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House Insulation FAQ

Most people in Ireland have lot of questions about house insulation because this is relatively new subject in the country. We have tried to collect most of frequently asked questions, which hopefully will explain this matter in the clearest way possible.


What are the materials when choosing a proper insulation?
There are a variety of insulations to choose from including fiber glass, mineral wool, expanded or extruded polystyrene, cellulose, urethane or phenolic foam boards and cotton. The two most common types of insulation for residential applications are expanded polysterene (EPS) for external insulation and fibre glass and urethane or phenolic foam boards for internal insulation. There are several things to consider before making an insulation decision like thermal performance measured by U-value, lifetime performance, fire safety, moisture and condensation, air infiltration and environmental benefits.

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What is lifetime performance?

In order to ensure the expected energy savings, it is important that the insulation does not deteriorate, or settle, over time. Fiber glass batts and rolls do not settle. Fiber glass and rock and slag wool loose-fill insulations may settle approximately 1-3% resulting in virtually no impact on the thermal performance of the insulation.
In contrast, cellulose insulation not only settles to a much greater degree (approx. 20%), but also at a higher rate. If cellulose insulation is being considered, make sure the installer understands that most cellulose insulations settle in attic loose-fill applications - that's a significant loss of insulating effectiveness. In fact, it is recommends that an additional 25% of thickness be added for cellulose insulation to compensate for this extreme loss of R-value.

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How fire safety affects insulation?
In case of fire, the choice of insulation material can become a vital issue in terms of casualties, material or environmental damage. Combustible insulation can fuel the fire and cause it to spread. Some of the most widely used combustible insulation materials are oil-based foamed plastics (eg. polystyrene, polyurethane or polyisocyanurate) and organic materials (eg. shredded paper/cellulose). The less combustible materials are mineral wool which withstands more than 1000°C and fibre glass which withstands up to 600°C. For more combustive materials it is important not to install this type of insulation in contact with any area, which could become very hot during use such as chimneys, heater vents and steam or boiler pipes.

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What is condensation?

Air always contains some invisible water vapour. The amount of water vapour that the air can hold depends on its temperature - warm air can hold more water vapour than cold air. When warm moist (humid) air comes into contact with a cold surface, it will cool and may become saturated. If it cools further, some of the water vapour will condense out on the cold surface.

Air always contains some invisible water vapour. The amount of water vapour that the air can hold depends on its temperature - warm air can hold more water vapour than cold air. When warm moist (humid) air comes into contact with a cold surface, it will cool and may become saturated. If it cools further, some of the water vapour will condense out on the cold surface.

The type of condensation where moisture appears on visible surfaces within the building is called surface condensation. It may be seen to occur at times when large amounts of moisture are being produced in the house or room, especially during cold weather when windows and vents are closed.

Another type of contensation is interstitial condensation that occurs within external walls, floors and roofs. It occurs when warm moist air from inside the house passes through gaps in the internal surface and condenses at colder parts within. Since it cannot be seen, it is more difficult to identify. It may give rise to a damp, musty smell, and possibly mould growth on the inside surface. However, other causes of dampness can produce similar effects. Internally insulated walls with a deficient or damaged vapour barrier are particularly vulnerable to interstitial condensation.

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What are Thermal Bridges?

Thermal bridging occurs in small areas where the insulation level is reduced significantly compared with the remainder of the element.

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What is Thermal Conductivity or lambda value?
A thermal insulant is characterized by its thermal conductivity named lambda value (λ). Thermal conductivity measures the capacity of a material to lead or to resist to heat transfer. The smallest the lambda, the best the thermal insulation . This standard measure is made in laboratories according ISO 8301 norm and is declared at 10°C temperature and expressed in W/m.K. It is admitted that materials are thermal insulants if their conductivity is less than 0,065 W/m.K.

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What is Thermal Resistance or R-value?
This value will measure the capacity of a product to fight against heat loss. It will depend on thickness and thermal conductivity (lambda). The highest the R, the best performing the product. R combines thermal property of the material itself and thickness of the product and is calculated by dividing thickness (t) and lambda (λ) value: R=t/λ.

The heat flow, going through the wall depends on temperature difference between inside and outside and thermal resistance R of the wall. Each element constituting the wall has thermal properties: bricks or concrete, insulation, rendering. Wall thermal resistance is the addition of thermal resistance of each components from interior coating to exterior rendering, and superficial resistances. With higher R, the wall will resist more to heat loss.

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What is U-value?
To put it simply, it is the measure of the rate at which heat is lost through a wall, for instance. As it is a measure of heat loss then the lower the U-value the better it is for your home comfort.

It is the coefficient which characterizes the ability of the wall surface to heat transfer and is calculated as inverse of R value and is expressed in W/m2.K.

Building Regulations Technical Guidance Document Part L gives maximum U-values for each fabric elements which should be met to comply with the Building Regulations Standards of energy conservation. This is also requirement for an approval of insulation material for Home Energy Scheme Grants. For more information please find maximum u-values table for each fabric elements.


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What are the Vital Factors to Consider While Going for Advanced Home and External Wall Insulation Works

Ireland with its extremely chilled and cold atmospheric conditions is one place, where you simply cannot survive inside your home without home insulation. A lot of people have a number of questions about the kinds of materials that should be used, the important factors to consider, about fire safety, thermal bridges, thermal conductivity and U-value to name some. Going to a professional external wall insulation company is indeed the right thing to do. They guide you about your home's wall insulation needs and solve your queries too. 

The most popularly used materials for external wall insulation are mineral wool, fiber glass, expanded polystyrene, cotton and phenolic foam boards. Expanded polysterene also known as EPS is used for external insulation while fiber glass and urethane are good for internal insulation. 


The important factors to consider during home insulation are: 


- U-value
- Lifetime performance
- Fire Safety
- Moisture and Condensation
- Environmental advantages 
- Air infiltration

To guarantee sufficient energy conservation it is important to prevent insulation deterioration. Fiber glass including rock & slag wool are better options. Choosing the right external insulation material effects fire safety factor essentially. Mineral wool, compared to polystyrene and polyurethane is less combustible. 

Insulated walls with internal dampness and vapour accumulation have a greater tendency of developing interstitial condensation, which is rather tough to identify. Your specialist must also guarantee to check the formation of thermal bridges that occur in areas where insulation is limited.

You should install materials that have smallest lambda or thermal conductivity capacity. Materials with less than 0,065 W/m.K are considered to be good thermal insulants. The insulant material should have higher thermal resistance or R value. Further, the U-value of the insulating fabrics must be compliant to the regular Building Regulations.

 


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