Residential UFH Integrated with Heat Pumps Can Support Decarbonization

Various heating systems exist, such as combustion heating through burning fuel, warm air heating through forced air, hot water heating by a radiator, and radiant heating through a water pipe under the floor, known as underfloor heating (UFH). Regarding occupant comfort, UFH may be the most suitable heating system for maintaining indoor air humidity in winter. Even if an occupant enters the room and has just turned on the heating, UFH warms the feet first, even when indoor air is cold or moderate, bringing comfort to occupants.

Growing Interest in UFH

In addition to enhancing occupant comfort, UFH provides energy efficient space heating compared with radiators because the system does not require a high input temperature. Radiators typically need an input temperature between 158°F (70°C) and 176°F (80°C) to heat a room effectively due to their small surface area. However, UFH requires a lower input temperature, sometimes as low as 95°F (35°C), because building floors have a much larger surface area. Furthermore, warming an entire room evenly from the floor up can enhance occupant comfort, which is contributing to interest in UFH.

According to the UK Department for Business, Energy & Industrial Strategy, most dwellings in the UK use heating systems with boilers and radiators, similar to other European countries. Nonetheless, the UFH market keeps growing due to its ability to help with climate change goals, though its market share is small. UFH can be a good sustainable heating solution using low temperature heat sources such as heat pumps, and it can replace radiators in the future.

Swedish company Vattenfall has launched a high temperature heat pump water heater (HPWH) with a CO2 (R744) refrigerant. As a sustainable heating solution, this HPWH can replace a conventional gas boiler for space heating and hot water generation and be integrated into a radiator or UFH. Also, Daikin, a Japanese HVAC manufacturer, has released the Altherma 3 H MT heat pump—the newest alternative for replacing fossil fuel or gas boilers in homes—as a range extension for the Altherma series. The system can also provide hot water up to 149°F (65°C) even with an outside temperature of 5°F (-15°C). This heat pump can be combined with existing radiators and UFH.

Market Entry Requires Understanding Regional Market Trends

Nevertheless, manufacturers and engineering firms seeking entry to the UFH market must understand regional trends to apply the most suitable system. For instance, South Korea is one of the largest UFH markets in Asia, and most households have UFH systems due to tradition (i.e., ondol). However, condominiums are a common residence type, so most homes do not have enough space to install HPWHs. Thus, a boiler that uses environmentally friendly fuel (e.g., biogas or hydrogen) can be an alternative sustainable solution for the future.

In North America, HPWHs with radiators or UFH could be a decarbonization solution because of the electrification trend. However, due to its cold weather, the northern region may need more advanced UFH solutions integrated with a cold climate HPWH, such as Daikin’s Altherma series or Vattenfall’s HPWH. As the outside temperature decreases, the heating capacity of a typical heat pump system decreases. To utilize UFH technology with a sustainable heat source as a decarbonization solution, manufacturers must develop technologies that are suitable for regional needs.