Building regs query

[PoP]

I don't understand the regs quite well enough so thought I'd ask for expert opinions on the following.

Went along to do a quote for loft boarding today. No problem with that, I've done plenty of loft boarding exercises.

However I was told by the homeowner that they were having an extension built (nothing to do with the loft....), and the local BCO had advised them that they have to beef up their loft insulation in order to meet the regs. This house is maybe 15 years old at most and already has a goodly amount of insulation. But BCO wants another layer put in.

This surprised me a little because if extra insulation is put in then it means that adding loft boards would compress the insulation, but apparently BCO was happy about the insulation being compressed.

I may be a bit of a cynic about these things but simple logic tells me that loft insulation only works if it is uncompressed? Am I wrong?

PoP

[Set Square]

My understanding is that compressed insulation will be less effective than the same amount of insulation uncompressed - because when compressed it will hold a much thinner layer of static air. However, the boarding will *add* to the overall insulation.

There's one thing I don't understand in your post. Is the BCO saying that additional insulation is required in parts of the loft which are above the

*existing* house rather than above the extension? My understanding is that the latest regs only apply to the new bit. When I extended my house, we had to put a ridiculous amount of insulation in the new bit - but nothing extra in the old bit, even though they joined up with each other. [The same applied to the rest of the construction. We had to put a highly insulated solid floor in the new bit - but there was no suggestion that we needed to dig up and re-do the rest of the floor! Similarly with the walls and windows.]

[River Tramp]

Could it that the BCO is offering some sort of compromise over a deficiency in the insulation of the extension, perhaps for some reason it being difficult to add extra to the extension, so add to existing loft instead? Otherwise, I can't see the logic.

IanC

[G&M]

It will be.

It may be that it is impossible for the loft extension to meet the new insulation regs on it's own and so the BCO is doing them a favour by allowing them beef up the insulation elsewhere to make up for it. Strictly speaking this isn't allowed but many will let it by as it shows good intent.

[Owain]

"Set Square" wrote | PoP wrote: | There's one thing I don't understand in your post. Is the BCO | saying that additional insulation is required in parts of the | loft which are above the *existing* house rather than above | the extension? My understanding is that the latest regs only | apply to the new bit. When I extended my house, we had to | put a ridiculous amount of insulation in the new bit - but | nothing extra in the old bit, even though they joined up | with each other.

Possibly the householder/BCO is using some 'whole house' method of calculating overall thermal insulation and better insulation in the existing loft is going to allow some compromise elsewhere?

Owain

[The Natural Philosopher]

It works if compressed up to a point.

[The Natural Philosopher]

Thats because regulations are not retrospective. You can live in a horsehair tent if you want and its been there long enough. But try and add a new bit on the side...and by golly it had better be to regs. ..theres an urban legend somewhere about some bloke who lived up a hill with stream water, a septci tank and no electricity or anything...he wanted to take a pipe from furher upstream or someting, and applied for planning and got slung of completely because his existing supply was now inadequate, and the proposed new one would never meet standards.

Its the same with a listed building. If teh kitchen has been plated in

50's formica, gawd help you if you want to rip it out and expose the 14th century lath and plaster wall.

[The Natural Philosopher]

I am not so sure it isn't allowed. One criterion is that the overall energy loss per square whatever shall be no GREATER than the old house was. Another is that the new bit should meet new standards. If the overall loss of the house with the new bit 'to spec' and the old bit untouched, is matched by the combined mods to the whole thing, they rate that a pass.

[PoP]

That's correct as I understand it.

PoP

[N. Thornton]

The insulating part of loft insulation is the air it traps, not the fibres themselves. 8" of insulation compressed to 4" is simply 4" of insulation, and will behave as such. Except that it will put a good deal of downwards force on your existing ceiling. If you want any insulation value from it, put it on top of the boarding if thats acceptable - though its often not.

It may be just a case of whatever allows you to get the job done.

Regards, NT

[The Natural Philosopher]

True, bu there is teh issue of how well it traps the air as well - i.e. reduces convection currents etc etc.

If things wer that easy, 60mm of celotex would not be twice as good an insulator as 60mm of rockwool..which it is.

Not totally true - see above.

That is almost certainly true.

[Hugo Nebula]

On Wed, 14 Apr 2004 10:32:09 +0100, a particular chimpanzee named The Natural Philosopher randomly hit the keyboard and produced:

I don't know if there is any inherent insulation value in the poly isowhatsit material, but it is a closed cell material. In other words there are small bubbles of trapped air (or other gas) which don't allow the flow of heat through the boards.

[Ziggy]

Surely this is a matter of interpretation. If I read you correctly, you are saying that the combined loss of the old + new cannot be greater than the old. My interpretation of this is that the loss per square metre (or whatever) in the new part cannot be greater than the loss per sq. metre in the old part.

Otherwise in the first interpretation, the implication is that the new bit should have 100% insualtion.

[The Natural Philosopher]

Excatly,wheras rockwool is leaky. Whether compressed rockowol is more orless leaky, or whether the compresed fibers form a cold bridge I don't know.

[The Natural Philosopher]

No.

What I THINK the BCO's do, is to say

(i) what is exsiting heat loss? (ii) What would heat loss be if totally to spec extension were added?

Add those two together and then

(iii) If the total heat loss of the house and extension arrived at by any means is as good as or better than the sum of (i) and (ii) then we have done our job as well as if they HAD built the extension to spec...

That is definitrely the case, but they go furher normally. The above is more lack of a reason for an instant fail, rather than instant pass.

No.

[Neil Jones]

That is a total fabribation, I;m afraid. I live in a listed building and we did not need listed building consent to rip out the old kitchen (in the loosest possible sense of the word 'kitchen'), nor to install the new one.

[The Natural Philosopher]

Slight exaggertin, but I can quote you at least one example where a stud wall was built halfway along an old mullion window, and permission to remove it and expose the old window was denied.

The lited building thing is very peculiar. It attempts to freeze a house

- normally an organic ever changing thing - into a particular point in the time space continuum.

I even talked to teh listed people once about buying a listed property. Basically reapir everything the way it is, or let it fall down, are the only two viable options.

Of course teh house may be listed but teh kitchen intrior not, in which cas its do what you like.

A frined onf mine bought a house where only the actual house structire - renedred timber framed - was listed.

Faced with an enormous rot problem, they simply built a new blockwork house inside it, and tied the old walls to it wherever sound material was to be found.

[G&M]

You would where we live. Obviously your conservation officer is overloaded and nods through things like this. And for grade 1/II* properties they even vet the paint.

[Neil Jones]

Yes, well with grade I and II* English Heritage get more involved and they can be 'difficult' I think.

Our conservation officer seems to be a sensible chap who appears to be happy for us to get rid of the worst of the 1970s which stills hangs over in our house :-)

[Neil Jones]

If that's what the conservation officer is like I'd probably not buy it in the first place. But if you did, you could always make his life as boring as possible by applying for loads of little listed building consents (no charge for that) and appealing every decision he turned down. AIUI some conservation officers think that there job is to prevent chnage - it is not - but a few decisions overturned by the ODPM might change their minds.

property.

structire -

Excellent bit of lateral thinking there then :-)