Regs for floor and roof insulation?
- Thread starter d000hg
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For anyone interested, I did some GCSE level math to get some sort of rough idea. You should be able to see it here:
https://drive.google.com/file/d/1gx8_jgpQyeb2_EvaEDRsoDJOoVG_UvDT/view?usp=sharing
It's quite possible I made a total mistake somewhere but some key things:
As are any thoughts whether this is even slightly likely to get approval in this area... it's a LOT better than my house but a lot worse than a modern house. On the other hand, I am not sure if residential and business rules are the same; for instance it will be used day rather than evening and will be full of warm people.
I think we're seeing the guy tomorrow so it'll be interesting to see. He was wary of the walls, but in a traditional log cabin that's a huge part of the appeal!
https://drive.google.com/file/d/1gx8_jgpQyeb2_EvaEDRsoDJOoVG_UvDT/view?usp=sharing
It's quite possible I made a total mistake somewhere but some key things:
- 70mm wood walls have approximately the same U value as typical double glazed windows at 1.4
- If the roof and floor were perfectly insulated, the overall U comes in just under 0.6
- I didn't include additional insulation from floorboards, underlay+flooring, the roof shingles, etc.
As are any thoughts whether this is even slightly likely to get approval in this area... it's a LOT better than my house but a lot worse than a modern house. On the other hand, I am not sure if residential and business rules are the same; for instance it will be used day rather than evening and will be full of warm people.
I think we're seeing the guy tomorrow so it'll be interesting to see. He was wary of the walls, but in a traditional log cabin that's a huge part of the appeal!
The thing is it's being built in our garden so could conceivably be used for residential purposes later. He did say if it wasn't heated it wouldn't matter, but that's not really an option
One might assume modern office buildings have to be super efficient though I was wondering about all these buildings where the walls are almost solid glass. Even triple glazing seems to struggle to real better than U=0.5 which is far worse than a modern cavity wall.
If I'm understanding things right then if it weren't heated then it isnt treated as a 'building'. It's more of a shed. Sheds don't need insulation.
Since it is being heated and it's over 50 M2 doesn't that mean it needs it's its own EPC?
Since it is being heated and it's over 50 M2 doesn't that mean it needs it's its own EPC?
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Presumably. Though I think the stipulation is 50m2 USABLE space.
What will the walls be made of?
Traditional interlocked log lap isnt the best option for our damp country.
If it was me, I would be constructing in timber frame with tyvek house wrap on the outside.
The tyvek site has detailed downloads showing sectional details.
For the size of the structure, I would suggest getting a SAPs test done -around £300 and you will get a full software simulation of the whole structure. No need for elemental values.
L
Leofric
Somebody else has said it - SAP calcs. The proposed construction of the external walls, floor and roof will need to be specified before these can be done. Next anticipated question - how do you know what to specify, as the man on here says I suppose - it's all down to experience.
As has been said on this forum many times, it is basically a case of somebody who knows about the design of buildings such as an architect or architectural technician preparing a set of architectural drawings for the building, otherwise questions could go on forever. Good luck with it anyway.
Yes, you don't want an unheated house
Building regs are the same for all of England. Scotland have their own bldg. regs.
L
Leofric
Any questions, just ask.
L
Leofric
Have Sap calcs done before work starts on site using this sort of form.(unless you want to do the calcs yourself of course )
The planning permission is explicitly for a log cabin structure, which will impact minimally in the wooded area it will be situated in - even such a 'light' construction was a pig to get permission for - so this is probably moot; the decision on the construction is already made. The question is how much extra we'll have to do to get someone to pass it; these cabins are generally sold for people to use as garden rooms or summer houses however we do know people have used them (from the same company) as extensions and even full domestic dwellings. If we could find such a person it'd be so much easier to ask them but no luck there so far.
And we know similar products have been used for other forest nurseries or such. We're trying to make contact with one locally to see what they had to do. Maybe we can even ask them if they used an architect and can pass on their details.
So this is basically the same sort of inputs I've done in my noddy spreadsheet - but then the actual calculations are much more involved, presumably using actual modelling of some sort (air flow, etc?) rather than just averaging the U values from each element? Is that form ALL someone would need to do the SAP test or just the starting point? I was surprised it doesn't ask how many windows and what size, for instance.
And, is the test entirely analytical and deterministic i.e. if I gave the exact same information to two people would I get the same answer, or is there some human subjectivity? Put another way when you pay someone £300 - which is not a lot of an architect's time, and I can see people charging MUCH less - are they poring over calculations or do they stick it in a computer and press a button, or is knowing how to get the information into the software correctly the skilled part in the same way that using CAD or Photoshop is? Looking at some of the prices I can see advertised, those guys cannot be doing much work at all - but maybe one SAP is NOT the same as another?
If you already have a SAP calculation/certificate, does that mean the building regs inspector will accept it for part L or does it only inform their decision?
Oh and - is the overall output of all this to determine your actual energy use, or your emissions, or your energy cost (like EPC)?
Yeah, is it epacs or something for commercial. Something like that, I heard it mentioned.LOL - three pages and its still just about insulation
BTW, SAP is only for domestic properties
It's not still just about insulation, it's about overall thermal efficiency. But in a building constructed without a cavity that's going to be the major source of thermal efficiency... a log cabin is basically a shed, like a solid-wall house from 1850 until you add insulation.
Well not quite, 70mm logs are about 2-3X better performing than solid brick.
So do you want to stop it heating up in the summer or staying warm in the winter? What plans do you have for air leakage and ventilation? What type of heating are you proposing and how are you going to match that with the choice of insulation? Is the design going to maximise solar gain, and are you planning to minimise the number and size of openings, and construction type to maximise this?
It looks like its all about insulation.
It looks like its all about insulation.
Is the construction solid log lap? Thats what Im asking.
Its possible to get log lap cladding, then the construction can be timber frame, but look the same.
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