25% area increase and BER B2

DM1983

Hi folks, buying a house that has an extension in place (35 m2 ish). I'm planning a further extension. Trying to figure out if this will trigger the requirement to get to B2. Is the increase calculated on the house's original floor plan or on the floor plan at the date when the new building regs came in (2018 or whenever that was?).

TIA

Calahonda52

Where do you read that floor area is the NZEB driver?
Is it not 25% of the fabric?
https://www.kore-system.com/low-energy-build/

is a useful link

as is this
https://www.xtratherm.ie/app/uploads/2019/12/Xtratherm-BR-Whitepaper-LR.pdf

sydthebeat

As above

Its 25% of the surface area, not the floor area.

Dunno who is spreading that fallacy?

DM1983

Thanks guys, my mistake. Same question then but on surface area. Is it based on the structure that I have now, which was extended prior to 2018 or on the original house. There was no planning needed for the existing extension obviously.

Metric Tensor

If it was extended previously there may be a need for planning now. Apologies if you already know that - it just wasn't clear.

Take the house in its current shape and work out whathe external envelope equals and then check the works you propose to see if they interact with more than 25% of this envelope area.

sydthebeat

DM1983 wrote: »

Thanks guys, my mistake. Same question then but on surface area. Is it based on the structure that I have now, which was extended prior to 2018 or on the original house. There was no planning needed for the existing extension obviously.

Based on the structure as stands today.

And remember, it's ANY change to the building envelope, so pumping existing walls, changing existing windows, internal dry lining to existing etc will all be reckonable as part of the 25% calculation

Calahonda52

sydthebeat wrote: »

As above

Its 25% of the surface area, not the floor area.

Dunno who is spreading that fallacy?

I have seen it in 3 LA's, we do some NZEB training and when you ask whats the 25% ...many planners think its floor area

DM1983

Still struggling a bit here. You're saying its all based on the current surface area of the house. So I can build an extension a mile long out from one wall and I won't be affected provided that wall constitutes less than 25% of the envelope? Is there no consideration of the finished house after renovation?

sydthebeat

DM1983 wrote: »

Still struggling a bit here. You're saying its all based on the current surface area of the house. So I can build an extension a mile long out from one wall and I won't be affected provided that wall constitutes less than 25% of the envelope? Is there no consideration of the finished house after renovation?

If the link is less than 25% the surface area of the existing house, then that section of part L does not apply.

You have to remember, it's called the "major renovation" section, not the extension section.
The whole reason for the regs is to encourage people to take a holistic approach to renovating, and not just focus on one aspect.

Extensions still have to comply with the applicable regs regardless

sydthebeat

Calahonda52 wrote: »

I have seen it in 3 LA's, we do some NZEB training and when you ask whats the 25% ...many planners think its floor area

That's very disappointing

BryanF

Calahonda52 wrote: »

I have seen it in 3 LA's, we do some NZEB training and when you ask whats the 25% ...many planners think its floor area

Not clear what understanding of Part L a planner needs. but given how most things they deal with are based on m2. I can see why they’d assume m2