Underfloor Heating

Underfloor Heating

underfloorfloor-heatingIn this system a series of hot water pipes connected to boiler or heat pump is placed underneath the ground floor area of your home. A water underfloor heating system can sit beneath stone, tile, wooden or even carpeted surfaces.
It can be used to heat specific rooms or can heat an entire house thus eliminating the need for radiators. Wet system are very difficult to install which means the cost will be very high. If your existing floor is made of concrete, for example, then this concrete must be removed prior to heating specialist being employed. It is important to get very good advice before proceeding with such works. Also it is extremely important that any contractor you commission to carry out structural works on the ground floor of your home must ensure that the radon barrier underneath the floor is properly reinstated. If your home does not have a proper radon barrier make sure that it forms part of the new ground floor structure. Ventilation under the ground floor is also crucial. Choose only competent contractors.

The ground or lowest floor in a building is the most important floor to consider for effective thermal upgrading, unless it is an unheated space, such as a cellar, in which case the floor above should be insulated. An estimated 15% of the heat within a traditional building is lost through its ground floor. In such buildings, lower floors are of varying construction types and have different finishes. Both ventilated and unventilated suspended timber floors are particularly common at ground floor level. Stone flags, tiles or brick paving laid on solid floors (often bare earth) are also common, particularly within basements. In a public building or church, a range of floor types is found, often for example, with a stone or tiled finish in the circulation spaces, typically with an unventilated timber floor beneath the pews or seating areas.

Improving the thermal performance of the ground floor reduces the overall heat loss from a building, and can also significantly improve comfort levels by providing a warm floor underfoot. In a historically important building it may, however, be difficult to upgrade a floor without loss or disturbance of significant finishes such as tiles or brick paving and therefore particular care needs to be taken when considering insulation works to such floors. Planning permission may be required when lifting such floors to allow for insertion of insulation. In some cases, because of the potential for damage to important finishes, such works may be considered inappropriate.

suspended_timber_floorSuspended timber floors were constructed in the past both as ventilated floors with vent bricks or grilles in the exterior walls and as unventilated floors. By the nineteenth century the latter were less common. Where vents are provided it is important to ensure that these remain unobstructed as they ensure that any moisture which may reach the floor timbers can escape, preventing a potentially damaging build-up of moisture levels in the space beneath the floor. If a floor is not ventilated it may be appropriate to consider providing vents subject to consideration of the effect on the visual appearance of the façade. If any vents have been blocked up in the past, it is important to reopen them. Vents should not be regarded as the cause of unwanted draughts as they are an essential part of the proper functioning of the building and vital to maintaining it in sound condition. Floor coverings such as rugs or carpets will eliminate draughts and the underside of the floor can be upgraded with insulation.

If there is a crawl-space beneath the floor it is usually easier to upgrade suspended timber floors from below as the joists and floorboards are generally exposed from the underside. However, if access beneath the floor is not possible then the floors should be upgraded from above by lifting the floorboards. Great care should be taken when lifting old floor boards, especially the wide boards found in many Georgian houses; if any are damaged or broken it will be very difficult to find matching boards for repairs. The fixings used for old floor boards can themselves be of interest and can be damaged or lost through careless lifting methods; strips of metal or timber dowels, were often used in high quality work to fix boards to each other.

decorative-floorDecorative and high quality floors are difficult to upgrade and require careful analysis of the time, cost and, above all, the potential damage that could be caused to the historic finish in exchange for improved thermal performance. Fine floor finishes such as these tiles should not be lifted

A floor vent to ventilate the ground floor was built into the wall between the cellar and ground floor windows as part of the original design.

Alternatively, floor boards may be tongued-and- grooved together which makes lifting individual boards difficult to achieve without damage. If working from below, quilted insulation such as sheep’s wool, hemp, rockwool or cellulose fibre can be fitted for the full width and depth of the joists and held in place with nylon netting stapled to the joists. If working from above chicken wire or plastic netting can be moulded around the joists to form trays between them which are then packed with quilt insulation before the floor boards are refitted. An alternative method of fixing from above is to fix battens to the sides of the joists and fit rigid insulation between them. Note that it can be difficult to cut the insulation to fit perfectly and any resulting gaps will compromise its insulating performance.

solid-floor-detailThe easiest way to upgrade an existing solid floor is to add a layer of insulating material above it with a new floor finish on top. The covering of an existing floor should only be considered if it is of no architectural or historical interest. Floor finishes such as decorative tiles, brick, wood block or stone flags should not be covered over although in some cases it may be possible to carefully lift these to allow for re-laying over the new, insulated floor. Floors which have previously been interfered with and have modern finishes such as concrete are the most appropriate candidates for covering with insulation. However, this will increase the height of the finished floor level and affect internal features such as skirting boards, window linings, doors and architraves and cause difficulty at the foot of stairs. Such alterations, in their own right, can be inappropriate in some interiors and will need to be considered on a case-by-case basis. The laying of a new insulated floor over an existing floor may also reduce the height of the space. Such modifications to the interior of a protected structure are likely to require planning permission and the planning authority should be consulted before any works are undertaken.

Basement floors are usually solid. The use of the basement should be considered prior to upgrading the floor and if it is used for activities not requiring heat it may be appropriate to insulate above the basement level instead. Expectations for a warm, insulated, dry basement may not always be realisable in older buildings.

If a building is undergoing restoration or major refurbishment, the opportunity may be taken to lift or excavate the existing floor and to lay insulation on a new subfloor. However, this option should be carefully considered for a number of reasons. The excavation of an existing floor and the laying of a new floor slab can in some cases undermine walls which have very shallow, or indeed sometimes no, foundations or footings. Vibrations arising from the works can also potentially cause structural damage. Care should be taken in buildings built over a high water table or with pre-existing problems with rising damp. It is possible that, as a new sub-floor will seal the floor, moisture which previously evaporated through the floor joints will now be trapped and may be forced to make its way over to the walls, thus increasing the risk of damage to fabric from rising damp. If it is decided to lift a floor for the purposes of adding insulation, it may be worth considering the installation of underfloor heating as part of this process. Underfloor heating is most effective when laid in solid floors with a hard floor finish such as stone or tiles. Traditional buildings may benefit from the low levels of consistent heating provided by underfloor heating at ground level as it will help keep the bottom of walls dry.

There is considerable interest in the use of vapour- permeable flooring construction, using concretes made of lime with hemp or expanded clay. These materials may be appropriate where there is a delicate moisture equilibrium to be maintained. Circumstances which require a radon barrier would make the case for using such materials less compelling. Building Regulations also imply that new floors should be impermeable.

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