Is Ground Cooling Feasible? Check Out the Project's Actual Measurement: No Cold Feet, No Condensation, Comfortable and Energy-efficient!

2025-05-09

As is well known, floor radiant heating is the most reasonable heating method. However, what is less known is that "ground cooling" has quietly emerged in the market!
I. Is the ground cooling technology mature?
There is a great deal of controversy about ground cooling. When it comes to ground cooling, most people's first reaction is to oppose and question it based on their own experience.
II. Is it feasible? Let's talk about the design with a case!
In fact, the floor radiant constant temperature technology is relatively mature. Xi'an Xianyang International Airport, Wuhan Tianhe International Airport, Beijing Daxing International Airport, etc. have all adopted the floor radiant cooling and heating system.
For those who have worked on or understood this technology, they can see the key points of the system design.
Therefore, floor radiant temperature adjustment is not simply about flowing hot water in winter and cold water in summer.

Is Ground Cooling Feasible? Check Out the Project's Actual Measurement: No Cold Feet, No Condensation, Comfortable and Energy-efficient!1746798799961

Instead, it uses the system design of "air handling unit convection + floor radiation" to achieve heating in winter and cooling in summer. And through the temperature adjustment control technology, condensation and dew formation are avoided, which greatly improves the cooling capacity, comfort, and energy efficiency of the heat pump dual-supply system in summer.
2.1 Let's look at a case in Fujian
To have a deeper understanding of the advantages and practical application effects of the air handling unit + floor radiant cooling system, the reporter of this magazine visited the Fuzhou Wulan Healthy Residential Training Center and conducted actual measurements of the operation data.
Let's take a look at the specific situation below.

Is Ground Cooling Feasible? Check Out the Project's Actual Measurement: No Cold Feet, No Condensation, Comfortable and Energy-efficient!1746798799838

Building situation
The building area of the training center is 255 square meters (the indoor usable area is 172 square meters), and the floor height is 4 meters. It is located on the middle floor. The entire floor has underfloor heating. Three walls are insulated with 3 centimeters of benzene board and double-layer boards are added. The thickness of the entire wall insulation layer is 5 centimeters, and ordinary glass is used.
System design
The design and calculation are carried out according to a floor area of 240 square meters. According to the conventional experience value, the cooling capacity index should be 130-150W. However, in this project, only a cooling capacity index of 70W per square meter was selected during the model selection. A variable-frequency cooling and heating unit with a power of 6.5kW (7HP) and a cooling capacity of 15.7kW was selected.
A secondary multi-stage system is adopted, and the buffer water tank is 100L. The power of the primary side water pump between the main unit and the water tank is 151W, and the power of the secondary circulation water pump is also 151W. A dual-temperature mixing water module is installed indoors, with a total of three water pumps, and the power of a single water pump is 97W.
The air handling unit is selected according to the standard, and the air change rate per hour reaches more than 5 times. 2 FP-102 air handling units are installed indoors, with a single-unit cooling capacity of 5.4kW, and 3 FP-136 air handling units are installed outside the exhibition hall, with a single-unit cooling capacity of 7.2kW.
Is a 6.5KW main unit matched with 240 square meters sufficient?
According to the conventional cooling index of 130W, the cooling capacity for 240 square meters is 31.2kW. But can a unit with a cooling capacity of only 15.7kW meet the cooling demand? Especially when all devices are fully open.
The project side conducted two actual measurements in June and August respectively. The energy consumption includes 1 main unit, 5 air handling units, and 5 water pumps.
June test: Only ground cooling, no air handling unit
The first test: From 8:00 am on June 17, 2019, to 8:00 am on June 18, 2019, for a total of 24 hours.
From 9:00 pm to 8:00 am the next day, a total of 11 hours, the indoor temperature was kept constant. The air handling unit did not start, and only the "floor radiant cooling system" operated at a constant temperature. A total of 8.5 kWh of electricity was used, with an average power consumption of 0.85 kWh per hour. The floor temperature was 26°C, the space temperature was 28°C, there was no wind, the humidity was 70%, and there was no condensation.
From 8:00 am on June 17, 2019, to 8:00 am on June 18, 2019, for a total of 24 hours, the total electricity consumption was 62 kWh, and the power consumption per hour was 62/24 = 2.58 kWh. There were 39 people indoors on that day. The outdoor temperature was 33°C in the morning and 36°C at noon.
The indoor working environment was comfortable, there was no uncomfortable feeling on the floor, and there was no condensation on the ground surface during operation.
August test: Air handling unit + ground cooling turned on simultaneously
The second test: From 9:00 pm on August 15, 2019, to 9:00 pm on August 16, 2019, for a total of 24 hours.
At 11:30 am on August 15 of that day, in order to test the stability of the system, the windows were opened for the test. There was no condensation on the ground surface, and no hot air entered from outside the window.
On the contrary, the radiant cooling provided a better sense of comfort and stronger cooling capacity.
According to the comparison of the actual measurement data, when the temperature difference between the ground surface temperature and the set target temperature is about 1°C, in the system without the "floor radiant cooling + air handling unit cooling", in the high-heat and high-humidity area, the treatment efficiency of the surface temperature of the house is very low.
However, in the dual-supply system with "floor radiant cooling + air handling unit cooling", after a period of operation and calculation, the supply and return water temperature of the main unit is 10-12°C, the ground surface temperature is 23-26°C, the indoor humidity is 65%, and the indoor temperature is 24-28°C. All the measured data meet the human thermal comfort index.
Result: Completely meets the demand and has high comfort
In conclusion, a variable-frequency cooling and heating unit with a power of 6.5kW (7HP) and a cooling capacity of 15.7kW can completely meet the cooling demand for an area of 240 square meters.
In terms of comfort, in the system equipped with the "air handling unit + floor radiant cooling system", the air handling units all operate at a low speed, which provides better comfort compared to the cooling of a single air handling unit of an air conditioner.
During the intermittent use period, the air handling unit can be stopped, and the indoor temperature can still be kept uniform.
The comfort level of the floor temperature can be maintained within the range of 23-26°C, achieving the highest comfort.
III. What are the key points of the design of the ground cooling system?
In the dual-supply system of "floor radiant cooling + air handling unit cooling", cooling is achieved through floor radiation, that is, the temperature-adjusted cold water flows in the underfloor heating pipes. It works in coordination with the fan coil units to drive the effective circulation of the air flow, reduce the air temperature, thereby reducing the latent heat in the air, and also taking into account dehumidification.
3.1 The role and model selection of the air handling unit
In summer, the cooling mainly relies on the air handling unit. When the ground cooling is always on, it accounts for about 40-60% of the total load. In winter, it is definitely mainly to meet the needs of underfloor heating, and the air handling unit is only used to increase the air flow organization and improve the comfort.
The cooling capacity required by the air handling unit is calculated from four aspects:
First, during the starting stage, to reduce the total heat in the air;
Second, when the floor radiation is normally supplying cold, it is the cooling load relative to the insufficient indoor load and dehumidification;
Third, the cooling load of the fresh air;
Fourth, when the floor radiation is normally supplying cold, it is the cooling load of the continuously generated radiant heat of the indoor enclosed building.
During cooling control, the air handling unit is the main part, and the floor radiant cooling is the auxiliary part. The floor radiant cooling is the same as the underfloor heating. When it is running, it will offset the heat of the ground building and stop working when the set temperature is reached.
If the room has not been occupied for a long time, it is definitely mainly relying on the air handling unit, and there is no need to start the ground cooling. If it is occupied for a long time, when the floor radiant cooling is started, the air handling unit can be selected at high, medium, or low speed according to people's activities.
If you have just entered the room, the floor radiant cooling and the air handling unit are started simultaneously. The air handling unit takes away all the heat (sensible heat and latent heat) in the air, and the ground cooling reduces the heat load of the building through radiation. After starting for a period of time, when the comfort level is improved, the air handling unit can be adjusted to the low speed.
3.2 Anti-condensation variable water temperature design
This system is equipped with a set of dual-temperature variable-frequency module, that is, two sets of variable water temperature adjustment modules are used inside to control the heating and cooling of different areas.
For the condensation control and treatment, the control system of the "air handling unit + floor radiant cooling system" is divided into a detection system/feedback system, an operation system/command system, and an execution system/(proportional valve mixing water/variable-frequency pump station). According to the comprehensive calculation of the dew point control technology based on the indoor temperature and humidity display of the room temperature and humidity, and adjusting the variable water temperature control according to the outdoor temperature feedback and the indoor secondary feedback at any time, it can be distributed by floor and controlled and distributed for the whole building.
Through the outdoor temperature compensation + indoor temperature and humidity dew point control, and then through the precise calculation method and the core components of the variable water temperature, precise control can be achieved. This method is called the "temperature and humidity dew point control + adjusted water temperature feedback technology".
IV. High technical difficulty and difficult promotion
Precisely because the ground cooling technology is relatively complex, some industry insiders have pointed out that -
How many merchants in the home market can really focus on studying the technology? This system is not impossible to implement, but if it is promoted everywhere and any company rushes to do it, it will be a disaster for the end-user market!
From this perspective, the ground cooling technology itself is very mature, but dealers should strengthen their learning, and when owners make a choice, they should also investigate more cases!