What is it about 100-year-old houses that prompts thousands of people to buy tickets to tour them, to spend entire Sundays oohing and aahing over their vintage millwork, stained glass windows and rambling staircases?

Is it the thrill of stepping back in time in a venerable building that has survived The Great Depression, world wars, industrial and technological revolutions and a hurricane or two?

Is it the opportunity to bear witness to the transformative power of a homeowner’s sweat equity, the kind of commendable commitment that turns a teardown into a 21st-century gem?

Is it the thesis that the greenest house is a house that is already built, and that in a region as young as ours, we should view our heritage roots through the lens of both nostalgia and eco-consciousness?

Diane Switzer, executive director of the Vancouver Heritage Foundation, says it’s all the above, and then some.

The VHF, founded in 1998, held its first Vancouver home tour in 2003 and is busy preparing for the organization’s 10th annual tour on June 3. There are 10 homes featured this year, including two that are marking their centenary.

Switzer says the unwavering popularity of the tour reflects a growing awareness, and appreciation, of Vancouver housing stock that has stood the test of time, and the realization that it’s simply not sustainable to endlessly demolish and build new houses in our cities, especially given a StatsCan tidbit she cites that notes 50 per cent of Canadian buildings were constructed before 1970.

“The notion of a 100-year-old house starts to give our city a sense of history ... it’s emotional, that sense of place, but it’s also practical, with reuse and rehab. There’s some cachet to saying you live in a 100-year-old house. All of a sudden you speak with pride about that, about recycling houses.”

There’s no question, she says, that the city’s beautiful old homes are the lure of the tour, or that many tour-goers sign up in the hopes of taking away ideas for their own DIY projects. But some, she adds, just want to learn more about know their city’s history.

There is also heightened interest these days in different house styles, from different eras. Additional tours offered by the VHF this year include the already sold-out mid-century modern bus tour, the Vancouver Special tour (Sept. 22) and the laneway house tour (Oct. 20).

The notion of opening private local homes to the public was hatched in New Westminster, where the annual heritage home tour and tea is celebrating its 33rd outing on May 27. Its 1,500 tickets are nearly sold out.

Catherine Hutson of the New Westminster Heritage Preservation Society says the tour’s popularity has remained strong over the years, but the organization has also witnessed a sea change.

The tour began, she says, in response to the wholesale demolition of old homes that began in the Royal City in the late 1970s, prompting a group of activists to launch the tour as a means to convince the public — and government officials — that the 1,000 or so heritage homes in the community are civic treasures worth preserving.

“When it first started, there was a need to save and highlight heritage and restoration, to save the city’s old homes. It was almost activism. But now it’s different.”

For one thing, says Hutson, the tour crowd is younger. While many ticket buyers are looking for rehab tips for their old homes, more and more tour-goers are interested in decorating and home improvement, fuelled by televisions shows on networks like HGTV.

And while city’s assortment of stately Queen Anne, Victorian, Edwardian and craftsman homes continues to be a huge draw on the New West tour, Hutson also says there is an increasing appetite for a wider range of “newer” old houses, which is why this year’s lineup features a house built in 1956.

Not to be forgotten, of course, is the other reason that home tours have us lining up around the block: Human nature dictates that we are hardwired snoops, perpetually curious about how others live and the places in which they do that living.

Or, as Hutson, says: “It’s a lookie-loo’s dream.”

The 10th annual Vancouver Heritage Foundation Heritage House Tour takes place on Sunday, June 3 from 10 a.m. to 5 p.m. The tour price is $40; go to vancouverheritagefoundation.org for more information.

For information on the New Westminster Heritage Tour & Tea, which takes place on May 27, go to newwestheritage.org.