Sustainability Checklist for Extensions & Refurbishments

Why Sustainability Matters

Every home we extend or refurbish has an impact — on your comfort, your bills, and the wider environment. Buildings account for nearly 40% of the UK’s carbon emissions. That means every improvement you make at home isn’t just about saving money — it’s also about healthier living spaces and a positive contribution to tackling climate change.

For homeowners, sustainable design has three big wins:

  1. Lower running costs — spend less on heating, cooling, and electricity.

  2. Greater comfort — warmer in winter, cooler in summer, fresher air.

  3. Future-proofing — homes that meet (and beat) tomorrow’s standards and are more resilient to energy price shocks.

This checklist is designed to help us work through sustainability options with you.

Energy Efficiency & Insulation

  • Loft/roof insulation

  • Wall insulation (internal or external)

  • Ground floor insulation

  • Airtightness improvements (sealing gaps, membranes, tapes)

Windows & Doors

  • Upgrade to double or triple glazing

  • High-performance frames (timber, aluminium, or composite)

  • Proper ventilation and solar shading design

Heating, Cooling & Hot Water

  • High-efficiency heating system (boiler or heat pump)

  • Underfloor heating for low-temperature systems

  • Mechanical Ventilation with Heat Recovery (MVHR)

Renewable Energy

  • Solar panels (electricity)

  • Solar hot water

  • Battery storage for self-use of energy

Materials & Finishes

  • Natural or recycled insulation

  • FSC-certified timber

  • Low-VOC paints and finishes

  • Reclaimed materials where possible

Water & Landscape

  • Low-flow taps and showers

  • Dual-flush WCs

  • Rainwater harvesting (butts or tanks)

  • Permeable paving for driveways/patios

  • Green or biodiverse roof

Smart & Future-Ready

  • Smart heating controls and zoning

  • Energy monitoring systems

  • EV charging point

Three Tiers of Sustainable Upgrades

To make this practical, we group measures into three tiers. Each tier builds on the previous one, so you can decide how far you’d like to go.

Tier 1: Fabric-First Starter

Indicative cost (3-bed terrace): ~£10–15k

Annual savings: ~£350–£600

Includes:

  • Loft/roof insulation

  • Airtightness improvements

  • Solar PV array (~4 kW)

  • Low-flow taps, showers, and dual-flush WCs

  • Smart heating controls

Benefits:

  • Immediate bill reductions and comfort improvements.

  • Tackles the “low-hanging fruit” that gives the quickest return.

  • Makes your home warmer in winter and cooler in summer without major disruption.

Tier 2: Electrify & Breathe

Indicative cost (3-bed terrace): ~£30–45k

Annual savings: ~£700–£1,000

Includes:

  • Everything in Tier 1

  • Wall insulation (internal or external)

  • Upgraded windows and doors (double/triple glazing)

  • Air source heat pump to replace your gas boiler

  • Underfloor heating (ground floor)

  • Mechanical Ventilation with Heat Recovery (MVHR)

  • Natural insulation / low-VOC finishes

Benefits:

  • Major step away from fossil fuels.

  • Fresh, filtered air means healthier living conditions (great for asthma/allergies).

  • More consistent comfort throughout the home.

  • Bills drop further — less exposure to volatile gas prices.

Tier 3: Near-Zero Bills Home

Indicative cost (3-bed terrace): ~£70–95k

Annual savings: ~£1,200–£1,800 (sometimes more with smart tariffs)

Includes:

  • Everything in Tier 1 & 2

  • Super-insulation & airtightness detailing to the highest standards

  • Triple glazing throughout

  • Larger solar PV system (6–8 kW)

  • Larger battery storage (10–15 kWh)

  • Solar hot water option

  • Full electrification (no gas supply)

  • Green or biodiverse roof

  • Permeable paving

  • Rainwater harvesting system

  • EV charging point

  • Full smart home energy monitoring & tariff optimisation

Benefits:

  • Bills reduced to near-zero, sometimes even net-positive.

  • Resilience: generate and store your own power, with less reliance on the grid.

  • Future-proofed home designed to meet 2030+ performance standards today.

  • Enhanced property value as buyers increasingly look for low-energy homes.

Mix & Match

Not every home needs every measure in the tiers above. We can mix and match elements depending on your specific property, budget, and goals. The checklist helps us identify the right combination for you — from a light-touch upgrade to a full “near-zero bills” retrofit.

Conclusion

Improving the sustainability of your home doesn’t have to be overwhelming. Some steps cost nothing and can be built into your daily life or included in the way we design as standard. Others require investment but bring long-term comfort, savings, and resilience.

By looking at your project through this checklist, we can create a pathway that balances budget, benefits, and ambition — from free quick wins to a near-zero-bills home.

Whether you want to reduce running costs, improve comfort, future-proof your property, or make a meaningful contribution to reducing carbon emissions, there is a clear starting point. Together we can shape a home that works better for you — and for the planet.