U Value whole window method of calculation?

[thatsnotafestool]

..... Will they actually ever know? ......

Well, Mark, not sure about round your way but round here there are plenty of people who have more than enough time on their hands to 'shop' someone.

With Listed Buildings I always tried to go the 'repair' route. But always made a call to the local Conservation Officer out of courtesy.

[Meccarroll]

I have a bit of a strange question, but why bother to tell them? Will they actually ever know?

t

With Listed buildings it is against the law , rather than just planning regs, to alter them without permission. Whilst some big firms and cowboys seem to be able to flout the regs a small conscientious local trader could well have the book thrown at them.

Put another way: It's a "Criminal Offence" and you might end up with Fletch' eating Porridge!

[jfc]

and Bubba eating C

[woodsmith]

and Bubba eating C

Put another way, getting consent is a way of avoiding future cock-ups!

[thatsnotafestool]

and Bubba eating C

Put another way, getting consent is a way of avoiding future cock-ups!

Is that literally or metaphorically ?

[mark270981]

I have a bit of a strange question, but why bother to tell them? Will they actually ever know?

t

With Listed buildings it is against the law , rather than just planning regs, to alter them without permission. Whilst some big firms and cowboys seem to be able to flout the regs a small conscientious local trader could well have the book thrown at them.

I know listed buildings have a completely different set of rules as we have worked on them ourselves.

I thinking more for buildings not on the list and the likes of

[Meccarroll]

The answer below in full from my previous lecturer.



Hello Mark.

You ask about thermal transmittance calculations so I will tell you a little (in fact almost all) of what I know on the subject. It is coming up to four years since retirement so I could be way out of touch.
The acceptable calculation procedures are defined in Part L of the Building Regulations and Approved and Associated Docs. – available freely on line (planningportal.gov.uk). BRE report BR443 is relevant. The calc used to be very simple (merely the reciprocal of the total resistance) but is now complicated by the need to apportion resistance values of cavities etc. But don’t let that put you off – it is fairly straightforward to work thro the standard pro forma. Some practices (e.g. try Elmhurst Energy) have produced computer progs to do this but to be acceptable for Bldg. Regs. applications the software must be third party accredited so there is likely to be a fee involved. If you are hot on Excel you may be able to design a spreadsheet to do the calcs but I couldn’t and of course it would not be accredited. The use of accredited "standard" details reduces the amount of calculation evidence required.

I remember that some of the larger materials suppliers e.g. Celcon, Rockwool had on their websites simple (not accredited) progs tied in with the application of their products.

Good luck and let me know if I can be of any more help

Regards, John

Good point that Mark........ "third party accredited calculations".........I think that's if you supply 'SUMMARY CALCULATIONS' for example without all the workings of how you achieved the final figure.
I think that's basically what you are saying?

I am still trying to figure out how to perform the calculations. I have no problem with calculating "u values" for multiple wall constructions and working out the point of interstitial condensation in them either. I am just having an initial problem deciding which way to set out the initial working calculations. There seems to be no complete example that I can find to follow. Lot's of info in ISO 10077-1 and ISO 10077-2 it's just using it in the correct way to obtain the working calculations necessary for incorporating in a spreadsheet.

You mentioned BR report 443 and I think that one we have not put a link to on this thread yet so it's here:



http://www.google.co.uk/search?client=s ... 0AWc4YCwBQ" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;



NB: for the above link, Try clicking on the second line down: BRE443 U-values (2006) - BRE

Many thank's for your input


Mark.

[thatsnotafestool]

......

Good point that Mark........ "third party accredited calculations".........I think that's if you supply 'SUMMARY CALCULATIONS' for example without all the workings of how you achieved the final figure.
I think that's basically what you are saying?

.......

No it isn't. Third-party accreditation means exactly that. There is a clue in the description ''''third party". That is someone else. Someone independent but recognised as an authority. So you can't get the bloke down the pub to act as your third party.

[Meccarroll]

......

Good point that Mark........ "third party accredited calculations".........I think that's if you supply 'SUMMARY CALCULATIONS' for example without all the workings of how you achieved the final figure.
I think that's basically what you are saying?

.......

No it isn't. Third-party accreditation means exactly that. There is a clue in the description ''''third party". That is someone else. Someone independent but recognised as an authority. So you can't get the bloke down the pub to act as your third party.

Let me explain my interpretation:

Summary calculations are just that, they summarise the process and do NOT show all the working calculations. They may show an equation or a set of final figures but not all the workings that have achieved them. Summary calculations are the type that may be performed on a computer software programme by an accredited person (recognised by professional bodies as competent to do the calculations). An accredited person may then sell you a set of summary calculations for you to present to Building Control.

On the other hand working calculations show all the calculations necessary to achieve the end result. Everything is in the working calculations to enable you to see how the end result has been achieved.

I am not sure where the "bloke down the pub" has to do with it, but it sound like a good idea to me right now...............Cheers

Thank you for your input.

Mark

[thatsnotafestool]

......

Good point that Mark........ "third party accredited calculations".........I think that's if you supply 'SUMMARY CALCULATIONS' for example without all the workings of how you achieved the final figure.
I think that's basically what you are saying?

.......

No it isn't. Third-party accreditation means exactly that. There is a clue in the description ''''third party". That is someone else. Someone independent but recognised as an authority. So you can't get the bloke down the pub to act as your third party.

Let me explain my interpretation:

Summary calculations are just that, they summarise the process and do NOT show all the working calculations. They may show an equation or a set of final figures but not all the workings that have achieved them. Summary calculations are the type that may be performed on a computer software programme by an accredited person (recognised by professional bodies as competent to do the calculations). An accredited person may then sell you a set of summary calculations for you to present to Building Control.

On the other hand working calculations show all the calculations necessary to achieve the end result. Everything is in the working calculations to enable you to see how the end result has been achieved.

I am not sure where the "bloke down the pub" has to do with it, but it sound like a good idea to me right now...............Cheers

Thank you for your input.

Mark

Whatever.

[jfc]

Let me explain my interpretation:

Summary calculations are just that, they summarise the process and do NOT show all the working calculations. They may show an equation or a set of final figures but not all the workings that have achieved them. Summary calculations are the type that may be performed on a computer software programme by an accredited person (recognised by professional bodies as competent to do the calculations). An accredited person may then sell you a set of summary calculations for you to present to Building Control.

On the other hand working calculations show all the calculations necessary to achieve the end result. Everything is in the working calculations to enable you to see how the end result has been achieved.

I am not sure where the "bloke down the pub" has to do with it, but it sound like a good idea to me right now...............Cheers

Thank you for your input.

Mark

I see what you are saying but to do a working calculation you would have to factor in every detail . Even the moisture content of the timber would change its value so you would need to test that before you could input its value into the calculation . You would need to do that for everything and every part to get a real calculation . It would take longer to work out the calculation than it would to make the window

[mark270981]

Let me explain my interpretation:

Summary calculations are just that, they summarise the process and do NOT show all the working calculations. They may show an equation or a set of final figures but not all the workings that have achieved them. Summary calculations are the type that may be performed on a computer software programme by an accredited person (recognised by professional bodies as competent to do the calculations). An accredited person may then sell you a set of summary calculations for you to present to Building Control.

On the other hand working calculations show all the calculations necessary to achieve the end result. Everything is in the working calculations to enable you to see how the end result has been achieved.

I am not sure where the "bloke down the pub" has to do with it, but it sound like a good idea to me right now...............Cheers

Thank you for your input.

Mark

I see what you are saying but to do a working calculation you would have to factor in every detail . Even the moisture content of the timber would change its value so you would need to test that before you could input its value into the calculation . You would need to do that for everything and every part to get a real calculation . It would take longer to work out the calculation than it would to make the window

Isn't it overkill though.

Surely with something like this, a rule of thumb would apply, all they would like is for the window to have the right thermal properties. I don't get why U values need to be worked out to the decimal point?? Is it the authorities employees trying to be clever and justify their jobs???

[jfc]

I think what Mark is saying is that by giving the actual calculations you are proving the u-value . Larger companies have had an actual window laboratory tested so can give basic calcs to back up the claim .

[mark270981]

Its fair comment, but is an actual U value needed to be given??

Surely it just needs to be greater than 'X' value.

I've just read this

http://www.architecture.com/Sustainabil ... INCOMPLETE).aspx

note the paragraph.

'Do not bother trying to work out the U value of a window, element by element. This sometime is required in PassivHaus calculations but manufacturers and reference books tend to give fixed values for various glazing types.'

[Meccarroll]

Its fair comment, but is an actual U value needed to be given??

Surely it just needs to be greater than 'X' value.

I've just read this

http://www.architecture.com/Sustainabil ... INCOMPLETE" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;).aspx

note the paragraph.

'Do not bother trying to work out the U value of a window, element by element. This sometime is required in PassivHaus calculations but manufacturers and reference books tend to give fixed values for various glazing types.'

I hope this link helps clear up a few grey areas regarding the need for Whole Window U Values.

http://www.part-l.co.uk/" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;


Regards Mark

[mark270981]

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.

Etc etc.

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?

[Meccarroll]

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.

Etc etc.

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.


Regards Mark


Corrections with reference are welcome.

[sainty]

Have you seen the buildcheck website? It has a calculator on there that will produce the numbers that you require, it's a subscription service and its about £200/year I think.

[jfc]

Just dropped three sash windows off today for a builder and I forgot the paper work for the last one I made for him . He told me BC passed the window yesterday , no stickers , no paper work . I guess the major hassle was a couple of years ago and that weeded out the cowboys so BC are not so hot on it now .
Some cowboys slipped through the net yeeeeeeaaaaaaaaaaaaahaaaaaaaaaaaaaaaaaaaaaaaaaaaaa ride em cowboy

[Meccarroll]

Have you seen the buildcheck website? It has a calculator on there that will produce the numbers that you require, it's a subscription service and its about £200/year I think.

Thank's for the post. I did notice Build Check advertised a window U value calculator, but only took a proper look at the site after your post. You are right, it's £200 for a years subscription + vat. It's just a shame the government has not introduce something like this FOC to help small businesses comply. It makes me wonder where the governments interests lie.

I am getting to grips with the methodology for the calculations now, I have had a fair bit of input from several members of this site which has been very helpful, including yours and I am very grateful to all.

I think it will take me quite some time before I have anything useful in terms of a "DO ALL SPREADSHEET", but I'm working on it and have had a lot of useful input.

It seems JFC makes good use of a couple of resources (mentioned by him in this thread) which seem worth considering if you make and or fit your own windows.

Regards Mark

[jfc]

I got my info from here aswell . This lot know how to get around anything the EU can throw at us

[Meccarroll]

Came across this site while surfing, it has some free web U value Calculators.
The site does not have a Whole Window U value calculator developed yet but they say one is on the way.
It may be worth making a note of the site and re-visiting from time to time to see if a Whole Window U Value calculator has been developed.

LINK BELOW

http://www.thermalcalconline.com/u-valu ... lator.html" onclick="window.open(this.href);return false;



Regards Mark

[Top Notch Joiner]

I have just had a conversation with a building inspector. All he wants to see is, and I quote, "a bit of paper, or a letter from the glazing supplier saying that my sealed units have a U Value of less than 1.6". In other words, all this 'whole window' nonsense is a waste of a joiners time and money!

It's like many things, CE Marking for example, the people that have the task of enforcing these regulations have only a basic knowledge of what's involved. The only people who really benefit from this sort of red tape and bureaucracy, are companies with a vested interest. Software companies like my dear old friends at Joinerysoft for instance .

Don't waste your time and money chaps. Just get "a bit of paper" from your sealed unit supplier