Which Radiant Heating System for a Loft Conversion?

Wall heating on the pitched roof

By converting the loft, the living space of a house can be extended, sometimes considerably. Living in such a converted attic can also be very attractive. However, the nature of the space places special demands on heating and air conditioning. Wall heating with drywall plasterboard on the roof pitches offers many advantages here.

When fitting out the attic, it is common to plan large open rooms in order to emphasise the special characteristics of the roof truss. Window openings installed subsequently should reach down to the floor to provide the room with sufficient daylight. This leaves little room for traditional wall-mounted radiators.

Underfloor heating can be a suitable heating solution if the attic floor's structural integrity allows it to be installed. However, conventional underfloor heating systems with thermal insulation and heating screed can place a considerable additional load on the loft.

In the case of ceiling heating, the area of the horizontal ceiling section - if any - is often insufficient to provide adequate heating.

In contrast, the wall surfaces in the attic are disproportionately large in relation to the room size. They are also not obstructed by furniture, which can hinder heat radiation. Wall heating on sloping ceilings utilises and supports the special features of the room. In addition, radiant heating on the wall not only offers energy benefits and potential savings on energy costs, but can also be used in conjunction with a reversible heat pump to cool the rooms under the roof in summer.

Substructure for radiant heating on the pitched roof

Sketch - Arrangement of the wall heating elements on the sloping roof

What to consider during installation

In most cases, the drywall plasterboard of the ceiling heating system with a length of 1,200 mm are suitable for the thermal activation of roof pitches. If larger areas are available, the wall heating elements with a length of 2,000 mm can also be used. However, the size and weight of the wall heating panels require two people to install them on a slope.

The substructure is fastened horizontally to the rafters at a distance of 400 mm from each other in accordance with dry construction guidelines.

The hydraulic connections between the panel heating elements and the RTL control boxes are carried out in the same way as detailed in the ceiling heating installation instructions.

The remaining areas of the roof slopes are sealed with inactive 12.5 mm thick plasterboard. Apart from using thermally activated plasterboard, the usual drywall construction standards apply for the attic extension with wall heating.

Roof insulation is essential

From 2014, the GEG (Building Energy Act) requires that roofs must be adequately insulated (U-value < 0.24 W/(m2K)). Insulation must be carried out in accordance with building regulations, but it is worthwhile in most cases. Good roof insulation saves about 8% heating energy, protects against heat in summer, is subsidised by the BAFA and contributes to climate protection. To find out what you need to consider when insulating your roof and how much different types of insulation cost, go to https://energysavingtrust.org.uk/advice/roof-and-loft-insulation/

 

Sketch - Combination of wall and ceiling heating in the attic

If the heating output over the surfaces of the roof pitches is not sufficient

If the output of the heating elements on the sloping roof is not sufficient due to the limited surface area, additional ceiling heating or wall heating on the straight walls could cover the heat requirement.

If there is limited space on the pitched roof or the layout of the heating elements is complicated by skylights, the drywall panels of a ceiling heating set can be divided between the roof and the ceiling.

For high requirements, particularly with regard to cooling capacity, drywall panels with integrated copper pipes can be used. These panels offer a heating and cooling capacity that is 40–50% higher.

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