How much would it cost to raise standards for energy?

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The Sustainable Housing Action Partnership chose CAR to examine the additional costs involved in going beyond the minimum performance requirements of current Building Regulations for energy conservation. We explored the costs of energy-related materials and components in homes designed simply to meet the Building Regulations, and then we explored the costs of three levels of performance going beyond the mandatory requirements:

Level 1 – comprehensive fabric improvements and a mechanical ventilation system with heat recovery (MVHR), with no renewable energy.

Level 2 – comprehensive improvements to fabric and ventilation plus renewable energy in the form of an air-source heat pump and a photovoltaic array.

Level 3 – comprehensive improvements to fabric and ventilation plus renewable energy in the form of an air-source heat pump and a large photovoltaic array.

SHAP asked CAR to consider the extra costs of exceeding Building Regulations for both traditional masonry (brick and block) homes and modern methods of construction using timber frame and/or timber panel construction.

Our brief was to go as far as possible using proven materials and systems, with the intention of achieving near-zero carbon if we believe this to be possible.

Findings
Our modelling using SAP 2012 suggested that it is possible to achieve a 30% saving in average gas use by improving the building fabric and using MVHR. There is a penalty in electricity use, which increases a little to drive the MVHR system, but there are likely to be accompanying improvements in air quality and comfort.

For small-scale developments of fewer than 10 homes this Level 1 scenario would add £6,800 to £7,100 to the cost of building a three-bedroom semi-detached home at present costs – roughly a 10% premium on above-ground construction costs. For larger scale projects of 30 or more units, the cost would fall further because of economies of scale – probably in the region of £5,600 per unit.

The cost range covers the extra-over costs for both masonry and timber frame. Removing the MVHR system would reduce this cost by around £3,800 (less for large developments), but this would bring an energy penalty because the heat in stale air leaving the home would not be recovered. Taking out the MVHR would also bring an air quality penalty because incoming air is unfiltered, and ventilation in rooms apart from the kitchen and bathrooms would be largely dependent on wind speed.

Our modelling also suggested that it is possible to reduce gas use to zero by carrying out the same fabric and ventilation system improvements, and at the same time incorporating an air-source heat pump and photovoltaics (PV). In this Level 2 scenario a 2.5 kWp PV array generates almost enough electricity over the course of the year to repay all of the electricity used for heating, ventilation and lighting (but not appliances) for the home. It brings annual carbon emissions to near-zero, and achieves an EPC ‘A’ rating.

For small-scale developments this scenario would cost £14,300 to £14,400 more than a three bedroom semi built to the minimum requirements of the Building Regulations – roughly 20% more, for either masonry or timber frame. (Again, the costs would be lower for larger schemes – in the region of £11,500.) As for Level 1, £3,800 would be saved by removing the MVHR, but at the cost of higher energy use and poorer air quality.

A Level 3 scenario (as for Level 2 but with a large PV array) would cost £17,800 to £17,900 more than a home built to the minimum requirements of the Building Regulations, but it would generate significantly more than the energy used in the house. (Once again, the costs would fall on large sites – say £14,100 for more than 30 units.) This is roughly 23% more than usual costs. Electricity generated by the PV could be sold into the grid to generate an income stream for either tenants or the property owner. (The EPC rating is unchanged at A-rated.)

If the improved specification was applied at scale, with thousands of units a year built to these levels of performance, allowing industrialized manufacture and prefabrication, all of these costs could fall by around half.

Over a 30-year time horizon, modelling suggests Level 1 would save more than 8 tonnes of CO2 for each improved home, Level 2 would save more than 43 tonnes of CO2 per home, and Level 3 would save more than 72 tonnes of CO2 per home. These improvements sound modest, but given that the UK is poised to build 225,000 to 275,000 or more new homes a year1, the aggregate savings potential is very considerable.

It is also significantly more economical to build to higher standards now than it would be to build to minimum standards now and retrofit in 2030 or 2050 to meet future standards of energy efficiency. Even excluding the disruption of carrying out work on occupied homes, it is simpler for almost all energy efficiency improvements (insulation, high spec windows, MVHR, air-tightness) to get it right from the outset rather than taking buildings apart and putting them together again later.

Download our report here.

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