ᐅ Air-to-air heat pump in a KfW 40+ house – Switching to a ground-source heat pump just before the building permit application?
Created on: 3 Apr 2021 12:27
P
Possmann
Hello everyone,
We are building a prefabricated house next year. Basically, all the prefabricated house manufacturers we have spoken to recommended the air-to-air heat pump from Proxon. We are just about to submit the building permit / planning permission application, so in principle, we can still change everything.
Key data:
- 200 sqm (2153 sq ft) KfW 40+ prefabricated house with timber frame construction, 120 sqm (1292 sq ft) on the ground floor, 80 sqm (861 sq ft) on the upper floor
- Plus a basement, partly for storage, partly possibly to be converted later into living space; currently no heating concept for the basement
- Plot size is 1,000 sqm (10,764 sq ft), of which 300 sqm (3,229 sq ft) in the rear area is an orchard
- Photovoltaic system still in planning, but I will cover the entire roof; 10 kWp should easily fit; battery storage is not worthwhile, so I will keep it minimal to meet the 40+ standard
Technical data I calculated:
- Envelope surface area 540 sqm (5809 sq ft) (roof 140 sqm (1507 sq ft), ground slab/ basement ceiling = 166 sqm (1786 sq ft), walls 234 sqm (2519 sq ft))
- Heated gross volume 530 m³ (18,714 cu ft)
- Transmission heat load 4318 W
+ Ventilation load 243 W
+ Domestic hot water load 400 W
= Total heating load 4961 W
I have researched a lot, and the reports on the air-to-air heat pump vary. Our situation is actually suitable for it, but we would need to find a solution for the basement.
I am worried about dry air (which seems unavoidable, so I will have to come up with something) and very high electricity costs, or that the system will not keep our 200 sqm (2153 sq ft) house comfortably warm.
My current preference would be to switch to a brine-to-water heat pump with either a horizontal collector or a loop trench collector, partially as a DIY project, since we have 1,000 sqm (10,764 sq ft) of land we could use.
- What would you recommend? As far as I understand, everything other than the air-to-air heat pump will ultimately be combined with underfloor heating. I currently have underfloor heating in my rented apartment and cannot get used to it – it is extremely slow to respond. Are today’s systems better? This experience was one of the main reasons I was initially attracted to the air-to-air heat pump.
- Can I simply lay the loop trench collector around the basement? Then it would be deep, and since the excavator will already be there, I could just have him dig a bit more (it’s only about 2 m (6.6 ft) deep).
- Will switching to another heat pump significantly delay the building permit / planning permission process?
- Are all heat pumps (air-to-air heat pump, air-to-water heat pump, brine-to-water heat pump) equally suitable for KfW 40+ standards?
Thank you for your support!!
We are building a prefabricated house next year. Basically, all the prefabricated house manufacturers we have spoken to recommended the air-to-air heat pump from Proxon. We are just about to submit the building permit / planning permission application, so in principle, we can still change everything.
Key data:
- 200 sqm (2153 sq ft) KfW 40+ prefabricated house with timber frame construction, 120 sqm (1292 sq ft) on the ground floor, 80 sqm (861 sq ft) on the upper floor
- Plus a basement, partly for storage, partly possibly to be converted later into living space; currently no heating concept for the basement
- Plot size is 1,000 sqm (10,764 sq ft), of which 300 sqm (3,229 sq ft) in the rear area is an orchard
- Photovoltaic system still in planning, but I will cover the entire roof; 10 kWp should easily fit; battery storage is not worthwhile, so I will keep it minimal to meet the 40+ standard
Technical data I calculated:
- Envelope surface area 540 sqm (5809 sq ft) (roof 140 sqm (1507 sq ft), ground slab/ basement ceiling = 166 sqm (1786 sq ft), walls 234 sqm (2519 sq ft))
- Heated gross volume 530 m³ (18,714 cu ft)
- Transmission heat load 4318 W
+ Ventilation load 243 W
+ Domestic hot water load 400 W
= Total heating load 4961 W
I have researched a lot, and the reports on the air-to-air heat pump vary. Our situation is actually suitable for it, but we would need to find a solution for the basement.
I am worried about dry air (which seems unavoidable, so I will have to come up with something) and very high electricity costs, or that the system will not keep our 200 sqm (2153 sq ft) house comfortably warm.
My current preference would be to switch to a brine-to-water heat pump with either a horizontal collector or a loop trench collector, partially as a DIY project, since we have 1,000 sqm (10,764 sq ft) of land we could use.
- What would you recommend? As far as I understand, everything other than the air-to-air heat pump will ultimately be combined with underfloor heating. I currently have underfloor heating in my rented apartment and cannot get used to it – it is extremely slow to respond. Are today’s systems better? This experience was one of the main reasons I was initially attracted to the air-to-air heat pump.
- Can I simply lay the loop trench collector around the basement? Then it would be deep, and since the excavator will already be there, I could just have him dig a bit more (it’s only about 2 m (6.6 ft) deep).
- Will switching to another heat pump significantly delay the building permit / planning permission process?
- Are all heat pumps (air-to-air heat pump, air-to-water heat pump, brine-to-water heat pump) equally suitable for KfW 40+ standards?
Thank you for your support!!
Possmann schrieb:
Indeed, we are currently a bit bothered by how slow the underfloor heating is. In the family, there is a common thought that with the air-to-air heat pump, individual rooms can be warmed up faster if desired.You don't actually "cool down" the rooms; the temperature is maintained continuously around the clock. So, inertia is not really the issue.
Hangman schrieb:
I recently had this discussion with friends: they were looking for a heating system for the children's rooms in their new build that can maintain 23°C (73°F) during the day and 17°C (63°F) at night 😳 Maybe I should recommend an air-to-air heat pump 🙄?I’m not familiar with heat pumps at all... we have gas heating... but I can report that we lowered the temperature by 2 degrees during the day. That works, at least I don’t sweat too much when cleaning the windows 😉 However, it’s not really practical to imagine constantly turning the valve up and down. Modern houses aren’t designed for that. It’s an outdated practice that we need to move away from.
We visited the show home in winter at -20°C (-4°F), which was heated with an air-to-air heat pump. Inside, it was comfortably warm, and we didn’t notice any negative effects. However, we were only inside for about 45 minutes.
We have also ordered an air-to-air heat pump combined with a photovoltaic system to offset the high electricity consumption with self-generated power. In summer, it can probably provide cooling as well (though not as strongly as an air conditioner).
We are moving in at the end of the year and I’m curious to see if it meets my expectations 🙂
We have also ordered an air-to-air heat pump combined with a photovoltaic system to offset the high electricity consumption with self-generated power. In summer, it can probably provide cooling as well (though not as strongly as an air conditioner).
We are moving in at the end of the year and I’m curious to see if it meets my expectations 🙂
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