Garber-Slaght R.,Cold Climate Housing Research Center |
Craven C.,Cold Climate Housing Research Center
Journal of Green Building | Year: 2012
In cold climates, a large amount of heat is lost through windows during the winter. For instance, a double-pane window might allow as much as 10 times the amount of heat to leave a house compared to the same area of a typical 2 × 6 wall. It makes sense to upgrade or insulate windows in order to improve the thermal envelope of a home, especially in an area with a long heating season; however, windows are a very expensive component of the building envelope to replace. Replacing a single window can cost several hundred to more than a thousand dollars; therefore, people often resort to cheaper methods to reduce heat loss, such as shutters or curtains. Others may already have high-performance windows, but want to reduce heat loss even further by placing movable insulation over their windows during the cold winter nights. To help guide these decisions, the Cold Climate Housing Research Center (CCHRC) in Fairbanks, Alaska, conducted a study of common window insulation methods and compared them in terms of thermal effectiveness, affordability, ease of installation, durability, functionality, and condensation resistance. The purpose of the study was to inform homeowners about the various advantages and disadvantages of different window treatments. As part of the research, CCHRC studied a variety of methods and windows in volunteers' homes to understand how the methods work in real-life situations. CCHRC also modeled the retrofit window treatments with Therm 6.3, a modeling program, to help explain more generally how they can help homeowners.
Craven C.M.,Cold Climate Housing Research Center |
Garber-Slaght R.L.,Cold Climate Housing Research Center
7th International Cold Climate HVAC Conference | Year: 2012
A common practice in residential construction is retrofitting above-grade walls with foam insulation to reduce heating demand. Structures in sub-arctic environments typically have an air/vapor retarder on the interior framing surface, therefore the addition of relatively water vapor impermeable exterior foam insulation on the exterior has the potential to significantly reduce the drying ability of wall systems. The reduced drying ability is problematic if the retrofit does not adequately prevent condensation within the wall framing. These retrofits may induce mold growth, thereby increasing susceptibility to indoor air quality problems and reduced service life of retrofitted structures. To investigate the likelihood of this retrofit strategy causing moisture accumulation in wood-framed structures in sub-arctic environments, nine nominal four ft (1.2 m) by eight ft (2.4 m) test wall sections were constructed using varying ratios of stud-fill fibrous insulation and foam insulation exterior to the wall sheathing. The use of a polyethylene air/vapor retarder varied; each test wall with an air/vapor retarder had unsealed penetrations common to past construction practices. The wall sections were tested in Fairbanks, Alaska over two winters under varying interior relative humidity and air pressure conditions and were monitored for temperature, relative humidity, and wood moisture content. Test walls with less than approximately 68% of the nominal wall R-value on the exterior performed poorly in terms of wood framing moisture content and relative humidity at the sheathing interior surface. Wall systems without a polyethylene air/vapor retarder had widespread visible mold growth at the end of the two-year empirical test. Wall systems with a polyethylene air/vapor retarder tended to have lower humidity at the sheathing surface and visible mold growth only near penetrations in the air/vapor retarder, but had higher wood moisture contents well into the summer drying season. Moisture accumulation and mold were largely absent from test wall sections that had 68% or more of the total wall R-value on the exterior, regardless of whether an interior air/vapor retarder was present. © 2012 ASHRAE.
Stevens V.,Cold Climate Housing Research Center |
Kotol M.,Technical University of Denmark |
Grunau B.,Cold Climate Housing Research Center |
Craven C.,Cold Climate Housing Research Center
Journal of Cold Regions Engineering | Year: 2016
Thermal mass in building construction refers to a building material's ability to absorb and release heat based on changing environmental conditions. In building design, materials with high thermal mass used in climates with a diurnal temperature swing around the interior set-point temperature have been shown to reduce the annual heating demand. However, few studies exist regarding the effects of thermal mass in cold climates. The purpose of this research is to determine the effect of high thermal mass on the annual heat demand and thermal comfort in a typical Alaskan residence using energy modeling software. The model simulations show that increased thermal mass can decrease the risk of summer overheating in Alaskan residences. They also show that increased thermal mass does not significantly decrease the annual heat load in residences located in cold climates. These results indicate that while increased thermal mass does have advantages in all climates, such as a decrease in summer overheating, it is not an effective strategy for decreasing annual heat demand in typical residential buildings in Alaska. © 2015 American Society of Civil Engineers.
Craven C.,Cold Climate Housing Research Center |
Garber-Slaght R.,Cold Climate Housing Research Center
HVAC and R Research | Year: 2014
Retrofitting walls with foam insulation is a common practice in residential construction to reduce heating demand; however, the implications of this practice for moisture control are less straightforward. Typically structures in cold climates have a polyethylene vapor retarder on the interior framing surface, therefore adding relatively water vapor impermeable exterior insulation greatly reduces the drying potential for the wall system. Furthermore, while condensation potential is reduced by the addition of exterior insulation, wood framing can be subject to a temperature and humidity regime more conducive to fungal growth relative to pre-retrofit conditions. To investigate the potential for exterior insulation retrofit strategies in subarctic climates to cause moisture accumulation in wood-framed structures, nine test wall sections were constructed using varying ratios of stud-fill and exterior insulation. The wall sections were tested in Fairbanks, Alaska, over two winters and were monitored for temperature, humidity, and wood moisture content. Test walls with less than two-thirds of the nominal wall R-value exterior to the framing performed poorly in terms of wood moisture content and relative humidity at the sheathing interior surface whether or not the test walls were equipped with vapor retarders. The findings are used to examine conventional moisture control frameworks. Copyright © 2014 ASHRAE.
News Article | March 16, 2016
"In the spring, after the permafrost thaws and the ground settles, Wilson Andrew Sr takes a wrench to the metal pilings that hold up the foundation of his house in Atmautluak, Alaska, and makes it level again. He cranks the screws until the foundation flattens out, level with the ground. At least for now. Andrew’s house, on a small island traditionally inhabited by indigenous Alaskans, is a prototype modular home designed by the Fairbanks-based nonprofit Cold Climate Housing Research Center (CCHRC) to be resistant to harsh weather and a quickly changing climate, while still being affordable and easy to build. These are the challenges of housing design in the far north, where seasonal variability is exacerbated by climate change – like the heave and twitch of permafrost and the slow creep landward of the edge of the sea ice – adds to the challenge of building in an already brutal environment. Pipes freeze, walls molder. It can be prohibitively expensive, if not impossible, to get labor and supplies, which has led to a huge shortage of housing. And then there’s the social challenge associated with providing permanent housing for population groups that have been living nomadic subsistence lifestyles for generations."