When roof space is tight

Reference Projects


CALOSTAT® for insulation between the rafters in a historic villa near Paris 


CALOSTAT® Steil- und Schrägdach

Property: heritage townhouse in a Parisian suburb

Year of construction: around 1900

Restoration: 2019

Service: insulation between the rafters with CALOSTAT® Sandwich F

Construction company: WEREYSTENGER, Gunsbach, France

Consultant: ISOLProducts, Sarreguemines, France 

A lot of energy is lost through the roof, which is why roof insulation plays an important role in energy refurbishment. In the ideal case insulation keeps out the cold in winter and—this is becoming increasingly important—the heat in summer. The advantages of CALOSTAT® are most particularly evident when there are also restrictions on space.

A mere four centimeters was available for insulation of the roof of a townhouse in Paris. Because the building is listed, and justifiably so, the roof could not be raised. Due to the very restricted space between the rafters, the insulation value of conventional insulating materials is lower than would be adequate for efficient insulation.

Insulation expert Philipp König of the French company ISOLProducts therefore recommended CALOSTAT®—which is how CALOSTAT® Sandwich F came to be used as inter-rafter insulation in the beautiful structure dating from around the year 1900. In such cases CALOSTAT® offers an ideal solution to the problem. Philipp König explains why: “Air circulation between the roofing and the insulating material must be ensured, and in this case not much space was available. In view of the beautiful but delicate roof truss, we naturally wanted to use a non-combustible material.” Under-rafter insulation would have taken up too much space. CALOSTAT® was cut to size at the site and adapted for the particular requirements. “I find it an exciting material,” says König. “Requirements on insulating materials are continually increasing. CALOSTAT® impresses us professionals by its combination of fire protection with an excellent insulation value.”

CALOSTAT® offers yet another advantage, particularly when used in the roof: In contrast to other insulating materials, the insulating capacity of CALOSTAT® is independent of temperature; this can make a decisive contribution toward protecting against summer heat, particularly where the intensity of direct incident sunlight, and the associated warming, is high. An unpleasant summer indoor climate in the attic can be prevented, even with low installation depth.   

CALOSTAT® for insulation between the rafters