Overview
We prepared the SAP calculations and energy strategy for a new residential development comprising 17 dwellings. The aim was to reduce operational energy demand and demonstrate strong performance against Part L requirements, while keeping the specification straightforward and cost-efficient for long-term operation.
Energy Strategy
A fabric-first approach was adopted to reduce heat loss and stabilise internal conditions before introducing low-carbon systems.
Key measures include:
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External wall U-values of 0.17 W/m²K
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Roof U-values of 0.11 W/m²K
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Glazing at 1.2 W/m²K
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Air permeability targeted at 3–4 m³/hr·m²
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MVHR providing controlled ventilation and improved heat retention
Space heating demand is low as a result, so the hot water system becomes a key energy driver. Each dwelling therefore uses a Dimplex Edel hot water heat pump cylinder, providing an efficient, compact and all-electric solution that is easy to maintain. The integrated heat pump recovers heat from internal air to produce domestic hot water with a significantly reduced electrical load compared to direct-electric systems.
A roof-mounted PV array is used to offset household electrical consumption and further reduce regulated emissions.
Performance Metrics
The combined specification achieves significant improvements in operational efficiency:
| Metric |
Result |
| Carbon emissions reduction |
~71% reduction in regulated CO₂ vs baseline |
| CO₂ emissions after PV |
~3.96 tonnes/year total across the site |
| On-site renewable contribution |
~47.5% of total annual energy demand met by PV |
| Typical Dwelling Emission Rate (DER) |
≈ 3.1 kgCO₂/m²·yr |
| Primary Energy Rate |
≈ 35.6 kWh/m²·yr |
Outcome
The development achieves strong compliance under SAP 10.2 with no gas connection, simple servicing and maintenance requirements, and stable running costs.
By prioritising fabric performance and pairing it with the Dimplex Edel hot water heat pump system and plot-based PV, the scheme delivers a clear and repeatable low-carbon strategy suitable for similar residential sites.