Seeking Switchable Heat Management Technology for Buildings

A SpecialChem client is looking for switchable heat management pigments (TC in the range of 20 – 45°C) for roofing applications.

The SpecialChem client is looking for a concept/material/technology that below a special transition temperature (TC; e.g. 40°C) shall transmit incoming radiation (especially IR) to the interior while at temperatures above TC the incoming radiation shall be reflected (see scheme below)



The proposed solution would have a very high potential in the building and construction market and should lead to promising market shares.

The SpecialChem Cient is seeking a new generation of inorganic nanoparticle coating additive with low-emittance (Low-E) at high temperatures and transmittance or absorbance at low temperatures:

“must have”:
• excellent IR reflectivity (range 800 – 2500 nm) of pigments at temperatures above TC and transmittance or absorbance at temperatures below TC
• high optical transmission without scarifying optical appearance of coating substrate
• high stability
• TC in the range of 20 – 45°C

“nice to have”:
• low cost
• high electronic conductivity

Beside known systems like NiS (TC = -10°C) or La1-xCaxMnO3 (TC

• thermochromism in α-VO2 results in a significant difference in transmission levels below or above TC (TC = transition temperature)
• TC 67°C, color change in near IR range
• phase transition temperature can be shifted by appropriate dopants (Mo4+ (regarded as best compromise),W4+, F-, Al3+ and Sn4+)
• application of 0.25% VO2 coating in a sun heating apparatus (W. Best) leads to decrease of internal temperature by 8-16°C

Challenges of known α-VO2 systems:

• current solution is IR-absorber at temperatures above TC; IR-reflector would be more favorable
• reduction of particle size to

IP protected solution are not of interest for the SpecialChem client. (See Other comments / important considerations)

The SpecialChem client would appreciate starting co-developing proposed solution before end of the year.