September 13, 2012
Cold

Abstract: 

Building Science Corporation (BSC) has been working with Byggmeister, a partner on the Building America (BA) team, on retrofit projects under the BA program. Byggmeister is a local design-build firm that specializes in energy efficient retrofits and new construction. The Byggmeister multifamily test home located in Jamaica Plain, Massachusetts (Jamaica Plain or J.P. Three-Family) is a three-story brick row house. The test home is examined with the goal of producing a case study that could be applied to similar New England homes. Basic areas of research that this report is expected to contribute include finding the combination of measures that are feasible, affordable, and suitable for this type of construction and acceptable to homeowners.

Executive Summary

Building Science Corporation (BSC) seeks to further the energy efficiency market for New England area retrofit projects by supporting projects that are based on solid building science fundamentals and verified implementation. BSC has been working with Byggmeister, a partner on the Building America (BA) team, on retrofit projects under the BA program. Byggmeister is a local design-build firm that specializes in energy efficient retrofits and new construction. The Duclos, Eldrenkamp and Panish Energy Group (DEEP Energy Group), which is associated with Byggmeister, conducts design-phase energy analysis and monitors completed projects.

The Byggmeister multifamily test home located in Jamaica Plain, Massachusetts (Jamaica Plain or J.P. Three-Family) is a three-story brick row house. The test home is examined with the goal of producing a case study that could be applied to similar New England homes. This report will contribute to basic areas of research, including finding the combination of measures that are feasible, affordable, and suitable for this type of construction and acceptable to homeowners.

For the J.P. Three-Family retrofit, BSC weighed options for insulating load-bearing masonry buildings on the interior while considering unique conditions such as the appearance of the exterior, walls and roof shared between multiple housing units, bulk water management, and the building's susceptibility to freeze-thaw (FT) damage.

Energy modeling was performed with BEopt (Christensen and Anderson 2006) and EnergyGauge USA (Parker et al. 1999) software packages to determine energy impacts and cost effectiveness of various measures. While BEopt calculates estimated cost effectiveness of the retrofit measures, several limitations of the software prevent it from accurately modeling certain aspects of the building's energy use. The EgUSA results are shown in a step-by-step parametric model to evaluate the impact of individual measures. In addition, utility bill/energy use data were examined for trends and to "tune" the energy models to some degree.

Heat flow simulations were run using THERM 5.2 (LBNL 2003) Two-Dimensional Building Heat-Transfer Modeling Software to examine thermal bridging at the masonry walls. Due to the existing geometries of the walls, such as the tee or party walls between the units, several scenarios were examined for the interior and exterior insulation of the tee party walls.

In order to assess the FT risk to the bricks, material property tests were performed with the Wärme- und Feuchtetransport instationär (WUFI) 4.1 Pro hygrothermal simulation program. Simulations were conducted for both the west-facing rear wall and east-facing front wall to assess the impact of solar radiation and rain on different orientations and to determine the effects of adding thermal insulation to the inside of the walls.

1 Introduction

Building Science Corporation (BSC) seeks to further the energy efficiency market for New England area retrofit projects by supporting projects based on solid building science fundamentals and verified implementation. BSC has been working with Building America (BA) partner, Byggmeister, a local design-build firm that specializes in energy efficient retrofits and new construction. The Duclos, Eldrenkamp and Panish Energy Group (DEAP Energy Group), which is associated with Byggmeister, provides design-phase energy analysis and conducts monitoring of completed projects.

The Byggmeister multifamily test home located in the Jamaica Plain neighborhood of Boston, Massachusetts (J.P. Three-Family), is a three-story brick row house. BSC examined the home with the goal of producing a case study that could be applied to similar New England homes.

This study contributes to several basic areas of research that include finding the combination of measures that are feasible, affordable, and suitable for this type of construction and that are acceptable to homeowners. This report also examines the package of measures considered, initial energy use results, material properties test results of the brick, and heat flow simulation results for the party walls.

This test home is a candidate to participate in the National Grid Deep Energy Retrofit Pilot Program (National Grid 2009), which provides financial incentives and technical support to participants. The program’s goal is to achieve at least 50% better energy performance than a code-built home. BSC has partnered with National Grid, providing technical guidance and support for the program. Through this partnership, BSC began working with the owner of the J.P. Three-Family to provide recommendations for retrofitting the building.

1.1 Context and Relevance to Other Homes

The J.P. Three-Family test home is a three-story row house with load-bearing mass masonry (brick) walls located in the Jamaica Plain neighborhood of Boston. The building and the adjacent properties were built circa 1906–1918. The test home is divided into three apartments: a onebedroom first floor unit and two-bedroom units on the second and third floors. All units are typically occupied with vacancies between rental terms that provide an opportunity to perform
retrofit upgrades.

Figure 1: Preretrofit Jamaica Plain Three-Family in Boston, Massachusetts

2 Site Assessment for Jamaica Plain Three-Family

2.1 Exterior Masonry Condition Assessment

The front and rear of the building are predominantly east and west exposures, respectively, although there is some shielded south-facing wall, due to the narrow light well at the side of the building.

Figure 2: Exterior front and overhead view of masonry townhome project

The test building was cleaned and repointed more recently than identical buildings on the street were, as depicted in the exterior photos (Figure 2).

Figure 3: Front window sill and head details, showing end dams on solid stone sill

The front face brick is a smooth finish brick (likely chosen for appearance), with fine mortar joints; the transition between the front face brick and side/rear utility brick is shown in Figure 5.

The brick wall at the front and rear of the building is two wythes thick, with a 1-in. space between the wythes that is filled with mortar droppings and air space. The interior is finished with wood strapping (with an approximately1-in. air space cavity) and wood lath with horsehair plaster.

Figure 4: Exterior 1-in. mortar/air space and interior wall (strapping and wood lath with plaster)

The front façade has water shedding details such as stone band courses at the window sills and above some window heads. At grade, the brick terminates to a stone (likely granite) base course. This base course reduces brick capillary water uptake.

Figure 5: Front face brick/side brick transition (left) and brick termination at grade (right)

End dams carved into the stone sills (Figure 3 and Figure 7) direct water accumulation from the window face out from the surface of the masonry. However, efflorescence and signs of water runoff were noticeable below the windows at most floors. The lack of a drip edge detail at the window sill band was noted (Figure 6).

Figure 6: Efflorescence pattern under window sills (left); lack of drip edge at window sill band detail (right)

At first, the team suspected that the efflorescence might be caused by the window sill planter boxes; however, adjacent identical buildings without planter boxes also showed a pattern of water runoff and mortar joint erosion concentrated under window sills (Figure 7).

Figure 7: Adjacent building showing severe mortar erosion under window sills

An initial assessment of a building for freeze-thaw (FT) vulnerability starts with an examination of the most exposed areas, in terms of rainfall deposition and concentration, and cold temperatures. Typically, the most exposed and unheated area is a building’s parapet: rainfall accumulates at top corners, and flow of heat from the interior is reduced due to the greater surface area. The parapet at J.P. Three-Family showed no signs of FT damage (Figure 8). A metal cap detail is installed over the parapet, and the brick is detailed to enhance water shedding and reduce accumulation on the wall below. This detail tends to reduce risks of wetting, and therefore, FT damage. . .

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