In came energy-efficient windows, water-saving plumbing, dimmable lighting.
The result of this and more is enough to warrant the highest sustainability rating - platinum - from a national building certification program known as LEED, or Leadership in Energy and Environmental Design.
In truth, many of the changes were made in part because Milkman and Hankin also wanted to renovate and enlarge the 180-year-old home.
But as two of the region's greenest green building advocates - she's head of the Delaware Valley Green Building Council, and he's CEO of the Hankin Group, which has been building LEED projects for half a decade - they couldn't do it any other way.
The ensuing "full gut rehab" is a study in the ultimate greening of a home, albeit not the first LEED platinum home in the region. According to the U.S. Green Building Council, Philadelphia has 36 platinum single-family homes - 28 of them gut rehabs.
And it holds lessons for all of us.
After her experience, Milkman found that her priorities in making a home more efficient would begin with insulation, caulking, and flashing. "Often replacing older HVAC units and appliances is very cost-effective since they are so much more efficient now," she said. Windows, too, although that can be expensive.
LEED presents a whole new way of thinking about a house. Perhaps one of the most surprising elements is that where a house is located ranks right up there in importance with what kindof house it is.
Achieving a particular LEED certification involves getting points for various aspects of the home, and it counted that Milkman's home is near community resources, including multiple public transit options and the public green spaces of Fitler Square and Schuylkill River Park.
In the first iterations of LEED, Milkman said, "you could get platinum if you were in the middle of nowhere, with access to nothing." But the program has evolved to favor renovation over new construction, dense communities over sprawl.
And although this may seem picayune, it shows again what elements - not necessarily new elements - make a house green: Milkman's got credit for having a tree out front because its shade reduces the urban heat-island effect.
Although Milkman has been a green building advocate for years, she confesses to having been a bit of a skeptic about LEED.
Her "aha" moment was realizing what "an incredibly useful tool" it was. "It actually makes you focus on very practical things," she said. "It helps you understand how a house works."
She's now conversant in lighting and air flow and the R-factor of insulation.
Likewise Andy Peifer, of Mill Creek Design L.L.C., the general contractor for the project. Moisture control is his new building mantra. "Think like a raindrop," he says.
That would explain the upgraded flashing around all windows and doors to protect these leak-prone sites.
If you're wondering what moisture has to do with sustainability, it speaks to the durability of a house, something LEED is focused on more than ever.
Durability can be achieved in myriad ways - including one that might seem insignificant: the paint used inside Milkman's home. Besides being fume-free, it's also ceramic-based, which results in a flat finish that's also washable, meaning you don't have to paint as often.
More ways the house went green: It has a radiant-floor heating system, which is more efficient than hot-air heat. The air-conditioning system has three air handlers, so each of the floors can have a separate thermostat. If the third floor isn't being used, it doesn't have to be cooled.
Down in the basement is a plumbing system that sends hot water to each individual faucet.
All the appliances are Energy Star, which means they use less electricity.
The roof is painted white so it reflects heat. The windows have blinds - something LEED is big on, to keep out the hot summer sun. They're simple, cheap, and practical.
Wood used for the flooring is certified as sustainably harvested by the Forestry Stewardship Council.
Out back where you might expect to see a garage is a small bike shed, and its roof is green, planted with sedum to stall stormwater runoff.
Of course, there are big-ticket items such as the solar panels, which were designed to handle about 30 percent of the power load for the house. (Actually, they're not so sure how cost-effective the solar system will be. But Milkman initially hadn't thought they could reach platinum status, and when it began to look possible, they went for all the points they could.)
One of the things the full-gut rehab did for them was give them the best shot at maximum insulation - something that's often logistically tough if you're not tearing a house apart.
Milkman actually moved out for seven months while the project was under way.
One of the little things that wowed Hankin was the $30 timer he attached to the soaker hose that runs under the drought-tolerant plants in the backyard.
"It really works!" he said. (It's also the one thing he was able to install himself.)
Hankin and Milkman haven't sorted out the cost of the green aspects - the project is too complicated.
Indeed, it's tough to come up with "typical" costs, said Cortney Baker, with the U.S. Green Building Council. "It's not a commodity you can just take off the shelf." Until you get deep into it, "you have no idea how many factors you're going to have to address."
Plus, how do you calculate something like the open staircase, which is definitely a design feature, but which also lets a lot of light from the skylights into the house - when the blinds aren't closed - reducing the need for electric lighting?
One thing Hankin and Milkman do know is that it costs about $3,000 for what you might call the paperwork part of the LEED process. Various aspects have to be documented, quantified or certified by outside professionals.
As part of the certification, Milkman has to agree to an educational role - including showing others the LEED-worthy features. That's one of the reasons she likes the dual flush toilets - a small flush for liquids, a bigger one for solids. They have to be explained.
2405 Pine Street will be on the annual fall house tour of the Center City Residents Association on Oct. 21 from 1 to 5 p.m. (Go to www.centercityresidents.org for more information.)
Visitors may be surprised. Peifer said Milkman's house is "a great illustration that you can do a lot with an existing structure. I don't think you're as locked in as people may perceive."
Overall, he likes that LEED encourages people to use existing structures. "A building that sits empty and ultimately is torn down," he said, "is kind of the ultimate sin."
"GreenSpace" appears every other week, alternating with Art Carey's "Well Being" column. Contact staff writer Sandy Bauers at 215-854-5147, firstname.lastname@example.org, or @sbauers on Twitter. Visit her blog at www.philly.com/greenspace.