
For example, I personally did not see any benefit in that and just chose gas plus MVHR plus solar thermal.
Llehsif schrieb:
What should I pay attention to with a mechanical ventilation system with heat recovery? I have heard of a Swedish company called Östberg. The advantage is supposed to be that the technology uses a rotary heat exchanger, which is better (because of humidity and mold?!). A rotary heat exchanger is not necessarily the best choice.
Disadvantages compared to a plate heat exchanger include:
Noise
Higher maintenance costs and wear
Higher power consumption
Possible mixing of exhaust and supply air
I would choose a conventional unit with an enthalpy heat exchanger from manufacturers like Wolf, Helios, Zehnder, Brink, or similar.
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boxandroof4 Apr 2019 15:29Llehsif schrieb:
What should I pay attention to when choosing a mechanical ventilation system with heat recovery? I have heard of a Swedish company called Östberg. The advantage is said to be that the technology uses a rotary heat exchanger, which is supposedly better (because of moisture and mold?!).We have a mechanical ventilation system with heat recovery from Östberg that uses a rotary heat exchanger. Rotation is rather uncommon and has both advantages and disadvantages. Moisture and mold are not among them. For mechanical ventilation systems, I would recommend going with whatever the installer is comfortable installing, because in my opinion the choice of manufacturer and even the type of heat exchanger is not that crucial—what really matters is proper installation and planning.
What is important: moisture recovery and avoiding undersizing.
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robin19885 Apr 2019 13:53dhd82 schrieb:
If you use gas, then try to meet the energy saving ordinance without solar thermal, but with controlled residential ventilation plus heat recovery.Are you sure that is possible? I spoke with an energy consultant yesterday and happened to ask about this exact point. He said that controlled residential ventilation cannot replace solar thermal because controlled ventilation does not use renewable energy (or something like that; I don’t fully recall the exact reasoning). To comply with the energy saving ordinance using a gas boiler, solar thermal is therefore required despite having controlled ventilation with heat recovery.
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