Stressline cold-bridging

How to reduce cold-bridging in floors

Andrew ALL, Developers, Flooring Leave a Comment

SAP calculations, u-values, psi values; thermal efficiency in construction can be a minefield, but with the world’s resources in decline, and the government putting more regulations in to ensure construction is as efficient as possible it is more pertinent than ever to understand how to build and live as efficiently as possible.

What are cold-bridges?

In the construction industry, and particularly when builders and developers are building new homes, thermal efficiency is right up there in terms of priorities. So what is a cold bridge, or a thermal bridge?

Our little video below shows what a cold bridge is. In simple terms it is where the cold air from outside is allowed to penetrate the building and reduce the temperature, thus making the building less thermally efficient. Some areas of the building are more susceptible than other parts; in this case the floor. In the case of flooring, when floor beams are laid, if they are not insulated the cold air can penetrate the beams and reduce the temperature resulting in heat loss, and as mentioned above thermal inefficiency.

Why are cold bridges significant in building and construction?

Apart from the desire to build a house that doesn’t require the occupants to wear coats throughout the winter, there are all sorts of regulations that builders and developers must adhere to in order to legally construct new houses.

SAP (Standard Assessment Procedure) calculations are required before a building inspector can sign off on the building or dwelling. SAP calculations are basically a system for assessing the energy rating of a new home.  Improving thermal efficiency of the house under construction should improve the SAP rating.

As well as SAP calculations, some specifiers indicate a required U-value for certain elements of the construction.  U-values measure thermal transference which is the rate of transfer of heat through a structure (heat loss). In order to meet the required U-values, builders and developers must investigate the products they are using to ensure they can achieve the required or specified U-values.

The table below looks at typical U-values using our thermal flooring system.

Example U-values (W.m-2.K-1) - Single beams at full centres
EPS panel thickness (other depths available)
T Beam Plus (grey)
Beam depthp/a ratio290350450260290350420
1500.40.140.110.140.120.10
0.60.150.120.150.130.10
0.70.150.120.150.130.10
0.90.150.120.150.130.10
2250.40.140.100.170.120.09
0.60.150.100.180.130.10
0.70.150.100.190.130.10

How can you reduce cold bridging in floors?

The most common form of reduction of cold bridges is insulation. Houses are designed and built with insulation throughout the property envelope. As mentioned above, however, there are areas that suffer more than others.

Floors are susceptible to cold-bridges because of their contact with the ground, and floor beams, if left uninsulated can cause significant heat transference.

To combat this one such solution is our thermal flooring system. The simple design includes standard prestressed concrete floor beams laid as normal. Instead of standard blocks in between the beams we use bespoke EPS (Expanded Polystyrene) blocks which act as an insulator between the cold air and the building. The EPS blocks are designed in such a way that they overlap underneath the beams to ensure exceptional insulation. In addition to this, we use insulation strips around the perimeter to reduce the cold bridging at the floor-to-wall joins.

For help on the installation of our thermal flooring system please see our video installation guide.

If you would like a quote or further information please email floors@stressline.net.

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