By David Chazan
BBC News, Stockholm
If you have to endure the daily grind of commuting by train, you'll know how unpleasant it can be to be jammed like a sardine into a grumpy crowd of hot, sweaty passengers.
Body heat could provide 15% of the building's heating needs
And you might take comfort from the idea that in future, some of the collective body heat can be harnessed and used to reduce energy consumption.
In Sweden, the Jernhusen company, which owns Stockholm's central station, is planning to channel passenger warmth to heat a 13-storey office block being built next to the station.
Heat exchangers in the station's ventilation system will convert the body heat into hot water, which will be pumped into the heating system of the building.
It is not yet certain how effective the technique will be.
But Jernhusen engineers hope it will meet up to 15% of the heating needs of the building, which will provide about 40,000 square metres of space for offices, hotels, restaurants and shops.
Some existing buildings already recycle body heat from people in the building to contribute to heating requirements.
But this is the first time excess heat is to be transferred from one building to another.
The building is to be completed by 2010.
The idea came from "thinking out of the box", says Mr Berggren
The concept is innovative - but like many good ideas, it's quite simple.
"It's based on old technology," says Jernhusen's managing director, Per Berggren.
"It's more like thinking out of the box, being environmentally smart and using the heat from the station to produce and transport heat to a new building."
The idea arose because the architects and engineers designing the new office block set a goal of reducing its energy consumption to half the level of a similar building.
“Everybody was on board, trying to make the building as environmentally friendly as possible,” says project manager Karl Sundholm.
"We were sitting and discussing how we could achieve that, and the idea just came up. We’ve already been approached by a number of other companies interested in applying the same concept to other projects."
The building will also incorporate a number of other environmentally friendly features, for example the facade, designed to minimise heat loss.
"We hope this office block will attract tenants who are keen to work with us to achieve sustainable energy use and maintain an exceptional level of environmental consideration," says Mr Berggren.
Mr Sundholm hopes the project will attract tenants who "think green"
"Our ambition is for this building to become a role model for the modern property market."
He says the design of the building reflects an increasing awareness of the need to combat climate change.
And recycling body heat from the adjacent station should help office workers keep warm in the depths of thel Swedish winter with minimum damage to the environment.