Let people build up to go green

How to insulate old homes without spending billions

Britain’s housing stock is the oldest in Europe. In fact, just under two-fifths of all homes in Britain were built before WW2 and, of those, more than half were built before WW1.

Old homes tend to be more expensive to heat up and keep warm. According to the Office for National Statistics, a building’s age is the single biggest factor in how energy efficient it is. This is a problem because heat pumps, probably the best solution we have to decarbonising home heating, work best when a home is well insulated.

Older buildings aren’t just less energy efficient, they’re harder to make more efficient too. 

In part, regulation deserves some blame. The older your property is, the less freedom you have to make changes to it. In some ways this is a good thing, older buildings are easier on the eye than new builds and nobody wants to see our heritage damaged, but there’s a drawback. 

When energy prices spike, homeowners respond by making their home more energy efficient. They get their walls and loft insulated, swap out single-glazed windows, and may even trade their boiler for a heat pump (or simply a more efficient boiler). A study by Hilber, Palmer, and Pinchbeck found people who own homes that are either Listed or in Conservation Areas are much less likely to respond in the same way.

The problem is historic preservation protections rule out cheap forms of insulation such as PVC double glazing. And even more expensive upgrades can get blocked. 

The impact is huge. Warwick University’s Thiemo Fetzer compared the energy consumption of homes inside conservation areas with similar properties just outside. He estimates that planning restrictions in Conservation Areas are responsible for up to 3.2mn tonnes of excess domestic CO₂ emissions. 

It is still possible to upgrade your property’s energy efficiency in a Conservation Area, but the rules are often unclear and disproportionate.

Islington council recently published a guide on how to improve the energy efficiency of your property if it is in a Conservation Area. There was just one problem: the house they used to illustrate the piece was refused planning permission to add slimline double glazed windows.

Even when historic preservation rules don’t explicitly ban an upgrade, they still can add an uncertain and often-expensive layer of bureaucracy. Sometimes national guidance from Historic England can say one thing and local conservation officers can say another.

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But, red tape isn’t the only barrier to retrofitting an older property to be more energy efficient. Older buildings, particularly those built before the 20s, are more likely to have solid (rather than cavity) walls and solid walls are more expensive to insulate. The Energy Saving Trust estimates that it’ll cost around £7,500 to insulate a three-bedroom semi with solid walls compared to £2,700 for one with cavity walls. 

Before any insulation work can take place, damp needs to be addressed. Some older properties, particularly early Victorian properties, have big issues with damp. Others, particularly Georgian homes, beat back damp by being extremely breathable. Attempts to make Georgian properties more ‘air-tight’ through insulation can trap in damp as a result. Navigating all of this requires specialist help and that doesn’t come cheap.

Insulating solid walls also means sacrificing space too – a non-trivial consideration in some parts of London where a square metre of floor space can be worth more than £10,000.

Updating an older-home in a sympathetic way is more expensive too. Wooden and aluminium double-glazed windows cost more than the uPVC alternative.

Some people retrofit their property out of a desire to go green and are willing to bear a large upfront cost, but for most people retrofits are about saving money sooner rather than later. 

Solid wall insulation pays off in the long-run, but using the Energy Saving Trust’s estimate of a £380 annual saving, it’ll take almost 20 years. Cavity wall insulation on the other hand pays off in less than a decade. And this is assuming that people can afford to pay upfront and don’t also have to take into account interest payments on a loan.

How do we make retrofitting more attractive?

To start with we need to remove the pointless red tape. Historic preservation shouldn’t be a barrier to making thoughtful energy efficiency improvements. Councils should listen to campaigners like Green Conservation and update planning rules to give people the freedom to sensitively retrofit their homes even if they are in a Conservation Areas or their property is Listed.

But we need to address cost too. Grants are the obvious solution. Yet, past schemes designed to subsidise energy efficiency haven’t had high levels of uptake. The Green Homes Grant, for example, was criticised for being too complicated and failing to hit its targets. The new Great British Insulation Scheme (GBIS) will hopefully fare better.

One problem with grants is that public money is scarce so schemes like GBIS focus on lower-cost easy wins like loft insulation. It’s not clear there’s a public appetite to fund deeper (and more expensive) retrofits on valuable older properties. As the recent somewhat-contested Treasury costing of Labour’s insulation plan showed, including these properties can dramatically increase the costs of any scheme. 

Here’s a better approach

Build up to go green

In large parts of Britain, there’s an extreme housing shortage caused by planning restrictions. In fact, the shortage is so extreme in places like London and Cambridge that houses sell for four times what they cost to build. When planning permission for houses is granted on agricultural land, its value shoots up. In some cases, it can become more than 100 times as valuable.

The freedom to add an extra floor (or two) is similarly extremely valuable. In fact, if you owned a two storey Victorian terraced house in Islington adding an extra floor could add over £300,000 to your home’s value netting you a substantial profit at current build costs. It’d leave more than enough left over to fund an extremely ambitious retrofit.

Why not let residents build up an extra-floor on the condition that they improve their properties' energy efficiency at the same time?

In other countries, similar schemes have been used to incentivise expensive upgrades designed to address fire and earthquake safety.

Take Israel’s TAMA 38 policy, which was designed to make it easier and more attractive to reinforce old apartment blocks in the wake of a deadly earthquake in Northern Turkey. Age is not just the biggest predictor of a building’s energy efficiency, it also predicts how safe it is. As a recent Works in Progress article notes:

“The modern Israeli standard for earthquake-proof construction only became mandatory in 1980, and shoddy buildings built before it came into force were and are common across Israeli cities, today making up about 30 percent of the total housing stock.”

To improve the safety of Israel’s housing stock, TAMA-38 enabled flat owners to vote to knock down and redevelop their apartment block to make it earthquake proof. Developers would take on the cost of funding their building safety upgrade in return for being able to sell the new units. While residents benefitted from new more spacious apartments. The policy was responsible for around a ⅓ of all new homes built in Israel. In Tel Aviv, where housing demand is highest, TAMA 38 along with its precursor Pinui Binui, is delivering more than half of all new homes.

Source: Works in Progress magazine

A version of this approach is already being applied in the Borough of Kensington and Chelsea. They are using a Local Development Order (LDO) to allow a row of houses in a Conservation Area to add an extra mansard floor. As floorspace in Kensington and Chelsea (£10,000 per square metre) is more expensive than almost anywhere else in the country, the borough is able to insist that all new mansards include solar panels.

Kensington and Chelsea’s approach is bespoke and targeted. The mansards, for instance, must be built simultaneously and it only applies to one street.

It’s a good start, but we can and should go further. Let’s empower homeowners and allow single-storey extensions on older buildings when they meet the following conditions:

1. The new floor is in keeping with the building’s original design;

2. When completed the building is substantially more energy efficient.

Not only would this ensure that every upgrade pays off (and then some), it’d also make it easier to access bank finance as homeowners could borrow against the property value increase.

Upgrading Britain’s older properties is set to be one of the hardest (and most expensive) bits of getting to Net Zero, but it doesn’t have to be. In places like London, Cambridge, and Oxford, a new freedom to build up if you retrofit your property would give homeowners a powerful incentive to go green.