Executive summary
This project explores the implementation of external insulation and over-cladding strategies in brick masonry buildings in Chicago. The strategy was implemented in a two-story detached single-family house and a larger detached multi-family building. The test homes selected for this study represent the dominant housing types in the Chicago area. The high energy consumption for heating, which is characteristic of these buildings, threatens the affordability of housing. Uninsulated massive masonry walls also have a very detrimental effect on comfort. If the properties of these masonry buildings are to be brought up to a level corresponding to today's standards, significant changes in the performance parameters of the walls will be necessary.
Significant changes to the performance of drywall assemblies are generally beyond the scope of typical weather protection (Wx) program resources. The Cook County Community and Economic Development Association, Incorporated (CEDA) has received a Sustainable Consumer Energy Resources Innovation Grant (SERC) sponsored by the United States Department of Energy (DOE). This grant provides CEDA with the opportunity to pilot innovative approaches to drywall refurbishment. This research project is evaluating the implementation of an exterior insulation and cladding approach in two masonry buildings that represent the dominant types of housing stock in the Chicago area. Retrofitting measures are assessed against feasibility, cost and efficiency.
The insulation and exterior cladding strategy is designed to be implemented by contractors active in CEDA Wx programs and to use materials and methods familiar to those contractors.
The study identifies:
- Conditions where external insulation and masonry wall cladding are recommended.
- Significant implementation challenges for external insulation and masonry wall cladding
- The levels of airflow control that can be achieved with a given strategy.
- Risks inherent in the approach that needs to be addressed
- Basic measures and practices to achieve the performance of external insulation and masonry wall cladding.
- Effective strategies for integrating windows with external masonry insulation and cladding systems.
The research described in this report, through observations of implemented strategies, identifies critical performance measures as well as conditions for wider application. The study also identified common factors to consider when determining whether an exterior insulation and cladding strategy is appropriate for a building.
1 problem description
The dominant construction types of residential buildings (detached single-family and multi-family) in Chicago include load-bearing masonry walls. Methods for isolating these sets of walls are often beyond the scope of the Wx programs. However, the need to improve the thermal performance of these masonry buildings is clear. Residential buildings in the Chicago area show significantly higher heating energy consumption than other building types and other cold climate regions of the country (AGA 2010). Energy costs are an increasing burden on household income. Uninsulated massive masonry walls with low-performance glazing also have a very detrimental effect on thermal comfort. If these masonry buildings are to be brought up to performance levels comparable to current minimum standards, significant changes in the thermal performance of the walls will be required.
Adding insulation to the walls of such masonry buildings in cold, and especially cold and humid, climates can cause performance and durability issues in some cases. Problems and solutions are described by specialists such as Maurenbrecher et al. (1998), Gonçalves (2003) and Straube and Schumacher (2002, 2004).
Examples of internal insulation problems in massive masonry walls include freeze-thaw damage (due to reduced outward heat flux) and deterioration of wooden structural members (usually floor joists) that are embedded in assemblies of dough (due to higher equilibrium moisture content) . . . The issue of freezing and thawing walls was dealt with, among others, by Mensing et al. (2010) and Straube et al. (2012). The problem of the deterioration of embedded floor beams has been studied by some specialists (Dumont et al. 2005; Morelli 2010; Ueno 2012), but many problems remain unresolved.
In addition to the risks of insulating interiors from massive masonry, this strategy has limitations in performance due to factors such as the frequent presence of integrated floor or wall assemblies that act as thermal bridges. The amount of insulation that can be placed in a solid masonry wall without changing the configuration of the interior space is typically limited to the depth of the internal frame or strip cavities and the capacity of free blown insulation materials in these cavities.
When a building is occupied, implementing an internal insulation strategy can be very damaging to the occupants. Working with the schedules and possessions of residents also greatly complicates implementation. Adding insulation to the exterior of existing buildings has been shown to be an effective way to overcome these limitations and provide higher effective R-values for building wall assemblies. The benefits of this approach go beyond simply adding thermal resistance; Benefits in the form of increased durability and airtightness of the building are also often emphasized (Ueno 2010).
The basic concept of insulating the exterior of existing masonry walls has many advantages in terms of air barrier durability and continuity (Hutcheon 1964; Lstiburek 2007). In addition, retrofitting the external insulation often allows for greater thermal resistance than is usually achievable with retrofitting the internal insulation. Practice should be simple; however, several issues hinder its widespread implementation. For example, manufacturers of siding systems and exterior insulation materials typically limit the thickness to 1½ inches in their warranties; Therefore, fixing the liner is a problem. Various researchers and practitioners deal with this issue (Straube and Smegal 2009; Pettit 2009; Joyce 2009; Ueno 2010; Baker 2012). Demonstrations by members of our research team have shown that it is practical to use external insulation up to 8 inches thick outside buildings and masonry structures (Lstiburek 2009).
The lack of widespread acceptance of fastening methods by manufacturers has created obstacles to official and building acceptance. In addition, the construction industry does not know the details of water management and the integration of window and door systems, terraces, balconies and roof-wall connections in assemblies with thick external insulation. Baker (2012) proposed a designed foundation and support for the installation of thick layers of external insulation in existing masonry and frame walls. Their report also outlines the water management details required to integrate windows, doors, patios, balconies and roofs.
Long-term solutions to the energy cost and comfort issues of existing masonry buildings will require measures to improve the performance of masonry assemblies. Widespread adoption of one potential solution, drywall exterior insulation, will require demonstration projects that demonstrate the feasibility of these techniques and assess the challenges. Thanks to the SERC Innovation Grant, CEDA has the opportunity to demonstrate and test such measures. Through a partnership with Building America, Building Science Corporation (BSC) has partnered with CEDA to provide technical guidance and evaluation of the implementation of retrofit measures. In providing technical guidance on the details of water management and cladding fixation, BSC relied on previous and contemporaneous studies on retrofitting exterior insulation.
2 Project context
2.1 Masonry buildings in Chicago
Masonry buildings are the dominant type of apartment buildings in Chicago. While this is to be expected for large, older multifamily buildings, it is also true for smaller apartment buildings in Chicago. According to the Cook County Assessment Department, 57% of the single-unit and 58% of the two- to four-unit housing stock in Cook County is masonry.1
Utilities data collected shows that Illinois has the second highest average consumption of gas per individual customer in the United States (AGA 2010). Only individual gas customers in Alaska consume, on average, more than individual gas customers in Illinois (seeFigure 1). Households in the CEDA service area use even more on average than the rest of the state, exceeding the Alaskan residential average and using nearly twice as much gas per home as in other areas with a warm climate such as Minnesota.
Figure 1.Average gas consumption per individual customer for various cold climate states and CEDA territory
2.2 CEDA air conditioning
The Illinois Multi-Family Home Weather Assistance Program (IHWAP) is for owners of buildings that provide housing to residents of Chicago and suburban Cook County who meet the income criteria. The program is free for the building owner if 66% or more of the tenants have qualifying income.
The CEDA Wx program serves income-eligible customers for households residing in multi-family buildings in Cook County, Illinois. A multi-family building is eligible for the service if at least two-thirds of households in a multi-family building have qualified income. CEDA Wx is one of over 30 social action agencies participating in IHWAP. The program is administered by the Illinois Department of Commerce and Economic Opportunity; its Energy Aid Office monitors all agencies in the IHWAP network. The services provided by CEDA Wx are based on a comprehensive energy audit conducted by a CEDA Wx consultant. The audit leads to the development of a work order, which may include activities from the following categories:2
- Modernization activities: insulation, compact fluorescent lamps, replacement of refrigerators, shower heads and low-flow faucet aerators, replacement of the heating system, replacement of doors and windows
- Air Seal Measures
- Health and Safety Measures (limited to $600 each): Handrails, fire extinguishers, gutters, downpipes, and removal of unventilated radiators.
- Occasional repair (limited to $500 each).
DOE Wx funding requires the entire building or home to achieve a savings-to-investment ratio of 1 or greater before it can be weathered.3Software tools are used to estimate savings from various activities. Approved contractors present the costs of individual elements of the works in their offer. The statewide IHWAP administration sets a spending limit of $5,200 for each eligible unit. Approved contractors participating in CEDA Wx programs carry out the scope of work. Upon completion of the assignment, the CEDA Wx assessors inspect the thermal performance of the drywall units and conclude that there is no room for improvement at the investment level consistent with typical Wx schedules. The fur cavity between the brick wall and the interior trim does not provide adequate space for effective insulation. The program did not include measures to construct internal walls for insulation due to anticipated costs and complications. The measures available also do not include insulation and external coatings. Overall, these strategies were considered too unfamiliar to contractors and potentially posing a fire safety risk.
In 2011, CEDA received a special grant from the SERC program, the DOE's innovation grant program. This grant allowed CEDA to allocate resources beyond normal Wx program allocations to a limited number of selected projects. Thanks to the subsidy, the budget of a single-family unit increased by $9,600, and the budget of a multi-family unit by $6,400.
The SERC Innovation Grant provided CEDA with the ability to implement, on a limited basis, several strategies to address weaknesses in building performance that had hitherto been outside the scope of the Wx programs. One of the innovations that CEDA decided to implement with this funding is exterior insulation and masonry wall cladding.
2.3 Cooperation in BSC-CEDA research
In 2010, CEDA and BSC teamed up with selected CEDA Wx staff, management and consultants to develop a pathway to significantly increase the efficiency of CEDA-registered homes, particularly masonry buildings. These meetings identified important packages of measures that will be explored in the form of prototypes and/or pilot implementations. In conclusion, the basic packages describe a comprehensive high-performance update. The first package that the collaboration evaluated through a series of implementations was the Wx advanced approach to the roof of 1.5-story brick bungalows (see Neuhauser 2012).
The SERC grant provided a potential BSC-CEDA collaboration opportunity to evaluate another important package for masonry buildings: masonry wall cladding and insulation. BSC and CEDA have started preparatory work by developing schematic details of the cladding assembly and evaluating a number of potential design candidates.
After BSC and CEDA began preparatory work, two factors emerged that caused disruption to the joint effort. On the one hand, management changes within the CEDA organization have resulted in uncertain support for the project. On the other hand, the wider domestic political climate created some uncertainty as to whether the BSC would be able to support their participation in the project. As a result, the financing and implementation of the siding and insulation project was uncertain for much of the project's original schedule. This affected BSC's ability to participate in the project. In fact, BSC's participation was essentially suspended from the time the bid was submitted by the contractor until just before the start of construction. As a result, critical opportunities to provide guidance to contractors and obtain performance data prior to retrofitting were lost. During the project, the availability of CEDA resources was also limited. This made it difficult to collect some post-upgrade performance data. . .
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Footnotes:
- The percentages given are based on 2010 data.
- Please note that since the investigation period, the list of drugs allowed in the program has changed slightly.
- Typically, the value of savings is taken as the present value of recurring savings in a given period at a standard discount rate. The current value of the savings is then compared to the initial cost or investment of the asset.