GLASS SPECIFICATION AND GLAZING BAR DETAIL New Box and Casement Windows: Double Glazed (to comply with part L of building regulations) 4mm 'low E' glass internal 12mm warm edge spacer Argon filled cavity 4mm float external Internal glazing bars manufactured as part of the sash frame, ovolo or lambs tongue profile, external bars bonded to glass with VHB tabe, glazing bars in standard widths: 20mm or 25mm. Single Glazed Windows 4mm float glass bedded into acrylic, faced off using dry seal glazing compound. Glazing bars manufactured as part of the sash frame, ovolo or lambs tongue profile; glass bedded into acrylic and faced off with dry seal. Note: Safety glass is fitted as appropriate to comply with Building Regulations.