ᐅ Which heating system? Air source heat pump / gas / geothermal heating
Created on: 26 Mar 2015 19:57
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Nina132
Hello everyone,
we are building a single-family house with 155m2 (1,670 sq ft) and want to try to meet KfW55 standards (at least that is what is stated in the contract). Underfloor heating is mandatory. We are working with an architect who also acts as the general contractor, so the house will be delivered turnkey.
The challenges are as follows:
1. North-facing slope – no opportunity for solar panels
2. Sloped site – the ground floor (GF) will be partially built into the hillside at the back. The bedrooms will be on the GF, while the living area is on the upper floor (UF) with a level exit “onto” the slope. By embedding the GF on one side, we can have a reasonably flat garden at the top.
3. There are currently just two of us, but a child is planned in about five years
4. We want a large bathtub and will therefore need a lot of hot water
5. I like to ventilate frequently and thoroughly
6. The utility room is on the GF along with the bedrooms. Could there be noise issues?
Now about the heating decision.
Originally, especially my partner wanted a ground source heat pump. That is probably the best option in terms of quality and ecology, but it is very expensive.
An air source heat pump is of course an alternative, but I’m concerned about electricity costs in winter because I suspect that, especially the GF, will cool down quickly due to the hillside situation.
Our architect recommends a gas condensing boiler, saying this is standard for 80% of new builds. We actually wanted to move away from gas and oil, but electricity also involves fossil fuels – at least indirectly. Of course, this would probably rule out KfW55 compliance, but I think KfW70 would also be acceptable.
What are your thoughts?
we are building a single-family house with 155m2 (1,670 sq ft) and want to try to meet KfW55 standards (at least that is what is stated in the contract). Underfloor heating is mandatory. We are working with an architect who also acts as the general contractor, so the house will be delivered turnkey.
The challenges are as follows:
1. North-facing slope – no opportunity for solar panels
2. Sloped site – the ground floor (GF) will be partially built into the hillside at the back. The bedrooms will be on the GF, while the living area is on the upper floor (UF) with a level exit “onto” the slope. By embedding the GF on one side, we can have a reasonably flat garden at the top.
3. There are currently just two of us, but a child is planned in about five years
4. We want a large bathtub and will therefore need a lot of hot water
5. I like to ventilate frequently and thoroughly
6. The utility room is on the GF along with the bedrooms. Could there be noise issues?
Now about the heating decision.
Originally, especially my partner wanted a ground source heat pump. That is probably the best option in terms of quality and ecology, but it is very expensive.
An air source heat pump is of course an alternative, but I’m concerned about electricity costs in winter because I suspect that, especially the GF, will cool down quickly due to the hillside situation.
Our architect recommends a gas condensing boiler, saying this is standard for 80% of new builds. We actually wanted to move away from gas and oil, but electricity also involves fossil fuels – at least indirectly. Of course, this would probably rule out KfW55 compliance, but I think KfW70 would also be acceptable.
What are your thoughts?
We were offered two options:
A townhouse with a standard gas heating system (KfW 70) and a ventilation system with heat recovery
The same townhouse with an air-source heat pump for an additional €9,000 (KfW 55 contractually guaranteed), also with a ventilation system with heat recovery
-The plot is south-facing, with no large windows facing north/west or north
The calculations included:
- €2,500 savings from the KfW 55 loan
- Approximately €1,000 savings from lower interest rates over 10 years
- €1,500 savings from no longer needing a gas connection
Effective additional cost: €4,000
To be honest, I’m not particularly interested in the environmental aspect. The electricity required still has to come from somewhere, and electrical energy is considerably more expensive. Whether or when you might recoup the €4,000 remains uncertain. Also, heating with electricity can be a pretty bad idea in my opinion. On the other hand, the underfloor heating would then be prepared for future solar use (or suitable for lower flow temperatures) and would remain up-to-date with current technology for a few more years.
On the other hand, we are reaching the practical limits here, the savings are partly not really tangible (for example, interest rates), or they are offset by other costs (for example, two electricity meters or the KfW 55 inspector, who wants €1,000 for one signature…).
A townhouse with a standard gas heating system (KfW 70) and a ventilation system with heat recovery
The same townhouse with an air-source heat pump for an additional €9,000 (KfW 55 contractually guaranteed), also with a ventilation system with heat recovery
-The plot is south-facing, with no large windows facing north/west or north
The calculations included:
- €2,500 savings from the KfW 55 loan
- Approximately €1,000 savings from lower interest rates over 10 years
- €1,500 savings from no longer needing a gas connection
Effective additional cost: €4,000
To be honest, I’m not particularly interested in the environmental aspect. The electricity required still has to come from somewhere, and electrical energy is considerably more expensive. Whether or when you might recoup the €4,000 remains uncertain. Also, heating with electricity can be a pretty bad idea in my opinion. On the other hand, the underfloor heating would then be prepared for future solar use (or suitable for lower flow temperatures) and would remain up-to-date with current technology for a few more years.
On the other hand, we are reaching the practical limits here, the savings are partly not really tangible (for example, interest rates), or they are offset by other costs (for example, two electricity meters or the KfW 55 inspector, who wants €1,000 for one signature…).
E
ErikErdgas16 Jul 2015 15:56Hello,
For a KfW-55 house, the requirements are very high, and the critical factor is usually the HT' (specific heat transmission loss). This depends on the building envelope and the building geometry. By building geometry, it is meant that the thermal envelope surface area (heat-transferring surface) should be as small as possible and very well insulated. Protrusions, bay windows, and similar features should be avoided. The primary energy factor (QP) for a KfW-55 house must not exceed 55% of the reference building. This value can be achieved by using as much renewable energy as possible. For a KfW-55 house, it is essential to determine the thermal bridge correction factor (DUWB in W/m²K). With a low heating load and a well-designed heating system, it is conceivable that the building can also be heated with a gas boiler. Of course, this must be calculated on a case-by-case basis.
Every heating system has its advantages and disadvantages. A gas boiler converts the energy used (gas) as efficiently as no other heating system.
When calculating the heating load, domestic hot water consumption plays a minor role, because the heating load is usually higher than the domestic hot water heating load (DHW heating load). If the heating system is a heat pump, a sufficiently large DHW storage tank must be provided.
If you ventilate often and like to do so, a ventilation system with heat recovery is recommended. The ventilation system exchanges the indoor air with outdoor air. Through heat recovery, you can reduce heat losses to a minimum.
If you plan the utility room next to the bedroom, noise can be neglected, as the utility room will not be in use while you are sleeping.
Best regards, Erik
For a KfW-55 house, the requirements are very high, and the critical factor is usually the HT' (specific heat transmission loss). This depends on the building envelope and the building geometry. By building geometry, it is meant that the thermal envelope surface area (heat-transferring surface) should be as small as possible and very well insulated. Protrusions, bay windows, and similar features should be avoided. The primary energy factor (QP) for a KfW-55 house must not exceed 55% of the reference building. This value can be achieved by using as much renewable energy as possible. For a KfW-55 house, it is essential to determine the thermal bridge correction factor (DUWB in W/m²K). With a low heating load and a well-designed heating system, it is conceivable that the building can also be heated with a gas boiler. Of course, this must be calculated on a case-by-case basis.
Every heating system has its advantages and disadvantages. A gas boiler converts the energy used (gas) as efficiently as no other heating system.
When calculating the heating load, domestic hot water consumption plays a minor role, because the heating load is usually higher than the domestic hot water heating load (DHW heating load). If the heating system is a heat pump, a sufficiently large DHW storage tank must be provided.
If you ventilate often and like to do so, a ventilation system with heat recovery is recommended. The ventilation system exchanges the indoor air with outdoor air. Through heat recovery, you can reduce heat losses to a minimum.
If you plan the utility room next to the bedroom, noise can be neglected, as the utility room will not be in use while you are sleeping.
Best regards, Erik
P
peter_segel25 Oct 2015 22:03Is it really such a big problem with the pellets? Can't you just stack them outside like many generations before you did and cover them?
Umbau-Susi25 Oct 2015 22:53xycrazy schrieb:
Hello everyone,
a different question: have you considered a zeolite gas heat pump? Also, just asking around: does anyone here have the device or know someone who does... I would be very interested in any experiences.Me too.
Sylvia
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