Regs for floor and roof insulation?

[d000hg]

It depends on the design.

You need to broaden your thinking and not be fixated on insulation thickness.

So what do the regs say and how does one go about figuring out what is required? My build is not complicated, it's a single storey11x6m log structure on a floating suspended floor. It can't be that hard if I know what my target is to figure this out.

It's all very well saying "broaden your thinking" but I don't see a single number or regs requirement mentioned, and there must be specific requirements for overall thermal efficiency, etc.

 

[Leofric]

It's all very well saying "broaden your thinking" but I don't see a single number or regs requirement mentioned, and there must be specific requirements for overall thermal efficiency, etc.

If you think you are capable of working out how to comply with building regs the relevant part is Approved Document L which you can view on the Planning Portal or LABC websites free of charge. Good luck

 

[d000hg]

If only there was a forum about building regs where one could ask about it. Because it's quite complicated.

Do you know of one?

 

[Leofric]

If only there was a forum about building regs where one could ask about it. Because it's quite complicated.

Exactly, that's why you can't expect it all to be explained on a DIY forum People make a living advising others, including architects , how to comply with Part L of the building regs, they are called energy rating consultants.

 

[d000hg]

I mean I've read bits about electrical regs and it's all quite straightforward under the terminology, is THIS area really that complicated or do consultants just like to belabour that view so they can charge £100+/HR. Surely it just boils down to adding up the energy leakage of your walls, windows, floor and roof? I ran into this with EPC reports, I'm convinced it's quite simple (they can do it in an hour or two) but nobody will tell you how is calculated!

 

[Leofric]

Surely it just boils down to adding up the energy leakage of your walls, windows, floor and roof?

You might have been right if you were talking about building regs several years ago when it was possible to comply with Part L by achieving certain U values for walls, floor and roof under the Elemental Method but there is more to it than that now.

I'm convinced it's quite simple

How can you be convinced it is quite simple when you don't understand how it is done You can buy a computer programme but you need to know what information to feed in i.e. the proposed construction specification , heating system etc
As stated previously ,thermal insulation is just one aspect of building regs and you need to consider the design/construction of the whole building.

 

[cdbe]

I'm doing my own extension, on a building notice. As far as I'm concerned (for a straightforward domestic extension - rather than a grand designs job with acres of glass) it's just a matter of meeting the published values for floors, walls roofs and windows (I think there is a % limit on window area) . I told my building inspector what I was doing - 100mm celotex under the slab, 300mm mineral wool in the roof, A rated windows, he queried the walls a bit because I only have a 75mm cavity (mainly because I picked up a job lot of cheap 75mm cavity batts), I emailed the tech department of the manufacturer and they supplied a spec that met the requirement for me to give to building control:

If you are going to be spending £000's on celotex or kingspan I suspect they'd probably do the whole thing for you if you send them a few drawings.

 

[^woody^]

If only there was a forum about building regs where one could ask about it. Because it's quite complicated.

Do you know of one?

This one?

Building Regulations are not prescriptive, like those other easy regulations you mention.

What building regulations do is give a performance guide (the building shall be dry, the building shall be insulated, the building shall not fall down etc) and it’s up to you to prove that the your building conforms.

That’s why you don’t concentrate on one thing and don’t ask, “what insulation do I need in my roof and floor”, because it depends on the design of the roof and the design of the floor and how those interact with the rest of the building.

Taking Grenfell as a good classic example, you don’t concentrate on meeting regulation for insulation, and then have the whole place burn down. So you design a building to not only meet the required regulations individually, but also so that all the components work together. So your choice of 200mm of mineral wool, or 150mm or polystyrene, or 100mm of PIR as insulation will each meet the requirement for insulation, but will that work with the timber sizes, the, the cladding, the vented structure and prevention of fire spread?

You are building a commercial building for use by children and you appear to be bent on cobbling something together that you don’t have the knowledge of. So it seems that you need to employ someone who does.

And don’t rely on building regulations or the inspector to guarantee the work is correct and inspect it correctly. Inspectors have no liability that you building will actually perform as you say it will.

 

[Leofric]

As far as I'm concerned (for a straightforward domestic extension - rather than a grand designs job with acres of glass) it's just a matter of meeting the published values for floors, walls roofs and windows (I think there is a % limit on window area) .

interesting - so which method are you using to show compliance with Part L , the good old Elemental Method
ps and what would you recommend for doohg's log cabin

 

[Leofric]

you appear to be bent on cobbling something together that you don’t have the knowledge of. So it seems that you need to employ someone who does.

Yes, that would be best.

 

[d000hg]

We spoke to our local council advisor today. He told us that the building should have a U value of .28. But that if it doesn't, it must be .7 or better. He said they use a complicated spreadsheet but it is essentially doing an average over the whole envelope.

Which on the one hand sounds like what someone described as the "Elemental Method"? i.e. straightforward and based on common sense maths like anyone trained in a scientific discipline would expect.
But on the other somewhat confusing - is it .28 or is it .7? He did mention .7 is a limit where condensation starts to be an issue which makes total sense, but not when .28 is required and when .7 is!

DOES anyone here actually work in this area themselves, and know how the calculations ARE done? Because anyone with GCSE maths can calculate an average u-value for comparison but clearly there is more to it than that (draughts as one example). However, is it all just done in software these days meaning even the people doing the inspections don't know what the calculations are?

 

[d000hg]

How can you be convinced it is quite simple when you don't understand how it is done You can buy a computer programme but you need to know what information to feed in i.e. the proposed construction specification , heating system etc

Firstly, a solid scientific background. There is no magic here. People love making what they do seem murky and mysterious but I have never come across an area when talking to an actual person who does it, it doesn't turn out to be based on straight-forward principles. The stuff I do people think is tremendously 'brainy' but it's not.
Secondly, the people doing this work are not rocket scientists. They are regular people like you or I.

As stated previously ,thermal insulation is just one aspect of building regs and you need to consider the design/construction of the whole building.

Yes absolutely however thermal efficiency is one that we realise is a tricky one. Lots of things can be retro-fitted or addressed quite easily, but if the overall structure is remiss in some key detail like this, that's potentially a huge problem.

 

[Leofric]

Firstly, a solid scientific background.

What has that got to do with it ?

There is no magic here.

nobody said there was any magic

People love making what they do seem murky and mysterious but I have never come across an area when talking to an actual person who does it, it doesn't turn out to be based on straight-forward principles.

read Approved Document L and then come back

Secondly, the people doing this work are not rocket scientists. They are regular people like you or I.

thanks for telling us ,never knew that !

Yes absolutely however thermal efficiency is one that we realise is a tricky one. Lots of things can be retro-fitted or addressed quite easily, but if the overall structure is remiss in some key detail like this, that's potentially a huge problem.

isn't that what people on here have been trying to tell you, you need to consider the whole building.

I don't understand where you are coming from on this, you admit you don't understand what to do but what do you expect people on here to do, obtain building regs approval for you ​

 

[d000hg]

isn't that what people on here have been trying to tell you, you need to consider the whole building

I don't remember disagreeing on that. The conversation has moved on in the last several days from my original question.

I don't understand where you are coming from on this, you admit you don't understand what to do but what do you expect people on here to do, obtain building regs approval for you

I don't know, I thought people might do more than tell me to read the entire of section L of the planning regs but might give an idea on what overall basis regs would be approved i.e. minimum overall thermal efficiency. Maybe mention some actual numbers at some point, or give a rough idea how those numbers are arrived at. Or talk about their own experiences, what they had to achieve.
If you look at @cdbe or @^woody^ you'll see they are offering such things. Do you actually know ANYTHING about this yourself @Leofric? I know I don't know, that's why I asked. Telling me my question about not knowing something demonstrates a lack of knowledge - well that's hardly a surprise is it?

 

[Leofric]

Do you actually know ANYTHING about this yourself @Leofric?

I only had about 40 years experience working as an architectural technician preparing drawings and specifications etc for planning and building regulations applications for various types of buildings before I had to retire , so no, I don't know anything about this myself , but cdbe seems to know all about it
ps I think U value is the coefficient of thermal transmittance measured in W/m2 K (whatever that means)

DOES anyone here actually work in this area themselves, and know how the calculations ARE done? Because anyone with GCSE maths can calculate an average u-value for comparison but clearly there is more to it than that (draughts as one example). However, is it all just done in software these days meaning even the people doing the inspections don't know what the calculations are?

I am sure somebody on here will be able to tell you how to do SAP calculations, they are the fellas you need

pps might be best to get somebody to prepare a Full Plans Submission for building regulations approval though.
Edited U value should have been W/m2 K of course