FAQ: The abbreviation FENSA stands for FENESTRATION - SELF ASSESSMENT.
The uk dictionary definition of the word fenestral or fenestrate is " belonging to or like a window" The word fenestration is "the arrangement of windows in a building". FENSA is used by double glazing uk trade companies to certify that their replacement windows and doors installed comply with Building Regulations Document L (and more), actually checking av. 1% of all replacement windows installations.
Did You Know?
Glass Sealed Units.
In single glazing as an example, because glass is a good conductor of heat, the single pane does not insulate well, and if it is warm as toast indoors and freezing cold outdoors, the glass temperature in single glazing will somewhere between the two, i.e. still very cold.
Enter 'double glazing'.
Unlike glass, air is a poor conductor of heat, and so double glazing works by having two panes of glass held apart by a 'spacer bar' with an 'air gap' between, and then sealed up around the perimeter, hence the name 'sealed unit'.
Unfortunately air is a good convector, which means circulation inside the unit if the air gap becomes too large. That is why we cannot make sealed units even thicker than today's and then get even better insulation, the widest optimum air gap has been achieved, and almost surpassed in some ways.
An air gap of between 12mm and 20 mm is fine, but the difference in insulation between the common 16mm air gap and the 20mm air gap is minimal. Some manufacturers have tried to fix this problem by filling the air gap with a 'thicker' gas (commonly Argon), but this is not without it's own problems.
More: Because this is a pretty big subject I have split it into a number of sub-categories so that you can easily find very specific and detailed information about what you want to find out more about.
Just a thought: in 1983 some 6 million square metres of double glazed sealed units were made for the uk., now in 2002 that figure is up to 25 million square metres - interesting/boring fact.
Drool over the fancy coloured and bevel designs, so many to choose from: