Renovation is being revolutionised

I come from a generation of dedicated doer-uppers. Relentless climbers of the housing ladder, we spent years sitting on orange boxes, downing baked bean dinners while constantly looking for another barely habitable wreck to buy, renovate and sell on to finance the next project.

To be honest, we only managed it twice before discovering self build. But I know one family who spent a decade renovating and moving every two years in order to eliminate their mortgage.

Rising house prices, falling incomes and mountainous stamp duties have stripped the rungs from that particular housing ladder. Today, renovations are more common among existing homeowners who can no longer afford to move. But they are still popular among those who prefer a period home or who find renovation the only way of moving to a chosen location where building plots are unavailable.

Gone, however, are the days when costs could be saved by DIY electrics and central heating. Legally only suitably qualified professionals can fit a gas boiler or carry out most electrical upgrades. But the biggest change is in energy efficiency.

Until recently this would mainly involve draughtproofing, laying insulation on the attic floor and between the joists of suspended ground floors – all DIY-able. Meanwhile professionals would inject insulation into empty cavity walls, fit double-glazed replacement windows and install an energy-efficient new condensing boiler. These, of course, are all still valid, but today’s building regulations are more stringent – at least in principle.

Broadly speaking, if more than 25 per cent of the surface of the building envelope – ie the whole outer shell of the house – is renovated, any floor, wall or roof which doesn’t meet certain insulation values must be upgraded. The measure used is a U-value – the lower the figure, the more effective the insulation. So, for example, a floor that doesn’t meet a minimum U-value of 0.70 must be upgraded to at least 0.25. Upgrading must also occur if more than 50 per cent of any floor, wall or roof is renovated.

But there’s a significant let-out. If meeting the regulations isn’t technically possible, or payback isn’t cost-effective within 15 years or less, then simply do the best you can.

Since you will almost certainly need to hire a professional to make these calculations, could you save money by simply ignoring the regulations?

Well, the work still has to be approved by Building Control – mainly for your own safety, but also to ensure you have a completion certificate demonstrating approval. Future buyers, or their lenders, are likely to insist upon it.

The question then is: how far do you want your upgrade to go? The key word here is ‘retrofit’ or, for the seriously eco-minded, ‘deep retrofit’.

Passivhaus

Retrofitting involves improving the energy efficiency of an existing house to as close as economically viable to current Building Regulations for new builds. Deep retrofit goes much further – typically as close as possible to the current ‘gold standard’ for energy-efficient homes, the German Passivhaus system.

A passive house is so well-insulated and airtight mechanical ventilation and heat recovery are needed to refresh the air regularly and keep the house at a constant temperature. The energy savings are substantial – around six times less than that used by a typical house built to current Building Regulations. But for most Passivhaus homeowners the biggest plus is the unrivalled level of comfort.

EnerPHit is the Passivhaus standard for renovations. Less stringent, it still promises energy savings of between 70 and 90 per cent. So why aren’t all renovators using it?

Well, Passivhaus requires levels of expertise and detailed workmanship which aren’t exactly widespread in UK construction. Deep retrofits, by their nature, are also highly bespoke, and therefore costly – sometimes too costly to be economic.

But that shouldn’t last. To meet the government’s climate change and energy efficiency commitments, huge numbers of Britain’s existing houses will need to be retrofitted over the next 30 years. For now most in the UK are taking place in social housing where low heating bills, low maintenance and a healthy internal atmosphere are regarded as long-term investments.

One example is in Nottingham, where 10 local authority homes were upgraded in 2017 using a radical new approach to retrofit from Holland.

Known as Energiesprong – Dutch for ‘energy leap’ – it aims to industrialise retrofit, producing a customisable system which can guarantee energy savings and indoor climate performance for 30 years. The cost is paid for by consequent savings in energy bills, maintenance and repairs, which, because they are guaranteed, provide collateral for low-interest loans.

Each of the Nottingham homes was first laser-scanned externally in order to prefabricate precisely sized, storey-high insulation panels. These were then fitted to the outside walls, together with new windows, doors and insulated roofs, complete with photovoltaic panels. Solar thermal panels, heat pumps and electric panel heaters replaced existing gas heating and hot water systems.

The system not only made the retrofitting easier, it minimised installation times. Work began in November 2017 and was finished by Christmas. The inhabitants didn’t even need to move out.

The result is warm, draught-free, healthy homes, which produce more energy through their PV panels than they actually use. They have also, according to Energiesprong UK’s Ian Hutchcroft, increased in value by 25 per cent.

The Nottingham retrofits cost just over £75,000 each, but economies of scale are intended to cut costs dramatically, starting with another 41 properties in the UK. Currently Energiesprong is targeting local authority or housing association dwellings for the volumes and also for designs which tend to be both standardised and fairly simple, easing prefabrication.

Whether the system will be able to cope with Britain’s vast number of period houses, especially with planning departments insisting that existing facades remain unchanged, is another question. But Energiesprong, or something similar, looks very much like the best, most cost-effective answer to date.

May 2019