Building Insulation for Civil Engineering

Building Insulation for Civil Engineering

This post gives some of the basics of building insulation for civil engineering. This contains, what is building insulation, uses, types, materials for building insulation including some international standard requirements.

Now a days, energy efficiency enhancement in any buildings is very essential part. There are many ways for this which Builders, Architects and Service Consultants are constantly looking.

Building insulation is a key part in enhancement of overall comfort as well as, has a potential to reduce energy consumption to an extent of 5-8 %, which helps lower monthly energy bills.

Building insulation in civil engineering helps to maintain comfort temperature by reducing leakages.

With the initiation of green technologies and practices, today the potential to save energy by design can be as high as 40-50 %.

Why building Insulation is essential?

Most of the energy wastage in any buildings is due to leakage and without insulation and least air-tight envelope.

Building insulation Benefits:

• As stated above, energy savings approx.. 5-8% with a payback of 1-2 years
• Sound proof (acoustical) and thermal insulation.
• On account of leakage proof, reduction in moisture.
• Reduce air pollution or resistant to air infiltration

Applications of Building Insulation materials

• Exterior walls
• Interior walls
• Over the deck (roof)

Heat balance of a building would reveal that at least 15 to 20 % of the heat ingress into a building can be through walls and roof. Hence, insulating walls and roof is extremely critical in the energy performance of a building.

The insulation applications are given below:

Wall insulation

Walls can be insulated on exterior or interior depending on the architectural aesthetics required. Typical way of insulating an exterior wall is shown in figure 1.

Insulation on the exterior

• Brick work
• Plaster
• Insulation
• Polymerised mortar, 2 coats
• Reinforced fibre
• Elastomeric coat

In many of the buildings, insulation can be done on interior also as shown in figure 2.

Insulation on the interior

• Brick work
• Plaster
• Insulation
• Polymerised mortar, 2 coats
• Reinforced fibre
• Elastomeric coat

Air cavity walls

Air can also be an excellent insulator. Many of the buildings have been constructed with the masonry brick walls with an air gap of 20 to 30 mm, which provides good insulation.

Roof insulation

Roof can be insulated either over the deck or under the deck. Generally, over deck insulation is preferred, so as to avoid the absorption and retention of heat by the concrete surface.

Under deck insulation can also be considered but the thickness of insulation should be higher. Typical way of insulating the roof over the deck is shown in figure 3.

Over-deck Insulation

1. Final screed
2. Separation layer
3. Insulation
4. Water proof membrane
5. Base screed
6. Concrete roof deck

Types of insulation materials

A range of insulation materials can be installed in the building.

Autoclaved Aerated Concrete Blocks

Autoclaved Aerated Concrete (AAC) blocks are produced using materials including silica sand, lime, cement, gypsum, water, and fly-ash and aluminum powder. The special combination of these substances yields a material with excellent construction properties such as thermal insulation, structural strength, density and fire resistance.

Extruded polystyrene

Extruded polystyrene (XPS) is a type of insulation material with a high R-value, good moisture resistance, high structural strength and low weight. Extruded polystyrene is used extensively as thermal insulation in industrial, commercial and residential construction. It is commonly used in wall and roof applications.

Expanded polystyrene

Expanded polystyrene (EPS) is a type of insulation that provides thermal and acoustical insulation with characteristics such as low weight, high moisture resistance and high structural strength. Expanded polystyrene can be used to insulate the walls and roofs. Commercially this is often referred to as thermocol.

Glass wool

Glass wool is an insulation material which gives efficient thermal insulation. It is light in weight and provides good acoustic insulation also. It is commonly used for duct and wall thermal insulation.

R-value: Insulation is rated in terms of thermal resistance, called R-value, which indicates the resistance to heat flow. The higher the R-value, the greater the insulating effectiveness. The R-value of thermal insulation depends on the type of material, its thickness and its density.

R-value is the reciprocal of the time rate of heat flow through a unit area induced by a unit temperature difference between two defined surfaces of material or construction under steady-state conditions. R-value is expressed in m² K/W.

U-factor (thermal transmittance) is the heat transmission in unit time through unit area of a material or construction and the boundary air films, induced by unit temperature difference between the environments on each side. U-value is expressed in W/m2 K.

The relationship between U-factor and R-value is not always exactly the inverse and therefore R-value cannot be precisely extrapolated for a material of different thickness. However, assuming an inverse relationship may be adequate.

 ASHRAE – American Society of Heating, Refrigerating and Air-Conditioning Engineers specifies some Building Envelope Requirements

Opaque Elements(Insulation)	Non Residential		Residential
	Assembly Maximum(W/m2K)	Insulation Minimum R value (m2K/W)	Assembly Maximum(W/m2K)	Insulation Minimum R value (m2K/W)
Roofs, entirely above deck	U-0.360	R-2.6 ci #	U-0.360	R-2.6 ci
Roofs, entirely under deck	U-0.720	R-5.2 ci	U-0.720	R-5.2 ci
Walls, above grade	U-3.293	–	U-0.857a	R-1.6 cia

# ci – continuous insulation

Typical thermal properties of insulation materials:

The typical U values of walls & roof materials are given below:

Material	U-value (W/m2 K)	Thickness (mm)
RCC Walls	1.95	225
AAC Blocks	0.67	230
Concrete Roof	2.5 – 3.0	150

The U-values of common insulation materials are given below:

Material	U-value (W/m2 K)	Thickness (mm)
Extruded Polystyrene (XPS)	0.028	60
Glass Wool stuffing	0.25	150
Expanded Polystyrene (EPS)	0.30	100
Air (Still)	0.20	30

LEED India Rating and Insulation

Leadership in Energy and Environmental Design (LEED India rating system) of Indian Green Building Council (IGBC) awards ratings to green buildings by recognizing environmental performance. Selection of insulation materials can contribute to the following prerequisite and credits in the LEED India rating system.

EA Prerequisite 1	Minimum energy performance
EA Credit1	Optimize energy performance
MR Credit 4	Recycled content
MR Credit 5	Regional materials