Insulation
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Table of Contents
Insulation found behind the bricks of a home being built [1]. |
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What is Insulation?
Insulation is a critical part in keeping pipes, containers, homes, and other components within a set temperature range [3]. The objective for using insulation is usually to reduce heat loss and prevent freezing. The type and quantity of insulation needed will depend on the situation. For instance, more extreme weather or industries with extreme temperatures may need more insulation. This is because a physical/chemical system wants to go to equilibrium.
Through energy transfers, the heat is transferred either to the environment or the object in use. This transfer can be seen on the image to the right with energy shown by the arrows going in different directions. Insulation increases the time it takes for the system to reach equilibrium, and good insulators increase this time significantly. There is no perfect insulator so heat loss/transfer is inevitable.
Image showing what an extra layer of insulation may look like [2]. |
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Thermal Resistance and Conductivity
Thermal resistance ("R") is the resistance of a material to the known flow of heat. This will help indicate the effectiveness of a material as an insulator. More information on the thickness required to meet the R-value can be found online. As well, it will indicate the required insulant thickness. For instance, the table below shows the R-values of different materials and the required thickness.
| Insulated R-values of different materials [4]. |
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The environment that the item is in is also important to consider. A home in Northern Canada will need more thermal resistant insulation than a house near the Equator. Consider that for the insulation type.
The table below shows the differences between thermal conductivities and their values would influence one's decision to choose one. There are other ways to measure the thermal properties of an insulator, such as the thermal conductivity (denoted "K").
The table shows different thermal conductivities of building and insulating material [5]:
| Material | Apparent Density at Room Temperature (p, lb/ft3) | T, °C | k (Btu/(h ft2)(°F/ft) |
|---|---|---|---|
| Celluloid | 87.3 | 30 | .12 |
| Coke, petroleum | - | 100 | 3.4 |
| Coke, petroleum (20-100 mesh) | 62 | 400 | 0.55 |
| Coke (powdered) | - | 0-100 | 0.11 |
| Wood (Across grain), Oak | 51.5 | 15 | 0.12 |
| Wood (Across grain), White Pine | 34.0 | 15 | 0.087 |
| Wood (Across grain), Maple | 44.7 | 50 | 0.11 |
| Wood (Across grain), White Fir | 28.1 | 60 | 0.062 |
Choosing a Material
Different materials have different specific heat capacities and thermal capacities. For instance, wood is not very good for insulation. Wool on the other hand would be a good insulator.
There are three main classifications of insulation: low, intermediate, and high temperature thermal insulation [6]. The temperature range and compatibility is important to understand when choosing a material [6].
| Type of Insulation | Temperature Range | Applications | Example |
|---|---|---|---|
| Low | -273 °C to 15 °C | Refrigerant pipes, chilled water surfaces, cryogenic | Polyethylene insulation, cellular glass |
| Intermediate | 16 °C to 315 °C | Steam, high temperature water | Glass fibre, calcium silicate, mineral fibre |
| High | 316 °C to 815 °C | Boiler, turbine, exhaust | Ceramic fibres, cements |
Considerations for Different Insulators:
Removable / Reusable
Some insulators are easy to remove. They require less time to install and can be removed and reinstalled to other applications. A good example is removable blankets that can be installed on valves, flanges, and other components that can be removed. If the removable insulator has problems such as being torn or broken, it can be replaced easily.
Fibrous Insulation
There are fibers that may be placed in parallel or perpendicular to the surface that is insulated. Some examples include rock wool and silica. The material resistivity to heat will need to be found online to compare the two.
Form
The form in which the insulation comes in may be different. For instance, it may be a foam, cement, or flexible blanket.
Flammability
Certain materials are more flammable in the presence of a heat source. This can create an unwanted fire hazard.
Price and Quantity
Depending on how much insulation one might need, the selection of the insulation may differ. Some insulation can be more expensive. More can be found on the insulation manufacturer's website.
Accessories
Wires, straps, tape, adhesives, and other securement accessories will need to be used to support the insulation in place. When buying insulation, consider how it will best attach to the surface it is being placed on.
Layering
Using Layers
The first layer will reduce heat loss by 85% [7]. More layers can be added to reduce the heat loss, although it will cost more and the benefits with each additional layer decreases.
Jackets
Jackets may also be added over the insulation to reduce corrosion, bacteria, and vapour build up. On the image to the right, a jacket or insulation covering can be seen protecting the copper pipe from the outside elements (e.g. water).
Placement of Insulation [8] |
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Sound Dampening using Insulation
Decibels (dB)
This is the measurement of how loud a noise is [9]. By adding a wall or insulation, there can be a transmission loss (TL), which can stop the sound. This is important for rooms where soundproofing is a priority. Some good, common materials for soundproofing include fibre glass, polyester fibre, and silicone.
Factors that Impact Sound Damping/Soundproofing: [10]
1. Density - Density is the mass per unit volume of a substance. By packing the molecules closer together, the sound waves will be damped. If it is considered too low, it will absorb the sound.
2. Cell size - The material cells must be smaller than the wavelength of sound. As well, the arrangement of cells is importance. An open cell arrangement is better at absorbing sound, whereas a closed cell arrangement is better for blocking sound.
Applications
Insulation for Piping
Precast insulation is usually used as it is more convenient to make in advance in a factory rather than at a construction site. The insulation material and pipe are wrapped together by metal banding. As well, it is cheaper to precast the tube for long sections.
For sections of the pipe that bend (e.g. at joints, elbows) a liquid insulation may be used.
House Insulation
In a house, there are a number of places that insulation is placed. In between the roof and ceiling of top floor, insulation is put. As well, there is insulation for all the rooms and the basement in particular.
Typically the insulation on the top is used by blowing an insulation material such as loose fiberglass.
Some homes built pre-1970's used asbestos which was one of the best insulators before, and more information can be shown in the next section.
Insulated Pipes that is pre-fabricated [11] |
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Safety Associated with Insulation
When looking at different insulation materials, be sure to look at the Safety Data Sheet (SDS) and follow the guidance. There are also municipal and federal rules that will need to be followed and may impact selection.
Piping
For piping, if no insulation is used, the pipes can freeze and burst. Since piping may be in hard to reach/access areas, the consequences of pipes bursting can be significant and not be easy to repair. In many municipalities, it is a requirement to have pipe insulation based on their municipal codes. Insulation will help protect the pipes from extreme temperature conditions.
Asbestos
Asbestos was a commonly used insulator in the 1950's and 1960's because it was a good insulation with special properties, such as a strong resistance to heat [12]. Later, in the 1970s it was discovered that when asbestos is inhaled it can cause mesothelioma, a type of lung cancer and other chronic respiratory conditions [12]. Some buildings may still have asbestos as insulation. It is important to not disturb asbestos and get a specialist with proper equipment to remove and replace it.
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Faculty Advisor: Mary Robinson, Rachel Malevich (alumni)