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Case Study

Gut Rehab Creates Office Space With an Apartment Above

Location: Portland, ME

In Portland, Maine, a leading green architect walks the talk on his home and office, achieving LEED Platinum

Architect Richard Renner and his wife Janet Friskey, a graphic designer, wanted a commute in downtown Portland, Maine that involved just a flight of stairs. “We jumped at the opportunity to purchase an old clothing store with an apartment above,” says Richard.

That turned out to be the easy part. “Our goals for the first-floor office and residence loft were an efficient building envelope, plenty of daylighting to the interior, and open floor plans for both spaces. And while we were at it, make the loft a LEED for Homes Platinum gut rehab.”

The best laid plans for the foundation

Renner feels that green principles should touch every part of his projects, including the waste management plan. “I really wanted to only gut what we had to, not what we could. But right off the bat with the foundation, we ran into trouble,” admits Renner.

Careful excavation around the perimeter of the first floor slab to install perimeter drains revealed that the exterior walls lacked any footings. It turned out that both the slab and the walls were so uneven that the entire slab ended up in a dumpster. But Renner quickly adds, “While we ended up not being able to reuse the slab, it all ended up in a crusher for recycling.”

And Renner ended up capitalizing on this twist to his plans. “With the old slab out, we changed the floor level to add 11 more inches of height to the 1st floor, installed a gravity foundation drainage system, and installed sub-slab insulation as well as a capillary break between the soil and our floor system.”

A continuous air and thermal barrier for the building envelope

The first challenge in creating a high-performance envelope for this building is the brick exterior walls. “You have to lose that great brick look on one side or the other,” says Renner. “We decided to give up some precious floor space and get a new brighter surface on the interior by studding in walls to be filled with foam, spacing the stud walls 1 to 1.5 inches off the brick to eliminate thermal bridging and also allowing space for a drainage mat.”

New triple-glazed windows were installed flush to the interior in part to make the window installation detail simpler but also to keep alignment with the interior insulation and air barrier.

At the roof line, a combination insulation system was used: 2 inches of closed-cell foam as the air and vapor retarder with the rest of the 12-inch plus framing cavity filled with dense-packed cellulose. With the exterior brick walls air-sealed and insulated on the interior, it was easy to make the roof air and thermal barrier continuous with the wall system.

“We must have done it right — our blower-door test result came in at 2.39 ACH 50 (0.12 ACHnat),” Renner proudly states. “Not bad for a gut rehab.” Not bad, indeed.

NOTE: With this type of insulation approach — flash-and-fill — the relationship between the R-values of the foam and remaining cavity fill is important and affects the need for an interior vapor retarder and the potential for wintertime interstitial moisture accumulation. See these three GBA blogs:

  • Vapor Profiles Help Predict Whether a Wall Can Dry)
  • Are Dewpoint Calculations Really Necessary?
  • Calculating the Minimum Thickness of Rigid Foam Sheathing

LEED Platinum and the Thousand Home Challenge

A HERS rating of 43 certainly helped quite a bit toward the LEED for Homes Platinum goal, but Renner was a bit disappointed in not meeting the Thousand Home Challenge. “Our actual first-year total energy use came in at about 28 MMBtu, and we needed to be at about 23 MMBtu for the Thousand Home Challenge under Option B (Option A in the THC is based on comparing pre- and post-retrofit actual total energy use while Option B is based on building- and climate-specific performance algorithms).”

One factor is that only two people are living in a space that could easily accommodate three occupants; there is a second full bedroom. Since the actual overall energy use is quite low, it is hard to think of anything dramatic that could have been done differently. (See images #19 and #20 in the image – Energy Use Bar Graph and Energy Use Summary.)

Elegantly green interior elements

There are a number of really fine interior touches in this Portland residence: a loft-within-a-loft work space (image gallery #11), interior hardware made from steel window frame cut-offs (image gallery #13), perforated interior kneewall screens that hide clutter but allow deeper light penetration (image gallery #11), solar tubes for a windowless bathroom (with city night light pollution meaning they work for more than just day time). “The interior layout and design was a team effort,” asserts Renner. “My wife and I did much of it together, but my staff also collaborated quite a bit.”

The Renners will walk the talk

The Renners know that even the most energy efficient design and construction require follow-up by the occupants. Here is the Renner energy “to-do” list:
1. Aggressively address passive (“vampire”) loads.
2. Closely coordinate heat-recovery ventilation with open windows in warmer months. When the windows are open, turn the system completely off.
3. Turn down the heat in the winter. Daily setback will not work well, because the system is radiant, but overall set points could be lower. Bedroom zone is currently set at 62 degrees; the rest of the loft is set at 65 degrees. Both could be reduced somewhat.
NOTE: Renner adds: "The heating component of overall energy use meets the Thousand Home Challenge goal; one could turn down the heat, but we have chosen not to do so. It is worth noting that the annual cost of heat and hot water is only $320. I track these costs using heating bills."
4. Put coffee in a thermos instead of using the coffee maker’s heating element to keep the coffee warm.
5. The outside light at the front door is left on all night, because there is a graffiti problem in the neighborhood. Installing a motion sensor would reduce energy use. Renner is currently finding that he can keep this outdoor light off except when entertaining.
6. Install an exterior sunshade at the south-facing clerestory windows to reduce heat gain in the summer.
7. Use the roof deck for drying clothes when possible.
Renner is experimenting with running the HRV less frequently, and turning it off completely when the house is empty.

Lessons Learned

Richard Renner is very forthcoming about what worked well and what did not on his projects. Here are his lessons learned on their Portland loft:

The high windows in the clerestory are only ten feet above the windows on the main level, but this is enough of a difference to create air flow for natural ventilation. These high windows deliver sufficient daylight on all but the darkest days. A shade, which was planned but omitted for budget reasons, would have reduced solar gain in the summer.

The bathroom has no windows, but Solartube skylights provide plenty of daylight.

An unexpected benefit of triple glazing is that the loft is quiet in spite of its urban location.

The loft’s open plan and long interior views make it feel larger than its actual size.

Locating the heat-recovery ventilator above the bathroom ceiling makes maintenance more difficult. However, there was no other place to put it.

Recessing the windows to maximize size and thermal efficiency required complicated head, jamb, and sill flashing. Snow frozen on the deep sill occasionally restricts the operation of the awning windows.

At today’s prices, the 1-kW grid-tied photovoltaic system is not cost-effective. The building geometry created a less-than-optimal collector orientation, and the adjacent building and nearby trees reduced the solar aperture.

If Renner had it to do over again, he would install an induction cooktop instead of the gas cooktop.

And here is a closing comment that Richard believes about all of his work: “There is no conflict between high levels of building performance and good design.”

General Specs and Team

Location: Portland, ME

Bedrooms: 2

Bathrooms: 1

Living Space: 1600 sqf

This space is a full floor of loft residence above an equivalent area of office space below.

Design and Project Management: Richard Renner, Richard Renner Architects
Design collaboration and interiors: Janet Friskey, Friskey Design
Engineering: Becker Structural Engineering
Petersen Engineers
Marc Rosenbaum, Energysmiths
Terry Brennan, Camroden
Lighting: J&M Lighting Design
Construction: Kolbert Building
Millwork: Wright-Ryan Construction
Interior finished metalwork: Jon Chalfant, Chalfant Design


  • R-54 roof
  • R-34 above-grade walls
  • Accurate-Dorwin triple-glazed windows (U-factor=0.15; SHGC=0.29)
  • Tankless gas water heating (0.95 AFUE)
  • Baxi Luna condensing boiler
  • Ductless mini-split air conditioning (13 SEER)
  • Energy Star fluorescent lighting & appliances
  • 1 kW PV system, grid-tied

  • Water Efficiency
  • Toto toilets
  • Toto Aquia (CST414M), dual flush toilets
  • low-flow faucets
  • Delta low-flow showerhead
  • GreenGrid roof trays
  • Indoor Air Quality
  • Low or no-VOC paint throughout
  • Formaldehyde-free plywood for cabinet structures
  • RenewAire HRV
  • Green Materials and Resource Efficiency
  • Recycled doors
  • FSC-certified birch flooring & wood trim
  • FSC-certified framing
  • Wheatcore interior doors
  • Bamboo plywood cabinetry
  • Recycled-content tile
  • PaperStone counters


USGBC LEED for Homes Platinum

Image Credits: James R Salomon, Richard Renner, Peter Vanderwarker, Fine Homebuidling

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