Building Regs U Values
In 2022, the UK building regulations were updated to include revised U values for new builds and renovations.
These updates are designed to improve the energy efficiency of buildings and reduce their carbon footprint.
According to the updated Part L documents, the U values for new builds will be as follows:
- Roofs: 0.11 W/m²K
- Walls: 0.18 W/m²K
- Floors: 0.13 W/m²K
For new elements in existing dwellings, the U values will be:
- Roofs: 0.15 W/m²K
- Walls: 0.18 W/m²K
- Floors: 0.18 W/m²K
For existing elements in existing dwellings, the limiting U values will be:
- Roofs: 0.16 W/m²K
- Walls: 0.30 W/m²K
- Floors: 0.25 W/m²K
It is important for builders and contractors to be aware of these updated U values and ensure that they are met in order to comply with building regulations. Improving the U values of a building can result in energy savings, improved comfort, and a lower carbon footprint.
|Approved Document Part L, Conservation of Fuel and Power, Volume 1: Dwellings,, 2021 Edition - England
|Table 1.1 - Summary of notional dwelling specification for new dwelling
|Table 4.2- Limiting U-values for new Fabric elements in existing dwellings
|Table 4.3 - Limiting U- values for existing elements in existing dwellings
|Roof(Including flat roof)
|0.35 W/m2K / 0.16 W/m2K
|0.08 -0.15 W/m2K
|Wall (Including dormer cheeks)
|Wall - cavity insulation
|0.7 W/m2K / 0.55 W/m2K
|0.08 - 0.15 W/m2K
|Wall - internal or external insulation
|0.7 W/m2K / 0.3 W/m2K
|0.08 - 0.15 W/m2K
|0.7 W/m2K / 0.25 W/m2K
|0.08 - 0.15 W/m2K
|1.4 W/m2K *
|1.2 W/m2K - 1.7 W/m2K
|Doors with >60% of internal face glazed
|See window requirements
|1.4 W/m2K **
|1.4 W/m2K *
|* or Window Energy ration Band B
|** or Window Energy ration Band C
|* refer to floors adjacent to soil and unheated basements, not internal floors
Building regulations in the UK dictate standards for the construction and alteration of buildings in order to ensure the safety, health, and welfare of occupants. One important aspect of building regulations is the requirement for certain U values, which measure the heat loss through building elements such as walls, windows, and roofs. In this blog post, we will delve into what U values are, how they are calculated and regulated in the UK, and ways to improve U values in existing buildings. By understanding and optimising U values, builders and homeowners can improve the energy efficiency and comfort of their properties, ultimately saving money on heating and cooling costs and reducing their carbon footprint.
II. What are U values?
U values, also known as thermal transmittance or insulation values, measure the rate of heat loss through a building element. They are expressed in units of watts per square metre per degree Celsius (W/m²K) and represent the amount of heat that is transferred through a building element over a given area for a temperature difference of 1°C. In other words, the lower the U value, the better the insulation of the building element and the less heat is lost.
U values are an important consideration in building design and construction, as they can significantly impact the energy efficiency and comfort of a building. Poor insulation can result in high heating and cooling costs, drafts, and temperature fluctuations, whereas well-insulated buildings are more energy efficient and comfortable to live in.
U values can be calculated for various building elements, including walls, floors, roofs, windows, and doors. The U value of a building element is determined by its material, thickness, and any additional insulation or coatings applied to it. For example, a thick brick wall with insulation will have a lower U value than a thin wooden wall without insulation. It is important to ensure that all building elements meet the required U values as stipulated by building regulations.
III. Building Regulations in the UK
In the UK, building regulations set out standards for the construction and alteration of buildings to ensure their safety, health, and welfare. These standards apply to new builds, as well as renovations and extensions to existing buildings.
One aspect of building regulations that is relevant to U values is the requirement for energy efficiency. Building regulations in the UK require that new builds and renovations meet certain energy efficiency standards, including U values for various building elements. These standards are regularly updated to reflect advances in energy efficiency technology and techniques.
To ensure compliance with building regulations, builders and contractors must calculate the U values of all building elements and provide evidence of their compliance. This can be done using specialised software or by consulting tables of U values for common building materials.
Enforcement of building regulations is carried out by local authorities, which have the power to carry out inspections and issue fines for non-compliance. It is important for builders and contractors to ensure that their work meets the required U values to avoid any potential penalties.
In addition to ensuring compliance with building regulations, optimising U values can have long-term financial and environmental benefits. Energy efficient buildings are cheaper to heat and cool, which can save homeowners money on energy bills. They also have a lower carbon footprint, making them more sustainable and environmentally friendly.
IV. Improving U values in existing buildings
If you own an existing building that does not meet the current U value requirements, there are several techniques you can use to improve its energy efficiency and reduce heat loss. Some options for improving U values in existing buildings include:
- Adding insulation: Insulation is one of the most effective ways to improve U values and reduce heat loss. It can be added to the walls, floors, and roof of a building to increase its insulation properties. There are various types of insulation available, including fiberglass, foam, and mineral wool, each with its own pros and cons.
- Double glazing: Replacing single-paned windows with double-glazed windows can significantly improve the U value of windows. Double-glazed windows have two panes of glass separated by a layer of air or gas, which acts as insulation to reduce heat loss.
- Upgrading doors: Replacing old doors with newer, more insulated models can also improve the U value of a building. Look for doors with a high R-value, which measures the resistance of a material to heat flow.
- Draught-proofing: Simple measures like sealing gaps around windows and doors can significantly reduce drafts and heat loss. This can be done with weatherstripping, sealant, or draught excluders.
Before embarking on any improvements, it is important to conduct a cost-benefit analysis to determine the financial and environmental benefits of upgrading U values. While some improvements may have a high upfront cost, they may result in long-term savings on energy bills and a reduction in your carbon footprint.
In conclusion, U values are an important factor in building regulations for energy efficiency and comfort. They measure the heat loss through building elements and lower U values mean better insulation and less heat loss. Building regulations in the UK dictate U values for new builds and renovations, and builders and contractors must ensure compliance to avoid penalties. Improving U values in existing buildings can have long-term financial and environmental benefits, such as reduced energy bills and a lower carbon footprint. Techniques for improving U values include adding insulation, double glazing, upgrading doors, and draught-proofing. By understanding and optimising U values, builders and homeowners can create more energy efficient and comfortable buildings.