Research Reports are technical reports written for researchers but accessible to design professionals and builders. These reports typically provide an in-depth study of a particular topic or describe the results of a research project. They are often peer reviewed and also provide support for advice given in our Building Science Digests. The most recent documents posted are at the top of the list below.
In multifamily buildings, central (typically rooftop) ventilation systems often have poor overall performance, overventilating some portions of the building (resulting in excess energy use), while simultaneously underventilating other portions of the building (resulting in diminished indoor air quality). These issues are often tied to multistory stack effects (warm air rising at cold outdoor conditions), and a lack of compartmentalization (airtightness) between floors and between units. These issues are exacerbated by the presence of multistory shafts (e.g., elevator shafts, stairwells, and ventilation shafts). Central corridor supply and makeup air systems combined with rooftop central exhaust systems are particularly problematic. The recommended solution is to isolate the units from one another and from corridors, shafts, elevators, and stairwells by means of greater airtightness.
This guideline pertains to design and application guidance for combination space and tankless domestic hot water (DHW) heating systems (combination systems) used in residential buildings, based on field evaluation, testing, and industry meetings. As residential building enclosure improvements continue to drive heating loads down, using the same water heating equipment for both space heating and domestic water heating becomes attractive from an initial cost and space-saving perspective. This topic is applicable to single- and multifamily residential buildings, both new and retrofitted. Before committing to wide-scale implementation of such combination space and domestic water heating systems for high performance buildings, whether new or retrofit, design decisions and site conditions affecting performance, maintenance, and occupant acceptability should be well understood. Current performance rating procedures for this type of hot water heating system and its many variants are inadequate to provide convincing prediction of estimated savings. In order to be assured of meeting the Building America savings goals, and the persistence of those savings after installation, continued sharing of lab and field testing results is needed.
This research project developed baseline engineering analysis to support the installation of thick layers of exterior insulation (2” to 8”) on existing masonry walls and wood framed walls through the use of wood furring strips (fastened through the insulation back to the structure) as a cladding attachment location. Furthermore, water management details necessary to connect the exterior insulated wall assemblies to roofs, balconies, decks, and windows were created to provide guidance on the integration of exterior insulation strategies with other enclosure elements.
Basements can account for up to one quarter of the typical energy consumption in a house. Therefore, insulating foundations is a critical measure for achieving high performance buildings. This is important in both new construction and retrofits of existing buildings. The fundamental problems and “best practice solutions” for moisture-safe basement insulation have been well established. However, many foundations are damp (either due to bulk water or capillary “wicking” of moisture) or of a type of construction that is not easy or straightforward to insulate (such as rubble foundations). Damp foundation repair methods can be “leveraged” to provide energy efficiency benefits. An example of this “hybrid” approach is spray foam insulation, which can be an effective means of liquid phase water control (leaking basement), vapor phase water control (diffusion and air leakage transported condensation) as well as an effective insulation.
Historically, weatherization programs have required that cellulose insulation materials be dense-packed to a minimum installed density of 3.5 pcf. This density limit was, in part, required to realize beneficial reductions in air leakage. The Building Performance Institute (BPI) currently has under development two standards that will set requirements for the airflow resistance of insulations used in retrofit cavity (i.e. dense-pack) installations (BPI-102) and define acceptable test methods to measure the airflow resistance of insulation materials used in dense-pack applications (BPI-103).
The following report is an excerpt from the 2010 Building Science Corporation Industry Team Building America Annual Report. Many concerns, including the rising cost of energy, climate change concerns, and demands for increased comfort, have lead to the desire for increased insulation levels in many new and existing buildings. Building codes and green building codes are being changed to require higher levels of thermal insulation both for residential and commercial construction. This report will review, and summarize the current state of understanding and research into enclosures with higher thermal resistance, so-called “High-R
Enclosures”. Recommendations are provided for further research.
This paper is from the proceedings of the Thermal Performance of the Exterior Envelopes of Whole Buildings XI International Conference, December 5-9, 2010 in Clearwater, Florida. This paper summarizes some of the limitations of the various approaches to assessing the freeze-thaw resistance of brick masonry units and presents a detailed methodology for using frost dilatometry to determine the critical degree of saturation of brick material. Test results are presented for bricks from several historical load-bearing masonry. Recommendations are made for applying this approach together with hygrothermal model in the design of retrofit insulation projects.
The following report is an excerpt from the 2010 Building Science Corporation Industry Team Building America Annual Report. The main focus for this research project is the integration of a combination space and domestic hot water heating system (“combi
system”) with a high-efficiency air source heat pump to optimize efficiency and comfort.
The following report is an excerpt from the 2010 Building Science Corporation Industry Team Building America Annual Report. A wide variety of ventilation systems are installed in US houses to reduce interior contaminant levels and safeguard occupant health. The relative merits of these systems are subjects of ongoing research. Prior work by Building Science Corporation has investigated the effects of air distribution and mixing on pollutant levels within the building. The present work is aimed at discovering the energy costs of various ventilation approaches in operation, through modeling of typical houses across the TMY2 location set. Both measures are helpful in recommending a particular ventilation system.
The following report is an excerpt from the 2010 Building Science Corporation Industry Team Building America Annual Report. The goal of this research is to find optimally designed, cost effective roof insulation systems that can be included with other enclosure details to help reduce whole house energy use by 70%. This report will compare a variety of roof insulating strategies and present their advantages and disadvantages according to several comparison criteria.
The following report is an excerpt from the 2010 Building Science Corporation Industry Team Building America Annual Report. This report investigates the implementation of advanced framing in both production and prototype built homes built in a variety of climate regions across the USA. This work is part of a large research project on High R-value enclosures. The current industry standard wall is being replaced by a 2×6 frame at 24-inch centers with single top plates, two-stud corners, no jack studs, no cripples and single headers (and in many cases no headers at all). The advanced framing system is cheaper because it uses 5% to 10% less board feet of lumber, and it is faster because it uses 30% fewer pieces. It saves energy because it provides a 60% deeper cavity (which allows 60% more cavity insulation) and because it reduces the framing factor. Advanced framing can save energy, greenhouse gas emissions, and money if properly implemented. Through BSC’s experience we have found that builders can save $1000 per house on advanced framing. To maximize cost savings and energy savings for the homeowner, the builder financial savings are best shifted to implementing more energy saving measures.
The following report is an excerpt from the 2010 Building Science Corporation Industry Team Building America Annual Report. Many concerns, including the rising cost of energy, climate change concerns, and demands for increased comfort, have lead to the desire for increased insulation levels in many new and existing buildings. Building codes are improving to require higher levels of thermal control than ever before for new construction. This report considers a number of promising foundation and basement insulation strategies that can meet the requirement for better thermal control in colder climates while enhancing moisture control, health, and comfort.
This paper describes a hygrothermal modeling study, including all of the US climate zones, a range of interior humidity levels and numerous arrangements and types of insulation. The results showed that so long as airtightness is provided, and wintertime humidity is controlled, numerous unvented solutions using either or both spray foam (open and closed cell) and fibrous insulation (cellulose and mineral fiber) can be successful. Climate, the solar properties and exposure of the roofing, the air and vapor permeance of the insulation(s) and interior humidity are the most important factors to be considered in the design of moisture-safe unvented roof systems.
The following report is an excerpt from the 2009 Building Science Corporation Industry Team Building America Annual Report.
The balance between wetting, drying, and safe storage is critical to the long term performance of building enclosures. Where wetting cannot be controlled to acceptable levels, safe storage and drying become critical.
This paper documents the experimental methodology, details, and results and discuss how this information can be applied to modeling drained wall systems. Practical applications and research questions arising from the work are presented.
Advanced framed wall systems that use a stud spacing of 24 inches on center and eliminate the plywood or OSB sheathing from the wall and replace it with insulating sheathing is a type of enclosure assembly that has been designed to be energy efficient combined with efficient material use.
This report considers a number of promising wall systems that can meet the requirement for better thermal control. Unlike previous studies, this one considers performance in a more realistic matter, including some true three-dimensional heat flow and the relative risk of moisture damage.
This report is available from the Canadian Urethane Foam Contractors Association (http://www.cufca.ca/home_e.php). It is reproduced here for convenience. A common question encountered by SPF applicators, building designers, and code officials is the need for an additional vapor barrier or retarder. Experience by many contractors and some consultants suggest that special low permeance layers such as polyethylene are rarely needed in many types of walls. Theory indicates that closed cell foam is sufficiently vapor impermeable to control diffusion condensation and that low-density open-cell foam applications may require additional vapor diffusion control in some extreme environments. However, the need for, and type of additional vapor control layers remains unanswered to many.
This document summarizes the theory behind thermal insulation and building system heat flow control metrics and presents a literature review of selected research into this area.
