Overall Insulation R-Value

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What is the R-value?

Insulation is rated by thermal resistance (R-value), which indicates the heat flow resistance. The higher the R-value, the greater the insulating effect. The R-value of thermal insulation depends on the type of material, its thickness and density. 

When calculating the R-value of a multi-shift system, the R-values ​​of the individual offsets are added. The effectiveness of an insulated ceiling, wall or floor depends on how and where the insulation is installed. The pressed insulation does not give the full R-value. This can happen if you add thicker insulation in addition to lighter insulation in the attic. 

This also happens when placing approved thickness slats in a thinner cavity, e.g. insulation between beams, rafters and supports does not impede heat flow through these beams or supports. These areas through which heat flow is more unimpeded compared to the surrounding areas are called thermal bridges. 

The total R-value of the wall or ceiling is therefore slightly different from the R-value of the insulation. For this reason, it is important that the upper edges of the beams are covered with attic insulation, which is why we often recommend using insulation on the walls. The short circuit through the metal frame is much larger than through the wooden walls of the frame; sometimes the total R-value of an insulated metal wall can only be half as high as the R-value of the insulation.

Check the Information

No matter what type of insulation you buy, check the information on the product label to see if the product is suitable for the intended use. To protect consumers, the Federal Trade Commission has very clear regulations regarding the value of R, which must be placed on all home insulation products, both installed by professionals and bought at a local hardware store. These labels include clear R-values and information on health, safety and fire hazards. 

Take some time to read the label before applying the insulation. Insist that any contractor who installs insulation presents product labels from EVERY packaging (which also shows how much packaging has been used). 

Many special products have been developed to achieve higher R-values ​​with lower thickness. On the other hand, some materials require a larger initial thickness to compensate for any settling or to ensure that the nominal R-value is obtained at different temperatures.

Rigid and Reflective Insulation

Rigid insulation is often used for foundations and as insulating wall cladding. Reflective insulation systems are made of aluminium foils with various supports, such as wrapping paper, plastic film, polyethylene blisters or cardboard. Heat flow resistance depends on the direction of heat flow, and this type of insulation is most effective in reducing downward heat flow.

Hard Foam Insulation

During installation between wall posts, even excellent wall insulation only eliminates heat conduction through insulation, but heat loss through materials such as glass windows and posts remains unchanged. Insulation installed between columns can reduce heat loss due to air leakage through the building envelope, but usually does not eliminate it. By installing a continuous layer of hard foam insulation on the outer surface of the wall cladding, the formation of thermal bridges is interrupted by studs, while the rate of air leakage is reduced.

Spray Foam Insulation

Heat losses in apartments occur mainly in two ways: 1) heat conduction and radiation loss directly through the walls, windows, roof and floor of the house, and 2) air leakage through holes and cracks between the walls, windows, roof and floor. Most insulation is designed solely to reduce conductivity and radiation losses, while a separate air barrier is required to reduce air leakage. Spray foam insulation can improve this standard approach by performing both functions simultaneously.

Air Barrier Installation

The lack of a complete air barrier in the same place as the insulation barrier leads to heat loss and increased convection. Some insulation products contain an air barrier that needs to be sealed around the edges to limit convection heat. The basic way of heat transfer, which is affected by insulation, is heat conduction. However, insulation also reduces heat loss in all three heat transfer modes: conduction, convection and radiation. Insulation significantly slows down natural convection, making heat conduction the primary mode of heat transfer. Porous insulation accomplishes this by trapping air, eliminating significant convective heat loss and leaving only conduction and low radiation transmission. The main task of such insulation is to improve the thermal conductivity of the insulation relative to closed, standing air.

Avoid Insulation Deterioration

Mark roof trusses with spray paint to ensure the correct depth and uniformity of insulation. Unless otherwise stated about built-in lights, uncovered kitchen pipes, motors or other equipment, insulation must always be installed clearly and away from heat sources to reduce the risk of equipment failure or fire. Ensure easy access to all parts of the attic and connect cables, wires and other insulation systems that are accessible through the maintenance platform to reduce insulation deterioration.

Most builders carefully seal the perimeter of each floor panel with construction adhesive. Typically, these vents are cut through a perimeter beam, where they move the insulation and encourage air to enter the insulated room. It is better to block creeping ventilation holes in the foundation wall, where they do not affect the insulation.

Statistics

  • Buildings currently consume 30% of global energy consumption and about 30% of that is wasted. 
  • Although mortar joints can be taken into account when calculating the percentages given above, when assessing the percentage of mortar surface in relation to the wall embedded in it, it should be remembered that this is a rough technique compared to the more reliable method described in BS EN ISO (organisations which initiate, publish and maintain standards).
  • As a rule, at least 25% of the total R insulation value is used outside the steel frame. 
  • Wool insulation is made of sheep wool fibres that are either mechanically held together or combined into insulation mats and rolls with 5% to 15% recycled polyester glue. 
  • Hemp batts or rolls usually consist of 85% hemp fibres, and the rest consists of polyester binding and 3 to 5% fireproof soda. 
  • Glass mineral wool batts and rolls are made of molten glass, usually from 20% to 30% of industrial recycled and post-consumer waste. 
  • If moisture is a high risk (moisture penetration or relative humidity above 95%), a suitably resistant material must be determined. 
  • Hemp walls must be used together with a frame made of another material that can withstand vertical loads in construction since the density of hemp is 15% of the density of conventional concrete. 
  • It has been found that the total heat flow through typical wall assemblies due to thermal bridges is underestimated by up to 70%, but it has been shown that adding thermal insulation to the walls does not necessarily reduce energy consumption in the building. 
  • It has been shown that these thermal bridges reduce the insulation efficiency (R-value) by up to 50% in conventional steel pole assemblies, which means that wall assemblies and interface details do not meet the current Energy Code requirements for the minimum U-value