Dynamic insulation, a form of ‘Breathing Wall’ construction which allows the movement of air and moisture through the external walls of a building, was seen as one possible method for reducing building envelope heat losses and achieving high indoor air quality.
The paper of Taylor and Imbabi's describes the practical results of the 1-D analytical model. It was shown that the dynamic U-value for a multi-layer envelope can readily be calculated from the total thermal resistance of the wall (R_) and the air flow through the wall (v). Equation followed can be readily incorporated into an air flow and energy balance for a whole house to calculate the heat loss through the air permeable parts of the envelope.
Table below illustrates how the material thermal conductivity and the air flow combine to determine the dynamic U-value for 200 mm of cellulose insulation and 200 mm of porous masonry block (Pumalite).
Taylor and Imbabi's study lays the foundation for later research.
Salmaan and Jonathan describe a method for designing building materials as heat exchangers, so that incoming fresh air can be efficiently tempered with low-grade heat while conduction losses are kept to a minimum. They conducted two experiments: one measured the convection at the surface of a porous layer (heated plate) as air blowing or sucking; the other tested the performance of glass, wood and concrete sample as heat-exchanging porous media (designed with parallel channels).
Fig. 1. Salmaan Craig, Jonathan Grinham, Building envelope with porous material optimized to exchange heat to the incoming air Fig. 2. Salmaan Craig, Jonathan Grinham, Left: porous milli-fluidic panel fabricated for both experiments. Right: proprietary capillary tubing could also be used (sample with 4 mm diameter tubing shown).
The porous material must first receive heat on one side before it can transfer heat to the air flowing through it. Therefore, the performance of the heat exchange wall depends on the method of heating the room and how the heat reaches the interior surface. Remote radiant heating is one way to control surface temperature. The method used in this experiment is to integrate a closed loop water circuit into the surface. This ensures direct thermal contact between the heating (or cooling) source, the internal environment and the incoming air supply. The heated surface regulates the incoming fresh air and tempers the occupants by radiation. This is an accurate way to keep the porous layer serving only as heat exchanger. However, the heating layer with water circuit also serve as part of insulation and increase the internal temperature directly by conduction. Combining heating water circuit and porous material into one layer may be one possible solution to avoid that error. Instead of water, other liquid, like gas and oil, also can be used as heating media. A kind of porous matter play a role on both air- flowing channels and heating pump can be a new type of breathing wall.
Fig. 3. Mohammed, Breathing wall test cell 
Fig. 4. Mohammed, Total U-value of a typical breathing wall as a function of airflow
Fig. 5. Analysis of air flowing
Mohammed's study shows that the dynamic U-value of the resulting breathing wall system decreases as the air flow is increased, allowing the building to be ventilated at higher levels than would otherwise be possible without cost penalty. Combined with the filtration of incoming air, this means that very healthy indoor environments can be achieved even in the polluted urban environment of a large city such as London, New York, or Shanghai. The air exhausted will be cleaner than that taken in to ventilate the building, which also means that a breathing building of this type will clean the local environment. However, in this experimental box, the hot air will go up after passing the first lower entrance, and then go inside through the second upper entrance, which means that the U-value of the entire wall won't be consistent. Besides, heat loss in dual air lays has an influence on the levels of U-value.
Resouces: B J Taylor and M S Imbabi The application of dynamic insulation in buildings, Renewable Energy IS (1998) 377-382
Salmaan Craig, Jonathan Grinham Breathing walls: The design of porous materials for heat exchange and decentralized ventilation Energy and Buildings, Volume 149, 15 August 2017, Pages 246-259
Mohammed Salah-Eldin Imbabi, Modular breathing panels for energy efficient, healthy building construction, Renewable Energy 31 (2006) 729–738
 Andrea Alongi, Analytical modelling of Breathing Walls: experimental verification by means of the Dual Air Vented Thermal Box lab facility, AiCARR 50th International Congress; Beyond NZEB Buildings, 10-11 May 2017, Matera, Italy