Any Architects out there?

[Virtualmeuk]

I am building a small 2.4 x 2.4m extension above my gatage. I have got planning permission and i have instructed an approved inspector who has said he will put the application in as Building Notice Application. I am a steel fabricator by trade so it has been designed as a steel framed box on top of 4 posts. No issues with the design apart from wall and roof construction. The approved inspector has asked for the U values and i have no idea how to work it out. Can anyone look at the attached picture and tell me how to work it out or if i have it all wrong?

Any advice would be appreciated

 

[Zimmerframe]

Wow ! It should be GOOD !! I think I'd be happy lowered into a volcano with that around me ...

Not what you want but a starting point which might help when someone gives a proper answer. Though you could work it out from this by looking up the R values of each of your layers.

To calculate a U-Value you have to start with the R-Value or resistivity of the elements that make up the building element you are trying to calculate the U-Value for. The R-Value refers to a material’s ability to resist heat transfer at a certain thickness – the higher the better when looking for an insulation material. It is measured in m2.K/W. The R-Value is calculated as R = l/λ where l = the thickness of the material in metres and λ (lambda) is the thermal conductivity of the material in W/m.K.

So, for example, to work out the R-Value of 60mm of Kingspan Kooltherm K8 Cavity Board, which has a thermal conductivity or λ value of 0.021W/m.K:

R-Value = l/λ = 0.06/0.021 = 2.86 m2.K/W

U-value formula
For a particular application, such as a cavity wall, which is built up of a concrete block outer leaf, 50mm clear cavity, Kingspan Kooltherm K8 Cavity Board, dense block and skim coated plasterboard, then the R-Value for each of the elements would be calculated in order to work out the U-Value.

U Value is the reciprocal of all resistances of the materials found in the building element. To calculate the U-Value of the building element the R-Value of all the different components that make up that element will be considered.

U-Value = 1/(Sum of all R-Value)

U-Value (of building element) = 1 / (Rso + Rsi + R1 + R2 …)

where Rso is the fixed external resistance, Rsi is the fixed internal resistance and R1, R2 etc. are resistivity of all elements within the application, including that of cavities within the construction.

This is the basic formula, and by using this you could work out the U-Value for a particular application. However, there are also other factors which need to be taken into account including thermal bridging factors of fixings or stud work.

A more indepth explanation complete with a couple of apps to work it out ..

U Values for Dummies

U-Values can be a little confusing. Use our expert guide to help you better understand what U-Values are, what they mean & what effects they can have.

www.ecomerchant.co.uk

 

[Frankieboy]

WOW! Every day is a school day???

 

[steve_sordy]

Not such a muppet after all.

An explanation of what the terms are in m2.K/W and W/m.K would assist matters (IMO).
Then it would be perfect!