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Celotex TD4000 provides a quick and easy method of achieving effective thermal insulation in light traffic, ventilated, lead covered, warm flat roof applications - includes 5.5mm WBP plywood. Thermal conductivity – 0.022W/mK
Price: £ 106.13
(£127.36 inc VAT)
Rockwool Rollbatt provides effective, medium density thermal insulation in loft spaces and suspended ceilings, reducing energy consumption and preventing fuel bills in all building types from going through the roof.
Price: £ 53.65
(£64.38 inc VAT)
Rockwool Cavity provides a completely reliable and cost-effective method of insulating new masonry cavity walls.
Price: £ 27.55
(£33.06 inc VAT)
A U value is a measure of heat loss in a building element such as a wall, floor or roof. It can also be referred to as an ‘overall heat transfer co-efficient’ and measures how well parts of a building transfer heat. This means that the higher the U value the worse the thermal performance of the building envelope. A low U value usually indicates high levels of insulation. They are useful as it is a way of predicting the composite behaviour of an entire building element rather than relying on the properties of individual materials.
U values are important because they form the basis of any energy or carbon reduction standard. In practice, nearly every external building element has to comply with thermal standards that are expressed as a maximum U value. Knowledge of how to simply calculate U values at an early stage in the design process, avoids expensive re-working later on in a project. It allows the designer to test the feasibility of their project at an early stage to ensure it is fit for purpose and will comply with regulatory frameworks.
U values are calculated at stages D onwards in the design process. A critical milestone in any building project is obtaining building regulation approval. For this a SAP calculation for housing or an SBEM procedure for non domestic work is obligatory. As part of this process, the build up of any external construction element must be specified and from this its U value can be derived. How to use U values
R = (1/k) x d
where k is the thermal conductivity of the building material and d is the material thickness.
U(element) = 1 / (Rso + Rsi + R1 + R2 ...)
where Rso is the fixed external resistance where Rsi is the fixed internal resistance and R1… is the sum of all the resistances of the building materials in the constructional element.