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100% browser-based · no account · instant answers

Green building math,
without the guesswork

Six free calculators for sustainable building and home energy retrofits: how much heat a wall or roof is really losing, the embodied carbon in your materials list, how fast an energy retrofit pays for itself, what a window upgrade actually saves, how much rainwater your roof can harvest, and what a green roof adds in weight and cost.

Insulation heat lossEmbodied carbonRetrofit paybackFree forever
Insulation R-Value & Heat Loss CalculatorEnter a surface's area, R-value and the indoor-outdoor temperature difference to see its rate of heat loss in watts, then compare it against a higher R-value upgrade.Embodied Carbon Calculator for Building MaterialsEnter quantities of concrete, steel, timber, brick and insulation to see the total embodied carbon of your project and which material contributes the most.Energy Retrofit Payback CalculatorEnter the upfront cost of a retrofit, its expected annual energy savings and an energy price escalation rate to see the simple payback period and total savings over time.Window Upgrade Energy Savings CalculatorEnter window area, old and new U-values, the indoor-outdoor temperature difference and heating season length to see the annual energy and cost savings from upgrading.Rainwater Harvesting Tank SizerEnter roof catchment area, local rainfall, collection efficiency and daily water demand to see how much rainwater you can harvest annually and what tank size to install.Green Roof Load & Cost CalculatorEnter roof area and choose an extensive or intensive green roof type to see the added structural load and installation cost, with a reminder to verify load capacity.

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Plan a greener build or retrofit with real numbers

Start with the insulation heat loss calculator to see where a building's envelope is losing the most energy, then check the embodied carbon calculator to see which materials carry the biggest upfront carbon cost. The energy retrofit payback calculator and window upgrade savings calculator turn an upgrade decision into a clear number of years and dollars, while the rainwater harvesting sizer and green roof load & cost calculator help plan water and roof-greening projects.

More tools

Insulation R-Value & Heat Loss CalculatorEnter a surface's area, R-value and the indoor-outdoor temperature difference to see its rate of heat loss in watts, then compare it against a higher R-value upgrade.Embodied Carbon Calculator for Building MaterialsEnter quantities of concrete, steel, timber, brick and insulation to see the total embodied carbon of your project and which material contributes the most.Energy Retrofit Payback CalculatorEnter the upfront cost of a retrofit, its expected annual energy savings and an energy price escalation rate to see the simple payback period and total savings over time.Window Upgrade Energy Savings CalculatorEnter window area, old and new U-values, the indoor-outdoor temperature difference and heating season length to see the annual energy and cost savings from upgrading.Rainwater Harvesting Tank SizerEnter roof catchment area, local rainfall, collection efficiency and daily water demand to see how much rainwater you can harvest annually and what tank size to install.Green Roof Load & Cost CalculatorEnter roof area and choose an extensive or intensive green roof type to see the added structural load and installation cost, with a reminder to verify load capacity.

Frequently asked questions

Is EcoKit really free, with no account needed?

Yes — every calculator runs entirely in your browser with no sign-up, no data collection and no cost. Nothing you type is sent to a server.

Who is EcoKit built for?

Homeowners, renovators, architects, builders and anyone planning a green-building or energy-retrofit project who wants quick, practical numbers on insulation performance, embodied carbon, retrofit payback, window upgrades, rainwater harvesting or green roofs — without needing specialist software.

Does EcoKit cover solar panels or battery sizing?

No — solar panel sizing, kWh output, solar payback period and battery/off-grid sizing are covered by Toolbench's dedicated SunWatt and WattBench suites. EcoKit focuses on the building envelope, materials and water side of sustainable building instead.

Can these tools replace a structural engineer, architect or energy assessor?

No — they're planning and estimation tools built on realistic average figures, not certified engineering, energy-modelling or structural calculations. Always confirm final numbers with a qualified professional before construction, especially for anything affecting structural load.