Future Homes Strategy

Here is my take on the Future Homes Consultation - February 2020

Future Homes Strategy and SAP 10

Review of probable changes to Part L, SAP and Part F in the next five years

Background:

Buildings form a significant part of sum of national carbon emissions. New buildings are a relatively soft target for reducing carbon emissions.
2016 was the original zero carbon target for new dwellings. This slipped.
Other issues have come to bear such as overheating, air quality and the performance gap between calculated performance and actual performance. Technologies and understanding have changed and the grid has gradually decarbonised.
Draft changes to the Standard Assessment Procedure (SAP) were proposed in 2018 (amended 2019) and these were intended to accompany changes to Part L of the Building Regulations.
These changes have been delayed, but in 2019 a consultation document on ‘The Future Homes Standard’ was issued proposing changes in 2020 and more significant changes in 2025 to Part L and Part F of the Building Regulations. That consultation closed last week.
The consultation proposes changes to Part L in 2020 and a Future Homes Strategy for implementation in 2025.

Consultation Proposals Summary – What the practical effects might be

Although there are likely to be significant procedural and SAP results impacts , the 2020 proposals are unlikely to have a great effect on current design - if the favoured option 2 (see below) is adopted by government.

SAP methodology is likely to change significantly, creating work for the designer, assessor and contractor particularly in the areas of thermal mass, lighting, and ventilation (all relating to overheating), thermal bridging (ACDs out, calculations in), and evidence collection.

Heat pumps will increasingly become the default heating and by 2025 will be specified on all new dwellings and probably as all replacement boilers (regardless of gas connection).

Technologies where improvements will be deemed significant to the proposals include PV, glazing, waste water heat recovery, heat pumps and heating controls

Unlike the 2020 proposals, the 2025 changes include 75 to 80% CO2 reduction targets - will have a significant impact on design.

2.Proposals – A bit more detail2020 proposed Part L changes summary:

Two options have been proposed and are being consulted on.

Option 1: 20% reduction in carbon emissions compared to the current standard with a heavy reliance on fabric improvement. Triple glazing, good fabric insulation and water heat recovery are specifically mentioned.
Option 2: 31% reduction in carbon emissions compared to the current standard achieved though carbon saving technologies such as photovoltaics and with a less focus on improvements in fabric – so typically double glazing.
Option 2 is the one favoured by Government

Measurement metrics in SAP 10 change to:

Primary energy target, CO2 emissions target, Householder affordability rating.
The Fabric Energy Efficiency rating to be dropped.
There will be improved minimum fabric standards – but not an overall fabric standard (FEES)
One of the likely effects of this is that it will be possible to design dwellings with lower fabric standards than at present and still pass!

Proposed 2020 minimum standards for fabric performance:

These are marginally more stringent than present ones, but designers normally have to do better than these new standards to achieve an overall pass now anyway.

Air tightness will be mandated even on small dwellings.

This is usually necessary now to achieve a SAP pass anyway.

Reference values for the notional dwelling will not be improved by much in Option 2
Low temperature heating systems will be mandated

The effect of this will be to install larger heat emitters (or underfloor) as this future proofs against the anticipated widespread use of heat pumps

Closing the ‘performance gap’ 2020 proposals include:

More onsite checks, more post construction paper trails and photographic evidence will be required to evidence the SAP inputs.
A standard ‘BREL’ (Building Regulations Part L) report requirement will be introduced for SAP compliance ( similar to non domestic BRUKL report) requiring photographic evidence of :
Insulation levels and insulation product types, main and secondary heating systems, ventilation system, domestic hot water system type (only applicable if separate from heating system) – i.e. electric showers for example, evidence of LZC technologies and relevant data, construction details.

SAP 10 proposals:

Fuel Factor Favours Electric Heating

Because of the gradual decarbonisation of the grid, the electricity fuel factor (CO2 per KWh) is being more than halved.
Effect: Using Electric Heating will become even more attractive but PV will not provide such big gains. Heat pumps will become the default heating even in gas supplied areas.
A side effect of this measure alone may be that heating costs actually increase as electricity remains more expensive than gas.

Thermal Bridging :

Because these are out of date and often not followed, ACDs will no longer be available as a design tool and SAP saving.
Thermal Bridging / junction requirements are likely to change - This could be significant.
It is likely that calculations by manufacturers for heat loss at junctions will be available more widely, or will have to be calculated on a bespoke basis.

Overheating

SAP 10 will reduce the amount of ventilation that can be assumed thus making the assessment of overheating risk a bit more accurate.
For similar reasons, the SAP assessor will need to do Thermal Mass calculations rather than using ‘Indicative values’.
Lighting will need to be more accurately specified.

On site generation and storage

PV calculations will be more demanding and give better results. Battery storage and PV diverters and more accurate over shading calculations will be allowable and calculable in SAP.

Shower types and flow rates will be needed so that hot water demand can be better estimated
SAP10 will have more detailed heating patterns built into it – more accurately reflecting actual use

Part F Proposals

Background

Air quality has deteriorated in homes owing to increased air tightness, external pollutants and VOCs.
Noise of extractor fans and drafts from trickle vents are recognised as deterrents to proper use.

New regulations are proposed to ensure quality in ventilation systems

Ventilation systems must be installed and commissioned in accordance with a procedure approved by the Secretary of State and that air flow rates for mechanical systems should be measured in all new dwellings.
This will be additional work for the contractor

Ventilation strategies

A dwelling with either a design air permeability lower than 5 m3/(h.m2) at 50 Pa or an as-built air permeability of lower than 3 m3/(h.m2) at 50 Pa. will be deemed to be highly air tight and will require continuous extract ventilation or mechanical supply and extract systems.

Future Homes StandardThe 2025 Future Homes Standards aspiration is for dwellings to be produce 75% to 80% less carbon than at present.
This will be achieved through fabric improvements and low carbon heating (mainly heat pumps – some heat networks).
Whilst not spelling this out, there is a clear intention to derive all space heating from electricity and effectively exclude all fossil fuel boilers, from new dwellings and as replacement heating systems .
Heat pumps will be the norm by 2025.

3.Some additional opinion / commentary:

The preference in the consultation for C02 savings to be achieved more by renewable electricity generation than by fabric improvements has been criticised as short sighted.
Electric heating is most efficient in very well insulated homes -so fabric should logically take priority.
If fabric improvements do not drastically reduce demand, and the overall electricity based heating load increases the way that is anticipated, the capacity of the grid to supply the need comes into question.
Embodied energy gets no consideration despite its increasing overall share of a dwelling’s energy as ‘energy in use’ decreases.
Savings to occupants are not prioritised.