Roof Thermal Transfer Value

Overall thermal transfer value ottv is meant to measure the envelope thermal performance of air conditioning buildings that is followed an energy efficiency standard.

Roof thermal transfer value. Q winter u a ti to ti inside air temperature. Thermal benefits of green roofs. Yik and wan 2005 stated that the ottv is an appropriate building envelope energy performance index for use in regulatory control. Insulation is only one component of your roofing system but it performs multiple functions that you can optimize for your building.

In this paper a new rttv model is proposed with new formulation for modelling the equivalent thermal resistance increment due to the solar reflectance effect on opaque roofs using the previously developed crht cool roof heat transfer model. Modulate heat flux through the roof by. The new formulation is incorporated into the u value estimation of the heat conduction gain component. To outside air temperature.

In summer the solar radiation affects the outside surface of wall and roof. In winter the heat loss is simple transmission based on the inside and outside temperature and u value of composite structure. U value thermal conductance is a measure of a material or assembly to transfer heat. Plants and substrate require energy and mass balance.

Results of reviewed studies show that thermal behavior of green roof is subject of different conditions like type and thickness of growing medium leaf area index and density of vegetation ceiling temperature transfer coefficient r value of roof and climate of studied region. The rttv model is very similar to the ottv model except that due to different orientation the model coefficients are different. Roof and wall are analyzed in the same way. Roof thermal transfer value rttv model is prescribed for air conditioned non residential buildings as guidelines for thermal performance of roofs in numerous southeast asia countries.

Not a conventional insulation material. In a typical meteorology year the modeling results show that the shingle and thermoplastic polyolefin roof transfer 78 9 294 1 kwh m yr and 8 5 128 2 kwh m yr of heat into the. In order to address the inherent limitations in the existing models this study proposes a novel method to incorporate the effects of surface solar reflectance of the opaque portion of roofs into. To differentiate between the walls and the roof the term roof thermal transfer value rttv is used instead.

Roof thermal transfer value rttv 6 roof thermal transfer value rttv 6 1 if the roof of an air conditioned building is provided with skylight the ettv concept is also applicable to its roof.