Daly Renewables detached house – Heat pump in a Passive House building

This detached house in Northern Ireland shows the potential of buildings designed and constructed to meet high energy efficiency standards. The construction demonstrates that a ground-source heat pump can be an essential piece of equipment in a low-energy house, capable of producing cooling, heating, domestic hot water (DHW) and pool heating. As a result, the installation with a heat pump is able to guarantee the comfort of the house all year round and not only in the winter months. This installation is also a good example of how a fully integrated system with a renewable energy source (in this case, PVs) can drastically reduce operating costs.

Heat pump installation in hybridisation with PVs

The heat pump is in the plant room towards the back of the house and provides heating, hot water, and cooling to our house plus heating and cooling to a separate building that hosts the garage and home office. In total, the heated space is to 390 square meters /4,200 square feet. The heat and cooling is provided by a Roth underfloor heating system. The system is controlled by three Ecoforest Th-T thermostats which control the ground floor, the first floor and the garage. In addition, 2 pipes have been left ready to be connected to a future hot tub or outdoor pool. The system is complemented by a DHW tank and an ecoSMART e-manager (now in-built in all Ecoforest heat pumps) to ensure hybridisation with the PVs consisting of a 5.67kw DC array linked to a 3.68kw AC Inverter.

The collection is linked to 600m of 40mm geothermal collector pipe work. Our pipe work was installed in horizontal trenches which were 1.2m deep and 1m wide laying under the garden of the house.

Heating, DHW and cooling all year long for £132 / 156€

The Ecoforest heat pump works in hybridisation with photovoltaic solar panels thanks to the Ecoforest ecoSMART e-manager. This hybridisation makes it possible to use surplus photovoltaic energy as thermal energy and raise the setpoint temperatures, for example, at zero cost. In this case, the heat pump has a DHW setpoint of 45ºC and a heating setpoint of 20.5ºC. The hybridisation system instructs the heat pump to raise the DHW temperature to 58.5°C when a surplus of 0.5 kW is obtained for more than 5 minutes. This situation occurred almost every day from March to September and also on sunny winter days. In addition, once the DHW overrun temperature is reached, the system raises the heating setpoint to 22ºC. As a result, in the period from March to September a large part of the DHW and heating was done at zero cost. As a result of the low demand of a Passive House and the heat pump system, the cost of heating, DHW and cooling for six people for one year was £132 (approximately €156.1).

Passive House: low demand with a thermal load of 11W/m2

The owner of the house, Ryan Daly, is also the head of installation company Daily Renewable Ltd. through which he has been installing HVAC systems in homes and commercial buildings since 2007. Since then, he has observed how low-temperature systems work best in buildings built to low-energy standards such as the Passive House one. Following these principles, the house was built to ensure that thermal bridging and airtightness met the highest standards. The windows are triple glazed by Zyle Fenster and the structure was made of timber by Kudos Timber Frame, which prevents the concrete from acting as a heat accumulator in summer. As a result the thermal load of the house is estimated at 11W/m2 . In the figure below it can be seen how the temperature of the house remains constant throughout the year.

The choice of screed plays a very important role in this type of Passive House construction. In this house, 100mm of sand and cement was chosen on the ground floor, with 10mm of chippings to retain heat and fibre to reinforce the floor screed. This provided the thermal lag needed to minimise running costs. The slow release of heat means that the house is more comfortable at night, when heat is most needed, as it takes between 6 and 10 hours to rise through the floor. On the first floor, by contrast, the screed is 50 mm on the first floor, as most of the rooms are bedrooms and do not need the same level of heating.

The house also has a large south-facing window. Thanks to the heat pump system, which is able to generate enough cooling to keep the house at a comfortable temperature in the summer months, it is not necessary to install any blinds, curtains or protective elements on the façade. The heat pump makes it possible to adjust the switching points between passive cooling (with direct heat exchange with the ground at minimum cost) and active cooling. As a result, the house never exceeds 25ºC in summer.

Quality and service

Daly was one of the first installers of Ecoforest heat pumps in 2013 when they started manufacturing and has been very impressed with the quality of their equipment and back up service. Daly Renewables had fitted numerous manufacturers heat pumps going back to 2007, before settling with Ecoforest, and he is adamant it is the best heat pump system in the sector. Daly highlights that “as a family we never have to think about the heating and hot water as it is always so consistent. We have never once ran out of hot water. The fact that the system is powered by a Solar PV array for the majority of the year is a an added bonus! We love it!”. You can find your nearest Ecoforest installer on the contact form: https://ecoforest.com/en/request-quote/