H
ha_celine28 Mar 2014 18:49Hello everyone,
I have been following this forum for a while and would now like to ask for your advice or help.
We are planning to build a house this fall. Currently, we are in the preliminary decision stage regarding which heating system to use. Our shortlist includes:
1. Heat pump with ground collectors + solar thermal system + water-based fireplace + ventilation system with heat recovery
2. Gas condensing boiler + solar thermal system + water-based fireplace + ventilation system with heat recovery
We aim to achieve KFW 55 standard.
Here are some details about the house:
Heated living area: 250m² (2690 sq ft)
3 full floors (including 1 basement)
U-value ceiling: 0.13 W/m²K (0.023 Btu/h·ft²·°F)
U-value exterior walls: 0.19 W/m²K (0.034 Btu/h·ft²·°F)
U-value ground slab: 0.16 W/m²K (0.028 Btu/h·ft²·°F)
U-value windows: 0.9 W/m²K (0.16 Btu/h·ft²·°F)
Is there anything missing?
What do you think of the plan, and which of the two options would you recommend and why?
In the case of the heat pump, would it be more sensible to use photovoltaics instead of solar thermal to power the pump?
It would be great if some of you could comment on the project.
Thanks in advance for your efforts and have a nice evening.
Best regards
ha_celine
I have been following this forum for a while and would now like to ask for your advice or help.
We are planning to build a house this fall. Currently, we are in the preliminary decision stage regarding which heating system to use. Our shortlist includes:
1. Heat pump with ground collectors + solar thermal system + water-based fireplace + ventilation system with heat recovery
2. Gas condensing boiler + solar thermal system + water-based fireplace + ventilation system with heat recovery
We aim to achieve KFW 55 standard.
Here are some details about the house:
Heated living area: 250m² (2690 sq ft)
3 full floors (including 1 basement)
U-value ceiling: 0.13 W/m²K (0.023 Btu/h·ft²·°F)
U-value exterior walls: 0.19 W/m²K (0.034 Btu/h·ft²·°F)
U-value ground slab: 0.16 W/m²K (0.028 Btu/h·ft²·°F)
U-value windows: 0.9 W/m²K (0.16 Btu/h·ft²·°F)
Is there anything missing?
What do you think of the plan, and which of the two options would you recommend and why?
In the case of the heat pump, would it be more sensible to use photovoltaics instead of solar thermal to power the pump?
It would be great if some of you could comment on the project.
Thanks in advance for your efforts and have a nice evening.
Best regards
ha_celine
KFW 55 is naturally easier to achieve with a heat pump. Water-based fireplace? How often do you really use it? I’m afraid the effort and benefit are hardly worth it. Solar thermal system? My heat pump consumes on average 1.5 kWh per day (about 30 cents) for hot water production for two (wasteful) people. When the sun is shining, I don’t need heating. Thanks to large window areas, not even in winter. So solar thermal would never be cost-effective. But then it depends on whether you want to look at it from a financial or an ecological perspective. Photovoltaics for the heat pump are pointless. If you have enough electricity from the photovoltaic system, the heat pump doesn’t run. When the heat pump really needs to work, the photovoltaic system doesn’t produce power. The overlap is very small. If there were a practical and affordable storage option, I would immediately add photovoltaics. But that will probably take a while.
I would rather invest the money for a water-based fireplace and solar systems into the windows. 0.9 is relatively high.
Sometimes the simplest solution is the best.
I would rather invest the money for a water-based fireplace and solar systems into the windows. 0.9 is relatively high.
Sometimes the simplest solution is the best.
Get rid of the water-based fireplace.
Use a regular stove instead. Plan the layout fairly open so the heat can spread throughout the house, and/or (which is better) install a controlled ventilation system with heat recovery.
0.9 U-value windows? Which company still installs such outdated models?
Personally, I am not convinced by solar thermal panels; no one has yet convincingly shown me what savings you actually get from them. Photovoltaics are (today) more a matter of belief or personal preference.
We have photovoltaics, but we also invested significantly in technology and home automation. Whether it pays off? I’ll find out in a few years.
You can easily reach KfW55 standard with insulated slab foundation (around 3000–5000 euros) and a ground-source heat pump, as long as you have a decent builder with "real" windows.^^
We opted for additional window area, a ground-source heat pump, and an insulated slab, and we just missed KfW40 by 0.8%.
Use a regular stove instead. Plan the layout fairly open so the heat can spread throughout the house, and/or (which is better) install a controlled ventilation system with heat recovery.
0.9 U-value windows? Which company still installs such outdated models?
Personally, I am not convinced by solar thermal panels; no one has yet convincingly shown me what savings you actually get from them. Photovoltaics are (today) more a matter of belief or personal preference.
We have photovoltaics, but we also invested significantly in technology and home automation. Whether it pays off? I’ll find out in a few years.
You can easily reach KfW55 standard with insulated slab foundation (around 3000–5000 euros) and a ground-source heat pump, as long as you have a decent builder with "real" windows.^^
We opted for additional window area, a ground-source heat pump, and an insulated slab, and we just missed KfW40 by 0.8%.
H
ha_celine29 Mar 2014 15:20Hello waldorf and milambar,
Thank you for your quick replies. What I’m hearing from both of you is that the hydronic (water-based) fireplace is not a good idea—in my case.
I actually considered it because we wanted a fireplace in the living and dining rooms for coziness. Since we would occasionally use it for heating, I thought it made sense to use the energy efficiently. However, I’m not set on having a hydronic fireplace—as I said, a regular one is fine with me as well.
Here are a few more details that might provide better insight:
The gas connection is already available on the property, but since it’s a long lot, we would need to install about 40 meters (130 feet) of gas piping on our property from the connection point to the house.
We have about 1500 m² (16,000 ft²) of space available—more than enough for ground collectors.
Regarding the KfW funding, our main focus is on insulation, meaning how efficient our final energy consumption actually is. Of course, if we can receive any subsidies, that would be great.
The windows with a U-value of 0.9 are what our energy consultant used as a calculation basis. They have a g-value of 0.5 and a frame area of 32%.
It would be great if more people could share their opinions. Many thanks again to the first two responses.
Best regards,
ha_celine
Thank you for your quick replies. What I’m hearing from both of you is that the hydronic (water-based) fireplace is not a good idea—in my case.
I actually considered it because we wanted a fireplace in the living and dining rooms for coziness. Since we would occasionally use it for heating, I thought it made sense to use the energy efficiently. However, I’m not set on having a hydronic fireplace—as I said, a regular one is fine with me as well.
Here are a few more details that might provide better insight:
The gas connection is already available on the property, but since it’s a long lot, we would need to install about 40 meters (130 feet) of gas piping on our property from the connection point to the house.
We have about 1500 m² (16,000 ft²) of space available—more than enough for ground collectors.
Regarding the KfW funding, our main focus is on insulation, meaning how efficient our final energy consumption actually is. Of course, if we can receive any subsidies, that would be great.
The windows with a U-value of 0.9 are what our energy consultant used as a calculation basis. They have a g-value of 0.5 and a frame area of 32%.
It would be great if more people could share their opinions. Many thanks again to the first two responses.
Best regards,
ha_celine
Yes, I’m not telling you anything new, but water-bearing fireplaces are a bad idea... you either have to use them continuously or not at all. The necessary additional equipment (controls, piping, etc.) required costs many times more than what you can save by occasionally heating with it.
Otherwise, if you have enough space, why not consider a ground collector? At least it provides some benefit when properly sized and professionally installed...
Otherwise, if you have enough space, why not consider a ground collector? At least it provides some benefit when properly sized and professionally installed...
Quick info..
We have about 153m² (1645 sq ft) of living space and needed around 180m² (1940 sq ft) of surface collectors.
So you have more than enough space to easily supply several houses.
I can warmly recommend the company AEN (headquartered in Rostock) for your question.
These guys know exactly what they’re doing, and their documentation is impressive!
(Quote from the environmental agency: “Can you please take those folders away, we don’t need that much data.”)
We are building in central Lower Saxony. So AEN also works “outside” their region.
Regarding gas…
Have the local utility provider calculate what it would cost you—connection fees, groundworks, piping...
And keep in mind that some building regulations prohibit constructing anything stationary (house, garage) over the gas line.
For us, all the connection expenses would have cost about the same as the brine-water heat pump plus the collectors and earthworks...
And yes, the cost of a warm-air fireplace bears absolutely no relation to its benefit... The key words here are: open floor plan and/or controlled ventilation system with heat recovery.
Regards
We have about 153m² (1645 sq ft) of living space and needed around 180m² (1940 sq ft) of surface collectors.
So you have more than enough space to easily supply several houses.
I can warmly recommend the company AEN (headquartered in Rostock) for your question.
These guys know exactly what they’re doing, and their documentation is impressive!
(Quote from the environmental agency: “Can you please take those folders away, we don’t need that much data.”)
We are building in central Lower Saxony. So AEN also works “outside” their region.
Regarding gas…
Have the local utility provider calculate what it would cost you—connection fees, groundworks, piping...
And keep in mind that some building regulations prohibit constructing anything stationary (house, garage) over the gas line.
For us, all the connection expenses would have cost about the same as the brine-water heat pump plus the collectors and earthworks...
And yes, the cost of a warm-air fireplace bears absolutely no relation to its benefit... The key words here are: open floor plan and/or controlled ventilation system with heat recovery.
Regards
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