In 2007, England was developing its route to zero carbon via the "energy hierarchy" triangle — a framework that required roughly 70% of carbon reduction to be achieved on site, effectively mandating micro-generation on most new homes. This paper argued that Wales should take a different approach: one that pushed fabric performance further and removed the requirement for on-site generation, instead enabling a regulated market in off-site renewable energy capacity.
The central proposal was two principles: drive the performance of building fabric much further, achieving 30–40% energy reduction compared to current regulations through the envelope alone; and remove the on-site generation requirement, allowing developers to purchase a proportionate share of new renewable energy capacity from energy suppliers operating in Wales' rich renewable geography.
Why Wales Needs a Different Route
Wales has known differences to England that merit a context-specific approach to zero carbon:
- Wales has rich potential for renewable power generation through its geography — wind, hydro, tidal — with much of this capacity located away from populated areas, not on domestic rooftops.
- Wales has a smaller average development scale, typically delivered by smaller builders less equipped to specify, install and maintain complex building-integrated generation systems.
- South Wales has a considerable population in north-south valleys that offer limited solar orientation and little opportunity for meaningful on-site renewable generation.
The English approach — requiring 70% carbon compliance on site — does not translate well to this context. Requiring small builders in valley towns to achieve carbon reduction through micro-generation results in under-sized, poorly-maintained systems; it does not achieve the stated goal and imposes cost on parties least equipped to deliver it.
Fabric First: The Foundation
The proposal's first principle is to push the energy performance of the built environment in Wales to a very low energy demand level — 30% or more energy reduction compared to current regulations through the fabric alone, with an ambition to approach 40%. For new housing, this could equate to thermal performances in the region of 0.15 W/m²K.
The emphasis on high performance building envelopes is justified on several grounds:
- Fabric performance can be achieved on practically any development site in Wales, regardless of orientation or geography — something that cannot be said of solar PV or solar thermal.
- High fabric performance delivers reduced energy demand reliably for the life of the building through passive components, rather than active mechanical systems whose performance degrades with age and poor maintenance.
- Fabric performance can be regulated at construction completion through established Building Control checking procedures — it does not require ongoing monitoring of operational systems.
Reduction of demand is preferable to increase in supply, even when that supply is renewable.
Wales Is Blind to Energy Generation Location
The second principle proposes that the long-term goal for Wales' built environment is to achieve an overall carbon reduction as a combination of regulated fabric performance and renewable energy generation — with no requirement for a fixed percentage of that generation to be on-site.
Under this proposal, a developer would purchase, via a regulated open market, sufficient "energy generation capacity" to make up the difference between the building's fabric performance and the required 100% carbon reduction. That purchase would fund new renewable energy sites in Wales — wind farms, hydro, tidal — operating at a scale and in a location where renewables are genuinely effective, maintained by energy companies with the expertise to do so.
The benefit of this approach is threefold:
No site orientation or geography restrictions. Valley towns, urban infill, sheltered locations — all can achieve zero carbon through fabric performance and purchased generation capacity.
Grid-scale renewables are inherently more efficient per unit of energy generated than fragmented domestic micro-generation. Lower total material use, professional maintenance, genuine redundancy.
Professional energy companies maintaining large-scale renewable assets is significantly more likely to achieve the stated carbon reduction than untrained homeowners maintaining rooftop systems over a 60-year building life.
Stimulates investment in large-scale renewable energy generation across Wales, in locations where the resource is richest — delivering economic and environmental benefit beyond the individual development.
Recommendations
The paper made two primary recommendations for the Welsh Assembly Government:
First, consultation and research with energy suppliers to establish the viability and legal status of a moderated carbon marketplace and the assignment of new renewable energy sites to specific developments.
Second, consultation and research to determine the target fabric performance values for all new and refurbished building types, beginning with new-build housing.
Subsequent work could then identify the full process for delivering zero carbon development in Wales — building on, rather than replicating, the English approach.
Full Positioning Paper
Delivering Zero Carbon Buildings in Wales — PDF (RevD, April 2010)