Heat pump in a farmhouse and a large, older house

An old farmhouse, a villa from the Gründerzeit era, a residential building with extensions that has grown over generations: such houses have a large heated area, thick walls, and often a heating history with several chapters. A heat pump is not out of the question here. However, it requires more planning than in a compact detached house because the heating load is higher and the rooms are used in very different ways.

What makes large, older houses special

High heating load. Large area and external walls, often little insulation, old windows.
Different building components. The main house, extension, and converted loft come from different decades and behave very differently.
Not all rooms are used. Guest rooms, parlour for holidays, former utility rooms.
Multiple heat sources. Tiled stove, wood-burning stove, old central heating boiler.
Plenty of land. What is missing in a terraced house is often available here: space for a geothermal system.

First: how much heat is actually needed

The larger the house, the more expensive a planning error becomes. klimaaktiv warns that heating systems are often oversized, which harms the lifespan and efficiency of the heat pump. According to klimaaktiv, empirical values or estimates are not enough; the heating load should be calculated according to the applicable standard.

For a large house, this means: do not just adopt the output of the old boiler, but have it calculated room by room. Our heating load calculator provides a first orientation.

klimaaktiv also lists questions that you should clarify with the planner beforehand. They are particularly important for a large house:

Will all rooms be heated in future?
Is the heated area expected to grow in future through conversion or extension? For example, a converted loft or a granny flat.
What room temperatures do you need where?
How will the hot water demand change? For example, when children move out or a second generation moves in.

The clearer your answers, the better the system can be designed.

Partial heating: not every room has to be equally warm

In many large houses, part of the area is empty for most of the year. Instead of bringing the whole house up to living temperature, it can make sense to define zones: fully heated living spaces that are in use, and rarely used rooms kept only at a moderate temperature.

Checklist questions:

Which rooms do you use daily, and which only occasionally?
Can unused areas be thermally separated by doors or staircase partitions?
Where do heated rooms border unheated ones, and how well insulated is this boundary?
Are there rooms where dampness is an issue? Leaving them completely unheated is not a good idea there: clarify this with your installer.

Important: You must tell the planner about partial heating beforehand. It changes the heating load and therefore the size of the unit.

Geothermal energy: often worth considering in a large house

According to klimaaktiv, ground-source and groundwater heat pumps work more efficiently than air-source heat pumps thanks to the consistent source temperature all year round, resulting in a higher seasonal performance factor (SPF). With a high heating load, this makes a noticeable difference in electricity consumption over the years. At the same time, according to klimaaktiv, installation is more complex. Another advantage: ground-source systems can provide gentle cooling in summer without the heat pump itself having to run.

klimaaktiv lists deep boreholes of up to 150 metres or horizontal collectors at a ground depth of around 1.5 metres as typical designs. Horizontal collectors require a correspondingly large amount of free space, which is often available with farmhouses.

Geothermal energy is regulated under water law. In Upper Austria, for example, geothermal probes and horizontal collectors are generally subject to a notification procedure under Section 114 of the Wasserrechtsgesetz (Water Rights Act). According to the Land Oberösterreich (State of Upper Austria), a permit is required, among other things, in water protection areas or in closed residential areas without a central drinking water supply, and for probes from a depth of over 300 metres. Groundwater heat pumps always require a permit there. Other federal states regulate this differently in detail: ask your Bezirkshauptmannschaft (district authority). Read more under Permit.

This is particularly relevant for old farms with their own domestic well: according to the Land Oberösterreich (State of Upper Austria), the protection of the drinking water supply takes precedence over thermal use.

Whether air or geothermal energy is better suited to your property is compared in the guide Air or Geothermal Energy.

Combining a tiled stove and a heat pump

Many farmhouses have a tiled stove or wood-burning stove, and hardly anyone wants to do without them. And you don't have to. A tiled stove can provide some of the heat for the living room and adjacent rooms during the coldest weeks, taking the load off the heat pump.

What you should look out for:

Tell the planner. Whether and how the stove is included in the design is a conscious decision. If you include it, it must actually be heated on cold days.
Coordinate the control system. If the stove heats up the living room significantly, the heat pump should scale back in this area and not work against it.
Note public subsidy rules. The federal public subsidy „Kesseltausch“ requires, according to the info sheet for the 2026 relaunch (eligible from 7 October, registration from 2 November), that all remaining fossil fuel heating systems (in particular oil, gas, coal or coke) are decommissioned when switching. A wood stove does not count as fossil fuel, but a multi-fuel burner that is also used for burning coal may be affected. You can check what applies to you in the Förder-Manager.

Renovate first or replace straight away?

In a large old building, the question of the order of steps is particularly important. klimaaktiv lists the insulation of the roof, external walls, windows or cellar ceiling as the basis for low flow temperatures and operating costs. If you plan to renovate in the next few years anyway, plan the heat pump for the state after the renovation. An energy advisor from your federal state will help you organise the steps. Whether your house can manage the required flow temperature is explained in the article Flow Temperature.

Your next step

For a large house, you need an installer that takes the time for a thorough on-site inspection. Through our request for quotes, you will receive quotes from at most three checked installers. Mention which rooms you want to heat and whether a tiled stove will remain: this saves time during the on-site appointment.