What is the R value of a concrete slab?
R-value Calculation for Concrete Slab. A reasonable R-value for a normal concrete slab can be estimated using an R-value, the thermal resistance per inch of thickness, between 0.1 and 0.2 and multiplying it times the slab thickness. however, the following expression can be used to compute R, this equation is provided by ASTM C 168:
What does R value mean in construction?
In construction, the R-value is the measurement of a material's capacity to resist heat flow from one side to the other. In simple terms, R-values measure the effectiveness of insulation and a higher number represents more effective insulation. R-values are additive.
What is the mass-enhanced R-value of a precast concrete panel wall?
The Mass-Enhanced R-value of a precast concrete sandwich panel wall is that R-value that provides the same energy loads (for heating & cooling) as a wall of lightweight construction. The Mass-Enhanced R-value is derived from the Steady State R-value taking into account the beneficial effects of mass.
What is precast concrete?
Precast concrete’s low water-cement ratio means precast is extremely durable. Its long life offers minimal maintenance and reuseable, recyclable structures which contain less concrete and steel and absorb CO
Is precast concrete a good insulator?
Precast concrete's edge-to-edge insulation, combined with the nonconductive connectors between the interior and exterior concrete layers, can create an efficient thermal break that prevents heat and moisture from penetrating the building and eliminates thermal loss and vapor transmissions present in other wall ...
What is R-value of concrete?
How do you calculate R-value?MaterialThicknessR-value (F° · SQ.FT.)Concrete Masonry Unit (CMU)8″1.11Concrete Masonry Unit (CMU)12″1.28Concrete 60 pounds per cubic foot1″0.52Concrete 70 pounds per cubic foot1″0.4226 more rows
What are the disadvantages of precast concrete?
Disadvantages of Precast ConcreteHigh Initial Investment: For installing a Precast Concrete plant, heavy and sophisticated machines are necessary which requires a high initial investment. ... Transportation Issue: The construction site can be at a distant location from the Precast Concrete plant.More items...
How do you calculate the R-value of a concrete wall?
3:368:573-7 - Calculating R-Value for a Wall (Part 1) - YouTubeYouTubeStart of suggested clipEnd of suggested clipThe half inch of stucco. The two inches of foam. Board the four inches of concrete. And then we haveMoreThe half inch of stucco. The two inches of foam. Board the four inches of concrete. And then we have the interior film coefficient. And we need to have our values for each of these layers.
What is the R-value of 6 inches of concrete?
1.23The R-value listed by PCA for a normal-weight (144 pcf) 6-inch concrete wall is 1.23 and includes inside and outside air-film resistances, which contribute to overall thermal resistance.
What is the R-value of 8 thick concrete?
The R-value of an 8-inch poured concrete wall is R-1, with two or more inches of insulation needed to increase the value. An 8-inch solid wall has a thermal mass of about 21 Btu/ft2/°F.
How long does precast concrete last?
100-yearPrecast concrete structures can be designed for 100-year service life with minimal upkeep.
Is hollow blocks better than precast?
Poured concrete walls meanwhile, are typically more expensive and labor extensive to build. However, they are stronger by at least five times than concrete hollow blocks. Poured concrete also carries the benefit of being better load bearing walls and are known to better withstand earthquake impacts.
Are precast concrete walls good?
Advantages of Precast Concrete Walls Precast concrete walls can be designed to be reused for future building expansions. Precast concrete's durability creates a low maintenance structure, which stands up to harsh climate conditions.
What is the R-value of ICF walls?
ICF walls consist of a center cavity to contain concrete between two layers of EPS which provide two continuous layers of insulation rated at R-22 and higher.
What material has the highest R-value?
Vacuum insulated panels have the highest R-value, approximately R-45 (in U.S. units) per inch; aerogel has the next highest R-value (about R-10 to R-30 per inch), followed by polyurethane (PUR) and phenolic foam insulations with R-7 per inch.
What is a good R-value?
Depending on where you live and the part of your home you're insulating (walls, crawlspace, attic, etc.), you'll need a different R-Value. Typical recommendations for exterior walls are R-13 to R-23, while R-30, R-38 and R-49 are common for ceilings and attic spaces.
What is the mass enhanced R value of precast concrete?
The Mass-Enhanced R-value is derived from the Steady State R-value taking into account the beneficial effects of mass. Deemed-to-Satisfy (DTS) R-values for wall elements are given in the Building Code of Australia (BCA). The Mass-Enhanced R-value described in this Standard will give calculated energy loads over a large range of buildings and designs no greater than the BCA DTS solutions. The BCA for both commercial buildings (Volume 1) and domestic buildings (Volume 2) provides for adjustments to the Steady State R-value to account for mass walls with a surface density greater than 220 kg/m2. This Standard describes a rigorous method to account for the mass effects of precast concrete sandwich panels. The Mass-Enhanced R-value in general allows for an improved economy of this form of construction. Determination of the Mass-Enhanced R-value of a precast concrete sandwich panel wall element is facilitated by a publically accessible Calculator available on the National Precast Concrete Association’s website at www.nationalprecast.com.au. A printed certificate available via the Calculator provides documentary evidence of compliance to the BCA – DTS requirements. Details of the methodology employed to derive the Mass-Enhanced R-values has been peer reviewed by international experts who found it to be sound and an advance on the Steady State traditional R-value.
What is the purpose of the National Precast Concrete Association?
National Precast Concrete Association Australia was established in 1990 to represent and promote the Australian precast concrete industry . Membership is made up of precast manufacturers (Corporate Members), as well as suppliers to the industry (Associate and Professional Associate Members), overseas precast manufacturers (Overseas Members) and affiliated organisations (Affiliate Members). National Precast members manufacture high quality precast construction elements such as walling, flooring, structural sections, drainage, civil and environmental products.
What is the purpose of National Precast?
National Precast’s mission is to be the recognised agency of the Australian precast concrete industry promoting and representing manufacturers of high quality factory-made precast concrete components and promoting precast concrete as the material of choice to the building and civil construction industry.
What software was used to simulate buildings?
All simulations were conducted using the CSIRO AccuRate energy simulation software for buildings version 1.1.4.1. MsDOS batch routines were written to perform the many simulation runs and data manipulations. These batch programs employed the sed text file editor to alter as required the AccuRate “Scratch” file that holds input data to the computational engine. Occupancy profiles (e.g. thermostat settings, casual loads, times of occupation etc) were altered to comply with BCA requirements for Class 1 and 2 buildings. As part of the batch procedures a Fortran routine was written to interrogate the various output files and write the required data to an Excel comma delineated *.csv file for analysis. Following the initial “lightweight” case, walls were altered to precast concrete sandwich panel construction. The internal layer thickness was varied to result in a range of surface density solutions from 169 kg/m2to 841 kg/m2. The limitation of any particular Mass-Correction Factor calculation is that it is specific to a climate and the building variation considered in the simulation. Figures 7 to 11 show the results of a series of simulations as described for several locations.
Does precast concrete have energy?
The results show that (within the limits of rounding errors, etc) the building with the precast concrete panel walls has an energy performance less than or equal to the lightweight wall case.
Is precast concrete fire resistant?
Structures are also fire resistant and perform well acoustically. When incorporated into passive solar design, the high thermal mass of precast concrete can reduce heating and cooling costs.
Is precast concrete sustainable?
Sustainable design takes into consideration the environment, society and economy. Precast concrete’s inherent properties make it a natural choice for achieving sustainability in today’s modern buildings. Locally manufactured using local products (lower transport costs) in reuseable moulds, precast produces minimal waste and most manufacturing waste is recycled. Recycled or waste materials can be included in the concrete mix, such as slag, flyash, aggregate, steel and water. Exact elements are delivered to site meaning fast construction, less disruption to neighbouring properties, less site trades (WHS benefits) and less site waste (less transportation and disposal of waste). Precast concrete’s low water-cement ratio means precast is extremely durable. Its long life offers minimal maintenance and reuseable, recyclable structures which contain less concrete and steel and absorb CO
What is the difference between R value and U value?
R-value is the measurement of concrete slab (or other material) capacity to resist heat flow i.e. it measures the effectiveness of insulation or thermal resistance. However, U-value is the measurement of heat transmission through concrete slab from ground into the closed space or vice versa .
How to convert an American R value to a European U value?
So, to convert an American R-value into a European U-value, divide 1 by the R-value,then multiply the result by 5.682.
Is lower density concrete better than higher density concrete?
Due to the fact that thermal insulation varies inversely with density, lower density concrete provides better insulation than higher density concrete. Finally, it orders to decide the on the ability of the reinforced concrete slab to resist heat transfer, it would be required to calculate R-value and U-value of the reinforced concrete slab ...
