Net zero: should you care? | C-Link

Net zero: should you care?

by Kristina Smith

The Government’s commitments to cutting carbon emissions will start to impact on new housing soon

Back in October 2019, the Government launched a consultation into its Future Homes Standard, aimed to make new-build homes highly energy efficient, with low carbon heating from 2025. The standard is part of the plan to meet the UK’s carbon reduction commitments.

As a stepping-stone to the Future Homes Standard, the Government is proposing changes to Part L of the Building Regulations, which deals with energy efficiency, as well as Part F, which covers ventilation. The consultation on the standard and the changes to the Building Regs closed in February this year and we were expecting a response in Autumn 2020. Since it’s already November, perhaps the end of the year is a more reasonable deadline now.

The proposed changes to Part L could be significant, involving much higher insulation levels and new technologies for heating and heat recovery. But there’s no way of knowing exactly what these changes will be; responses to the consultation were many and varied, with some suggesting that the changes didn’t go far enough and others arguing the opposite case.

What is net zero?

Nationally, net zero means reducing the greenhouse gases we produce – dominated by Carbon Dioxide – to zero by a combination of measures. First by reducing emissions and second by doing things to remove the greenhouse gases (like planting more trees and developing carbon capture technologies). Hence, ‘net’ zero.

The UK has committed to achieving net zero as a country by 2050. According to the Climate Change Committee (CCC), an independent public body that advises the Government, energy use in homes accounts for 20% of UK greenhouse gas emissions; reducing that would make a big dent on the targets.

Net zero can also apply to single buildings or developments. The UK Green Building Council (UKGBC) has come up with some definitions of what that means. UKGBC splits emissions up into the construction stage – from manufacture of a building’s elements to practical completion – and the operational phase.

For net zero carbon during construction, says UKGBC, you would have to balance the carbon generated by product manufacture, transport and installation with offsets (paying towards projects that reduce greenhouse gas emissions) or exporting on-site renewable energy. Operational net zero would mean a building with zero or negative energy use each year, using on-site or off-site renewables, combined with high energy efficiency and offsetting if needed.

Since the operational energy used by buildings is falling, thanks to better insulation and lower carbon energy sources, we are seeing more interest in the construction phase carbon, which is sometimes called upfront carbon or capital carbon. (Others use the term embodied carbon, but technically this includes all the carbon spent on a material throughout its lifetime; during maintenance and demolition as well as manufacture and assembly).

By far the largest proportion of upfront carbon comes during the manufacturing phase. Concrete is the real killer, as it produces carbon when its elements are heated up and in the chemical process itself. Steel is also a big hitter, since most of it is made by energy from coal – although it is easier to see how that will change over time with non-fossil fuel energy sources.

Changes to Part L

In its consultation on changes to the Part L of the Building Regs, the Government proposed two different approaches to increasing the energy efficiency of new homes.

The first option would involve very high fabric standards such as triple glazing and would give around 20% reduction in carbon emissions compared to the current standard. The second option – preferred by the Government – would allow a combination of measures and would likely see the introduction of low-carbon heating such as air-source heat pumps or district heating systems, leading to a 31% reduction in emissions. (These targets are for England only; Wales is looking at different targets of 37% or 56%, with the lower target preferred.)

Both the options outlined in the consultation suggest that wastewater heat recovery systems would become standard. These are heat exchangers that extract heat from shower or bath water that is heading down the drain.

Though higher levels of insulation, low-carbon heating and wastewater heat recovery will mean lower bills for occupants, they will inevitably mean higher build costs. The CCC estimates that it would cost an additional £4,800 per home to include an air source heat pump and ultra-high level of fabric efficiency. However, it makes the point that it’s best to do that now rather than retrofit – which would cost a whopping £26,300 per home.

One of the criticisms raised during the consultation period is that the second option could lead to homes being built with lower insulation values than today. Rather than raising the bar for the U-values of roofs, walls, windows and the like, the proposal is to use a new metric, Primary Energy, for the calculations. So, developers could use lots of renewables that will lower U-value building fabric to get the right answer. Organisations like the CCC are concerned that building less well insulated houses could lead to higher energy bills down the line and potentially more fuel poverty.

What are the big builders doing?

Some of the major housebuilders have already taken action to change the way they build houses. There was a flurry of activity in 2019, as housebuilders and housing associations rushed to set up timber frame operations. Countryside Properties set up a new timber frame plant in Warrington and will open a second in Leicestershire; L&Q made a deal with Stewart Milne; Barratt bought Oregon Timber Frame in Scotland.

One of the benefits of working with offsite-manufactured panels is that they make it easier to ramp up energy efficiency. One of the big pluses is improved airtightness – as long as assembly and tolerances are tightly overseen on site. Offsite manufacture also reduces waste, which in turn reduces the carbon footprint of construction activities as well as the ever-increasing costs of waste disposal.

Some housebuilders are already committing to more demanding carbon reduction targets. Barratt has pledged to deliver all homes to a net zero standard by 2030 and to reduce its greenhouse gas emissions from its own operations to net zero by 2040. For a publicly listed company, this is probably a very sensible move: the appetite from investors for companies with good environmental and social governance (ESG) is burgeoning. (And the opposite is true for companies such as Shell and BP, which are seen as environment harmers).

It may not make sense for smaller housebuilders to make dramatic commitments like those from Barratt, but it certainly does make sense to start looking at how to achieve better energy efficiency standards now.

Changes may come faster than expected because the transition period from the old Part L rules to the new ones may not be as generous as in the past. Currently there is a lot of leeway, which means that some houses are built years after planning permission has been granted to older standards. This ‘loophole’ is likely to be removed so that homes must be built after a ‘reasonable’ period.

About Kristina Smith

Kristina Smith is a writer and editor with a passion for construction, and a career that began - rather a long time ago – on site, as an engineer.

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