ᐅ Heating in a Newly Built House Using Only Split Units. Any Experiences?

After extensively renovating our small house, which was built to 1950s standards, four years ago, we are now outgrowing it and planning to move to another plot for professional reasons as well.

The plan is to convert an existing barn into a two-story living space with a single-story extension.
The focus here is on heating. Once the plans are finalized (which could still take a few months), I look forward to discussing the layout and other aspects.
Since the building has not been heated or used as living space until now, the renovation will bring it up to at least the 2020 Building Energy Act standard, or possibly lower depending on the funding scenario.
I estimate a heating load of no more than 40 W/m² for approximately 100–110 m² (1,076–1,184 sq ft) on the ground floor and 60 m² (646 sq ft) on the upper floor, plus additional hot water demand for two adults and three children.

Technically, heating the rooms using only air-to-air heat pumps with multi-split systems (three indoor units on the ground floor and four on the upper floor) and providing hot water through a domestic water heat pump should not pose any problems.

Why this approach?
The existing structure (roughly 8 x 10 m (26 x 33 ft) intended for residential use) does not have particularly high ceilings, and in keeping with the barn’s architectural style, wooden floorboards will be used extensively. Underfloor heating or ceiling heating would therefore be difficult to implement. The south and west exterior walls will mainly consist of windows (great views), so radiators in those areas are not an option either.
Currently, the prices quoted by installers for air-to-water heat pumps including installation are exorbitant, and a lot of the work will be done as DIY, except for connecting the units, which will be left to professionals.
The barn is overall 30 x 10 m (98 x 33 ft) and provides sufficient useful area to install the domestic water heat pump, allowing it to use pre-warmed, frost-free air even in winter.
Due to the large windows (with shading considered), summer air conditioning might be sensible and is included in the plan.
New units have a very good coefficient of performance (COP) without risk of incorrect sizing by the heating technician and operate down to -15°C (5°F). We live in Schleswig-Holstein near the Baltic Sea; temperatures that low have been rare recently, and a wood-burning stove will also be installed on the ground floor.
The building will be ventilated with decentralized units featuring heat recovery due to the ceiling height.

Has anyone had practical experience heating exclusively with split units? I have found very little information apart from one DIY channel on YouTube so far.

An alternative would be a ventilation system with heat recovery combined with a heat pump. However, we would need to carefully consider the upper floor and construction details, and the insulation standard would have to be very high. There is still enough space above the upper floor towards the roof, but the first joist layer restricts the ceiling height on the ground floor. I would prefer to avoid direct heating via the ventilation system to prevent dry air in winter and for maintenance reasons (long duct runs can encourage microbial growth). Also, the cost for such a complete system would likely be significant.

What heights are we actually talking about? If you are aiming to comply with the building energy regulations or planning a better renovation, you won’t be able to avoid floor insulation on the ground floor anyway.

P.S. I haven’t used heat purely from climate sources yet, but I have installed two heat pumps myself with low installation height and underfloor heating. That’s why I’m asking about the height.

Yep, good point. There are systems with about 4 cm (1.5 inches) installation height.

Regarding air-to-air heat pumps: I have two of those units. You can use them for heating quite well, which I've done occasionally during heating failures or transitional periods. BUT they will never be as comfortable as radiant heating systems. There is always some air circulation, even if slow. Due to installation near the ceiling, this circulation is also forced. (Console units could help here…)
That means it can never be completely silent, even though modern units can be very quiet. Also, because there is no radiant heat component, it is less comfortable. Depending on what is under the floorboards, you might still need warm socks…

Therefore, I would only use permanent heating with air conditioning units if the heating load is close to passive house levels. This has nothing to do with efficiency—which is no longer a problem even at temperatures well below freezing with high-quality systems.

A small addition about the floorboards: We had floorboards on a substructure over a raw concrete slab in an old building. We removed them and used the 4.5 cm (1.75 inches) height of the substructure to install a thin-film underfloor heating system, bringing us back to the original floor height. There is no insulation underneath, but since it’s an upper floor, that’s not too critical. The top layer is now three-layer oak parquet, which we like much better than the floorboards, even though the floorboards were freshly sanded and still quite attractive.

Benutzer200 schrieb:

What are the actual ceiling heights involved? If you plan to renovate according to the Building Energy Act or better standards, you won’t be able to avoid adding floor insulation on the ground floor anyway.

Currently, there is an old concrete floor with a slope towards the exterior walls (an old cowshed). At the exterior wall, the concrete floor is 5–10 cm (2–4 inches) above the railing edge, and the distance from the floor slab to the underside of the ceiling joists is 232 cm (7 ft 7 in), or 250 cm (8 ft 2 in) to the top edge. I would leave the ceiling joists exposed and install plasterboard between them below the upper floor, or build up the floor from above.

The entire concrete floor would naturally be removed; otherwise, achieving the Building Energy Act standard won’t be possible. Only the strip foundations under the exterior walls and two strip foundations in the middle would remain. Posts that also carry load are still standing there. The concrete inside looks like it was added later. A structural engineer will need to determine if it can be removed without any issues.

For the floor construction, I would then use foam glass gravel with wooden floorboards on battens above that. All this without installing a new concrete slab or screed. In the end, the clear height will be about 230 cm (7 ft 7 in). It can’t be any lower due to the finished floor level.

The state building regulations in Schleswig-Holstein specify a minimum ceiling height of 240 cm (7 ft 10 in) for living spaces. The response to an initial inquiry at the building authority (which I regularly interact with professionally) was positive, but of course not guaranteed.

I don’t see a way to install underfloor heating here. Maybe it’s possible, and we will certainly discuss this along with the architect and planner who will be involved anyway.

The question was whether it is realistic to heat the house solely with split air conditioning units, and especially if anyone has experience with this. I have little personal experience with these devices, and certainly not with newer models.

The point about air circulation is valid, and radiant heat from the floor is also pleasant. However, I find the combination of forced air and a wood stove quite interesting, since you want to distribute the warm air effectively throughout the room. The entire energy concept needs to fit together in the end; we’ll see how it goes. The goal is to provide the small amount of additional heat needed as cost-effectively as possible.

Thank you in advance for the suggestions. Perhaps someone else will have other points that I might have overlooked.

I am familiar with this type of heating from the USA, where I grew up. Part of my family still lives there, and I have to say I appreciate Germany as a place to live because the heating systems here are better. Houses there are generally not very well insulated, which further reduces comfort, and the heat feels quite unpleasant, stirring up a lot of dust. This is especially problematic for allergy sufferers. Warm air also tends to stay near the ceiling, leaving the feet cooler while the head feels warm. The energy consumption is also significant. It would be the last heating system I would consider for a permanently occupied house.