What are the Maximum Allowable Ug-values in the Latest Building Regulations?

What are the Maximum Allowable Ug-values in the Latest Building Regulations?

What are the maximum allowable Ug-values in the latest Building Regulations?

As the cost of energy continues to rise, so does the demand for effective insulation.

High-performance insulation is a sustainable solution to the problem of heat loss. It retains the warmth generated by heating appliances and prevents it from escaping through walls, doors and windows.

What is a Ug-value?

The Ug-value of a product is a measure of its insulation properties. The lower the Ug-value, the better the insulation.

Ug-values are measured in Watts per square metre, per degree Kelvin (W/m²K).

As a guide, here are some products and their typical/average Ug-values:

Product:  Ug-value:
Solid timber door 3.0 W/m²K
Solid brick wall 2.0 W/m²K
Cavity wall with no insulation 1.5 W/m²K
Insulated wall 0.18 W/m²K
Single-glazed window 5.3 W/m²K
Double-glazed window 2.8 W/m²K
Triple-glazed window 1.0 W/m²K
Roof Maker double glazing 0.6 W/m²K


You can see how the Ug-value comes down with each layer of insulation.

There is a demand for high performance.

Nobody wants to pay more than they have to for their energy.

As prices have increased, many consumers have become savvier about finding ways to economise and make the energy they use go further.

For example, they understand that having effective home insulation means their heating appliances don’t have to work so hard to maintain a steady temperature.

To meet this demand and to satisfy environmental objectives, building standards have also tightened, calling for Ug-values to be continually reduced.

What are the maximum allowable Ug-values?

The current Building Regulations were last updated in 2016.

The maximum allowable Ug-values are specified in Approved Document L, which deals with the conservation of fuel and power.

The following maximum Ug-values are taken from Table 2, which can be found on page 15 of the Approved Document L1A.

Product:  Ug-value:
 Roof 0.2 W/m²K
Wall 0.3 W/m²K
Floor 0.25 W/m²K
Party wall 0.2 W/m²K
Swimming pool basin 0.25 W/m²K
Roof windows, glazed rooflights 2.0 W/m²K
 Pedestrian doors 2.0 W/m²K

Notional domestic building Ug-values.

The Building Regulations also set out Ug-values for the notional domestic building.

If a home is constructed entirely to these notional specifications, it will meet the CO2 and fabric energy efficiency targets and the limiting values for individual fabric elements and buildings services.

These Ug-values are substantially reduced when compared to the maximum allowable.

The Ug-values for the notional domestic building are as follows:

Product:  Ug-value:
Roof 0.13 W/m²K
Wall 0.18 W/m²K
Floor 0.13 W/m²K
Party Wall 0.00 W/m²K
Roof windows, glazed rooflights 1.40 W/m²K
Glazed doors 1.40 W/m²K

Roof Maker Ug-values.
So now we know the maximum allowable and notional Ug-values, let’s see how Roof Maker products compare.

 Product:  Maximum Ug-value:  Notional Ug-value:  Roof Maker Ug-value:
 Roof windows, glazed rooflights  2.0 W/m²K  1.40 W/m²K  0.6—1.0 W/m²K
 Glazed bi-fold doors  2.0 W/m²K  1.40 W/m²K  0.6 W/m²K

As you can see, Roof Maker’s glazed products have extremely low Ug-values — even lower than the notional specification suggested in the Building Regulations.

For builders, there is peace of mind that the product complies with current regulations.

For homeowners/buyers there is the benefit of exceptional insulation, which will keep heating bills down.

For more information, talk to our experts

For further information on our rooflights, glazing options or the maximum allowable Ug-values, please call 0116 269 6297to speak to one of our experts.