Heat pumps in new builds: plan early, size small

In new builds, heat pumps have long been standard in Austria: according to laerminfo.at, a platform of the Ministry of the Environment, around 58 per cent of heat generators in new residential buildings were already heat pumps in 2018. In addition, there is a legal reason: according to the Erneuerbare-Wärme-Gesetz (Renewable Heat Act), which has been in force since 29 February 2024, the federal government's business service portal states that heating systems that can be operated with fossil fuels may no longer be installed in new buildings. This also applies to decentralised gas appliances.

So in a new build, the question is rarely 'whether', but 'how'. And that is exactly where the typical mistakes happen: planned in too late, sized too large, installation location forgotten.

Why a new build is such a good fit

A new house has a low heating load and can be planned with surface heating from the very beginning. Both play into the hands of the heat pump. klimaaktiv describes heat pumps as an environmentally friendly and cost-effective heating system, especially in low-energy and passive houses.

The key is the low flow temperature. According to klimaaktiv, every degree less reduces the heat pump's electricity consumption by about 2 to 2.5 per cent per year. Underfloor, wall or ceiling heating emits heat over large areas and therefore requires a significantly lower temperature than radiators. Why this is so important is explained in the article Flow temperature.

Low heating load, small unit

Oversizing is also a typical planning error in new builds. klimaaktiv points out that heating systems are frequently sized too large, which damages the lifespan and efficiency of the heat pump. The heating load should be calculated according to the applicable standard, not based on empirical values.

For a well-insulated house, the required output can be surprisingly small. It is important that the calculation is based on the actual building plan: window areas, insulation thicknesses, airtightness. For new builds, klimaaktiv explicitly mentions good workmanship, building airtightness, the avoidance of thermal bridges and correct window installation. The heating load calculator provides an initial guide.

Why you should plan the heat pump early

In a new build, many decisions are made long before the installer arrives on the construction site. Some of these directly affect the heat pump:

1. Installation location of the outdoor unit. It should already be included in the submission plan. Later, there is often a lack of space, or the unit ends up in a corner that is acoustically unfavourable.
2. Distance to neighbours. According to an information sheet from the Umweltbundesamt (Environment Agency Austria) and the Ministry of the Environment (Forum Schall), a target value of 30 dB at night should be aimed for at the property boundary to residential areas, and 25 dB in front of the windows of living areas. According to the information sheet, installing the unit on the side facing away from the neighbour can bring a reduction of 5 to 20 dB. You can compare options using the noise calculator.
3. Heat source. For geothermal probes or horizontal collectors, the area must be prepared before the outdoor facilities are built. The Air or geothermal energy guide compares what suits your plot.
4. Plant room. Cylinders, hydraulics and potentially an indoor unit need space and access for maintenance.
5. Pipe routes and foundation. Core drilling, conduits and the foundation for the outdoor unit should be included in the structural shell planning.
6. Permits. klimaaktiv advises clarifying the legal framework and necessary permits before deciding on a system. Find out more under Permit.

Plan for photovoltaics

According to klimaaktiv, heat pumps and photovoltaics go very well together. Although the electricity yield is low in November, December and January, over the year as a whole, a significant proportion of the heat pump's electricity can be generated on your own roof. For a detached house with a heat pump, klimaaktiv suggests economical PV system sizes of 5 to 10 kWp, which corresponds to an area of around 25 to 55 square metres.

According to klimaaktiv, you can increase your self-consumption with simple control measures, for example by prioritising hot water heating in the early afternoon.

For a new build, this means: plan the roof orientation, roof area and pipe route to the plant room right from the start, even if the PV system is only added later.

Cooling in summer

New, well-insulated houses can overheat in summer. A heat pump can help here, in different ways depending on the heat source:

• Geothermal energy and groundwater: According to klimaaktiv, gentle cooling is possible without the heat pump itself having to start up. The cold from the ground or groundwater is brought into the house via the surface heating system.
• Air source heat pump: According to klimaaktiv, temperature control is only possible when the heat pump's compressor is running.

If you want cooling, say so early on: the surface heating, control system and condensation protection must be designed for this. And the best cooling remains external shading on the windows.

Checklist for the planning phase

• Is the installation location of the outdoor unit marked on the plan, with clearance to the property boundary?
• Is there a standard-compliant heating load calculation based on the building plan?
• What flow temperature is the surface heating system designed for?
• Is cooling required in summer, and is the system planned for this?
• Are the roof and pipe routes prepared for a PV system?
• Is there a plant room with enough space?
• Are heat meters and electricity meters planned? klimaaktiv recommends them so that the efficiency of the system is visible.

Public subsidies for new builds differ depending on the federal state. You can find the current status in the subsidy overview and in the subsidy manager.

Your next step

Get the heat pump installer on board as soon as the submission plan is ready, not just when the structural shell is finished. Via our request for quotes, you will receive quotes from a maximum of three verified installers. Enclose the plan and, if available, the Energieausweis (energy performance certificate): this allows the system to be designed appropriately right from the start.