Heat pumps: a 'green' alternative for energy efficiency in apartment buildings

Heat pumps are a “green” alternative to the boiler, in both single-family homes and apartment blocks. It is no coincidence that when it comes to the energy requalification of a building, i.e. the combination of all activities aimed at improving its performance and cutting energy costs, replacing a boiler with a heat pump is one of the first operations to be thought of and planned.

Choosing the most suitable heat pump for the apartment block’s requirements cannot be done without sizing it correctly. Of course, a model that is good for one building may not have enough power to heat, cool and produce domestic water for another. In such cases, this is called undersizing. On the other hand, if the heat pump is oversized during the design stage, those living in the different apartments of the building may experience a considerable waste of energy.

And that’s not all: besides having to size the heat pump in the best possible way, depending on the thermal demand of the entire apartment block, the designer will have to adapt the new installation to the existing thermal power plant. Or, alternatively, make use of any other technical rooms or external spaces.

Sizing the heat pump

In order to calculate the capacity demand to generate the thermal energy needed to heat an apartment block, there are a few guidelines to be followed. First of all, the building’s energy demand, a value that can be calculated by multiplying the useful surface area to be heated (in square metres) by the annual thermal energy demand (in kWh/square metres per year). Other factors that allow the designer to calculate the sizing in the best possible way are the climate area, the minimum design outdoor temperature, the degree-days value and the permitted daily heating hours.

Each country is divided into climate areas, symbolically marked with a series of letters or numbers. Depending on the climate area, the so-called Degree-Days (D-D) also changes, i.e. the sum over all 365 days of the year of the only positive differences between the conventional temperature set at 20°C and the average daily outdoor temperature. A very high value, such as the one in Cuneo, Piedmont, which stands at more than 3,000, is an indication of prolonged annual heating periods and significantly lower average temperatures.

Another element to be considered, due to the need of municipalities to reduce air pollution, is the maximum number of hours in which heating systems can be used. A value that is naturally affected by the climate area in which the apartment block is located and which plays a key role in the designer’s choice, since the heat pump must be able to heat the building within the timeframe set by the regulations. Lastly, there is the minimum design outdoor temperature, the lowest value of the averages of the coldest annual decades recorded in different locations.

Choosing the heat pump: air-to-water or water-to-water?

Unlike boilers, which require gas or methane, heat pumps have no combustion, thus reducing harmful emissions. And that’s not all: this innovative technology ensures high efficiency with the added bonus of being able to provide heating capacity for heating and cooling capacity for cooling, as and when required. Heat pumps “use” natural and sustainable resources and differ according to the energy source (air, water and ground heat) and heat transfer fluids (air and water).

Air-to-water heat pumps, such as the SHEEN EVO 2.0 (for medium/small apartment buildings) or LARGE EVO line (for large apartment buildings).

These are solutions specifically designed for centralised systems in apartment buildings, and are an excellent solution for both new builds and requalification work. 

As they do not use air as an energy source, water-to-water heat pumps and geothermal heat pumps do not need to be installed outdoors, nor do they require indoor spaces with special openings for ventilation. This does not mean that these units do not entail other logistical difficulties. For the former, the technical spaces must be designed in the best possible way so that the pumps can be connected to the pumping and extraction wells, while for the latter, particularly invasive drilling operations are required to bury the geothermal probes 170 metres deep.

Find out more SHEEN EVO 2.0 Find out more LARGE EVO

These systems use air taken from outside as the source and water as the heat transfer fluid, so it becomes essential to ensure a sufficiently high air flow-rate. This is why, in the event of renovations where the Thermal Power Plant is too small or does not have any openings to ensure proper circulation of outside air, the perfect solution is to position the unit outdoors. This allows a suitable air flow-rate to ensure operation of the heat pump while achieving optimal natural ventilation. The only measure, in the event of outdoor installation, is to pay particular attention to the acoustic aspect and choose a model that ensures significant noise reduction. Sheen EVO and Large EVO heat pumps use eco-friendly R-32 refrigerant gas, which fulfils this requirement as it is one of the quietest models on the market. And that’s not all: the product is also available in three different acoustic modes: standard, silent and super silent.