Passive House Energy Savings Calculator
Calculate Your Savings
Estimate how much you could save on energy costs by building a passive house in Ireland.
How Passive Houses Work
A certified passive house uses under 15 kWh per square meter per year compared to 200 kWh for a standard Irish home. That's a 92.5% reduction in energy consumption.
Key Benefits
- 90% less energy for heating and cooling
- Annual heating bill under €150 (vs. €2,000)
- 90% heat recovery from ventilation
- Up to 10-15% higher resale value
Your Results
Estimated Annual Energy Use
Passive house: kWh
Standard home: kWh
Cost Savings
Annual savings:
Payback period:
Why This Works
Passive houses meet strict standards for airtightness, insulation, and heat recovery. In Ireland, where winters are damp and cold, this system dramatically reduces energy needs while maintaining comfortable indoor temperatures.
When you ask what the most environmentally friendly house to build is, you’re not just looking for a list of green materials. You’re asking how to build a home that doesn’t just reduce harm-but actually gives back. The answer isn’t a single style, but a system: one that cuts energy use by 90%, uses zero synthetic insulation, and grows its own walls. That system is the passive house.
Why Passive House Is the Gold Standard
A passive house isn’t just a house with solar panels slapped on the roof. It’s built from the ground up to need almost no heating or cooling. In Ireland, where winters are damp and cold, a typical home uses 200 kWh per square meter per year. A certified passive house uses under 15 kWh. That’s not a small difference-it’s the difference between paying €2,000 a year on energy and €150.
How? Five rules:
- Super-insulated walls, roof, and floor-up to 30 cm thick, made from wood fiber or cellulose.
- Airtight construction-tested with a blower door to ensure less than 0.6 air changes per hour.
- High-performance triple-glazed windows-facing south to capture winter sun, shaded in summer.
- Thermal bridge-free design-no metal studs poking through insulation to leak heat.
- Heat recovery ventilation-brings in fresh air while keeping 90% of the heat inside.
These aren’t suggestions. They’re strict standards certified by the Passive House Institute in Germany. Over 60,000 passive houses have been built worldwide since 1991. In Austria, over 1 in 4 new homes are passive houses. In Ireland, the number is still low-but rising fast, thanks to new building regulations.
What About Straw Bale or Cob Houses?
You’ve probably heard about straw bale homes or cob houses. They sound ancient, natural, and perfect for the planet. And they are-up to a point.
Straw bale walls offer excellent insulation (R-value of 1.4 per inch), are made from agricultural waste, and sequester carbon. But they need perfect protection from moisture. A single leaky roof or poor foundation can turn straw into mold. In Ireland’s rainy climate, that’s a real risk. Most straw bale homes here require steel frames and waterproof membranes-adding hidden embodied energy.
Cob, made from clay, sand, and straw, is even more natural. But it’s slow to build, heavy, and doesn’t meet modern insulation standards without thick walls-making it impractical for urban plots. Plus, cob doesn’t come with a certification system. You can’t easily prove its energy performance to a bank or inspector.
Passive house, on the other hand, has third-party verification. Every component is tested. Every result is documented. That’s why banks in Germany and Austria now offer lower interest rates for passive homes. That’s why local authorities in Dublin are fast-tracking permits for them.
The Hidden Cost of ‘Green’ Materials
Many people think bamboo flooring or recycled steel makes a home eco-friendly. But that’s like saying a hybrid car is green because it has leather seats.
Embodied energy-the energy used to mine, transport, and manufacture materials-is often ignored. Steel has high embodied energy. Concrete, even recycled, still emits 0.9 kg of CO₂ per kg. Even ‘natural’ materials like cork or hempcrete have footprints. Hempcrete is great-it’s carbon-negative-but it needs lime binders, which are energy-intensive to produce.
Passive house doesn’t care what the walls are made of-as long as they meet the insulation and airtightness targets. That means you can use:
- Wood fiber insulation (made from sawmill waste, stores carbon)
- Recycled denim insulation (no toxic chemicals)
- Cellulose (ground-up newspaper, treated with borax for fire resistance)
These materials are cheaper than spray foam, safer for builders, and don’t off-gas. The key isn’t the material-it’s how well it performs in the system.
Energy Generation Is Secondary
Solar panels? Great. But they’re not the answer to a green house. A passive house needs so little energy that even a small 2 kW solar array can cover its needs. You don’t need a 10 kW system with batteries and inverters. That reduces cost, complexity, and the environmental burden of manufacturing those components.
And here’s the kicker: a passive house built in 2025 will offset its own embodied carbon in under 4 years. That’s because it saves so much energy. A typical home takes 20-30 years to break even. By then, the roof might need replacing.
Real-World Example: A Passive House in County Wicklow
In 2023, a couple in Glenmalure built a 120 m² passive house for €280,000. They used locally sourced timber, cellulose insulation, and triple-glazed windows from a Dublin supplier. They didn’t install geothermal. They didn’t buy a heat pump. They used a small 1.5 kW air-source heat pump-only for backup.
Annual heating bill? €87. Their electricity bill? €140, mostly from lighting and appliances. The house stays at 21°C in winter without turning on the heat pump. The windows stay warm to the touch. No drafts. No condensation on the walls.
They didn’t go ‘off-grid.’ They went ‘low-grid.’ And that’s the smarter path.
What Doesn’t Work
Not every ‘eco’ trend holds up.
- Earth-sheltered homes? Great insulation, but high risk of damp in Ireland’s wet soil. Expensive to waterproof.
- Modular prefab homes? Some are efficient, but many use plastic composites and synthetic foams. Check the insulation type.
- Living roofs? Beautiful, but require drainage layers, root barriers, and maintenance. They help with stormwater, not heating.
The biggest mistake? Thinking you can ‘green’ a bad design. A big, poorly oriented house with single-glazed windows won’t be saved by solar panels. You can’t out-solar a bad layout.
How to Start Building Your Eco-Friendly House
If you’re serious about building the most environmentally friendly house possible, here’s your roadmap:
- Work with a certified passive house designer. Find one through the Passive House Institute Ireland.
- Choose a site with good sun exposure-south-facing is ideal. Avoid shaded valleys.
- Design small. 100-120 m² is plenty for a family of four. Less space = less material = less energy.
- Use locally sourced, low-embodied-energy materials. Ask suppliers for EPDs (Environmental Product Declarations).
- Insist on a blower door test before drywall goes up. No exceptions.
- Install a heat recovery ventilation unit. Don’t skip it. It’s not optional.
- Use LED lighting and A+++ appliances. They’re cheap now and cut your final energy bill.
You don’t need to go full off-grid. You don’t need to live in a yurt. You just need to build smarter.
Why This Matters Beyond Your Utility Bill
Building a passive house isn’t just about saving money. It’s about resilience. When energy prices spike, or the grid fails, your home stays warm. When air quality drops, your ventilation system filters it. When you sell, you’ll get a premium-studies show passive homes in Europe sell for 10-15% more.
And the climate impact? One passive house saves about 3.5 tonnes of CO₂ per year. Multiply that by 10,000 homes-that’s the emissions of a small town.
This isn’t a niche trend. It’s the future of housing. And it’s already here.
Is a passive house more expensive to build?
It costs about 5-10% more upfront than a standard home in Ireland-but that gap is shrinking. With bulk material purchases and trained builders becoming more common, the premium is dropping. Most homeowners break even on energy savings in 7-10 years. After that, it’s pure savings.
Can you build a passive house with timber frame?
Yes-timber frame is actually the most common structure for passive houses in Ireland. The key is using thick insulation around the frame, not letting the wood act as a thermal bridge. Many builders use structural insulated panels (SIPs) or advanced timber frame with external insulation.
Do passive houses need heating systems?
They need very little. Most use a small air-source heat pump (1-2 kW) as backup, but many rely only on body heat, appliances, and sunlight. In mild winters, some passive homes in Ireland don’t turn on their heat pump for weeks.
Are passive houses only for new builds?
No. Retrofits are possible and growing. A ‘retrofit to passive house standard’ is called EnerPHit. It’s harder and more expensive than building new, but many older homes in Dublin and Cork have been upgraded with external insulation, new windows, and ventilation systems. The result: 80-90% energy reduction.
What’s the biggest mistake people make when building green?
Focusing on materials instead of performance. Buying bamboo floors or recycled tiles feels good-but if the house leaks air and has single-glazed windows, you’re wasting money. The system matters more than the stuff.
What to Do Next
Start by visiting the Passive House Institute Ireland website. Download their free guide for homeowners. Talk to three builders who’ve completed certified projects. Ask to see their blower door test results. Visit a completed passive house-many are open for tours in Wicklow and Kildare.
You don’t need to be an expert. You just need to ask the right questions. And then build a home that doesn’t just live on the land-but respects it.