These are cold, expensive-to-heat houses, transformed into highly-insulated units that generate their own electricity.
Dutch company Energiesprong renovates a house in under 10 days.
It's refurbished houses across Europe.
They use pre-fabricated facades, smart heating and cooling installations and insulated rooftops equipped with solar panels To pay for the renovation tenants pay the same or less than their old monthly energy bills.
Energiesprong's Jon Warren.
"I would say, here's a home energy makeover that can be in-part funded by energy savings that you can make on your home and it will give you a guarantee performance for 30 years and a clear maintenance plan so you know what you're going to need to do over those 30 years.
A low cost of ownership and on top of it all, a really attractive and comfortable, warm home." It costs around €60,000 per home in the Netherlands and £70,000 in the UK.
"That seems super expensive I know, but if you take into account all the maintenance savings you're going to make over that guaranteed 30-year period and all the energy savings you are going to make over that period, then the cost is essentially neutral." The company is targeting UK social housing, renovating more than 150 homes in Nottingham by 2020.
It says there are millions of homes that can benefit as EU countries aim to stop contributing to climate change by 2050.
Building carbon-neutral homes may not be the issue, when we have millions out there costing the Earth to heat.