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Insulation Calculator

Find the recommended R-value for your climate and component, and how much insulation you still need to add.

Related tools

All Energy & power tools →
Appliance Energy Cost CalculatorTurn any appliance's wattage and daily use into a daily, monthly and yearly running cost in your currency.Heat Loss CalculatorAdd up the conductive heat loss through walls, windows, doors and roof from their area and R- or U-value.Home Energy Audit CalculatorEstimate your home's annual energy use, cost, intensity and HVAC share from its shell and major appliances.HVAC Sizing CalculatorEstimate the heating and cooling load of a room in BTU/hr, kW and tons from its area, climate and insulation.Light Bulb Savings CalculatorCompare LED, incandescent and CFL bulbs on yearly energy plus replacement cost, and see your LED savings.Power Factor CalculatorCompute power factor, apparent and reactive power, and PF-correction capacitance.Amperage CalculatorConvert a load in watts and a supply voltage into the current drawn in amps.Appliance running cost calculatorEstimate what an appliance costs to run per day, month and year.

Open Insulation Calculator and you get an answer straight away, with no account to create. You will find it under Energy & power, with Appliance Energy Cost Calculator and Heat Loss Calculator for the neighbouring cases.

How to use it

  1. Open the tool — no signup or install needed.
  2. Enter your input or adjust the available options.
  3. Get your result instantly, then copy or download it.

Frequently asked questions

What does Insulation Calculator do?

Find the recommended R-value for your climate and component, and how much insulation you still need to add.

When would I actually use this?

Putting a number on a bill: what an appliance costs to run, whether a solar array covers the load, and how much heating a room actually needs.

What is the most common mistake?

Confusing power with energy. A kilowatt is a rate and a kilowatt-hour is a quantity; a 2 kW heater on for half an hour uses 1 kWh, and only the second figure appears on a bill.

Is there a tool for the next step?

Heat Loss Calculator is the closest one after this: Add up the conductive heat loss through walls, windows, doors and roof from their area and R- or U-value.

What else is worth having open alongside it?

Home Energy Audit Calculator and HVAC Sizing Calculator — they come up in the same task often enough to be worth a second tab.

Where do the figures come from?

The arithmetic is exact for the rating and the tariff you enter. Nameplate wattage is a maximum, not an average, and solar output depends on latitude, orientation and shading that no formula can guess.

Further reading

All guides →
ExplainerR-Values, U-Values, and What an Insulation Number HidesR and U are reciprocals, and the two markets that read this site use different ones in different units — so an R-value quoted without its system means nothing. Worse, the number on the batt is not the number your wall achieves, because the studs are a parallel path.ComparisonInsulate or Replace the Heating: Which Repays First, and Why the Answer InvertsPut both on one axis — euros paid per kilowatt-hour a year of permanent saving — and the comparison becomes decidable. The same loft job costs 0.83 euros per kilowatt-hour a year in a 1965 house and 5.00 in a 2005 one, a factor of six. That, and not the age of the building by itself, is what inverts the verdict.ExplainerWhere Household Water Actually GoesPeople picture taps and showers, and metered end-use studies say the biggest single line is somewhere else. Here is the ranked budget from named national agencies, plus the arithmetic that changes behaviour: the dripping tap, the running tap, and the shower flow rate at which a bath becomes the cheaper option.How-toHow Much Tile and Grout You Actually NeedFloor area divided by tile area is the answer everyone reaches for, and it is always short. Count the grid instead, add the layout allowance, round to full boxes, keep attic stock — then derive the grout from the joint geometry rather than trusting the bag.How-toHow to Estimate the Running Costs of a HomeAdd up energy, water, heating, and maintenance with simple rules of thumb so you know what a home really costs to run each month.How-toHow Much Does a Space Heater Cost to Run?Multiply the heater's kilowatts by hours used and your price per kWh — a 1.5 kW heater for 5 hours a day adds up fast at typical tariffs.
Insulation Calculator — OneKitly