Does insulating your floor reduce heating costs?


Did you know that as much as 10% of the heat in a room can be lost through uninsulated ground floors and potentially higher, up to 15%, if the house has been well insulated or thermally improved in other areas? With that in mind, upgrading and insulating existing solid or suspended floors should be one area homeowners should not forget about. Insulating your floor will help reduce heating costs and a properly insulated ground floor will leave rooms feeling more comfortable and require less time to warm up. When looking to upgrade your own floor insulation, the options available to you depend on the type of floor you’ve got – suspended floors, solid concrete or timber floors.

The first and most simple option is to add a layer of insulation over your current floor finish and new flooring grade chipboard laid over this with your desired floor finish. Alternatively the floors may be excavated and new insulation laid and selected screed pored over. This option tends to be a much more onerous decision, but can achieve a much better u-value, while allowing the opportunity to install underfloor heating or other new services during the works.

Floating Floor

A floating floor is a construction detail where a layer of the Kingspan Thermafloor TF70 is loose laid over the existing floor finish, and a minimum 18mm tongue & groove chipboard placed over the insulation. Joints are then bonded together, to give a secure floor finish which is now suitable to take carpets, laminate flooring or a selected floor finish of your choice. For domestic applications where the thickness of insulation must be kept to a minimum the Kingspan Optim-R flooring insulation may be used. The Kingspan Optim-R will provide the highest thermal performance while also retaining the slimmest floor build-up possible. While both options may be the quickest solution with the least amount of disturbance caused to the occupants, consideration has to be given to the changes in overall floor height which can affect door thresholds, skirting board details and head height within rooms. This limits the thickness in the depth of insulation that may be installed, and the achievable u-value.

While these options do provide a huge thermal improvement in existing floors with little or no insulation, it may not be enough to bring them up to the more stringent and high spec standards required by today’s building regulations.

Suspended Floor

In properties with existing suspended timber floors insulating over the existing flooring boards will result in the existing flooring finish being hidden beneath the insulation and the character, design of the room or building can be negatively affected. As such insulation installed beneath the floor boards and between the flooring joists is the preferred option. However due to the lack of or restricted access to any voids or access space that may be beneath the floor, the existing floor boards may have to be removed entirely or in sections to allow the Kooltherm K3 to be filled between the flooring joists and refitted on completion. Make sure that insulation boards are fitted tightly between joists and any gaps are filled with expanding urethane sealant.

It would be considered best practice to fit a fully sealed membrane over the top Kooltherm K3 and the flooring joist to act as a vapour control layer and also reduce and improve potential unwanted drafts air movement. Care should be taken when caring out works to ensure any air spaces beneath the suspended floor are maintained and kept well ventilated to the outside in order to avoid dampness and wood rot.

Concrete Floor

A concrete floor is the most popular and common type for construction for residential new builds. Kingspan Kooltherm K3 boards can be loose laid onto the concrete slab or hard-core. Kingspan Kooltherm® K3 Floorboard is not recommended for use in direct contact with subsoil and must be used over a DPM. The board joints should be tight butted, and if installing two layers joints staggered and laid to a break bond pattern. Before the screed is laid onto the insulation a separating membrane is required above the insulation. This may be either a polythene sheet or builders paper and will prevent liquid screeds shifting boards during installation and weeping between board joints leading to cold bridging through the insulation layer.
When laying a new concrete floor a 25mm thick vertical strip of insulation should be used to insulate the perimeter of the floor slab. The perimeter strip is cut flush with the level of the finish floor screed and is laid butt joint over the horizontal floor insulation, forming a right angle. By insulating the full depth of the screed, cold bridging will be greatly reduced if not eliminated. They are not required on floating timber floors as the timber does not offer the same path for heat loss.

Kingspan Kooltherm K3 Floorboard can be used in conjunction with under floor heating systems, and will provide maximum thermal performance.

In all scenarios it is important to know what the desired u-value for the project is to be and what thickness of insulation is needed to achieve this specified u-value. This is determined by the perimeter and area ratio which can have a large effect on the thickness on insulation required. This calculation determines the ratio of floor slab exposed to unheated or external spaces as a proportion of its total area, the higher the ratio the more insulation is need to achieve the particular u-value.