The ultimate challenge is secondary glazing will never hold the thermal effectiveness of primary glazing. The hole between the panes will almost always be larger than 12mm as it can be mounted to the pre-current frames. An ordinary two-by-four stud wall with batt insulation and wallboard and Wooden siding https://high-performancelightingp34455.idblogz.com/35108025/not-known-details-about-fire-rated-secondary-glazing