Understanding U-Values and Air Tightness

We've mentioned "U-Values” - what exactly are they?

A "U-Value" is a theoretical calculation of a structure's thermal resistance, or its ability to retain heat. In other words a "U-Value" will give an approximate measurement of how difficult the material will make it for heat to pass through it. This also applies in summer conditions when cooling is desired. Open-cell sprayed foam insulation offers the best "U-value" of any breathable insulation material on the market.

Is the U-Value of an insulation all you need to know?

No. These U-Value calculations are achieved in laboratory conditions and have only a vague connection to real world situations, where poor installing methods and inaccurate measurements are commonplace and often shifting or sagging of materials occurs. These elements severely impact on the overall performance of the insulation system. In addition to these problems many materials have a propensity to retain moisture, given that they are neither breathable nor permeable such as rigid high density boards or glass fibre quilts.

In effect, the "U-Value" is only half the story.

Commonly, an insulation material can have a fantastic "U-Value" on paper but doesn't seem to be doing its job in practice, it is only then you realise that "U- Values" are only half of the picture and that without air tightness they just don't work. In the home, office or commercial building the only way to really impact on costs and comfort is make it air tight.

Air Tightness - the other piece of the puzzle!

The ideal system is one that not only has a low "U-Value" but is also forms an air tight seal while allowing the structure to breathe. Sprayed foam insulation is the only system available on the market today which performs all of these tasks in one simple step.

Don't we need air flow for ventilation?

Yes, but in a controlled fashion. Air leakage is the uncontrolled flow of air through gaps and cracks in the structure or fabric of a building (sometimes referred to as infiltration or draughts) which result in discomfort for occupiers and rising costs. This is not to be confused with ventilation, which should be a controlled flow of air into and out of the building through purposed built ventilators for the comfort of the occupants.

Too much air leakage leads to unnecessary costs, heat loss and discomfort to the occupants from cold and draughts. The increasing need for higher energy efficiency in buildings and the need in future to demonstrate compliance with more stringent "Building Regulation" targets mean that air tightness has become a major performance issue. The aim should be to 'Build tight- make it airtight'.

Heat loss / air leakage directly impacts on the performance of any building. From running costs to general comfort the benefits of an air tight structure are obvious,. Air tightness of existing buildings has been proven to be poor, which leads to unnecessary heat loss, greatly increased costs but also widespread occupant dissatisfaction.

How does spray foam make it air tight?

With spray foam, there is no cutting, no measuring and no waste, it is simply sprayed in place and expands at a ratio of 1/100 creating a perfect air tight fit. Even in those difficult places where it is physically impossible to gain full access.

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Page created : 15 | NOV | 2014