If we are serious about net zero, don’t fudge future homes standard


The Future Homes Standard and Part L consultation offers government the chance to show it is serious about decarbonising buildings and heat. Its response will be telling, suggests the Ground Source Heat Pump Association’s Bean Beanland.

The outcome of the Future Homes Standard and Part L consultation is likely to have significant mechanical services and architectural implications, if the principal recommendations are accepted.

As one would expect, with the rise of Extinction Rebellion and the Greta and Attenborough effects, emissions reduction is front and centre and there are obvious implications for insulation and U-values. Whilst stopping some way short of the 100% PassivHaus approach for all new dwellings, as advocated by Lord Deben, significant energy and emissions reductions will be called for, with an expectation that a home built to the Future Homes Standard should produce 75-80% less CO2 emissions than one built to current Regulations. Implementation will be phased with the consultation seeking views on a reduction in CO2 emissions for 2020 of 20% or 31%. If we are serious about Net Zero 2050, 31% must be selected, anything less merely postpones the problem and leaves even more houses that will need to be expensively retrofitted before 2050. A terrible legacy for tomorrow’s new home owners.

A further fundamental question relates to whether CO2 should be the principal performance metric. One option is to migrate to measuring primary energy instead. Given that CO2 is the target of Net Zero, this should remain the principal measure. Primary energy could be a secondary assessment point, although there is an argument for measuring operational affordability instead. Household annual energy costs have most meaning for the homeowner.

Amongst the practical changes proposed is the move to limit the heating system flow temperature. The consultation seeks views on limiting the heating flow temperature to a maximum of 55°C. This would have the benefit of ensuring that fossil fuel boilers do operate in condensing mode. Many argue for 50°C, or even 45°C, to align with most under floor heating system specifications and, the lower the temperature, the more efficient any heat pump system would be. The implication for architects and mechanical contractors is one of radiator sizing. Accurate assessment of the room heat losses will be necessary (and are likely to be mandated for eventually) and this will drive radiator sizing. It will no longer be acceptable to measure the width of the window and use that to size the emitter!

Cylinders could be back in fashion; hot water storage to displace inefficient combi-boilers, thermal storage to provide for heat pump operational load-shifting. Both require space, although pushing plant out into garages, if adjacent to the dwelling, is one option. Alternatives include a greater use of heat networks. These have the potential to be space saving in the home, but are not without their challenges, especially potential monopolistic supply.

Giving developers extended periods before new versions of Building Regulations have to be applied is increasingly unacceptable. Land-banking and “starting” a development to freeze the version of Building Regulations that applies runs the risk of mis-selling to house buyers. The house might look new and they may be the first owners, but if it is built to previous (or even earlier) versions of Building Regulations, is this fair, if not made clear. It is proposed that the applicable version of Part L should be shown on the EPC. This would need to have a detailed explanatory note for the home buyer, but would act as a health warning – this house will require costly retrofit activity in order to meet the requirements of Net Zero 2050.

More controversial is the proposal to remove the rights of local planning authorities to impose additional carbon or energy efficiency standards. Whilst “standardising” planning, it ignores the fact that many LPAs have declared climate emergencies and are moving much faster than central government in reducing emissions.

All those interested in preparing for a Net Zero future must respond, even if only on the specific questions pertinent to their own skill, experience or role in the industry.

Carbon factors: Time for a smarter approach

A crucial part of the consultation covers carbon factors. The outcome will have a significant influence on technology choices going forward.

The GridWatch app on the GSHPA website demonstrates very clearly the importance of the carbon factor for grid electricity in the carbon emissions reduction debate.

In the screenshot above, the grid was operating at a carbon factor of 242gCO2/kWh at 5.30pm on Tuesday 4th February. The table shows the relative emissions from several heat generating technologies based on this figure. Direct electric heating would emit at 242gCO2/kWh of heat generated (in reality the figure would be slightly higher because efficiency isn’t 100%). The two figures to concentrate on are those for a natural gas boiler, at 215gCO2/kWh (based on 85% efficiency) and for a ground source heat pump operating at a very modest Seasonal Performance Factor of 3.2, at 76gCO2/kWh of heat. This is a reduction of 139gCO2/kWh or 65%. As the grid continues to decarbonise, the carbon performance of the heat pump just gets better and better.

In the current iteration of Building Regulations, the carbon factor attributed to grid electricity is 519gCO2/kWh. This dates from 2012 and clearly this no longer represents reality. This figure effectively over-rewards solar PV and CHP electrical generation (assuming that it displaces grid electricity at 519gCO2/kWh) and penalises heat pumps by computing in a carbon factor of 162gCO2/kWh. This is more than twice the figure that the same heat pump is actually operating at today.

The heat pump sector has been asking for the carbon factors to be updated in SAP and Building Regulations for years. The impact of failing to do so has been increasing years on year. For companies falling under the CRC reporting mechanism, DEFRA release an annual update to the carbon factor for grid electricity (currently 256gCO2/kWh). Similarly, if borrowing funds through SALIX (part funded by BEIS), the carbon factors are updated every year. SAP and Building Regulations are the only areas of significant government legislation where annual updating does not occur.

The consultation includes a proposal to select a figure for the carbon factor for grid electricity based on assumptions from BEIS on future continuing decarbonisation. This would favour heat pump technology now, but is obviously open to challenge.

Surely an annual update would be much more reflective of reality and can be delivered with ease.

Bean Beanland is chairman of the Ground Source Heat Pump Association and an associate of the Royal College of Science.

Related stories:

Net zero: How to decarbonise heat?

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