This condensation can accumulate as frost in cold weather, and subsequently cause “leaks” when the frost thaws and liquid water drains down, or cause rot if the moisture does not dry quickly upon the return of warmer and sunnier weather.In walls with sufficient exterior insulation, the dewpoint temperature of the interior air will be below the temperature of the back of sheathing: therefore condensation due to air leakage cannot occur within the studspace. However, while these permeable layers can essentially eliminate vapor diffusion condensation risks with lower exterior sheathing R-values, the risk of air leakage condensation does not drop as much: air leakage may still deliver more water vapor to the back of the sheathing than can be removed by diffusion through the sheathing, and hence condensation could still occur and accumulate.For important projects or situations in which the design team has little historical experience, investigation using widely available computer models such as WUFI-ORNL would be prudent if the necessary time and skills are available.Copyright 1997-2020, buildingscience.com Corporation| BSD-163: Controlling Cold-Weather Condensation Using Insulation As outdoor conditions become colder, the interior RH drops because interior moisture is diluted by increasingly dry exterior air. Some judgement is therefore called for. Hence, the choice of conditions for the analysis is very important. Heat flows from hot to cold, and in the wintertime the ground temperature is warmer than the outside temperature the majority of the time. Rigid insulation is typically the preferred choice of insulation contractors and building envelope professionals. In special occupancies, such as swimming pools, both the interior temperature and relative humidity levels will be higher (78°F/25 °C and 60%RH), resulting in very high absolute humidity levels.The moisture content of the exterior air always drops at very cold conditions as the maximum air moisture content drops. This report was prepared as an account of work sponsored by an agency of the United States government. More detailed calculations including the resistance of wood cladding and an air gap, and properly interpolating the results between an outdoor temperature of 0 and 5 °C show that sheathing insulating value of R-5 over an R-12 batt will control condensation as well.This type of simple analysis can be conducted on a monthly basis and plotted to help visualize the condensation risk. The December, January, and February temperatures for Toronto are -1.9, -5.2, and -4.4 °C respectively, leading to a wintertime average temperature in Toronto of -3.8 °C (25 °F). Although air barrier and vapor control layers can reduce the quantity and occurrence of condensation due to both mechanisms, the use of exterior insulation (even if that insulation is a vapor barrier and/or air barrier) can warm sensitive surfaces within a wall and thereby eliminate or reduce condensation risks. There are a number of different factors at play but the one thing that we always need to keep in mind is heat flow. Although data for outdoor air temperatures is readily available, even north-facing walls will have some exposure to diffuse solar radiation, which will warm the cladding (and hence the wall), above the outdoor air temperature for many hours of cold winter months.It is difficult to choose the exterior temperature to design for, since any level of condensation protection can be chosen by the analyst, from none to total.

There are a number of different factors at play but the one thing that we always need to keep in mind is heat flow. First, it helps increase the ground temperature, so heat loss is not as great. STEP 2: Identify your Application. STAR. Exterior Concrete Slab Insulation Options It is good practice to insulate concrete slabs in cold climates to protect the slab from frost penetration. In warm climates, the barrier should point to the outside of the house, blocking the vapor from the humid outside air that may seep into the walls or ceilings. Steel is also a great border for security.

Find the application and description below that most closely matches your project. The perimeter insulation and wing method, although effective on the edge, does not supplement a good overall frost reduction strategy in an outside concrete pad.No, placing the proper density of rigid insulation under the concrete slab does not contribute to concrete cracking. If we know where the heat is, we can harness it and have a better chance of holding back the frost. Diffusion usually does not move sufficient quantities of water vapor fast enough to generate a problem. This effect provides some protection against condensation, as the coldest week of the year is likely to coincide with some of the lowest interior humidity levels.The interior moisture content is usually defined by a combination of temperature and relative humidity. Note that the ratio of exterior insulation value to the framing cavity R-value defines the cold-weather condensation risk. If the sheathing layers are very vapor permeable (e.g., rockwool over fiberboard or gypsum sheathing, and housewrap) then very little insulation value is required outboard of the stud bay. When exterior insulation is applied, ... Energy efficiency renovation of historic buildings in cold climate is a very complex issue due to hygrothermal behavior of the building envelope. Cold: (Climate zones 5 & 6) Very - Cold: (Climate zone 7) Subarctic: (Climate zone 8) Marine: (Part of climate zone 3 & 4) (IECC Zone) You can also use the Building America Guide to help determine your climate region by county. This does two things. An example of a wood-framed wall in the Chicago climate is shown in Adding more air-permeable insulation to the stud bay (e.g., if a 6” stud is required structurally, a well-intentioned contractor may fill the stud cavity with an R-20 batt) will of course lower the safety against condensation—dangerously in this case. It is good practice to insulate concrete slabs in cold climates to protect the slab from frost penetration.