For many years, the energy efficiency spotlight has been on improving the performance of walls and roofs. But there’s another area of the superstructure that merits close scrutiny – and you might be surprised to learn that, in many existing houses, around 10%-15% of the heat generated is lost through the floor.
The Building Regulations are fairly relaxed when it comes to thermal performance of upper storey floor structures – although you will need to consider fire safety and acoustic insulation. It’s really only with ground floors that conserving energy becomes a major design factor.
In new homes, Part L of the regs specifies a threshold U-value (a measure of heat loss) of 0.25 Watts per metre square Kelvin (W/m2K). If you’re providing new thermal elements in an existing home (eg as part of an extension), the limit is 0.22 W/m2K – unless there’s a heritage-related reason this can’t be achieved. Bear in mind these backstop levels vary slightly in Wales and Scotland. And in practice, most self builders will achieve a significant improvement on this. Indeed, the government’s own guidance for a notional dwelling suggests a target of 0.13 W/m2K.
It’s worth pointing out that your floor insulation spec should be developed as part of a holistic design approach to achieve the best results for your project. This should take in details such as whether the materials will suit your property, how cold bridging will be minimised (particularly at junctions between the wall and floor) and how these choices will affect heating patterns. Incidentally, if you’re going to be insulating a new or existing concrete floor structure, it often makes sense to install underfloor heating (UFH) at the same time – as this is the perfect opportunity to embed it into screed or clip the pipework into specially-grooved thermal panels.
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About Build It
The December edition of Build It magazine brings you a wealth of information to help make your self build, renovation, extension or conversion project a success – including:
• A unique modular home (page 20)
• How to get basement extensions right (page 62)
• 15 renovation ideas to add value and kerb appeal (page 66)
• Will smart heating save you money? (page 73)
• The latest woodburner trends and costs (page83)
… and much more!