ᐅ Retrofitting an air conditioning system – will that affect KfW funding?
Created on: 10 Jun 2021 21:02
H
Helado
Good evening everyone,
Since October, we have been living in a prefabricated house built by Hanse Haus. We have been living here for about 5 months now and are very pleased.
However, at the moment, the indoor temperature in each room is between 26°C and 28°C (79°F and 82°F), even though it is similarly warm outside. The only way we can lower the temperature is by opening the windows at night.
We have a KFW55 standard and a Stiebel Eltron LWZ 5s Plus. Unfortunately, it does not have an active cooling function, but we have installed and activated the summer cassette in the menu settings. So far, this has not produced the desired result. The temperature remains the same.
We are now considering adding air conditioning, but we have been clearly advised that this might mean no longer meeting the KFW energy-saving regulation standards, and therefore, it might affect the eligibility for subsidies. Fortunately, it is not very hot outside at the moment, but when it reaches 35°C (95°F) outdoors, the temperature inside the house can easily rise to around 30°C (86°F), which is not exactly comfortable.
Does anyone have advice or experience with retrofitting air conditioning (in specific rooms) or with the same heating system?
Thanks & best regards
Helado
Since October, we have been living in a prefabricated house built by Hanse Haus. We have been living here for about 5 months now and are very pleased.
However, at the moment, the indoor temperature in each room is between 26°C and 28°C (79°F and 82°F), even though it is similarly warm outside. The only way we can lower the temperature is by opening the windows at night.
We have a KFW55 standard and a Stiebel Eltron LWZ 5s Plus. Unfortunately, it does not have an active cooling function, but we have installed and activated the summer cassette in the menu settings. So far, this has not produced the desired result. The temperature remains the same.
We are now considering adding air conditioning, but we have been clearly advised that this might mean no longer meeting the KFW energy-saving regulation standards, and therefore, it might affect the eligibility for subsidies. Fortunately, it is not very hot outside at the moment, but when it reaches 35°C (95°F) outdoors, the temperature inside the house can easily rise to around 30°C (86°F), which is not exactly comfortable.
Does anyone have advice or experience with retrofitting air conditioning (in specific rooms) or with the same heating system?
Thanks & best regards
Helado
H
Hausbauer202118 Jun 2021 12:08BBaumeister schrieb:
Only one indoor unit. However, we have a large open space opposite the bedroom, so a lot of cool air flows down to the lower floor, which is designed as an open plan. Unfortunately, the children’s area doesn’t get much of it. You can use a standing fan to blow the air over there during the day. It’s not the best solution, but it works. If I were to build again, I would install a second indoor unit.
In the end, it really depends on the floor plan. The mechanical ventilation with heat recovery doesn’t distribute much air and is basically switched off during the day, running at night with an open bypass.We are also in the planning phase and have a small open space opposite the bedroom. I’m going to do exactly as you did and think the idea is great. You said you would install a second indoor unit afterward. Where would you place it? In the children’s room or on the ground floor? Is there anything else one should consider during planning? Do you also have 22°C (72°F) in the children’s room during summer? Then one unit would be completely sufficient for us.B
BBaumeister18 Jun 2021 13:41I would place the second indoor unit in the hallway between the two children's rooms. Not enough cold air reaches this area. We use a fan to blow the air across the open space into the children's rooms. Since no one is home during the day, this isn’t really a problem, but if I could plan it again, I would do it differently.
Also, during the planning phase, it’s important to consider where the outdoor unit is installed to avoid disturbing neighbors. Although it is quite quiet, some neighbors can be sensitive.
Also, during the planning phase, it’s important to consider where the outdoor unit is installed to avoid disturbing neighbors. Although it is quite quiet, some neighbors can be sensitive.
H
Hausbauer202118 Jun 2021 18:40BBaumeister schrieb:
I would place the second indoor unit in the hallway between the two children’s bedrooms. Not enough cold air reaches that area. We use a fan to push the air sideways through the space into the children’s rooms. Since no one is home during the day, it doesn’t really cause any problems, but if I could plan it again, I would do it differently.
Also, during the planning phase, you should consider where the outdoor unit will be installed to avoid disturbing neighbors. It’s quite quiet, but some neighbors are sensitive.Ok, thanks. Yes, we will see where we can position the outdoor unit. For the AC to be reasonably effective, it can’t be too far away. Do you find that the fan cools the children’s rooms well enough? Upstairs we only have one children’s room and an office. If we can get temperatures between 22-23°C (72-73°F) in every room with one unit, that will be perfectly fine for us.R
Reltaw202121 Jun 2021 15:24Hello everyone!
A KW40 prefabricated house requires three times as much energy for cooling as it does for heating. Everything is optimized for retaining heat.
When I walk through our new development area, I notice that the north sides have either no windows or only tiny ones. This means that if you only shade the direct solar radiation, you end up sitting in the dark.
What is the connection between these two statements?
Much more emphasis and public funding are placed on heat generation—actually, too much. Because when building to 40+ standards, you especially have surplus energy from photovoltaics when you don’t need it for heating. Cooling is forgotten, postponed, or simply neglected.
I’m writing this specifically for homeowners using timber frame construction, since it is particularly difficult to install wiring parallel to the wall afterward so that it remains invisible. This must be done early on, before final selections are made.
And to the main topic: Since cooling is needed precisely when solar power generation is at its peak, the KW40 standard is not at risk.
A KW40 prefabricated house requires three times as much energy for cooling as it does for heating. Everything is optimized for retaining heat.
When I walk through our new development area, I notice that the north sides have either no windows or only tiny ones. This means that if you only shade the direct solar radiation, you end up sitting in the dark.
What is the connection between these two statements?
Much more emphasis and public funding are placed on heat generation—actually, too much. Because when building to 40+ standards, you especially have surplus energy from photovoltaics when you don’t need it for heating. Cooling is forgotten, postponed, or simply neglected.
I’m writing this specifically for homeowners using timber frame construction, since it is particularly difficult to install wiring parallel to the wall afterward so that it remains invisible. This must be done early on, before final selections are made.
And to the main topic: Since cooling is needed precisely when solar power generation is at its peak, the KW40 standard is not at risk.
B
BBaumeister22 Jun 2021 12:15Hausbauer2021 schrieb:
Ok, thanks. Yes, we’ll see where to place the outdoor unit. For the air conditioning to be reasonably effective, it shouldn’t be too far away. Are you able to cool the children’s bedrooms well enough with the fan? Upstairs, we only have one children’s bedroom and an office now. If we can achieve maximum temperatures of 22–23°C (72–73°F) in every room with one unit, that’s completely sufficient for us. Yes, the children’s bedrooms get cool enough. Last week, outdoor temperatures reached up to 37°C (99°F). Inside the house it was 20°C (68°F) in the bedroom, 21°C (70°F) in the living room, and 23°C (73°F) in the children’s bedroom.
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Deliverer22 Jun 2021 15:50Reltaw2021 schrieb:
A timber frame house built to KW40 standard requires three times as much energy for cooling as for heating. Everything is optimized for heat retention. I would like to see a source for that. Until then, I say: "Nonsense!"
The physics behind my statement:
Temperature difference (Δt) in winter ~ 35°C (63°F)
Temperature difference (Δt) in summer ~ 10°C (18°F)
So why should the latter require three times more energy with the same technology...
I would even go so far as to say that, with the same temperature difference and a properly sized heat pump, there should be no difference in energy demand.
On the topic: I would find it rather contradictory if BAFA promotes air conditioning systems and then, after installation, KFW demands repayment of the subsidies—both on the grounds of "energy efficiency."
And since there is no BAFA police: just have a regular HVAC specialist install the air conditioning system. For highly insulated houses, a 2.5 kW (8,500 BTU/h) unit placed centrally as high as possible and running at a low setting 24/7 with all doors open works well. Without an open staircase, a second unit needs to be installed on the ground floor (no multi-split system!). This won’t create 20°C (68°F) in every room, but it will lower the temperature by about five degrees and reduce humidity by 15% compared to before. As a result, you can sleep comfortably again. Estimated electricity consumption for such a setup: 250 kWh/year.