A mixing valve for mixing steam and water comprising an inlet chamber for steam, an inlet chamber for water, and a mixing chamber for mixing the steam and the water. The mixing chamber has at least one outlet connected thereto. A valve member arranged in the steam inlet chamber is coupled to a diaphragm. The valve is responsive to pressure differentials in the water inlet chamber, and is utilized to control steam flow from the steam inlet chamber to the mixing chamber. The mixing valve includes an internal partition between the steam inlet chamber and the water inlet chamber. The internal partition includes a thermal break that minimizes the contact between the steam inlet chamber and the water inlet chamber, thus minimizing the heat transfer therebetween.