Thursday, 2 July 2020

The future of home building

By the end of 2020, we will witness the first meaningful steps towards achieving net zero emissions. With energy usage in homes contributing to over one quarter of carbon dioxide emissions, it’s necessary that change is made in the housing sector, not only to benefit our planet but the end user.


So what is changing in Part L and F of Building regs?

England and Wales are set to publish the revised approved documents part L & F later this year which set out the standards for energy performance and ventilation in dwellings.

The reason for this is to prepare the construction industry for an even larger leap forward in 2025. We’ll see the likes of passivhaus standard wall, floor & roof make-ups, conjoined with the scrappage of gas heating and surge in heat pumps & electric boilers usage.

A change of performance metrics...

The current Performance Metric Part L models itself around is the ‘Target Emission Rate’. Setting the amount of CO produced per m² the property cannot exceed. The target emission rate is influenced by a notional dwelling of the same size, shape and ‘living area fraction’ which reaches compliance. There are five different space heating packages pre-calculated from gas to biomass, all with selected u-values and heating controls.

The first change is a new performance metric called ‘Primary Energy Factor’. ‘Target Emission Rate’ will become a secondary metric.

The consultation has seen two proposals for a reduction in Carbon emissions. They’re 20% or 31% improvements, unlike Wales who are leading the parade with reductions of either 37% or 56%. Why is it that Wales have set highly ambitious targets and we haven’t?

The primary energy factor gives a more accurate overall energy usage from baseline to end use. It’s created for each fuel type based on the Excavation, Processing, transformation and Transportation of the fuel in mind.

Also, when the overall energy demand is worked out, energy generated by renewable technologies can be subtracted from overall demand.

What is thermal bridging?

It has never been more important to both consider and understand the value of thermal bridging. Accredited construction details have been a lifeline for many a building project giving better psi values and enabling compliance. The shock will come next year when either default or independently assessed values will be required. Have you got a plan in place for this?

A thermal bridge is when heat is lost over a given length of a structure. A thermal bridge (cold bridge) occurs either when a more conductive material penetrates the fabric build-up, or when the insulated envelope doesn’t continuously join to the adjacent wall, floor, roof or window junction. Thermal bridging is measured as a Psi-value (ψ-value), and calculated over a metre length. This is not to be confused with a U-Value which calculates the heat loss over a square metre.

The removal of the Fabric Energy Efficiency Standard...

Fabric Energy Efficiency Standard came into use in 2014. It outlines the minimum energy performance required for a new dwelling. To keep the ‘simplicity’ of SAP they are opting to remove this metric. As a result, fabric performance will only be dictated by the back-stop U-values:

Heat loss elements

Current England ADL1A

Current Welsh ADL1A

England 2020 proposed

Wales 2020 proposed






External walls





(flats 0.21W/m²K)

Flat and pitched roofs





New regulations are proposing lower U-values build-ups with the removal of ‘FEES’. How drastically will this affect your build cost? Speak to Atspace to make sure your insulation, window and heating purchases stay low, and have little effect on your EPC rating!

Surely removing the Fabric energy efficiency standard is taking a backward step? It’s common knowledge that adopting a fabric first approach is not only more cost effective but benefits the end user as well by saving on heating costs... is this not what we need?

There’s convincing evidence that the end user’s heating costs will increase by up to fifty percent in some circumstances due to the lack of a ‘fabric first’ approach, as-well as opting for electricity which Is notoriously more expensive than gas heating. Are we entering a new era of fuel poverty? Will electricity providers lower their prices with the inevitable increase in usage?

What do you think? I would love to hear your opinion!



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