The new NPPF, which came into effect on 17 August 2026, tells planning authorities to give significant weight to improving the energy efficiency of existing buildings, including measures such as heat pumps and solar panels. But it also says that heritage policies still apply.

So there's a balance to strike. Not a blank cheque.

The important thing to understand, though, is that listed doesn't mean impossible.

I say this to clients all the time: many things are possible in a listed building. You've just got to get them right so you can articulate the argument for them.

That starts with understanding the building. What is significant about it? What are you actually proposing to change? What effect will that change have? And can you demonstrate that the benefits justify the impact?

That's where net zero for heritage buildings gets interesting.

On paper, existing buildings should be an obvious part of the solution. The building is already here. The carbon used to construct it has already been spent. We don't need to demolish it and start again.

But getting an old building to perform better isn't simply a matter of choosing a heat pump, adding insulation and putting solar panels on the roof.

There are a whole series of things that can catch you out if you don't understand them early enough.

Here are the five biggest to capture at the start of a project so they don’t become blockers further down the line.

01 UNDERSTANDING WHAT CONSENT IS NEEDED

You've decided to put solar panels on the stable block or the old workshop. It's not listed itself, so it should fall under permitted development, right?

Not necessarily.

If that building sits within the curtilage of a listed building, the permitted development rights that would normally apply may not be available. You may need planning permission and, depending on the circumstances, listed building consent too.

Curtilage is the land and buildings that have a functional and historical relationship with the listed building. A stable block that has always belonged to the main house can be part of that listing relationship even if it isn't listed in its own right.

The important point isn't that the rules are deliberately difficult. It's that the planning context needs to be understood before the net zero proposal becomes a fixed design.

A sustainability strategy might quite reasonably identify the stable block as a good place for solar panels. But if nobody has checked the planning and heritage implications, you've potentially built your programme around an assumption that isn't going to hold.

And that is exactly the sort of thing that is much easier to deal with at the beginning than halfway through the project.

02 FIND OUT WHAT THE BUILDING IS ACTUALLY MADE OF

Retrofit design relies on understanding how the existing building performs.

The problem is that you can't always tell how a building is constructed just by looking at it.

What looks like a solid wall might be timber frame with brick infill. It might be solid brick with lime mortar, or masonry that has been altered and repointed in cement. Different constructions behave differently, particularly when you start changing how heat and moisture move through them.

This matters when you're deciding how and where to insulate, what materials to use, and how the building is going to work with a new heating system.

You can't make the right decision about an existing building based on an assumption about what's behind the plaster.

Sometimes that means opening things up, taking samples or carrying out more detailed investigation. The point isn't to investigate everything for the sake of it. It's to find out the things you actually need to know before you commit to a design.

The better you understand the building, the better you can make the case for changing it.

03 UNDERSTANDING THE TRUE COSTS

You've worked out what you want to install and got a price for it. Surely that's the budget?

Not necessarily.

Renewable energy installations can benefit from zero-rated VAT, but the associated work needed to make a building work efficiently isn't necessarily treated in the same way.

If you're installing a heat pump, for example, you may also be looking at improvements to the building fabric, alterations to services, electrical work and other changes needed to make the system work properly.

There are circumstances in which some retrofit work can qualify for reduced VAT, but the rules are specific and can depend on the building and the work being carried out.

This isn't an area where I'd pretend to be an accountant. It is, however, an area where the question needs to be asked early.

The point is not to become an expert in every VAT rule. It's to make sure the right questions are being asked before you've fixed the scope, budget and programme.

Retrofit works best when the different pieces of the project are understood together, rather than one at a time.

04 KNOW WHAT ELSE YOU’RE LIKELY TO DISTURB

The moment you start opening up an old building, you're potentially disturbing more than just the building fabric.

There might be bats in the roof void. Nesting birds. Archaeology. Hidden drains. Asbestos. Historic fabric that nobody realised was there.

None of these things necessarily stops a project.

But discovering them after the programme has been fixed, the planning submitted, the contractor appointed and the funding agreed is a very different proposition from knowing they might need to be considered at the outset.

This is where early investigation really earns its keep.

You can't know everything an old building is going to reveal before you start work. But you can identify the things that are reasonably foreseeable, get the right surveys or advice, and build some flexibility into the project.

Again, it's not about finding reasons not to do something.

It's about understanding the constraints well enough to work out what you can do, and how to programme in the time to find out.

05 THE CASE FOR KEEPING THE BUILDING

This is the bit that can get lost when all the individual difficulties start piling up.

Yes, listed-building retrofit is complicated.

There are planning implications. Building physics. Ecology. Cost. Consent. And usually several other things that weren't on the original spreadsheet.

But complexity isn't the same thing as impossibility.

The building is already here. Its structure, materials and embodied carbon are already here too.

The question isn't whether we can make an old building behave exactly like a brand-new one. It's whether we can make it perform significantly better while understanding and respecting what is already there.

And that's where I come back to the thing I say to clients:

Many things are possible in a listed building. You've just got to get them right so you can articulate the argument for them.

For a listed building, that means understanding its significance, understanding how it works, understanding the impact of what you're proposing, and then putting a convincing case together.

You're not trying to retrofit a listed building despite its heritage.

Done properly, you're working out how to make the building perform better because you understand it well enough to change it intelligently.

START WITH THE BUILDING, NOT THE TECHNOLOGY

The temptation with net zero is to start with the technology: solar panels, heat pumps, insulation, new windows.

For a historic building, I think it's better to start somewhere else.

Start with the building.

Understand what you've got, what matters about it, how it works, what has already been changed and what the planning and heritage constraints actually mean.

Then you can start asking what improvements are possible, and how to make the case for them.

The earlier you do that, the more options you have.

If you're responsible for a listed or historic building and are starting to think about retrofit or a net zero strategy, that's exactly the sort of conversation I'm happy to have at the beginning of a project.

Historic buildings have always adapted to meet the needs of the day. This is just the latest challenge they're being asked to meet.