NZEB and an extension

Mousie32 · 22-10-2020 11:34pm #1

Hi there,

I have a quick question on NZEB and a proposed extension... Basically me and my wife are toying with the idea of buying a house (comes with it on problems here in Donegal trying to find a house without Mica) or putting an extension onto the existing home house (typical small Irish 3 bed bungalow) . My parents offered to sign over the home house so that a big extension (>40m2) ie. 3-4 bedrooms, living room, kitchen etc could be put onto it that would then be linked back into the home house where my parents will be. Basically, the only connection will be a link and I would forsee the link changing a lot less than 25% of the existing house walls. My question is - because it will be a lot less than 25% of the existing house wall will be altered will the NZEB regs be applicable and apply to both the new and existing? The footprint of the extension will probably end up more than the existing house. The exisitng house is heated by a solid fuel stove including the water and I would hate to have to go and upgrade the exisitng house. I know my folks would not be happy having to change the exisitng house much also. Any advice would be appreciated or any storeys if someone was in a similar situation...

sydthebeat · 23-10-2020 7:31am

Less than 25% then NZEB doesn't apply, only back stop values apply.

Remember however that if you pump the cavity or dryline internally that will affect your envelope and NZEB will apply

Mousie32 · 23-10-2020 9:24am

sydthebeat wrote: »

Less than 25% then NZEB doesn't apply, only back stop values apply.

Remember however that if you pump the cavity or dryline internally that will affect your envelope and NZEB will apply

Hi Sydthebeat,

Thanks for your response. That's what I was thinking it would basically extend the ope of the window down and replace with a door in one of the existing bedrooms. I thought I read somewhere that if the extension floor area is greater than 25% of existing floor area that NZEB applies but I might of picked that up wrong.

Mousie32 · 23-10-2020 9:25am

I forgot to say would NZEB apply to the extension then? I fancy and open fire or stove..

sydthebeat · 23-10-2020 9:29am

Mousie32 wrote: »

Hi Sydthebeat,

Thanks for your response. That's what I was thinking it would basically extend the ope of the window down and replace with a door in one of the existing bedrooms. I thought I read somewhere that if the extension floor area is greater than 25% of existing floor area that NZEB applies but I might of picked that up wrong.

Nope.

Nothing to do with floor area, it's too do with envelope area.

So as I said above, if you were not extending, but say, pumping the cavity, then NZEB would apply.

If you are extending, and the extension covers more than 25% of the existing dwelling (to which you are not doing any work) then NZEB applies.

In your case where there is a small link... Let's say you were changing the windows in the existing, and upgrading your ceiling insulation... If the areas of these, plus the link, equates to more than 25% the surface area of the existing building, then NZEB applies.

Anyone who quotes floor area to you, in regard to NZEB, doesn't understand the regs.

Metric Tensor · 23-10-2020 4:25pm

Just to clarify:

If you are adjusting more than 25% of the envelope the "Major Renovation" clause within the NZEB document (which is actually Part L of 2019) applies. As above this does not apply if less than 25% of the envelope is being addressed.

However the same document (Part L of 2019) has requirements for extensions and these will apply to you. As syd points out this is mainly to do with the levels of insulation in the building fabric but does have some requirements on services.

So "NZEB" technically applies regardless depending on what you mean by the term. It's easier to define it as follows:

"Which parts of TGD L 2019 apply to my project?"

Calahonda52 · 23-10-2020 6:13pm

In any event, with carbon tax CT now a reality, NZEB is the minimum i would be doing.
Its amazing the way the incremental CT shapes the cash flows on projects

Mousie32 · 24-10-2020 12:04am

Hi folks,

Thanks for all the replies it is much appreciated. The required regulations will be complied with for the extension it was just the thought of going back an retrofitting the existing house was putting me off due to budget etc. I must read up on TGD-L. I do note that these are only guidance documents. Yes you do have to comply with Part L1, L2 etc of the building regs and following the guidance demonstrates will prima facia demonstrate compliance with the building regs however different approaches can be implemented if you can demonstrate that this approach is in compliance with the building regs.

sydthebeat · 24-10-2020 1:48am

Mousie32 wrote: »

Hi folks,

Thanks for all the replies it is much appreciated. The required regulations will be complied with for the extension it was just the thought of going back an retrofitting the existing house was putting me off due to budget etc. I must read up on TGD-L. I do note that these are only guidance documents. Yes you do have to comply with Part L1, L2 etc of the building regs and following the guidance demonstrates will prima facia demonstrate compliance with the building regs however different approaches can be implemented if you can demonstrate that this approach is in compliance with the building regs.

Be very careful trying comply by means outside of the TGDs.

You must have your local building control officer accept that your method is still compliance... So it's up to you to prove that it complies

Mousie32 · 24-10-2020 7:48am

sydthebeat wrote: »

Be very careful trying comply by means outside of the TGDs.

You must have your local building control officer accept that your method is still compliance... So it's up to you to prove that it complies

Yea I know the hardship of this as in a former life I would of demonstrating compliance with Part B and M of the regs and unfortunately the likes of TGD-B and TGD-M did not cover certain scenarios so it was a pain trying to convince the fire officer / building control officer that what was being proposed was equal to or more than than that specified in the tech docs.

Metric Tensor · 24-10-2020 9:42pm

Believe it or not it is quite a bit easier to prove compliance with B and M via methods other than the TGDs than it is to do so for Part L!

In fact I don't think I've ever seen anyone successfully prove compliance with Part L without using TGD L. That's not to say it hasn't happened - I just haven't heard of a case. I have a few thoughts about how it might be done - but none of these would be cheaper that following TGD L in your case even if Building Control deemed them acceptable!

Mousie32 · 30-10-2020 6:56am

Metric Tensor wrote: »

Believe it or not it is quite a bit easier to prove compliance with B and M via methods other than the TGDs than it is to do so for Part L!

In fact I don't think I've ever seen anyone successfully prove compliance with Part L without using TGD L. That's not to say it hasn't happened - I just haven't heard of a case. I have a few thoughts about how it might be done - but none of these would be cheaper that following TGD L in your case even if Building Control deemed them acceptable!

Hi Metric,
Thanks for the reply that is good to know. We find it difficult at times as we would be dealing with FO/BCO in different counties and each one would have a different opinion and interpretation of the codes. It looks like it would make life handier and implement the guidance in Part L

NZEB and an extension

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