When all is said and done, Laura Blau’s Pine Street residence (with the boarded-up window in this photo) will be the healthiest, most energy-efficient house on its block. She, her husband Paul Thompson and her three tenants will be much better off for the effort. | Photos: Sandy Smith
Architect Laura Blau’s firm, BluPath, specializes in coming up with sustainable solutions to all sorts of design and construction problems. She was an early adopter in this region of the ultra-energy-efficient set of practices and standards that go by the name “passive house,” which in English carries a connotation that’s more restrictive than in the original German.
All the same, many of Blau’s projects have been residential in nature. She’s currently embarked on one of the more comprehensive such projects, namely, rebuilding her own 1850s townhome on Pine Street in Rittenhouse to meet passive house standards.
Blau purchased this home with her architect husband and BluPath partner Paul Thompson 20 years ago as both their own residence and a rental property; a previous owner had subdivided the large (5,205-square-foot) home into four apartments, one per floor. When the work is finished, Blau and Thompson, who had occupied the top-floor apartment, will live on the first floor, with the three upper units rented out. The third-floor tenant is currently riding the project out in temporary quarters elsewhere while work proceeds.
The rehab and retrofit have been a real learning experience, she says, one that will enable her and her contractors to gain valuable insights into how best to carry out such projects in the future.
This project also shows how builders back in the 19th century were just as prone to take shortcuts and use cheaper materials where possible as builders today are, and it also demonstrates that it is possible to rebuild structures for the long run that will save their owners a bundle in both maintenance and energy costs.
“Most builders build homes to last 25 years,” she says. “Here, we’re building to last a century.”
Fortunately for Blau, builders back then didn’t build with quite the short time horizons they do now, or else she wouldn’t have had an 1850s Rittenhouse townhouse to work with. But they did take shortcuts where they could, as she explained as she walked me through the project, and time and nature took their toll on some of this home’s structural elements, aided by poorly-designed and -built additions and modifications over the years.
These changes produced some surprises that added to the overall cost of the project. Blau hasn’t worked out the total cost figures yet, and won’t be able to until everything’s complete, but she estimates that meeting passive house standards will add about eight percent to the total project cost. When you consider that those standards will cut this home’s energy bills by 80 to 90 percent annually, and add to that maintenance savings from the use of more durable components such as windows, an extra eight percent up front is a small price to pay for a huge return on investment.
Here’s what that investment is going towards.
A Passive House Retrofit on Pine Street
"No gas?" I cried when I saw this sign. What's a good cook to do, then? Blau told me that today's electric induction cooktops are as responsive as gas - and safer for children and easier to clean to boot.
The main way the retrofit will announce itself to the outside world is through the windows facing Pine Street. Here's a "before" photo...
...and here's an "after." More on how these windows work later.
Just beyond the front vestibule and stairs is the large room that will become the main living space, dining area and kitchen of the Blau-Thompson residence.
Party walls on the sides of the building reduce the need for additional thermal insulation, but some changes still need to be made, especially around the floor joists.
In most cases, the plaster and stucco walls provide an adequate air barrier, but where new drywall is installed, there will be some additional sealing necessary.
When the house was converted into apartments, its owner built this staircase in place of the original.
The previous owner had also added a window bay in the between-buildings light well that ran the full height of the building. Blau said that the add-on had caused the building to sag, so she removed it and replaced it with a lighter-weight bay on the upper three floors.
Here you can see the outline of the original bay, covered by new flooring.
In addition to rebuilding this exterior stairway leading to the basement...
... a new interior stairway will be inserted at about where I'm standing in this picture. Behind that bucket, a small powder room will be built beneath the stairs.
Access to the powder room will be via this hallway leading from the main living area to the front parlor, which will serve as a bedroom.
The original fireplaces will all be preserved in the rebuilt structure. Blau is holding one of the new windowsills in this picture.
The new sills are made out of a composite material that resists rot and keeps air out better than wood.
The bulk of the retrofitting is taking place along the walls that are exposed to the outside; cuts are made in the floors to allow access to the walls.
This trench, however, was dug in order to repair and improve the sewer pipe channel that runs under this side of the back room on the main floor.
Where the previous owner had removed some floor joists, air barriers have been applied.
This water return pipe had to be relocated away from the exterior walls in order to allow for installation of thermal insulation.
Blau explained that most of the rear walls of the homes on her block and the one behind it are covered with stucco. This, she says, makes sealing a home to keep air out easier.
The wall of the Blau-Thompson residence, however, is brick. "And the builders went cheap with the brick on the sides and back of this house, which is of lower quality than the brick in front," she said. On the inside of the walls, Blau has had to apply new mortar to cover crumbling brick and decayed mortar in numerous places.
Cheap construction then, cheap construction now: Blau said that the owner of the house next door, which like hers is historically certified, covered the rear ell in vinyl siding with cheap windows without obtaining the necessary permits from Licenses & Inspections or the Historical Commission.
Even though the house is historically certified, the Historical Commission gives owners more leeway in redoing side and rear walls and windows than they do those in front. That permits use of modern building materials on the bay as well as windows without mullions.
Perhaps the chief distinguishing features of passive house construction are the windows and doors that seal tight with gaskets that prevent air from seeping in or out when closed. Here Blau explains how the sliding door to the side patio locks when the arm is raised.
A fuller view of the sliding door.
This fireplace is located in the living room of the second-floor apartment.
The casement windows on the front of the home have mullions for a historically accurate look but otherwise don't work like traditional windows. These can be opened two ways. One is from the top of the lower pane, providing a narrow opening for air...
and the other is from the side, swinging inward.
These windows are built with gaskets that make closing and opening them akin to opening and closing the door of a walk-in refrigerator. By preventing air leaks, they improve both the energy efficiency and the indoor air quality. They also all but eliminate outside noise.
Blau explained that the elements of passive house technology were all developed in North America in the years following the 1973 Arab oil embargo. "But after Jimmy Carter left office, we forgot everything we knew about them," she said. As a result, all the windows and doors are imported from Europe, where the technology was refined and improved over the decades that followed.
Extra air and thermal barriers are also applied over the windowsills. Another attractive feature of these windows is that they last much longer than even the best-made conventional windows. "We had put in top-of-the-line Martin windows 10 years ago," Blau said, "and they were already beginning to fall apart when we removed them."
Some of the original cabinetry in the second-floor apartment, which will be preserved.
Some extra air sealing and insulation will be necessary around the star bolts inserted to hold the front wall in place.
This space will become a bedroom.
A new bathroom is being installed next to the bedroom.
In addition to air barriers, moisture barriers are necessary to prevent damage from water seepage that would threaten the integrity of the exterior envelope.
Kitchen cabinets that will be reinstalled once work is complete.
The fiberglass insluation on the ceiling of this floor is for sound purposes only.
Blau said that she is structuring this project so that the total sealing of the rear rooms on each floor can take place later. Preliminary work, however, is being done now.
Blau points out the gap between the pipe and wall where insulation will be applied.
What's that pink stuff you see on the brick walls? Think of it as Pepto-Bismol for the home: it coats the brick to prevent air leaks and protect it from moisture damage.
As one might expect in a project involving a home that has been altered over the years, old beams and joists have been replaces in a number of spots.
One of the newer materials being used to make sure the bay stays in place is LVL - laminated veneer lumber, which is stronger than ordinary wood beams.
The fabric barrier is another piece of intelligent building technology: It prevents air from entering while wicking moisture out from inside, like a pair of gym socks.
The washers and dryers will be ductless: exhaust from the dryers will discharge into the interior air circulation system, where the heat from the exhaust will be sent outside via the same heat exchangers that keep the indoor air temperature constant.
The third-floor apartment, Blau said, requires the least amount of interior work. Almost everything in this hallway will remain untouched.
New mortar has been applied liberally to this section of wall in the third-floor bedroom.
The original wood flooring in this bedroom remains in good shape and will be preserved.
Plumbing hookups in the third-floor unit's bathroom.
Blau demonstrates how the bay windows work. Again, these windows both open inward like doors...
...and from the top like vents.
The third-floor kitchen, with cabinets that will be reinstalled.
New doors to the side balcony on this floor will be installed as well.
More of the original cabinetry. New appliances will be inserted in the openings.
This part of the third floor is actually the entrance to the top-floor apartment.
Blau incorporated the front room on the third floor into the fourth-floor apartment to make it a bi-level unit. The room serves as a bedroom.
Blau points to spots where air barrier coating has been applied to the plaster-covered walls, which in turn will be covered with new wallboard and thermal insulation.
The heat exchangers will go into this space that was created when the fourth-floor stairway was rebuilt.
The skylight over the stairway has been upgraded to passive house standards.
One unusual architectural element on the top floor that will be refinished and left exposed is this king's truss holding up a central ceiling support beam. The ceiling slopes toward this beam from both the front and the back of the home.
The living room of the bi-level unit, which is open to the stairwell.
A new window will be installed in the back bedroom. The bathroom had been accessed only from this room...
...but the remodeling will move the entrance to the hallway side of the room.
The electrical junction box for the apartment.
One of the biggest unexpected surprises Blau found was six layers of subfloor and a layer of crushed rock underneath the roof deck, all of which was bearing down on the rear wing and causing it to sag. She removed all six layers and the rock before building the new deck.
Tight-fitting doors for the top floor exit to the roof deck will have to be custom-built. That will come in a later phase of the project.
This photo should give you an idea of how little space the heat exchanger (technical name: "energy recovery ventilation unit") takes up. As it takes the place of a conventional heating and cooling system for each unit, it is the single biggest energy-saving item in the house.
One midcentury decorative element will survive the reconstruction as well: this 1940s-vintage school- and office-type pendant light fixture.
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