Diane Beckett peers through the iron bars surrounding 24 Sussex Drive and shakes her head.
"In the summer there is an air conditioner in one of the windows, just a window air conditioner. Old and creaky and it's not very efficient."
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The house was built in 1868, the National Capital Commission says, but 24 Sussex Drive wasn't turned into the prime minister's official residence until 1950.
'I was totally appalled'
Beckett, who is now the interim executive director of the Sierra Club of Canada, had a chance to see inside the crumbling official residence of the prime minister when she was invited in with a group years ago by Jean Chrétien's wife, Aline.
She came away shocked that a heritage building with stunning views of the Ottawa River had essentially deteriorated into an energy-sucking dump.
"I was totally appalled. There was a cheap patio door with cheap plastic sheeting like you have at your cottage to keep the drafts down," Beckett said in an interview outside the prime minister's official residence.
An auditor general's report from 2008 said "all the official residences, in particular 24 Sussex Drive, have elements in poor to critical condition." Repairs to the prime minister's residence alone are expected to cost $10 million and take at least 18 months.
Beckett said there is now a great opportunity to the turn the 147-year-old building into a model of energy efficiency and green stewardship.
The National Capital Commission, which manages federal heritage buildings, is expected to renovate the house before the new prime minister and his family move in.
The official plan for the building, though, is not yet clear.
As officials work out the details for what will be done with the property, the Sierra Club has launched an email campaign directed at prime minister-designate Justin Trudeau, asking him to make a bold environmental statement with the house.
"That it can be a zero net energy house. That it actually either uses no net energy or it produces more energy than it uses. And it can be done in a heritage home," she said.
In addition to the obvious — more insulation and better windows — Beckett suggests further steps and new technology.
"We could put in geothermal ... there could be solar collectors, there could be, maybe as a statement, a tiny micro wind turbine right by the cliff.
"I think we could have the greenest official residence in the world."
But Greg Furlong, senior energy strategist for EnviroCentre in Ottawa, says environmental goals for the residence need to be balanced with the harsh reality of renovating and insulating a stone house.
"It is an old building, we can definitely make huge improvements, but you know getting into the realm of the most energy efficient in Canada might be a little bit off the scale," he said in an interview with CBC News.
The EnviroCentre in Ottawa specializes in services and programs that help homeowners and organizations conserve energy. Furlong has done energy audits on hundreds of homes, including many embassies that are often old and draughty.
He says some strategic renovations and upgrades could help cut down on energy bills by at least 50 per cent, if not more.
Furlong helped CBC News compile a list of the options that could help turn the official residence into a greener building, and it turns out there are a few surprises.
1. Forget wind power
Even though 24 Sussex is built on a cliff, the Ottawa Valley in general doesn't have a lot of wind. Furlong said a micro wind turbine would be more of "gesture" than any significant source of power.
2. Solar is iffy
The roofs are oriented east and west, which isn't great for solar panels that should face directly south in Canada.
Furlong said solar panels could be installed separately on the large back lawn.
3. Stop the air leakage
"That would be the first place we want to target," advised Furlong. "To stop the air from coming into the building and getting heated and then passing straight outside."
That means plugging up holes in the walls and roofs and around electrical conduits and plumbing leading outside.
And of course replacing those famously leaky windows, although Furlong said upgrading windows can only do so much.
4. New insulation
This is key to improving the energy footprint of the house.
"You pretty much have to gut it," concluded Furlong. "You would have to rip it apart to add layers of insulation and other structures to hold the insulation in place, which is not a bad idea, because the wiring needs to be replaced and you can do it at the same time."
5. New heating system
If the building has hot water radiators, like many of its vintage, they can be combined with a new high-efficiency boiler that runs on natural gas. It can also be combined with a system that heats hot water for use in the house.
6. Geothermal energy
There is another option for heat at 24 Sussex, Furlong said. A geothermal system could be drilled into the limestone rock the house is built on.
Geothermal uses coils that are looped underground after drilling down. Water in the coils absorbs the consistent underground temperature, and combined with an electric pump, helps keep the building warm in winter or cool in summer.
7. Thermostats on every floor
"This is where you can get big energy savings," said Furlong. "You don't want to keep all the rooms in a big room house at the same temperature."
8. Basement insulation
Insulation is tricky in a stone house, said Furlong. Right now, the lack of insulation in the basement keeps the outside stone walls warm, warding off frost.
If you insulate the basement walls, the outside walls get cold, freeze and can crack. Insulating the outside of the basement works the best, according to Furlong.
But it will be up to the NCC to decide if that would affect the heritage appearance.
9. Chickens, yes, chickens
Suggestions in the Sierra Club's campaign to create a green 24 Sussex include a herb garden and chickens.
"There are several outbuildings there at 24 Sussex, perhaps one of them can be converted to a chicken coop, and they [could grow] some local farm produce and save on the transportation and energy involved," said Furlong.
Although he points out it's not clear the neighbourhood is quite ready for that.
"There might be complaints from the neighbours, especially if they have roosters."