Effect of cool roofs on commercial buildings energy use in cold climates

Hosseini, Mirata; Akbari, Hashem

doi:10.1016/j.enbuild.2015.05.050

Cited by 48 publications

(18 citation statements)

References 10 publications

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“…The most interesting conclusion that emerges is that the thermal gradient between the surface temperatures (Tsup) of a dark colored roof with respect to a cool roof depends more on the solar irradiance level than on the external temperature. Therefore, if during the summer season the positive contribution in reducing thermal loads due to the reflection of the sun heat gains is confirmed, a possible negative impact on the winter heating loads is a function of latitude and meteorology, i.e., the number of clear and extremely sunny days during the winter season: paradoxically, at very cold latitudes, where winter sunny days have a lower relevance, the ratio of cloudy to sunny days increase and the impact of global solar radiation on the roof is smaller [39], the cool roof has potentially less impact than at temperate or warm latitudes characterized by quite mild and sunnier winters.…”

Section: The Surface Temperatures Analysismentioning

confidence: 87%

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Assessment of the Impact of Cool Roofs in Temperate Climates through a Comparative Experimental Campaign in Outdoor Test Cells

Barozzi

Pollastro

2016

Buildings

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Abstract:Over the last few decades many bibliographical studies have been conducted on cool roofs, by analyzing both the energy performance during summer and winter seasons and their contribution in mitigating the urban heat island effect. This paper describes the experimentation carried out in three outdoor test cells to comparatively assess the behavior of a cool roof solution with respect to a ventilated-roof and a warm-roof. The monitored data have confirmed that in summer cool roofs are the best solution, with respect to traditional tile roofing, sensibly reducing surface temperatures as a function of the solar direct radiation level (15-25 • C for I > 600 W/m 2 and 5-15 • C for I < 300 W/m 2 , independently of the season). Furthermore, cool roofs involve an energy saving related to summer cooling by about 20% as to a warm-roof and 15%-20% as to a vented-roof. During winter, cool roofs improve the heating energy performance of a vented-roof by about 12%, against a slightly increased consumption (<5%) if compared to a warm-roof. These data confirm that, in temperate climates, cool roofs are appropriate solutions to sensibly improve summer energy performances with a negligible negative impact during winter, and to positively contribute to the mitigation of the heat island effect.

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Section: The Surface Temperatures Analysismentioning

confidence: 87%

“…In contrast, some other authors have demonstrated that winter heating penalties for cool roofs are negligible in cold climates-even without the effect of snow- [21,39], depending on: the ratio of cloudy to sunny days (which increases during winter), less total solar radiation available on the roofs, the effect of snow.…”

Section: Introductionmentioning

confidence: 85%

Assessment of the Impact of Cool Roofs in Temperate Climates through a Comparative Experimental Campaign in Outdoor Test Cells

Barozzi

Pollastro

2016

Buildings

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“…A single-story building model was selected because of the major influence of roof properties on the floor just below it. Additionally, office buildings are usually suitable for the application of cool roofs [12]. The standard office building model presented a rectangular prism shape with total floor area equal to about 510 m 2 (27.7 m × 18.4 m), 3 m height and aspect ratio equal to 1.5.…”

Section: Zone (Köppen-geiger)mentioning

confidence: 99%

“…For instance, heating energy use penalties in winter may be generated by the implementation of such materials in heating-dominant regions [10,11]. In this view, Hosseini and Akbari [12] focused on cold climates to demonstrate that cool roofs were able to provide annual energy savings in all considered climates for the simulated prototype office and retail buildings. With the aim of estimating the impact of using cool roofs in several climatic conditions, Synnefa et al [13] simulated the heating and cooling load of residential buildings in 27 cities worldwide.…”

Section: Introductionmentioning

confidence: 99%

Cool Roof Impact on Building Energy Need: The Role of Thermal Insulation with Varying Climate Conditions

et al. 2019

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Cool roof effectiveness in improving building thermal-energy performance is affected by different variables. In particular, roof insulation level and climate conditions are key parameters influencing cool roofs benefits and whole building energy performance. This work aims at assessing the role of cool roof in the optimum roof configuration, i.e., combination of solar reflectance capability and thermal insulation level, in terms of building energy performance in different climate conditions worldwide. To this aim, coupled dynamic thermal-energy simulation and optimization analysis is carried out. In detail, multi-dimensional optimization of combined building roof thermal insulation and solar reflectance is developed to minimize building annual energy consumption for heating-cooling. Results highlight how a high reflectance roof minimizes annual energy need for a small standard office building in the majority of considered climates. Moreover, building energy performance is more sensitive to roof solar reflectance than thermal insulation level, except for the coldest conditions. Therefore, for the selected building, the optimum roof typology presents high solar reflectance capability (0.8) and no/low insulation level (0.00-0.03 m), except for extremely hot or cold climate zones. Accordingly, this research shows how the classic approach of super-insulated buildings should be reframed for the office case toward truly environmentally friendly buildings.

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“…The presence of snow in most of the heating season, narrowed sun ray angles radiating during shorter days, increased cloud cover and nighttime heating schedules all contribute towards minimizing the impact a cool roof would have in preventing winter heat gains in the building. The effects of snow accumulation on cool roofs were studied by [37], [38] and [39], who concluded that its presence significantly mitigated their heating penalty in the winter in both Montreal, QC and Anchorage, AK. Considering that weather patterns are dynamic and often deviate from standard definitions, roof design practices for winter remains largely unchanged due to the permanent factors discussed above.…”

Section: Effects Of Highly Reflective Roofs (Cool Roofs) On Buildingsmentioning

confidence: 99%

Cooling and heating energy performance of a building with a variety of roof designs; the effects of future weather data in a cold climate

Hosseini

Tardy

Lee

2018

Journal of Building Engineering

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Building engineers commonly use the Typical Meteorological Year (TMY) weather data for simulation and design purposes. However, the nature of TMY in excluding weather extremes makes them less suitable to investigate the effect of potential climate change on building design as climate change likely increases the frequency and magnitude of those extreme conditions. The current practice of designing buildings has lacked a clear method to incorporate future climate change trends. An approach is used to compare present weather simulation results of a commercial building with varying roof reflectance and insulation thermal resistance parameters with future year-by-year results which are affected by potential climate change. Future weather data for year-by-year simulations is obtained by "morphing" historical weather data with a General Circulation Model (HadCM3). Mean energy consumption and optimal roof configurations are discussed with regards to climate change over the study period, and are compared to results obtained with TMY data. Results show that increased roof solar reflectance always lead to less mean and less variant cooling energy consumption. The study shows the importance of considering possible future climate scenarios and in building energy performance design.

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Effect of cool roofs on commercial buildings energy use in cold climates

Cited by 48 publications

References 10 publications

Assessment of the Impact of Cool Roofs in Temperate Climates through a Comparative Experimental Campaign in Outdoor Test Cells

Assessment of the Impact of Cool Roofs in Temperate Climates through a Comparative Experimental Campaign in Outdoor Test Cells

Cool Roof Impact on Building Energy Need: The Role of Thermal Insulation with Varying Climate Conditions

Cooling and heating energy performance of a building with a variety of roof designs; the effects of future weather data in a cold climate

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