Flooring Insulation in Ground Floors - Laying a Strong Foundation

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Key Learning outcomes

Understanding the core principles of flooring insulation
Knowledge of different construction techniques
How to calculate U-values
Understanding loading
Importance of correct insulation material

Since 1990, Building Regulations have required ground floors to be insulated in order to save energy. This CPD article looks at the factors that need to be considered when addressing ground floor insulation, including: construction techniques, thermal bridging, calculating U-values, and the impact of insulation on a project’s design.

1.0 Basic principles and floor construction

Ground floors may be classified as ground-bearing – in contact directly or indirectly with the ground – or suspended.

The ground absorbs heat from floors that are close to or in contact with it, mostly around the external floor perimeter where the ground is generally colder. High soil moisture content increases heat absorption. These effects, when combined with the natural temperature gradient in buildings, can lead to an uncomfortable internal environment, condensation at external wall/floor junctions and higher than predicted energy usage. These factors must be taken into account when calculating the insulation requirements for a ground floor.

All other floor types are, by definition, suspended. Here, heat is lost/gained uniformly across the entire surface.

A layer of thermal insulation in the floor construction, continuous with that in the rest of the building envelope, can reduce heat loss. It can also help avoid thermal bridges – breaks in integrity and continuity where the floor meets external or load-bearing internal walls. To minimise the potential thermal bridge, wall and floor insulation should meet or overlap where practicable.

Floor construction

Ground floors are typically constructed from ground-supported concrete slabs, suspended concrete floors (including beam and block systems), or suspended timber floors. (see BRE’s Good Building Guide 28, Part 1, for specific construction details).
A ground floor construction’s primary function is to prevent the transfer of moisture from the surrounding ground into the interior of the building. Damp-proof membranes (dpm) should be continuous with any vertical and horizontal damp-proof courses (dpc).

In structures below ground, groundwater must be prevented from reaching the interior of a building, commonly by waterproofing in the form of externally applied tanking membranes of mastic asphalt or bituminous sheet.

The thermal performance of a ground floor can be boosted by thermal insulation materials. These should be appropriate to each application and should have the required density or compressive strength, and relevant water absorption characteristics.
Ground floors can be retrospectively fitted with insulation, but this is usually only economically viable during a major refurbishment.

Insulating concrete ground floors above and below a structure require different approaches – described in Bites 2 and 3.

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Provider company overview

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About

Ravago Building Solutions

Ravago Building Solutions
Estuary Road
Kings Lynn
United Kingdom
PE30 2HJ

The information contained in the CPD article web pages is not intended and accordingly shall not be relied upon either as a substitute for professional advice or judgement or to provide legal or other advice with respect to any particular circumstance. RIBA Enterprises accepts no responsibility for loss occasioned to any person acting or refraining from action as a result of the information contained.

Flooring Insulation in Ground Floors - Laying a Strong Foundation

1.0 Basic principles and floor construction

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