Field measurements of moisture variation in cold ventilated attics with different ceiling constructions

Hansen, Thor; Møller, Eva B.

doi:10.1016/j.egypro.2017.10.023

Cited by 3 publications

(7 citation statements)

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“…It was expected that there would be a temperature difference. A rough estimation based on the Glaser method described in ISO 13799 (2012) and DS 418 (2011) showed there would be a temperature difference in the winter of up to 1°C, and consequently a difference of approximately 5% RH, depending on whether there were 150- or 400-mm insulation in the ceiling (Hansen and Møller, 2016). There is no significant difference in moisture content between attics with different amounts of insulation material.…”

Section: Discussionmentioning

confidence: 99%

Hygrothermal performance of cold ventilated attics above different horizontal ceiling constructions: Full-scale test building

Hansen

Møller

Tvedebrink

2019

Journal of Building Physics

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It is often assumed that reduced heat flux to a ventilated attic reduces the temperature and thereby increases the relative humidity. Consequently, the importance of having a tight air and vapour barrier in the ceiling becomes more important with increased insulation. Therefore, in Denmark, the recommendation is to have a tight vapour barrier when re-insulating ceilings against cold ventilated attics to a total of 150-mm insulation material. The recommendation is independent of the insulation material’s hygroscopic properties or the indoor moisture level. The aim of this project was to test the relevance of the recommendation through testing in a full-scale test building (7 × 22 m) with a series of six different ceilings with or without a vapour barrier and variation in the insulation material comprising insulation thickness and its hygroscopic properties. The examination was performed with a controlled indoor climate after an European humidity classes 1–3 and a natural outdoor climate. The study showed very little differences in temperature and relative humidity in the cold ventilated attics, while the humidity class of the indoor climate significantly affects the absolute moisture content in the attic. However, the climate in the attic did not cause mould growth in the test sections, even for humidity class 3. Consequently, in the test building the thickness or hygroscopic properties of the insulation material did not have a significant effect on the moisture level in attics and did not determine whether a vapour barrier should be installed. In this study with the given climate, a vapour barrier is unnecessary in well-ventilated attics if the ceiling is airtight.

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Section: Discussionmentioning

confidence: 99%

Hygrothermal performance of cold ventilated attics above different horizontal ceiling constructions: Full-scale test building

Hansen

Møller

Tvedebrink

2019

Journal of Building Physics

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“…However, full-scale studies as well as field studies have not been able to establish this effect [16,19]. Some measurements do however indicate marginally lower moisture conditions in cold attics with hygroscopic insulation materials [20].…”

Section: Additional Ceiling Insulationmentioning

confidence: 99%

“…Secondly, vapour barriers can vary significantly in conditions, even within one house. Similarly, installation of new vapour barriers is often omitted when refurbishing [5], due to costly and comprehensive work, and the airtightness is provided solely by a plastered ceiling.…”

Section: Vapour Barriers In Ceilingsmentioning

confidence: 99%

“…Furthermore, a lower temperature in the attic reduces the ventilation by stack effect, driven by temperature differences, and thus the ability to remove excess moisture is impeded. Some studies however, show that the amount of insulation does not have significant effect on the attic temperature [5,14] that appeared to be mostly dominated by outdoor temperature [15]. Most importantly, adequate ventilation of the cold attics with outdoor air seems important for the hygrothermal performance of the attic, and therefore, the application of postinsulation should not block any existing ventilation openings [16,17].…”

Section: Additional Ceiling Insulationmentioning

confidence: 99%

“…Moisture intrusion in these naturally ventilated, cold attics can be attributed to outdoor air in times of high humidities and, primarily, infiltration of moist air from the indoor environment, which causes raised levels of concern [4]. The infiltration of humid air to the attic from the dwelling is primarily attributed to convection through leakages in the airtight plane [5,6], which in these houses is located in the ceiling, but diffusion through the construction also occurs [7]. Leakages occur through cracks, insufficiently tight hatches and joints-all of which should be minimized in order to reduce the convection and associated moisture transport to the attic.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Danish Dwellings with Cold Attics—Ventilation Rates and Air Exchange between Attic and Dwelling

Hansen

2021

Buildings

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Naturally ventilated cold attics are traditional in many Danish single-family homes. The moisture balance of these attics is dependent on sufficient ventilation for removal of excess moisture. Moisture is generated in the dwelling below, and transported to attic spaces through convection and diffusion. Therefore, airtight ceilings are vital for reduction of excess moisture, which may yield mould growth in the attic. If mould spores migrate to the dwelling it can cause risk of health concerns for occupants. The presents study includes analysis of tracer gas and temperature/relative humidity measurements, in 30 dwellings/attics. The measurements yielded results of both air change rates in attics and dwellings, as well as air exchange between the two zones. Four of 30 houses, met the recommended air change rate of 0.5 h−1, and only in summer. The air change rate in the attics was found to be higher, and with larger variation compared to the dwelling. Visible mould growth was found in three attics, which all exhibited low air change rates. Air exchange between zones occurred in houses both with and without vapour barriers. The downward air exchange in summer, was however slightly larger in cases without vapour barriers. These results highlight the importance of airtight ceilings for both dwelling and attic performance.

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Energy performance of residential roofs in Canada – Identification of missing links for future research opportunities

Schreiber

Jandaghian

Baskaran

2021

Energy and Buildings

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Field measurements of moisture variation in cold ventilated attics with different ceiling constructions

Cited by 3 publications

References 0 publications

Hygrothermal performance of cold ventilated attics above different horizontal ceiling constructions: Full-scale test building

Hygrothermal performance of cold ventilated attics above different horizontal ceiling constructions: Full-scale test building

Danish Dwellings with Cold Attics—Ventilation Rates and Air Exchange between Attic and Dwelling

Energy performance of residential roofs in Canada – Identification of missing links for future research opportunities

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