Whitehall Museum is a 500 year old Grade II* Listed Tudor building which has received a well needed £1.6 million refurbishment and restoration. Originally the fenestration would have consisted of wooden mullions set in a gap between upright timbers and would have been unglazed but may have been covered in beaten leather or oiled paper to keep the weather out. The windows at the front of the building are improvements dating from more recent changes but still rich in architectural history so secondary glazing was specified to make the thermal enhancements required without damaging the architectural features. In total, 15 units were installed from the light weight range and 2 fire retardant units. Tapered and splayed timber grounds were used to take up the irregularities of the building structure which were scribed on site. Once these were in place the secondary glazing was installed. The treatment of the fire rated windows posed another challenge. Back in Tudor times, there were no fire regulations and local oak and elm, dating from c.1500, was used for the construction of the building. The approach had to be carefully planned and approved by building control. Durtnell & Sons created new fire resistant reveals into which the secondary glazing was installed ensuring the integrity of the treatment. Since this project was completed the Series 30 has been superceeded by the Series 31 lift-out.