The Future Homes Standard spells out the proposed changes for the future of UK housing for two intervals with specific deadlines, 2025 and 2050. For decades, the UK Government has lagged behind mainland Europe in terms of housing standards and thermal efficiency; I personally chalk this up to cheap fuel prices, and a maritime climate. But with housing shortages and fuel poverty issues really hurting people, it makes absolute sense to address climate change and make homes more efficient. Aiming for net-zero in 2050 really is one of the most ambitious legal carbon reduction targets in the world. I wish there were football songs about this.
When it comes to the housing sector specifically, there are two step-changes to get to the 2050 net-zero: 2020 (31% reduction in carbon emissions) and 2025 (80% reduction). As part of this effort, Part L will be updated at the beginning of 2020, and will come into force later that same year.
The government is trying its hardest to push the carbon targets as far as the industry will allow, in preparation for the Future Homes Standard in 2025.
To that end, the ‘options’ for 2020 are:
Because fabric can only take you so far, the additional carbon saved from the extra bits of M&E kit [RJ1] probably make more sense. Insulation, fabric performance and air tightness were historically so critical in the UK to reducing space heating demand because, historically, space heating (and associated losses) was the single largest factor in regulated energy consumption. Now that the current and soon-to-be-improved fabric standards have become so much better, effort should be directed instead towards reducing water heating demand, and looking at unregulated electricity consumption.
Mandating a particular technology is always tricky. The government can’t be seen to be effectively mandating certain technologies over others, and there needs to be wiggle room to allow new solutions to be developed to meet the ultimate goals. However, by setting such stringent targets, they are effectively doing this. There ARE only a few specific ways to heat a space, or volume of water, carbon-free. So it makes sense for them to state explicitly that they are preparing the industry for a heat pump solution, powered by carbon-low/neutral grid. The 31% carbon emission ‘option 2’, however, clearly still allows for gas boilers and other solutions to be used, but the homes will need to generate more electricity to offset that choice of gas boiler and lower fabric standards.
Falling carbon emissions coupled with lower PV install costs are putting serious economic pressure on fossil fuel technology, but the price/kWh of heat generated by oil and gas is still very low. If gas is roughly 2.5p/kWh, and electricity is still 12.5p/kWh, it’s not just familiarity that keeps gas as the standard in the UK. If we do a bit of simple maths : gas at 90% efficient = 2.7p/kWh. A heat pump at 300% efficient, with PV accounting for about 50% of the kWh on an annual basis, so 450%, also = 2.7p/kWh.
However, the install cost of the heat pump + PV will be considerably higher than a gas boiler, even if the system can run at that efficiency. For the 2025 target, both options still model gas boilers as standard.
Aside from carbon performance changes, the government propose the removal of the fabric energy efficiency metric, or FEE. FEEs have been around since 2010 SAP, and we’d normally expect just a tightening of the metric as we’ve seen in the past, not a complete removal.
They plan to replace it with the following: a primary energy target, and an affordability metric, which I think is very neat. On-site renewable energy technology will be much more powerful in the equations, even as the grid carbon is coming down (which would have the opposite effect). This paradigm shift toward decentralized energy is inherently more efficient then central plant solutions, assuming the energy distribution losses are higher than the inefficiencies seen at low scale. The reality is, on-site small PV systems will be much more cost-effective as their ongoing running costs are zero, and their carbon factors are so low, even when the primary energy is still grid electricity.
The primary energy numbers will mean that the PV that should be apportioned per dwelling should offset grid consumption as much as possible, but then any exported excess kWh/year generated from PV will be penalized in both cost and primary energy. It will be interesting to see the numbers play out in the expectant software programmes as they become available, and more accurate.
An affordability metric has been added because the carbon on the grid has decreased so much in the last few years. The carbon factors and associated costs have been relatively stable, until this proposal now. Look at the SAP table 12 assumed comparison, below:
Look at the figure highlighted in red. The carbon factor on the grid is actually lower than the gas figure by a wide margin! Goodbye gas boilers!
SAP 10.0 – which never got enacted – had the electricity carbon factor at 0.233, which was still slightly higher than gas. This is a clear sign to the industry that electrical heat is now seen as the future. Whether or not that’s true, adopting these SAP figures will drive the industry, which is perhaps the goal. But because heat pumps are still a relatively expensive and bulky piece of kit in comparison to direct-acting heaters or gas boilers, builders have been trying to push electric direct-acting panel heaters to meet their carbon targets. The affordability metric is, I think, intended to compensate for this created issue. The builders will have to look at ongoing running costs of the regulated energy consumption in the dwelling in question. This will hit at the heart of fuel poverty in new-build homes, and not just leave the electrical bill to the residents.
Last, but not least, for 2020 metrics is minimum fabric standards. It seems the government are going to take the Welsh approach to U-value standard. (It will be interesting to see how the Welsh industry deal with this section, considering their Wall and Roof U-values are even better than what’s being proposed.) I feel this approach is overdue. The minimum standard approach is so much simpler than the DFEE/TFEE [RJ2] . Also, it’s simpler for builders and designers, as they know exactly what values they have to meet every time, for every element – rather than working in an unhelpful grey area where they have to compensate on a different part of the building for this house type, but not that house type, and so on.
The last two big changes coming in 2020 are around building services, which will be tightened up. Starting with gas boilers: a well-performing system/combi boiler at ErP 92% will remove the ~5% carbon gain boilers add. Therefore, that carbon saved from a more efficient boiler will need to be found elsewhere. The background numbers are going to make that high-performing boiler standard, and most lesser boilers won’t be able to compete in the marketplace. Furthermore, the only way to keep the water heating demand down is by specifying a waste water heat recovery system. This equipment works by making the boiler draw less gas, and will become the assumed standard. Beside the gas boiler, the performance estimates of heat pumps, air conditioning, and lights have all been tightened.
The second big change is to the system temperatures at which the spacing heating can flow. Historically this means small, hot radiators at + 55˚C. They are proposing to make the design temperature lower, which will make the heat pumps run more efficiently. The trade-off is that the radiators will need to be larger, or have under-floor heating installed as well, to get the same heat output. Of course, as the fabric standards are tightened, the space heating loads are also decreasing, so the effect of this is still unknown. Perhaps people will get used to having a slightly cooler radiator on for longer, instead of putting the boiler on and feeling the heat immediately.
I’m not a Part F specialist so this will be brief, but the direction suggests that the government will make the document easier to understand and calculate. Instead of ‘systems’ they will only have designs, based on how air-tight the respective buildings are. There will also be a requirement for systems to be designed and installed/commissioned as intended, because at the moment it appears that the application of the installed ventilation systems is a little haphazard.
Fans have always been trickier to regulate, as factors such as the installation and how many turns the duct makes can significantly affect the energy consumed, the flow rate of the air being extracted, and the noise emitted. The proposals look to address some of these installed issues, which is welcome.
The new guidelines will also remove passive stacks as ventilation systems. A designer will need to use an active extract only (intermittent, MEV) with X amount of background ventilation/room, or else use input and extract of air (MVHR), which will make extra background ventilation unnecessary.
Air testing will change as sample testing is removed. Most of our clients test every unit anyway, but those that don’t will now have to. Sample testing had the potential to be convoluted, so this change should streamline the process.
Finally, there will be a requirement for every unit to have time-stamped, GPS-located photos proving that the buildings have been built in accordance with the design. This will prove interesting in practice, as the people on site will need to systematically take photos of each unit at varying stages of its construction. It may therefore take some education and procedural changes on site. The large builders should have the resources to cope with the change, but the small-to-medium companies may have to put in a disproportionate amount of effort for the extra paper work. However, the change should help allay the fears of consumers in the industry worried about poor build quality, which can only be a good thing.