mark270981 wrote:I know what you are saying.
But Mighton will say that won't they as they are trying to sell their system.
Ie it will cost £4100.00 per window to test, but thats bollox surely.
If a piece of glass has a u value rating of 1.6 then its compliant, the glass manufacturers will tell you this.
If a certain timber has a u value rating of 1.6 then that's also compliant
If the gaps are required to be sealed up, then if you find a manufacturer of say aqua seal (is this a brand name) that has a u value 1.6 then that's compliant.
we manufacture fire-door sets (using off the shelf fd30 or fd60 doors) which have a regs galore attached to them.
However all we need to do is use the materials that are compliant to make said doorset.
Ie a FD60 door frame must be made out of timber with a density of 640kg/m3 or greater which is only found in hardwoods which we always use Beech if its painted as this has a density of 700kg/m3
An FD60 door is already certificated.
Hinges are already certificated
Glass is already certificated
Intumescent seals are already certificated.
Then in our O and M Manual we state what we have used to make said doorset and is compliant.
I don't understand why this can't be done with windows?
We used to be able to use certain glass types that had "centre pane U Values" to satisfy the regulations.
Now we have to go a bit further and give the whole Window U Value.
If we look at the glazing (IGU) component of a window and how this affects the Whole Window U Value calculation:
How we used to calculate the glazing (IGU)
The "Centre Pane U Value"
could be calculated by taking the reciprocal of the sum of the resistance's across the glass at it's centre. This U value was generally given by the Glass Manufacturers
. All you had to do was select the correct glass and job done. The centre pane calculation only took into consideration the heat transmitted across the glazed area, it did not take account of the heat transmitted at the edges of the Insulated Glass Unit. It has been established that the spacer bar around the perimeter edge of an IGU can have quite an overall effect of the U Value performance of an IGU. So now this has become an important part of Window U Value Calculations.
In the new regulations you have to take account of the perimeter edge/s, of the glass unit and this generally means the spacer bar length incorporated in that unit. It is the double glazed unit as a complete unit that has to be calculated not just the Centre Pane U value
.Looking at the Glass Manufacturers.
Pilkington manufacture Glass not the insulated glass unit. They produce glass that can form the inner and outer layers of a Double Glazed Unit, but the edge spacer bar, infill gas and edge sealant all likely come from other sources.
It is only when you combine all the components to make an IGU can you properly determine the actual U Value of that unit.
It is important to consider the area of glass for a unit and the perimeter of that unit. If either of these changes then the corresponding U Value will also likely change too.
The only way to obtain an accurate U Value for each double glazed unit is to calculate it individually.
Unfortunately we can not use the old Centre Pane method...... "One Size Fits All"....... for Whole Window U Values any more.
Corrections with reference are welcome.