China
Africa
Explore chapters and articles related to this topic
Energy Basics
Published in Stan Harbuck, Donna Harbuck, Residential Energy Auditing and Improvement, 2021
The R-value is a number assigned to a material to quantify its resistance to the transfer of heat. It is typically expressed in terms of resistance per unit of depth. For instance, wood typically has R-1 per inch of thickness. The R-value is determined by guarded hotbox (Figure 2-46) testing. This testing is done by keeping an inner box, the guarded, at a known temperature and placing the material to be tested around it as part of an outer box. The R-value is determined by noting the temperatures on each side of the material being tested.
Factors affecting building materials choice
Published in David Thorpe, Passive Solar Architecture Pocket Reference, 2018
R-value is the thermal resistance of a unit thickness (how much heat passes across a unit thickness of a specific material). It is the ratio of the temperature difference across an insulator and the heat flow per unit area through it. It is equal to the depth/thickness of a material divided by its thermal conductivity – that is, Rvalue=lk
Your Home and Backyard
Published in Julie Kerr, Introduction to Energy and Climate, 2017
The next thing to consider is how much additional insulation is necessary. That depends on what the house is made of and other factors. One of the biggest factors is the climate and how cold or warm it gets. The Energy Star program has developed a guide that recommends the total amount of insulation needed based on an R-value. The R-value is a measurement of the amount of heat that can pass through the insulation. The higher the R-value, the better the thermal performance of the insulation. The map and table illustrate what levels of insulation are cost-effective for different climates in the United States (Figure 18.4).
Thermal resistance of ventilated air-spaces behind external claddings; definitions and challenges (ASHRAE 1759-RP)
Published in Science and Technology for the Built Environment, 2021
Mohammad Rahiminejad, Dolaana Khovalyg
In recent years, there has been a growing interest in analyzing the thermal characteristics of building envelopes to reduce energy use in buildings since thermal energy losses through the building envelope are responsible for about 50% of all building energy use (Feng, Sha, and Xu 2016). In particular, the properly chosen materials of the external wall can help in saving up to 50–60% energy use of the buildings (Shehadi 2018). Adjacent elements in multilayered walls can have an impact on the performance of the entire assembly as well. For instance, correctly designed ventilated air cavities behind the exterior cladding systems can contribute toward energy savings in buildings (Aelenei 2006). Reduction in energy use of buildings can be achieved by adopting building envelopes characterized by low thermal transmittance or high thermal resistance value of their elements. The thermal resistance coefficient, known as R-value, is the temperature difference across the element divided by the rate of steady-state or time-averaged heat transfer through one square meter of a building component.
Embodied energy data implications for optimal specification of building envelopes
Published in Building Research & Information, 2020
Shahaboddin Resalati, Christopher C. Kendrick, Callum Hill
In order to put the insulation materials in the context of their environmental performance relative to their thermal properties, the GWP and EE values per m2 material achieving R-value of 6.6 m2 K/W have been studied and presented in Figures 8 and 9. R-value or thermal resistance is a measure of a material’s resistance to heat transfer relative to a given thickness. R-value of a building element with the addition of surface resistances is reciprocal to the total heat transmittance known as U-value, measured in W/m2 K. The assumed resistance is equal to 0.15 W/m2 K U-value which is considered as a well-insulated building element for stricter building codes and standards.