I purchased an aluminium bi fold door system to replace an existing upvc sliding patio door. It is a quality product and was expertly fitted by Almark of Stockton and the colour option fits nicely with the style and colour of the existing brown upvc windows. However I have experienced condensation on the lower sill when the outside temperature drops below 3 to 4 degrees C and "I am assuming" the Thermal Break struggles to bridge the differential between inside and outside temperatures. This is the only negative aspect of what is an excellent product and I am looking forward to reaping the benefits in the summer months. .