U-Values

Your home energy efficiency is to a great part determined by the U value of U Values
your insulations and building envelopes.

U-Value is a complex energy transmission index presented in a simplified form.

Insulation and Energy Losses
Whether it is summer when the heat flow is inwards or winter when the Heat
Flow is outwards both unfortunately lose hard earned money of the householder by
way of lost heat Energy.




Heat loss of your home may be due to;

  • Insulation and structure with high U-value (depends on variable s like thickness, ‘r’ value, density etc.)
  • Damaged Insulation
  • Damaged or absence of moisture barrier in the insulation
  • Out side Air Leakage (infiltration)

Of these the most critical perhaps is the High U-value of the envelope.

Heat and Heat Flow
The insulating property of a material refers to it’s resistance to the transfer of heat energy. Heat that can be sensed is called Sensible Heat and as we all know is indicated and measured in degrees Celsius. Heat flows from a hotter area of a body (higher energy level) to a cooler area (lower energy level). The resistance to this flow of energy (Thermal Resistance) is called the ‘r’ value (given in sq m. deg C/watt).

It depends on the thickness of the material and the thermal conductivity (i.e. the ability of a material to
transfer thermal energy given in watts/meter. deg C). Also notably if a material of the building envelope (e.g. Glass, wall etc.) is exposed to out side, the ‘r’ value is different to that of side facing inside.

What is the U –Value?
If the structure is composite the reciprocal of the combined thermal resistances is called the U- value. This is an indication of the quantity of thermal energy in watts transferred over an area of 1 m for a temperature difference (in the composite) of 1 deg C.

This value therefore truly determines the thermal energy lost by you for every degree of temperature difference through your building envelope.

What determines U-Value?

The U –Value is determined by the reciprocal of thermal resistances of each component of a building envelope component.

The following are some typical U-values of building components. (This may widely differ depending on the composition of each item, variations in conditions, variations in physical properties etc.)U Value of Glass = 5.68 W/m2degC (single glazing)U Value of a wall = 1.76 W/m2degC (Brick & Plaster)U Value of a Roof = 0.971 W/m2degC (insulated concrete Roof Slab)


It is apparent therefore a lower value in your building envelope saves you quite a lot in energy bills. Services by ENTECH along with their associates is a major provider of services related to the issue of BER certifications such as;

  • Permission and “as built” Design guidance pertaining to building features related to BER assessment.
  • Obtaining for you the services of registered BER assessors
  • Supply, install and commission Heating Ventilating and air conditioning equipment
  • Supply and install Insulation, moisture barriers, attic insulation, and windows with double layer glazing with inert gas or low emission glass.

Free information regarding BER Certification, Advisory report, HES Scheme and the grants available
for retrofitting under this scheme etc.