The rising commercial vacancy rate is a concern for builders but renters are seeing it as a great opportunity.

In the past year-and-a-half, vacancy rates have jumped to eight percent, from one percent.

"The swiftness is causing great concern because the demand that was there when projects were started has evaporated. Meanwhile, five-million square feet of office space is chugging away being built," says Greg Quan from CB Richard Ellis.

One of those spaces being built is Eighth Avenue Place. When it's complete it will be Calgary's third largest tower.

Located on the old Penny Lane property, the 49-storey building will boast 1-million square feet of office space.

The building was planned during the boom on 2007 but, so far, not one square foot of space has been rented.

"You're building a building to lease it for income over the long haul. It's important to lease it but it doesn't all have to be in place when the building opens," says Jim Rae from Colliers International.

But what may be a bust for one sector is turning into a boom for another.

Those looking for business space to rent are benefiting from the vacancy rate.

"For the past several years there have been a number of companies who've balked at the cost of downtown office space in Calgary. Now there's an opportunity for these companies to consider coming to Calgary," says Richard Pootnam from Calgary Economic Development.

Exile Drilling says they are taking advantage of the rising vacancy rates.

The junior oil and gas company used to have field staff located outside the city while the management team worked in the city.

Now that rents are falling, the company can afford large new offices on the outskirts of Calgary.

"Now we have a presence in Calgary with our office staff and we have a presence in Calgary with our equipment and field staff and we're able to manage everything efficiently from the hub of the Canadian oilfield," says Clint Melenchenko from Exile Drilling.

Experts agree, it will be up to the energy market and the time it takes to recover that will dictate whether Calgary is a renter's or a landlord's market.